UNIT - I Mobile Communication and Mobile Computing
description
Transcript of UNIT - I Mobile Communication and Mobile Computing
Mobile Communication and Mobile Computing1
UNIT - IMobile Communication and
Mobile Computing
Mobile Communication and Mobile Computing2
Speech- and Data Communication location independent and mobile
New application areas, flexibility, improved workflows
Requirements:- Mobile end-devices- Radio transmission- Localization and signalization/management- Standards
- Application Concepts for mobile end-devices in distributed systems
- Control of heterogeneous, dynamic infrastructures
Mobile Computing
Motivation
Mobile Communication and Mobile Computing3
Building site
ArchitectBuilding ofenterprise A(main office)
Building ofenterprise B
Construction supervisor
X.25ISDNATM
ATM ISDN
GSM GSM
Selected drafts,Videoconferences
Material data,status data,dates
Large archives,Videoconferences
Drafts,urgent modification
Building ofenterprise A(branch office)
Application example: Civil Engineering, Field Service
Mobile Communication and Mobile Computing4
WAP-Example: Order processing
Order book
• Status of bond transactions.
• Executed and deleted orders are indicated in the order book for some days more.
• Partial execution of some order is presented as one open and one executed partial order in the order book.
• Details to an order could be indicated via dial-up of correspondent Links.
Mobile Communication and Mobile Computing5
Product Data
Main officeCaching
ClientLAN-Access
Maintenance technician
- very different performance and charges: radio networks versus fixed networks
Software-technical, automatic adaptation to concrete system environmentExample: Access to picture data/compressed picture
data/graphics/text
Mobile Access
Local Resources,Error Protocols
Perspective: Mobile Multimedia Systems
Mobile Communication and Mobile Computing6
Ethernet
Ethernet
Ethernet
E-Fax-OrderE-Fax-Order
ManagementDB-Access
ManagementDB-Access
FirmBranch office
Client X
GSM
xDSL
Application
Resource
Mobile Station
Communication path
DBDistributed Database
Distributed Database
Cache
Application Structure
Mobile Communication and Mobile Computing7
Internet
Content Provider
Main Office
Infrastructure
GSM
GSM
Radio/Infrared
ATM
GSM, RDS/TMC, DAB...
Beam Radio, ISDN
GSM
Traffic Telematics Systems
Content Provider
DAB: Digital Audio Broadcast
RDS/TMC: Radio Data System/ Traffic Message Channel
Mobile Communication and Mobile Computing8
GSM (Global System for Mobile Communications): worldwide standard for digital, cellular Mobile Radio Networks
UMTS (Universal Mobile Telecommunications System): European Standard for future digital Mobile Radio Networks
AMPS (Advanced Mobile Phone System): analog Mobile Radio Networks in USA
DECT (Digital Enhanced Cordless Telecommunications): European standard for cordless phones
TETRA (Terrestrial Trunked Radio): European standard for circuit switched radio networks
ERMES (European Radio Message System): European standard for radio paging systems (Pager)
802.11: International standard for Wireless Local Networks
Bluetooth: wireless networking in close/local area
Inmarsat: geostationary satellite systems
Teledesic: planned satellite system on a non-geostationary orbit
Mobile Communication Networks: Examples
Mobile Communication and Mobile Computing9
Mobile Communication: Development
2005200019951990
D (GSM900)C
Cordless Telephony
Mobile Phone Networks
Packet Networks
Circuit Switched Networks
Satellite Networks
Local Networks
Modacom
Mobitex
Tetra
Inmarsat
IR-LAN
MBS
IMT2000/UMTS
IEEE 802.11/Hiperlan
Radio-LAN
Iridium/Globalstar
E (GSM1800)
EDGEHSCSD
GPRS
CT2 DECT
Mobile Communication and Mobile Computing10
Used Acronyms
CT2: Cordless Telephone 2. Generation
HSCSD: High Speed Circuit Switched Data
GPRS: General Packet Radio Service
EDGE: Enhanced Data Rates for GSM Evolution
IMT2000: International Mobile Telecommunications by the year 2000
MBS: Mobile Broadband System
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2. Mobile Communication
Mobile Communication and Mobile Computing12
Principles
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Mobile Communication
Tied to electro-magnetic radio transmission
radio transmission
terrestrial orbital (satellite)
beam radiobroadcast radio
equatorial orbit
non-equatorialorbit
cellular non-cellular
Principles:– Propagation and reception of electro-magnetic waves– Modulation methods and their properties– Multiplex methods– Satellite orbits/Sight- and overlap areas
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Cellular Networks: Principles
Supply- (radius R) and interference areas (5 R)
7-Cell-Cluster (repeat sample of the same radio-channels)
Interference Zone
R
Channels801-1600
Channels 1-800
Channels 1-800
5R
15
6
6
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7
4
4
2
7
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1
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5
2
7
73
2
6
4
56 3
5
15
6
6
3
7
4
4
2
1
7
2
5
32
14 24
12
R
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Cell structure: Example
Reference cell
Cell in the interference area of the reference cell
Further cells, whose channel distribution should be known to the reference cell
Cellular Networks: Principles
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Kinds of antennas: directional & sectored
• Energy is radiated in definite directions, for instance x-Direction
• So called main propagation directions, for instance Satellite Antennas
• Often also used in Mobile Radio Systems, such as GSM, for creation of sectored cells
• Seamless radio supply via partial/overlay of sectors
x
y
x
z
Directional Antenna Sectored Antenna
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Media Access Methods
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Principles
• Multiplex– Multiple-shift usage of the medium without interference– 4 multiplex methods:
• Space• Time• Frequency• Code
• Media Access Methods– controls user access to medium
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SDMA (Space Division Multiple Access)
• based on SDM (Space Division Multiplexing, Space Multiplex)• communication channel obtains definite Space for definite Time on
the definite Frequency with definite Code• Space Multiplex for instance in the Analog Phone Systems (for each
participant one line) and for Broadcasting Stations• Problem: secure distance (interferences) between transmitting
stations is required (using one frequency) and by pure Space Multiplex each communication channel would require an own transmitting station
• Space Multiplex is only reasonable in combination with other multiplex methods
• SDMA for instance by base station dedication to an end-device via Media Access Methods or respectively by segmentation of a Mobile Radio Network to several areas
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SDMA: Example
k1 k2
s
s – secure distance
k3 k4 k5 k6
SDMA finds selection
f1
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FDMA (Frequency Division Multiple Access)
• Based on FDM (Frequency Division Multiplexing, Frequency Multiplex)
• i.e. to transmission channels several frequencies are permanently assigned, for instance radio transmitting stations
k1 k2 k3 k4 k5 k6
f1
f2
f3
f4
f5
f6
s – secure distance
s
FDMA findsselection
t
f
k1
k2
k3
k4
k5
k6
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TDMA (Time Division Multiple Access)
• Based on TDM (Time Division Multiplexing, Time Multiplex)• i.e. to transmission channels is the transmission medium is slot
assigned for certain time, is often used in LANs • Synchronization (timing, static or dynamic) between transmitting and
receiving stations is required
k1 k2 k3 k4 k5 k6
f1
t
f
k1 k2 k3 k4 k5 k6 k1
TDMA findsselection
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Combination: FDMA and TDMA, for instance GSM
• GSM uses combination of FDMA and TDMA for better use of narrow resources
• the used band width for each carrier is 200 kHz
t
f in MHz
TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7 TS0
TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7 TS0
TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7 TS0
TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7 TS0
TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7 TS0
TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7 TS0
890,2
915200 kHz
935,2
960
25 MHz
45 MHz
25 MHz
uplink
downlink
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CDMA (Code Division Multiple Access)
• based on CDM (Code Division Multiplexing, Code multiplex)• i.e. to transmission channels the definite Code is assigned, this can
be on the same Frequency for the same Time transmitted• derivates from military area• via development of cost-efficient VLSI components• via spread spectrum techniques a good communication security and
tiny fault sensitivity• but: exact synchronization is required, code of transmitting station
must be known to receiving station, complex receivers for signal separation are required
• Noise should not be very high
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CDMA
k1 k2 k3 k4 k5 k6
f1
CDMAdecoded
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The Principle of CDMA can be good illustrated by the example of some party:
• communication partners stand closely to each other, each transmission station (Sender) is only so loud, that it does not interfere to neighbored groups
• transmission stations (Senders) use certain Codes (for instance, just other languages), they can be just separately received by other transmission stations
• receiving station (Listener) attunes to this language (Code), all other Senders are realizing this only as background noise
• if receiving station (Listener) cannot understand this language (Code), then it can just receive the data, but it cannot do anything with them
• if two communication partners would like to have some secure communication line, then they should simply use a secret language (Code)
• Potential Problems:– security distance is too tiny: interferences (i.e. Polish und
Czech)
CDMA illustrated by example
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Sender A• Sends Ad =1, Key Ak = 010011 (set: „0“= -1, „1“= +1)• Transmit signal As =Ad *Ak = (-1, +1, -1, -1, +1, +1)Sender B• sends Bd =0, Key Bk = 110101 (set: „0“= -1, „1“= +1)• Transmit signal Bs =Bd *Bk = (-1, -1, +1, -1, +1, -1)
Both signals superpose additively in air• Faults are ignored here (noises etc.)• C = As+ Bs =(-2,0,0,-2,+2,0)
Receiver will listen to Sender A• uses Key Ak bitwise (internal product)
– Ae = C * Ak =2 +0+0 +2 +2+0 = 6– Result is greater than 0, so sent bit was „1“
• analog B– Be = C * Bk =-2 +0 +0 -2 -2 +0 = -6, also „0“
CDMA-Example in the theory
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Spread Spectrum Techniques
• Signal is spread by the Sender before the transmission (overblown) • dP/df value corresponds with so called Power Density, Energy is
constant (in the Figure: the filled areas)
Objective:• Increase of robustness against small band-width faults• listening security: power density of spread-spectrum signals can be
lower than that of background noise
df
dP
f
df
dP
f
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Spread Spectrum Techniques
• small band-width faults are spread by de-spreading in receiving station
• band-pass deletes redundant frequency parts
df
dP
f
df
dP
f
df
dP
f
t
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Mobile Radio Networks: Overview
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General technological development in mobile telephony
before 1970 1970 1980 2000 2005
Analog Networks...150Mhz
1990
Anal. cellular Networks...450 Mhz
Anal. cellular Networks...900 Mhz
Digital cellular Networks...900 Mhz
Digital cellular Networks...1800 Mhz
GSM Phase II+
UMTS
Satellite Systems (LEO)
Prognoses
Development of Mobile Radio
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Correspondent data rates
1995 2000 2005 2010
10kbit/s GSM
HSCSD/GPRS
EDGE
100kbit/s
1Mbit/s
10Mbit/s
UMTS (pico cell)
UMTS(macro cell)
DAB
Satelliten
DECT
(GEO)Satellites (GEO)
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365190830; 32%
369094290; 32%
137691590; 12%
165417440; 14%
37534680; 3%
20059880; 2%
53069620; 5%
1
2
3
4
5
6
7
Participant quantities in Mobile Radio – world-wide
November 2002: 1148 Mio. participants world-wide (1119 Mio. digital & 29 Mio analog)
1... Europe: Western 4... Americas (thereof 15.4 Mio. analog)
2... Asia Pacific 5... USA/Canada (thereof 5.4 Mio. analog)
3... Middle East 6... Africa
7… Europe: Eastern
(Source: http://www.emc-database.com)
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Frequency Assignment
TETRA
380-400
410-430
NMT
453-457
463-467
CT2
864-868
CT1+
885-887 890-915
GSM900 CT1+
930-932
GSM900
935-960
TFTS (Pager, aircraft phones) GSM1800
1670-1675 1710-1785 1800-1805
TFTS
1805-1880
GSM1800 DECT
1880-1900 (1885-2025
2110-2200)
TETRA
450-470
(nationally different)
UMTS
IEEE 802.11b
2400-2483
HIPERLAN1
5176-5270
MHz
Bluetooth
2402-2480
HIPERLAN2
(ca.5200,5600)
WLAN
2412-2472HomeRF...(approx.2400)
Circuit Switched Radio Mobile Phones Cordless Phones Wireless LANs
Notes: - 2,4 GHz license free, nationally different- () written : Prognoses!- today speech over license free frequencies up to 61Ghz -> interesting for high data rates
(ca.17000)
HIPER-Link
1GHz500Mhz
TFTS - Terrestrial Flight Telephone System
IEEE 802.11a: 5,15-5,25; 5,25-5,35; 5,725-5,825
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Broadcast/multicast networks
• several carrier frequencies but participant obtains carrier for short time only
• often in use by taxi- und logistics enterprises etc., each own separated frequency reaches
• can use the same frequency packs with FDM- and TDM- techniques, i.e. more efficient handling with narrow resource frequency spectrum
• improves transition to fixed network, speech- and data services
• not for public access • very reliable, cost-efficient
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TETRA (Terrestrial Trunked Radio)
• former name: Trans-European Trunked Radio• frequencies: 380-390, 410-420 MHz Uplink; 390-400, 420-430 MHz
Downlink• bandwidth of each channel: 25 kHz• 1991 started by ETSI• replace of national networks like MODACOM, MOBITEX or
COGNITO• Services:
– Voice + Data (V+D)- Service: Speech and Data, channel-oriented, uni-, multi- and broadcast possible
– Packet Data Optimized (PDO)- Service: packet-oriented, improves connection-oriented or connectionless service, as well as point-to-point and point-to-multipoint communication
• carrier services with data rate up to 28,8 kbit/s unprotected; 9,6 kbit/s - protected
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TETRA, advantages compared with GSM, UMTS
• confirmed and/or non-confirmed Group Call (however it’s already possible with GSM today: up to 16 participants)
• Group call• listening is possible (so called “open-channel mode”)• very reliable• fast dialing: approx. 300 ms (so called “push to talk”), GSM: several
seconds• certain independence of infrastructure (so called “direct mode”
between end-devices)• cost-efficient, especially for limited user quantity, because of the
„large“ cells x • 10 km• also especially suitable for emergency teams (fire department,
ambulance etc.)
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Cordless Telephony - DECT (Digital Enhanced Cordless Telecommunications)
• frequency reach: 1880 - 1990 MHz• other than GSM limited to short reaches (1km)• in buildings particularly under 50m• is not designed for use at high rates• mobile phones with GSM and DECT are available in the market• 120 full duplex channels• TDD (Time Division Duplex) for directional separation with 10ms
frame length• frequency reach is divided into 10 carrier frequencies using FDMA• each station 10mW averaged, max. 250mW of transmitting power,
GSM – radio phones transmit at 1 to 2W, fixed car phones up to 8W
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PA
PA
PT
PT
FT
FT
D4 D3 D2
Local Networks
Local Networks
HDB
VDB
Global Networks
D1
FT.. Fixed Radio Termination
PT.. Portable Radio Termination
PA... Portable TerminationsHDB.. Home Data BaseVDB.. Visitor Data Base
DECT – system architecture
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64 bit8 bit160 bit48 bit32 bit
Synchronization SignalizationUsed Data
(Speech)CRC Used Data
(Speech) CRC Secure marker
160 bit 8 bit
0,417 ms
DECT-timeslot structure
Transmission reach of fixed part (downlink) Transmission reach of mobile part (uplink)
carrier frequency 1:1 2 3 4 5 6 .... 11 12 1' 2' 3' 4' 5' 6' .... 11' 12'
1 2 3 4 5 6 .... 11 12 1' 2' 3' 4' 5' 6' .... 11' 12'
1 2 3 4 5 6 .... 11 12 1' 2' 3' 4' 5' 6' .... 11' 12'
.
.
.
.
.
.
.
.
.
1728kHz
Transmission principle of DECT-system
Channel 1 Channel 2 Channel 12 Channel 1’ Channel 2' Channel 12'. . . . . .
fixed part to mobile part mobile part to fixed part
Time duplex with 10 ms frame length
Structure of DECT-time multiplex frame
DECT - Multiplex
carrier frequency 2:
carrier frequency 10:
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Eurosignal
– to each participant 4 different audio signals using 4 diverse call numbers are assigned. Meaning must be agreed. Receiving stations are at a size of a cigarette packet
– 85 senders in the 87 MHz-reach (ultra short waves)
– called person location must be approximately known: 3 area codes: North 0509, Middle 0279, South 0709
Cityruf (city call)
– additionally to 4 audio- or respectively optical signals transmission of short numerical (15 digitals) or alpha-numerical messages (80 characters) exists optionally, receiving station is smaller than with Eurosignal
PEP (Pan European Paging)
– preparation for coupling of national services for ERMES
– D: Cityruf, F: Alphapage, GB: Europage, I: SIP
ERMES (European Radio Message System)
– ETSI-Standard for pan-European radio service, similar to PEP but in 169 MHz-reach with 60 Mio. addresses
Pager systems: overview
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UNIT - IIGSM: Global System for Mobile
Communications
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GSM: Properties• cellular radio network (2nd Generation)• digital transmission, data communication up to 9600 Bit/s• Roaming (mobility between different net operators, international)• good transmission quality (error detection and -correction)• scalable (large number of participants possible)• Security mechanisms (authentication, authorization, encryption)• good resource use (frequency and time division multiplexing)• integration within ISDN and fixed network• standard (ETSI, European Telecommunications Standards Institute)
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Providers in Germany (1)
• D1 T-Mobile – subscribers: 24,6 Mio (Stand 2003)
• Vodafone D2 – old name: Mannesmann Mobilfunk D2
– subscribers: 22,7 Mio (Stand 2003)
• E-plus
• O2 – old name: VIAG Interkom
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Providers in Germany (2)
Providers Subscribers, millions
2001 2002 2003 World-wide by 2003
D1 T-Mobile 22,6 23,1 24,6 82
Vodafone D2 21,9 - 22,7 112,5
E-Plus - 7,5 - -
O2 VIAG Interkom
- 3,66 - -
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AuC Authentication CentreBSS Base Station SubsystemBSC Base Station ControllerBTS Base Transceiver StationEIR Equipment Identity RegisterHLR Home Location Register
MS Mobile Station(G)MSC (Gateway) Mobile Switching CentreOMC Operation and Maintenance CentrePSTN Public Switched Telephone NetworkVLR Visitor Location RegisterISDN Integrated Services Digital Network
Fixed network Switching Subsystems
VLR
Radio Subsystems
HLR AuC EIR
(G)MSC
OMC
BTS
BTSBSC
BSS
MS
MS
Network ManagementCall Management
Data networks
PSTN/ISDN
MS
GSM: structure
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GSM: StructureOperation and Maintenance Centre (OMC)• logical, central structure with HLR, AuC und EIR
Authentication Centre (AuC)• authentication, storage of symmetrical keys, generation of
encryption keys
Equipment Identity Register (EIR)• storage of device attributes of allowed, faulty and jammed
devices (white, grey, black list)
Mobile Switching Centre (MSC)• arrangement centre, partial as gateways to other nets, assigned
to one VLR each
Base Station Subsystem (BSS): technical radio centre• Base Station Controller (BSC): control centre• Base Transceiver Station (BTS): radio tower / antenna
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1 TDMA-Frame, 144 Bit in 4,615 ms
8 TDMA-channels, together 271 kBit/s inclusive error protection information
124 radio frequency channels (carrier), each 200 kHz
2 frequency wavebands, for each 25 MHz, divided into radio cells
890
935
915 MHz
960 MHz
downlink
uplink
Radio technical structure
• One or several carrier frequencies per BSC • Physical channels defined by number and position of time slots
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GSM: protocols, incoming callVLR
BS
S
BSS MSC GMSC
HLRBSS
BSS
(4)
(2)(4)
(5)
(3)
(10)(6)
(11)(7)(8)
(8)(9)
(12)
(8)
(1)
(12)
(9)(8)
PSTN/ISDN
(1) Call from fixed network was switched via GMSC
(2) GMSC finds out HLR from phone number and transmits need of conversation
(3) HLR checks whether participant for a corresponding service is authorized and asks for MSRN at the responsible VLR
(4) MSRN will be returned to GMSC, can now contact responsible MSC
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GSM: protocols, incoming callVLR
BS
S
BSS MSC GMSC
HLRBSS
BSS
(4)
(2)(4)
(5)
(3)
(10)(6)
(11)(7)(8)
(8)(9)
(12)
(8)
(1)
(12)
(9)(8)
PSTN/ISDN
(5) GMSC transmits call to current MSC
(6) ask for the state of the mobile station
(7) Information whether end terminal is active
(8) Call to all cells of the Location Area (LA)
(9) Answer from end terminal
(10 - 12) security check and connection construction
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GSM: protocols, outgoing call
VLR
BS
S
BSS MSC GMSC
HLRBSS
(5)
(3)(4)
(2)(1)
(1) Demand on connection
(2) Transfer by BSS
(3-4) Control for authorization
(5) Switching of the call demand to fixed net
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GSM: channel strucureTraffic Channel• speech- / data channel (13 kbit/s brutto; differential encoding)• units of 26 TDMA - Frames• Half-rate traffic channel: for more efficient speech encoding with
7 kbit/sControl Channel• Signal information • Monitoring of the BSCs for reconnaissance of HandoverBroadcast Control Channel• BSC to MS (identity, frequency order etc.)Random Access Channel• Steering of channel entry with Aloha-procedurePaging Channel• signalize incoming calls
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DatabasesHome Location Register (HLR), stores data of participants, which
are reported in an HLR-area – Semi-permanent data:
• Call number (Mobile Subscriber International ISDN Number) - MSISDN, e.g. +49/171/333 4444 (country, net, call number)
• identity (International Mobile Subscriber Identity) - IMSI: MCC = Mobile Country Code (262 for .de) + MNC = Mobile Network Code (01-D1, 02-Vodafone-D2, 03-eplus, 07-O2) + MSIN = Mobile Subscriber Identification Number
• Personal data (name, address, mode of payment)• Service profile ( call transfer, Roaming-limits etc.)
– Temporary data:• MSRN (Mobile Subscriber Roaming Number) (country, net, MSC)• VLR-address, MSC-address
• Authentication Sets of AuC (RAND (128 Bit), SRES (128 Bit), KC (64Bit))
• charge data
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DatabasesVisitor Location Register (VLR)• local database of each MSC with following data:
– IMSI, MSISDN– service profile– accounting information – TMSI (Temporary Mobile Subscriber Identity) - pseudonym for data
security– MSRN– LAI (Location Area Identity)– MSC-address, HLR-address
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MSC-area = VLR-area
radio-cell
with BTS
Location Area (LA)
LA = smallest addressable unit
Handover
GSM: mobile telephone areas
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MSC-area
HLR
VLR
Location
area advantage of the architecture: Location Update at limited mobility, as a rule only at VLR, rarely at (perhaps far remote) HLR
Connection HLR, VLR
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LA 5
LA 3LA 2
LA 3
VLR 10 VLR 9IMSI LA 2
HLR 2632311 VLR 9 IMSI
participant call numberin HLR
country code number
net-entry code
Provider
+49 0177-26 32311
0x62F220 01E5z.B.
Localization at GSM
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Data transmission
• each GSM-channel configurable as a data channel; similar structure like ISDN-B and -D-channels
• data rates up to 9600 bit/s now
• delay approximately 200 ms
• speech channels have as a rule higher priority as data channels
• kinds of channels:– transparent (without error correction; however FEC; fixed data rate; error rate 10-3
up to 10-4) – non-transparent (repeat of faulty data frames; very low error rate, but also less
throughput)
• Short-Message-Service (SMS)– connectionless transmission (up to 160 Byte) on signal channel
• Cell Broadcast (CB)– connectionless transmission (up to 80 Byte) on signal channel to all participants,
e.g. one cell
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MSCBSC
UDI
BTS
IWF
TA
ISDN
Modem
PSTN
Internet
Modem
IWF - Inter Working Function
UDI - Unspecified Digital
TA - Terminal Adapter
Data transmission - structure
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Chip-card (Smart Cart) to personalize a mobile subscriber (MS):
• IMSI (International Mobile Subscriber Identity)• participant special symmetric key Ki, stored also at AuC • algorithm “A3” for Challenge-Response-Authentication• algorithm “A8” for key generation of Kc for content data• PIN (Personal Identification Number) for entry control
Temporary data:• TMSI (Temporary Mobile Subscriber Identity)• LAI (Location Area Identification)• Encryption key Kc
Security aspects: Subscriber Identity Module (SIM)
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Security in GSM-networks
SIM• Entry control and cryptographic algorithmsSingle-sided authentication (participant against network) • Challenge-Response-method (cryptographic algorithm:
A3)Pseudonyms of participants at the Radio interface• Temporary Mobile Subscriber Identity (TMSI)Connection encoding on the Radio interface • Key generation: A8• Encryption: A5
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Security aspects: Authentication
MSC, VLR, AuCMS
Authentication RequestRAND (128 Bit)
Random numbergenerator
iK
A3
SRES
SRES (32 Bit)
A3
iK
Authentication Response=
• Location Registration• Location Update with VLR-change• Call setup (in both directions) • SMS (Short Message Service)
max. 128 Bit
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Security aspects: Session Key
NetzMS
Authentication RequestRAND (128 Bit)
Random numbergenerator
iK
A8
A8
iK
cK 64 Bit
cK
• Key generation: Algorithm A8– Stored on SIM and in AuC
– with Ki parametric one way function
– no (Europe, world wide) standard– can be determined by net operator – Interfaces are standardized– combination A3/A8 known as COMP128
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Security aspects: encryption at the Radio interface
NetMS
Ciphering Mode Command
A5A5
• Data encryption through algorithm A5:– stored in the Mobile Station – standardized in Europe and world wide – weaker algorithm A5* or A5/2 for specific countries
cKcKTDMA-frame-number
TDMA-frame-number
Key block
+Plain text block
+Plain text block
Ciphering Mode Complete
Encrypted Text
114 Bit
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GSM-Security: assessment• cryptographic methods secret, so they are not „well
examined“• symmetric procedure
– consequence: storage of user special secret keys with net operators required
• low key length Ki with max. 128 Bit (could be hacked by using Brute Force Attack in 8-12 hours)
• no mutual authentication intended– consequence: Attacker can pretend a GSM-Net
• no end-to-end encryption• no end-to-end authentication• Key generation and -administration not controlled by the
participants
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GSM Phase II+HSCSD, GPRS
Mobile Communication and Mobile Computing67
HSCSD: High Speed Circuit Switched Data
Mobile Communication and Mobile Computing68
• higher data rate because of channel bundling• parallel usage of several time slots (TCH) of one
frequency on Um
• more efficient channel encoding (14,4 kbit/s per TCH)• Data rates from 9,6 up to 53,8 kbit/s• asymmetric transmission (1TCH Uplink /
3TCH Downlink)
Properties
Mobile Communication and Mobile Computing69
HSCSD data rates
transparent non transparent
up- / downlink 100% coverage 95% coverage 100% coverage 95% coverage
1 + 1 9,6 14,4 9,6 13,22 + 2 19,2 28,8 19,2 26,41 + 3 --- ---- 28,8 39,61 + 4 --- ---- 38,4 53,8
Mobile Communication and Mobile Computing70
MSCBSC
UDI
BTS
IWF
TA
ISDN
Modem
PSTN
Internet
Modem
IWF - Inter Working Function
UDI - Unspecified Digital
TA - Terminal Adapter
n time slots (TCH) of each
TDMA frame(theoretically max. 8)
HSCSD: structure
Mobile Communication and Mobile Computing71
Um Abis A
MSCBSCBTS
n time slots (TCH) of each TDMA frame
(theoretically max. 8)
multiplex of thetime slots
on each 64 kBit/schannel
certain changes are necessary at the componentseveral changes at the software/firmwareminimal changes at the software/firmware
HSCSD: changes
Mobile Communication and Mobile Computing72
• parallel usage of several time slots limited to one frequency
• Cost factor limits number of used TCH‘s to (2+2) or (1+3, uplink, downlink)
Required time for setting to receiving standby
7654321076543210
4321076543210765
Required time for setting to transmission standby
Required time for signal strength measure and setting to receiving standby
MS RECEIVE
MS TRANSMIT
MS MONITOR
HSCSD radio interface
Mobile Communication and Mobile Computing73
Assessment of HSCSD
+ existing net structure and accounting model maintained + in comparison to GPRS only around1/5 of investment
necessary+ HSCSD is still circuit switched
+ has defined QoS- settings (data rate, delay)– one logical channel will be switched on all interfaces for the time
of the connection– Non-efficient for burst-like traffic (Internet) or Flat Rate billing
(Logistics)– no international acceptance (Roaming!)
• uses also more resources on the radio interface– problems with handover into a new cell
Mobile Communication and Mobile Computing74
GPRS: General Packet Radio Service
Mobile Communication and Mobile Computing75
Properties
• Packet switching service (end- to- end)• Data rates up to 171,2 kbit/s (theoretical) • Effective and flexible administration of the radio interface• adaptive channel encoding• Internetworking with IP- and X.25 nets standardized• dynamic sharing of resources with „classical“ GSM
speech services • Advantage: Billing and Accounting according to data
volume• Disadvantage: cost intensive additional net hardware
necessary
Mobile Communication and Mobile Computing76
Properties
– point-to-point-Packet transfer service • PTP-CONS (PTP Connection oriented Network Service)
– connection oriented, similar to X.25• PTP- CLNS (PTP Connectionless Network Service)
– connectionless, similar to IP
– point- to- multipoint- group communication
Mobile Communication and Mobile Computing77
MSCBSC
BTS
Internet
GPRS: Structure
HLR
GSM
GPRS BackboneFrame Relay / ATM
GGSNGGSN
SGSNBorder
Gateway
GPRS Netsother operators
other packetswitching networks
SGSN - Serving GPRS Support Node
GGSN - Gateway GPRS Support Node
signalization data
user data
Mobile Communication and Mobile Computing78
GMSC
Circuit switched traffic
HLR/AuCGPRS register
MAP
MAPA
GGSN
GPRS: Changes
Abis
Gb
Gn
Gi
other packetswitching networks
publicremote fixed nets
Packet arrangedtraffic
Gs
Um
n time slots (TCH) per TDMA frame
(theoretically max. 8)per packet!
modified network components
new components or extensively modified components
Existing componentsPCU - Packet Control Unit
SGSN
MSC
BSCBTS
PCU
Mobile Communication and Mobile Computing79
SGSN:- mobility management- session management- QoS- security
External Data Domain
Intranet
SGSN
HLR
Internet
MAPSignalization(SGSN)
Tasks: SGSN, GGSN
BSSPCU
BSSPCU
BSSPCU
Client
GGSNClient
Server
MAPSignalization
(GGSN)
SGSN, GGSN:- Routing- Signalization - Resource management
SGSN
Mobile Communication and Mobile Computing80
Tasks of the SGSN• Packet delivery • mobility management
– apply/ sign off of terminals– localization
• LLC (Logical Link Control) management• authentication• billing
Mobile Communication and Mobile Computing81
Tasks of the GGSN• mediator between GPRS backbone and
external data networks (Internet, X-25 etc.) • converts GPRS packets, data Protocol
(PDP) into the corresponding structure • also converts PDP addresses of incoming
packets into GSM address of the receiver• saves current data for the SGSN address
of the participant as well as their profile and data for authentication and invoice
Mobile Communication and Mobile Computing82
Radio Link Control (RLC)• Segmentation of the LLC-Frames in RLC blocks• Block size dependent on short-term channel
conditions • Backward error correction and data flow control by
Automatic Repeat Request (ARQ) protocol– repeating not repairable RLC blocks selectively
Medium Access Control ( MAC)• Channel reservation contains:
- one/several time slots (Packet Data Channels PDCH) of one frequency– one uplink status flag (USF) per Packet Data Channel
(PDCH), channel partition of up to 8 ms
GPRS: air interface
Mobile Communication and Mobile Computing83
Medium Access Control ( MAC)• Reservation in the uplink (MS to BSS):
• MS sends reservation request on a Random Access Channel (Slotted ALOHA)– BTS allocates a (split) channel and sends packet assignment– MS sends data depending on the current priority (USF flag)
• Reservation in the Downlink (BSS to MS):
– BTS displays transmitting request and informs about the reserved channel
– MS supervises the reserved channel and receives
GPRS: air interface
Mobile Communication and Mobile Computing84
Physical Link Control• adaptive forward error correction (FEC) dependent on short-
term channel conditions • temporal scrambling (Interleaving) of the bursts and Mapping on
reserved PDCH (Packet Data Channel) • procedure to recognize overbooking situations on the physical
channel
GPRS: air interface
GPRS Channel Encoding
Scheme CodeRate
Payload BCS Pre-codedUSF
Tail bits Codedbits
Puncturedbits
Datarate
(kbit/s)
CS-1 1/2 181 40 3 4 456 0 9.05
CS-2 ~ 2/3 268 16 6 4 588 132 13.4
CS-3 ~ 3/4 312 16 6 4 676 220 15.6
CS-4 1 428 16 12 0 456 0 21.4
Mobile Communication and Mobile Computing85
Quality of Service• QoS profile agrees service parameters inside the whole network• Agreed for the duration of one PDP (Packet Data Protocol)
context (session, end terminal is obtainable for the duration of the context, e.g. obtainable over Internet ) :– temporary address (IP) for mobile station– tunneling information, among others GGSN, which is used for
access to corresponding packet arranged network – type of the connection– QoS profile
• QoS profile commits:– precedence class, priority against other services (high, normal, low)– packet delay class, times are valid for traffic inside the GPRS-
network– reliability class– peak throughput class– mean throughput class
Mobile Communication and Mobile Computing86
Quality of Service
Size 128 octets 1024 octets
Class Mean Delay 95% Delay Mean Delay 95% Delay
1 (predictive) < 0,5 s < 1,5 s < 2 s < 7 s
2 (predictive) < 5 s < 25 s < 15 s < 75 s
3 (predictive) < 50 s < 250 s < 75 s < 375 s
4 (best effort) Best effort
Probability for
Class Lost packetDuplicated
packet
Out ofSequence
packet
Corruptedpacket
1 10-9
10-9
10-9
10-9
2 10-4
10-5
10-5
10-6
3 10-2
10-5
10-5
10-2
Packet delay classes
Security classes
Mobile Communication and Mobile Computing87
Quality of Service
GPRS- using data ratesCoding # of timeslotsScheme 1 2 3 4 5 6 7 8
CS-1 9,05 18,1 27,15 36,2 45,25 54,3 63,35 72,4CS-2 13,4 26,8 40,2 53,6 67 80,4 93,8 107,2CS-3 15,6 31,2 46,8 62,4 78 93,6 109,2 124,8CS-4 21,4 42,8 64,2 85,6 107 128,4 149,8 171,2
• CS 3 and CS 4 are only reasonable in the second phase of GPRS introduction
• They will be used adaptively at corresponding good quality of radio connection
• CS 4 does not comprise error correction, code rate = 1!
Mobile Communication and Mobile Computing88
Assessment of GPRS
+ An up to 4 times higher data rate in comparison to ordinary GSM- data services
+ better resource management through packet arranged service+ „always on” data service (email, etc.)+ GPRS is a more suitable carrier for services like WAP
- IP-derivate, no true guaranties (QoS)
- development of the network infrastructure is relatively expensive, particularly regarding introduction to UMTS (return of investment)
- GPRS doesn’t give such data rates like advertising has sometimes promised
Mobile Communication and Mobile Computing89
9.6 kbit/s9.6 kbit/s
Da
ta r
ate
26.4 kbit/s26.4 kbit/s
13.2 kbit/s13.2 kbit/s
HS
CS
DC
ha
nne
l pa
ckin
g, N
TH
SC
SD
Ch
ann
el p
ack
ing
, NT
39.6 kbit/s39.6 kbit/s
CS 1CS 1
GP
RS
Pa
cke
t arr
ang
ed
GP
RS
Pa
cke
t arr
ang
ed
9 kbit/s9 kbit/s
18.1 kbit/s18.1 kbit/s
27.2 kbit/s27.2 kbit/s
13.4 kbit/s13.4 kbit/s
26.8 kbit/s26.8 kbit/s
40.2 kbit/s40.2 kbit/s
CS 2CS 2
Development of the GSM-data services
flow
Mobile Communication and Mobile Computing90
Enhanced Services - EMS (enhanced message service)
• Uses widespread existing infrastructure (SMS)• new Mobile telephones necessary• allows sending and receiving of messages with formatted texts,
melodies, graphics (32 x 32 Pixel) and animations (16 x 16 Pixel) – e.g. NOKIA
• new applications like Mobile Ticketing • tickets will be transferred to mobile phone like a bar code and
checked at the admission• EMS enables transition to MMS (multimedia messaging service),
which allows transmission of multimedia enriched messages over UMTS-Network (photos, parts of videos)
• MMS requires new network elements in the Infrastructure of the operators
Mobile Communication and Mobile Computing91
MMS - architecture
. . .
MMS Relay
MMS User Agent
MMS User Databases
MMS Server(e.g. E-Mail)
MMS Server(other service)
alien MMS Relay
SMTP
LDAP GSM-MAP or IS-41-MAP or TCP/IP
SMTP, HTTP, POP3,
IMAPv4
WAP or MExE (e.g. Java and TCP/IP)
HLR
MMS Server(e.g. Fax)
Based on materials from 3GPP, http://www.3gpp.org
Mobile Communication and Mobile Computing92
UMTS:Universal Mobile
Telecommunications System, 3G,3rd generation of mobile radio
Mobile Communication and Mobile Computing93
IMT-2000 - structure
source: www.UMTS-Report.com
• 3 systems - UMTS - CDMA2000 - UWC-136
• 2 core technologies - TDMA - CDMA
satellite- supported network expansion:- SW-CDMA: Satellite Wideband CMDA - SW-CDTMA: Satellite Wideband CDMA/TDMA (Hybride procedure) - SAT-CDMA: Satellite CDMA - ICO RTT: ICO Radio Transmission Technology
IMT-2000 family of radio interfaces :
– IMT-DS (Direct Spread)• UTRA-FDD (UMTS)
– IMT-MC (Multi Carrier)• CDMA2000, USA
– IMT-TC (Time Code)• UTRA-TDD (UMTS), TD-
SCDMA (Synchronous Code Division Multiple Access, China)
– IMT-SC (Single Carrier)• UWC-136, USA
– IMT-FT (Frequency time)• DECT
IMT-2000
TDMA
CDMA
individual carrier
multiple carrier
IMT-SC
IMT-FT
TDD
IMT-DS
IMT-MC
UWC-136 (EDGE)
DECT
UTRA-FDD
CDMA2000
UTRA-TDD
TD-SCDMA
FDD
IMT-TC
ICO RTT... Standard by ICO Global CommunicationsIMT ... International Mobile TelecommunicationsUTRA ... Universal Terrestrial Radio AccessUWC ... Universal Wireless Communications
In europeUMTS
Mobile Communication and Mobile Computing94
Worldwide frequency assignment for IMT-200• developed by ITU
PCS... Personal Communication SystemMSS...Mobile Satellite ServicePHS... Personal Handy-Phone System
Mobile Communication and Mobile Computing95
UMTS - Facts
• consideration: early 90ies
• Universal Mobile Telecommunications System, developed in the EU (ETSI: European Telecommunication Standards Institute)
• UMTS is the European implementation of IMT-2000 (International Mobile Telecommunications by the year 2000)
• Start of network expansion:
– in Europe: 2003 (some trials, e.g. British Telecom on Isle of Man, 2002)
– in the USA: 2005
– in Japan since 2000 : NTT DOCOMO
Mobile Communication and Mobile Computing96
1700 1750 1800 1850 1900 1950 2000 2050 2100 2150 2200
GSM1800Uplink
GSM1800Downlink D
EC
T
FDDUplink
FDDDownlinkT
DD
TD
DMSS MSS
230 MHz frequency range for IMT-2000
• at FDD symmetrical spectrum is necessary, not at TDD (time slots at same frequency)
• gradual new assignment of wavebands
• depending on development of the need up to 300-500 MHz frequency range in 2008
Frequency award in Europe
source: www.UMTS-Report.com
MSS…Satellite- based
Mobile Communication and Mobile Computing97
• system general , worldwide roaming
• high data rates: 144 kbit/s mobile, up to 2 Mbit/s at local area
• fusion of different mobile radio communications-, wireless- and pager-systems into
one common system
• speech-, data-, and multimedia- information services independent of used network
access
• support of different carrier services:
– real-time capable/not real-time capable
– circuit switched/ packet switched
• Roaming also between UMTS and GSM and satellite networks
• Asymmetrical data rates in up-/downlink
Characteristics
Mobile Communication and Mobile Computing98
UMTS- Disadvantages
• Technology not yet perfect
• rent ability of pico cells („Hotspots“) not yet analyzed
• strong contention by WLAN
• increased radiation exposure
• high data rate only obtainable sometimes (High-Tech-network expansion, stationary and exclusive usage necessary!)
• because of high license costs high charges necessary (around double GSM-costs)
Mobile Communication and Mobile Computing99
UMTS - PerformanceTransmission Real- time (Video) Not Real-time (SMS etc.)
Bit error rate 10-3 … 10-7 10-5 … 10-8
Permitted delay 20ms … 300ms > 150 ms
~ 0 sec 10 sec 1 min 10 min 1 h
UMTS
GPRS
ISDN
PSTN
GSM
Web
Web
Web
Web
Photo
Photo
Photo
Photo
Photo
Mail Report
VideoReport
VideoReport
Video
VideoReport
source: Mobilkom Austria
Mobile Communication and Mobile Computing100
UMTS - Hardware• big color displays
• high resolution
• True Color
Mobile Communication and Mobile Computing101
UMTS- cell structure
Quelle: Mobilkom Austria
GatewayMobile
SwitchingCentre
3GMobile
SwitchingCentre
HomeLocationRegister
GatewayGPRS
SupportNode
Internet
customerIntranet
packet-switched
BTS BTS BTS BTS BTS BTS BTS BTS BTS
GSM - BSS UTRAN- UMTS Terrestrial Radio Access Network
Base Station Controller Radio Network Controller Radio Network Controller
Radioaccessnetwork
PSTN/ISDN
UMTS-Core Network
VisitorLocationRegister
circuitswitched
3G- ServingGPRS
SupportNode
Mobile Communication and Mobile Computing102
Zone1: In-building
“Pico cell”
Zone 2: Neighborhood
“Microcell”
Zone 3: Suburban
“Macro cell”
Zone 4: GlobalSatellite
Integration with the fixed network
Basic terminal
PDA terminal
Audio/visual terminal
UMTS: cell structure
“World cell”
Mobile Communication and Mobile Computing103
GlobalLokal
Regional
Home/Office
World Macro MicroPico
UMTS: hierarchical cell structureprinciple: - all neighbor cells use same frequency channel- only one waveband is necessary for cellular construction- further wavebands are necessary for hierarchical structure
expansion Data rate (kbit/s)
Max. velocity (mph)
Special features
World Cell global - no UTRAN, other technology!
Macro Cell Up to 1,24 miles 144 310 complete national UMTS support
Micro Cell Up to 0,62 miles 384 74 Greater cities, commonly used
Pico Cell > 60miles 2000 6,2! „Hotspots“ – e.g. airport, station
Mobile Communication and Mobile Computing104
Classification
Mobile Communication and Mobile Computing105
• Virtual Home Environment (VHE): offered
services are freely configurable, configuration
still exists in the whole network
• choose of service quality and also arising costs
• behave at bottlenecks (data rates, etc.)
configurable
• dynamic customization to connection
Service concept
Mobile Communication and Mobile Computing106
• one phone number for several devices (Call-
Management)
• subscriber localization e.g. with SIM-card
• call passing
• virtual mobility of fixed networks
UPT: Universal Personal Telecommunication Service
Mobile Communication and Mobile Computing107
Intelligent networks
• Implementation of basic services like subscriber localization billing etc.
• supply of value added service (Voice-Mailbox, etc.)
– possibility of easy, fast introduction of new services
– flexible service administration
– usage of services also from foreign network possible
– better control of service parameters through subscriber
Mobile Communication and Mobile Computing108
UMTS: basic network structure
• Access Network: base stations, responsible for radio contact to mobile
end devices
• Core Network (Fixed Network): responsible for structure of connections
• Intelligent Network (IN): responsible for billing, subscriber localization,
Roaming, Handover
Intelligent Network
Core NetworkAccessNetwork
User Equipment (UE)
Mobile Communication and Mobile Computing109
General reference architecture
UE UTRAN
Uu Iu
CN
• UTRA: UMTS Terrestrial Radio Access
– UTRAN (UTRA- Network) contains several radio subsystems, so called Radio
Network Subsystems (RNS) and contains functions for mobility management
– RNS controls handover at cell change, capacitates functions for the encoding
and administrates the resources of the radio interface
– Uu connects UTRAN with mobile end devices, so called User Equipment (UE), is
comparable with Um in GSM
– UTRAN is connected over Iu with the Core Network, comparable with the A
interface in GSM between BSC and MSC
– CN contains the interfaces to other networks and mechanisms for connection
handover to other systems
Mobile Communication and Mobile Computing110
The UMTS-radio interface UTRA (UMTS Terrestrial Radio Access)
• Two modes defined:– UTRA/FDD (Frequency Division Duplex)
• mainly in suburban areas for symmetrical transmission of speech and video
• data rates up to 384 kbit/s, supra-regional roaming• for circuit- and packet switched services in urban areas
– UTRA/TDD (Time Division Duplex)• mainly in households and other restricted areas (company's
premises, similar to DECT)• for broadcast of speech and video, both symmetrical: up to
384 kbit/s • also asymmetrical:
up to 2 Mbit/s
Mobile Communication and Mobile Computing111
UTRA/FDD
t
f in MHz
190 MHz
uplink
downlink
1920,9
1979,7
carrier 1
5 MHz
carrier 12...
2110,9
2169,7
carrier 1
carrier 12...
• puts wide- band- CDMA (W-CDMA) together with DSSS (Direct Sequence Spread Spectrum) as spread spectrum technique
• channel separation by carrier frequencies, spreading code and phase position (only uplink)
• ca. 250 channels for used data, data rates up to 2 Mbit/s• complex performance control necessary
Mobile Communication and Mobile Computing112
UTRA/TDD• puts wideband- TDMA/CDMA together with DSSS • sends and receives on same carrier (TDD)• ca. 120 channels for used data, data rates up to 2 Mbit/s• channel separation by spread code and time slots • less spreading than at FDD• precise synchronization necessary• lower demand for performance control
t
f in MHz
1900,1
1920,1
carrier 1
5 MHz
carrier 4...
2010,1
2020,1
carrier 5
carrier 6uplink downlink
Mobile Communication and Mobile Computing113
Extension Band 1 (worldwide similar) – partly terrestrial, partly satellite- based
Extension Bands (for a future market potential ..from 2005)
2520 2670 MHz470 862 2290 2300 2700 2900
Existing Nets
880 1885MHz
GSM,DECT
1675 1710MHz
satellite-based
1885 19801920 2010 2025 2110 2170 60 GHzMHz
MBSterrestrial
satellite- based
Frequency award for UMTS
Mobile Communication and Mobile Computing114
UMTS-licenses in Germany
• E-Plus Hutchison 8.394.492.363 €
• Group 3G 8.408.706.278 €
• Vodafone (Mannesmann Mobilfunk)8.422.920.192 €
• MobilCom Multimedia 8.369.848.095 €
• T-Mobil 8.478.344.232 €
• O2 (VIAG Interkom) 8.445.008.001 €17.08.2000: each license got 2 x 5 MHz packets, 60 MHz have been given away altogether, 150 MHz are available altogether
RegTP determined:- till end of 2003 25 % network coverage- till end of 2005 50 % network coverage
Mobile Communication and Mobile Computing115
Summary• introduced variants are the proposals, which will be
supported by Europe, Japan and partly by the USA • worldwide accessibility can be realized only with
multimode end devices • even in Europe combined
UTRA-FDD/UTRA-TDD/GSM- devices are necessary (those are realized by the identical frame time of 10ms at relatively low costs)
Mobile Communication and Mobile Computing116
UNIT - IIIWireless Local Networks,
WLAN
Mobile Communication and Mobile Computing117
Why do we need wireless LANs?
Advantages• flexibility• Ad-hoc-network realizable with less expenditure• No problems with cables Disadvantages• high error vulnerability on the transmission link in comparison to
Standard-LANs• National restrictions, no international standards at used frequency
bands (Industrial Scientific Medical (ISM)- Band)• security, costs
Mobile Communication and Mobile Computing118
Application areas
• networks in exhibition halls• hospitals• warehouses• airports• structure of networks in historic buildings• extension of existing wired local area networks
in offices, universities etc.
Mobile Communication and Mobile Computing119
Problems with the use of WLAN‘s
– physical problems• interference: band spreading • echo: use of special antennas • Hidden Terminal problem: use CSMA/CA
– data security• Wired Equivalent Privacy (WEP) service
further development WiFi (Wireless Fidelity), WPA (WiFi Protected Access)
Mobile Communication and Mobile Computing120
Standards• IEEE 802.11 (a,b,g ; optional e,h,i)
– frequency band 2,4 GHz, also in the 5GHz - band– data rates: 1 bis 11 Mbit/s (at present, later up to 20 (2,4 GHz) or
54 Mbit/s (5,4 GHz))– WiFi: Wireless Fidelity, certificate from the WECA (Wireless
Compatibility Allicance), secures the interoperability between the Radio- LANs and contains improved security mechanisms
• HomeRF• Bluetooth (IEEE 802.15)
– Frequency band: 2,4 GHz– Data rate: 1 Mbit/s; in the future also 20 Mbit/s– connection of peripherals
• HIPERLAN (ETSI) / Wireless ATM– frequency bands 5,15 / 5,30 GHz and 17,1 / 17,3 GHz– data rates: 24 Mbit/s or 155 Mbit/s– however no practical relevance
Mobile Communication and Mobile Computing121
IEEE 802.11b
• frequency:– 2,4 GHz frequency band, also called ISM (= Industrial Scientific
Medical Band), not regulated– 850 - 950 nm at infrared
• transmission power:– min. 1mW– max. 100mW in Europe (1W in the USA)
• reach:– of 10m (IR) to 30km or more with the help of special antennas
(directional antennas)
Mobile Communication and Mobile Computing122
Basic WLAN- structureAd-hoc-network:
AP
APAP
STA4 STA5
3 connected infrastructure networks:
AP - Access Point
Mobile Communication and Mobile Computing123
System architecture IEEE 802.11
Distribution System
802.x LAN
802.11 LANSTA1
Access Point
Portal
BSS1
Access Point
STA2STA3802.11 LAN
BSS2
ESS
Mobile Communication and Mobile Computing124
System architecture IEEE 802.11, concepts
• Station (STA)– device with 802.11- concurring interface
• Access Point– allows the access to the distribution system for registered stations and
secures accessibility of the stations also beyond the BSS
• Coordination Function (CF)– logical functional unit, which decides when a station can send
• Basic Service Set (BSS)– consists of several stations, that were controlled by an CF, e.g. BSS2
and STA2, STA3
Mobile Communication and Mobile Computing125
System architecture IEEE 802.11, concepts
• Distribution System– connects several BSS over access points and forms a logically larger
net
• Extended Service Set (ESS)– Radio networks, which are connected over Distribution System
• Portal– allows transition into other networks
Mobile Communication and Mobile Computing126
Overview• 802.11 is the most frequently used solution for wireless connection;
very strong distribution on the market• interesting future option: „Seamless Handover“ between GSM and
IEEE 802.11; supported by Cisco, Intel etc. (alternative to UMTS?)• higher data rates already standardized or in use
– 802.11a: physical layer at 5 GHz – Band, data rates up to 54 MBit/s– 802.11b: extension to physical layer for the 2,4 GHz – band, data rates
up to 11 MBit/s, products available – 802.11g: at present the industry works on an extension, shall allow the
up to 54Mbit/s in the frequency band around 2.4 GHz– Study Group 5GSG: examines the harmonization between IEEE 802.11
and ETSI HiperLAN– Task Group e: MAC functions for QoS-Management and to refine
improved safety functions, introduction of service classes etc.
Mobile Communication and Mobile Computing127
802.11 – Norms for WLAN802.11 Since end of 1990; RadioLAN; B=1-2 MBit/s; ISM-Band F=2,4GHz; low Interoperability
and bit rate!
802.11b 11MBit/s, actual Standard, existed NICs and APs; ISM-Band F=2,4GHz; possesses further sub-standards
802.11a Since 2000; competition with 802.11b; up to 54 MBit/s; F=5,1 GHz, correspond. national restrictions: in the buildings
802.11g Ratification March, 2003; first pre-standard products; ISM-Band 2,4GHz; up to 54 MBit/s;
802.11e Sub-standard; planed for end 2003; use of QoS-approaches; realization of multimedia applications/ Voice over IP over WLAN
802.11h Sub-standard / method for 802.11a; optional functionality – transmission power control of radio interface by national via RegTP prescribed norms; correspond. especially for Germany 802.11a or h
802.11i Sub-standard; security approaches for WLAN (encryption, authentication)
WPA WiFi Protected Access; Substandard; competition with 802.11i
802.11c Sub-standard; Method of Wireless-Bridging
802.11d Sub-standard; country specifics for 802.11b
802.11f Sub-standard; Routing between radio cells of different vendors by IAPP (Inter-Access-Point Protocol)
Mobile Communication and Mobile Computing128
Parameters Standards 802.11
802.11 802.11b 802.11a / h 802.11g
Frequency band, GHz
2,4 (ISM-Band) 2,4 (ISM-Band) 5,1 2,4 (ISM-Band)
Bit rate, MBit/s 1-11 11 54 54
Use field building, territory building, territory in the buildings building, territory
Deployment End 1990 actually Since 2000 Since March 2003
Available Hardware
Marketable NICs and APs
Marketable NICs and APs
Experimental operation
Pre-standard Products
Data security WEP 64/128/256 bit WEP
802.11i - security approaches for WLAN (encryption, authentication);
WPA - WiFi Protected Access (competition with 802.11i)
QoS for multimedia-transmission
none none 802.11e (Ende 2003): use of QoS-approaches; realization of multimedia applications/ Voice over IP
Problematic • low bit rate• low
interoperability
low bit rate National restrictions
Pre-standard
Mobile Communication and Mobile Computing129
Example: Lucent Wavelan 802.11b WLAN Card
• Wireless connection that acts just like a conventional Ethernet link
• Technical specifications:– 11 Mbps wireless connection – 40-bit WEP or 104-bit RC4 link layer encryption – Interoperability with other cards of IEEE 802.11b (i.e.
Cisco Aironet or the Apple Airport Card) – Tiny size - a PCMCIA card less than 1 inch – Cross-platform support (Linux, Mac, and Win*) – Very low cost (comparable to a PCMCIA 10/100
Ethernet card)
http://www.lucent.com/
Mobile Communication and Mobile Computing130
Example: Globalsuntech 802.11b products
• Bit rates: 22/11/5.5/2/1 MBit/s per channel• WEP 64/128/256 Bit• Available devices:
– Card Bus– PCMCIA Card– PCI Card– Mini USB
• DSSS; selectable channels: – USA, Canada - 11 channels– Europe - 13 channels– Japan - 14 channels
• Sensitivity, range:– 80dBm for 22MBit/s– 92dBm for 1MBit/s
• Cross-platform support (Linux, Win*)
http://www.globalsuntech.com/
Mobile Communication and Mobile Computing131
Further Scenarios (1)
Wireless Access Point (Hub Type)
Wireless PCPCs
Scenario 1: Wireless Access
LAN
WLAN
Mobile Communication and Mobile Computing132
Ethernet Hub
Wireless Access Point (Bridge Type)
Wireless PCs
Scenario 2: Wireless Bridging
Further Scenarios (2)
WLAN LAN
Mobile Communication and Mobile Computing133
Further Scenarios (3)
Wireless Access Point (Router Type)
Scenario 3: Share Wireless AP
Cable/DSL-Modem
Internet
WAN
WLAN
Wireless PCs
Mobile Communication and Mobile Computing134
Cable/DSL- Wireless/ Wired Router
Wireless PCs
Scenario 4: Wireless/Wired Routing
Further Scenarios (4)
Cable/DSL-Modem
Internet
WAN
LAN
LAN
WLAN
Mobile Communication and Mobile Computing135
UMTS vs WLAN
Mobile Communication and Mobile Computing136
Mobility and data ratesmobility
Data rate [Mbit/s]
Source: http://www.netant.no
Bluetooth
0,1 1 10 100
2G
3G – UMTS
WLANLAN
Fixed
Walk
Vehicle
UMTS: better mobility, connectivity WLAN: higher data rates, more cheap, but no telephone
0,4
2,0
5,5
65,5
WLAN
UMTS (best support)
TDSL
ISDN
in minutes, trailer , 30 MBSource: Focus, 34/2002
Mobile Communication and Mobile Computing137
5200 5600 59005700 58005500540053005100
HIPERLAN HIPERLAN
High Speed wireless access
U-NII U-NII
Frequency [MHz]
License exempt.455 MHz
Sharing rules100 MHz
Unlicensed300 MHz
U-NII ... Unlicensed national information infrastructure
source: www.ist-mind.org, www.3gpp.org
WLAN- Spectrum Allocation
Mobile Communication and Mobile Computing138
Interworking UMTS/WLAN- User should be notified of any possible degradation- subscriber database could be shared, or separated in HLR/HSS (3GPP) or AAA (IETF) format
Three classes:- no coupling- loose coupling- tight coupling
UMTS/WLAN as completely independent
Contra:
Pro:- Rapid introduction- no impact on GSN nodes
- poor handover- no common database, billing
no coupling loose coupling tight coupling
UMTS/WLAN use same databasein AAA format
AAA ... Authentication, authorization, accounting
- poor handover
- good handling- no impact on GSN nodes
- improved handover performance
- HIPERLAN/2 have to support complete UMTS interface- feasible if operator have both networks
HIPERLAN/2 is connectedthrough UTRAN to UMTS,using special interface
Mobile Communication and Mobile Computing139
Data security in WLAN and UMTSData security for WLAN:• 802.11i
- new, additionally standards 802.11a/h and 802.11g
- complex solution for security- packet encryption- key distribution via RADIUS -Remote Access
Dial-In User Service - packet authentication- partial compatibility with IPsec- relevant against all attacks
• WPA - WiFi Protected Access − preliminary to 802.11i− properties similar to 802.11i− competition to 802.11i
• WEP - Wired Equivalent Privacy - additionally to standard 802.11b, partially
obsolete!!!- users mobility between several Access-
Points, without re-configuration (roaming)- disadvantages:
- short key of 64 / 128 bit - different, partially contradictory statements to
offered security
Data security for UMTS:• IPsec
- Client/Server based, Clients and IPsec-Servers negotiate dynamic keys
- tolerant, relevant for key assignment to IP-subnets and against all Internet-attacks
- secrecy on the network layer: • IP-datagrams• TCP/UDP-segments• ICMP/SNMP-messages
- Encryption via DES, 3DES and 40-bit-DES
- authentication via - “IP Encapsulating Security
Payload" (RFC 2406, 1998)- “IP Authentication Header” (RFC
2402, 1998)
Mobile Communication and Mobile Computing140
HomeRF (Radio Frequency)
• competitive standard to IEEE 802.11• Up to 128 network nodes• Frequency jump in separations of 3MHz or 5MHz • Low costs and support of synchronous services: DECT
speech support• 2,4 GHz (FHSS), transition power max. 100 mW,• Shared Wireless Access Protocol (SWAP):
– hybrid protocol of DECT (TDMA) and CSMA according to IEEE802.11 (modified)
• up to 6 wireless fixed network connections• however sinking market shares in comparison with IEEE
802.11
Mobile Communication and Mobile Computing141
HomeRF
• data rate 1-2 Mbit/s• 50 m reach within buildings• Supplier: e.g. Intel with ANYPOINT (wireless home
network)• future:
– HomeRF + Bluetooth: DUAL MODE SYSTEM (Symbionics)
+ ad-hoc possibly+ voice transmission
- today only few manufactures
Mobile Communication and Mobile Computing142
Wireless City Networking via 802.16
IEEE Wireless MAN/ ETSI Hiper MAN
Mobile Communication and Mobile Computing143
Wireless City Networking: scenarios
• new IEEE 802.16 standards can provide great regions with fast Internet services
• Use fields:– office materials shops– cafes– at the railway stations– to surf at the parks
Mobile Communication and Mobile Computing144
USA: Wireless MAN
• Wireless MAN: 802.16-version in USA
• Backgrounds: – competition to T-Mobile USA - mobile radio
network provider– great number of 802.11-Internet service
providers (ISP via Wireless LAN)– wide spread 802.11x – networks in the
country– via 802.11 provided approx. 2500 regions
Mobile Communication and Mobile Computing145
Europa: Hiper MAN
• ETSI (European Telecommunications Standard Institute): – activities in the range of 802.16 –
development of Hiper MAN
• new marketable products: since July 2004 (according to announcement of Fujitsu Europe)
Mobile Communication and Mobile Computing146
802.16 / 802.16a
• Wireless MAN Standard 802.16– developed end of month January 2003– frequency bandwidth: 10 up to 66 GHz – reach: up to 50 km (30 miles)– data rate: up to 134 MBit/s– new 802.16x standards can provide great regions with fast
Internet service, momentary trial operation in Boston/USA (ISP via Wireless MAN)
• Start-Standard 802.16a– frequency bandwidth: 2-11 GHz– reach: up to 50 km (30 miles)– data rate: up to 70 MBit/s only– predominantly conceptualized for fast links of hotspots– can be used to establishment of private DSL-links– final operation inset: January 2005
Mobile Communication and Mobile Computing147
802.16a-Forum
• Members: – Airspan Networks, Alvarion, Aperto Networks,
Ensemble Communication, Fujitsu of America, Intel, Nokia, Proxim, Wi-LAN
• Aims: – to provide compatibility of 802.16a-products
among each other
Mobile Communication and Mobile Computing148
Conclusion: 802.16 vs 802.11802.11+ advantage:
– in spite of sharp competition to Mobile Radio (IMT2000/UMTS) 802.11x gained the mass market
– well-elaborated 802.11x (x = a, b, c, d, e, f, g, h, i, WPA)
− disadvantage: – existing bandwidth problems (at
most up to 54 Mbit/s)– reach at most up to 100m without
directional antennas
802.16+ advantage:
– covers approx. 50km (30 miles)– substitution via 802.16 as access
techniques possible– in future cost-efficient in
comparison to 802.11
− disadvantage: – averaged investment for leased
circuits amounting to 1000$ per location necessary
– sharp competition to Mobile Radio (IMT2000/UMTS): to occupy the market is for Wireless Networks more important as for Mobile Radio!
– final operation inset: planned January 2005 only
Mobile Communication and Mobile Computing149
(2) via Wireless MAN
Access Point
Wireless PCs
Scenario: fast Internet
Better than UMTS: future use scenarios of 802.16
(1) via ISDN, Modem, DSL
Internet
WAN
Wireless MAN 802.16
WAN
PC/LAN
WWW-Server/
Intranet-Firewall
up to 50 Km (30 miles)
70-134 Mbit/s
ISP via Wireless MAN
Mobile Communication and Mobile Computing150
Bluetooth
Mobile Communication and Mobile Computing151
Bluetooth - Facts• Harald Bluetooth was the King of Denmark in the 10th century • 1998 started from Ericsson, Intel, IBM, Nokia, Toshiba• Open Standard: IEEE 802.15.1• Generally for wireless Ad-hoc- piconets (Range < 10m)• Goal: not expensive One-Chip-Decision for radio/ wireless
communication networks• Use fields:
– Connection of peripheral devices– Support of Ad-Hoc-Nets– Connection of different networks
• Frequency band in IMS-Range of 2,4 GHz
Mobile Communication and Mobile Computing152
Bluetooth
• Pico nets with up to 8 participants (ad-hoc) (one master, slaves)
• Scatter nets as an association of different pico nets• frequency hopping is used for improving of interception
safety and system robustness
Mobile Communication and Mobile Computing153
Bluetooth - properties
• Range:- 10 cm up to 10 m at 1 mW transmitting power
- up to 100m at 100mW
• Data rates:
– 433,9 kBit/s asynchronous-symmetrical
– 723,2 kBit/s / 57,6 kbit/s asynchronous-asymmetrical
– 64 kBit/s synchronous, voice service
– In future up to 20 Mbit/s (IEEE 802.15.3)
Basic set-up Bluetooth
2,4-Ghz- HF
Bluetooth-Baseband- Controller
Host-System
Mobile Communication and Mobile Computing154
Bluetooth-comparison
Source: http://www.okisemi.com
FUNCTION Bluetooth v1.1 IrDA Data 1.1 IEEE802.11 (WLAN)
Range w/o PA: 10 meter max. 1 meter max. 50 meter max.
Angle: omni-directional ca 30° omni-directional
RF Frequency Band:
ISM Band, 2.4 GHz Infrared Radiation ISM Band, 2.4 GHz
Mobility: mobile stationary mobile
Data rate: 721kBit/s 4MBit/s 2MBit/s
Security level: High Low High
Mobile Communication and Mobile Computing155
Bluetooth- functionalityStandby
Inquiry after unknownAddress
Page after unknownAddress
Send data connected
PARK HOLD SNIFF
MAC-Addressresigned
MAC-Addressavailable
t =2 m
s
t =2
ms
t =2 s
t =0,6 s
Not connected Standby
connection-status
active states
Low-Power-states
Mobile Communication and Mobile Computing156
Bluetooth – architecture (1)
Physical connection interface
connection between end devices
In hardware implemented !
connection between Hardware and upper protocol (only necessary, if L2CAP not implemented in Hardware!)
Applications
TCS,SDP,RFCOMM
L2CAP
LMP
Baseband
Radio
Dat
a
Dat
a
HCL
TCS …Telephony Control Protocol Specification SDP … Service discovery protocolRFCOMM … RF communication protocol (cable replacement protocol)LMP … Link Manager ProtocolHCL … Host ControllerL2CAP … Logical Link Control and Adaptation Protocol
Mobile Communication and Mobile Computing157
Bluetooth- architecture (2)Radio Layer
- work area: ISM-Band (2,4 Ghz) - Spread Spectrum Communication - Frequency Hopping- Technology- high error rate acceptability through CVSD-encoding at heavy micro wave load
Baseband- controls Radio- Layer2 Modes: - Synchronous, connection-oriented transfer (SCO)
voice connections need symmetrical, circuit-switched point-to-point-connections,
Master reserves two successive time slots (up- and downstream)
- Asynchronous, connectionless transfer (ACL) data transfers need symmetrical or asymmetrical, packet-switched point-to-point/multipoint- transfers, master uses polling
CVSD… Continuously Variable Slop Delta (Sprachkodierung)
Mobile Communication and Mobile Computing158
Bluetooth- architectureLink Manager Protocol
3 Functions
- Piconet management- link configuration- security functions
Logical Link Control and Adaption Protocol
Functions:- Mutiplexing (different applications can use connection between 2 devices
simultaneously)- Reduzierung der Paketgröße der Anwendungen auf akzeptable Baseband- Paket- Größe- Quality of Service
Mobile Communication and Mobile Computing159
Possible configurations
Master
Slave
Piconet Scatter net
Mobile Communication and Mobile Computing160
GSMBluetooth
possible configurations
• association of different pico nets• frequency hopping : jumps in k steps (k = 0…22 or 79) with Δf distances in ISM-band
a) Peer to Peer (or 1 Master and 1 Slave) b) Multi-slave (up to 7 "slaves" with 1 Master)
ScatternetPiconet
Master Slave 4 Master
Slave 3Slave 1
Slave 2
Slave 5
Piconet 1 Piconet 2Scatternet
Mobile Communication and Mobile Computing161
Bluetooth - Frequencies
Source: http://www.mobileinfo.com
- different frequencies around the world Goal: Harmonization of wavebands
Country Frequency range [MHz]
RF channels Multiplier
Spain 2445 – 2475fk = 2449 + k Δf k = 0,…,22
France 2446,5 – 2483,5fk = 2454 + k Δf k = 0,…,22
Japan 2471 – 2497fk = 2473 + k Δf k = 0,…,22
other Europe / USA 2446,5 – 2483,5fk = 2402 + k Δf k = 0,…,78
Δf… frequency distance between channels
Mobile Communication and Mobile Computing162
Bluetooth - Framestructure
Single slot frame Multi slot frame
source: http://www.intel.com
oneSlotPacket
Framefk fk+1
oneSlotPacket
Mas
ter
Sla
ve
625 µsone slot
three slot Packets
fk fk+1
oneSlotPacket
Mas
ter
Sla
ve
3- Slot-packets
625 µsone slot
Frame
Mobile Communication and Mobile Computing163
Bluetooth – security
source: http://www.intel.com
PIN PIN
E2 E2
Link Key Link Key
E3 E3
Encryption Key Encyption Key
Authentication
Encryption
user input(Initialization)
(possible)permanent storage
temporarystorage
- 128 Bit Key encryption and authentication- every device has own 48 Bit- address- over 281 .1012 devices can keep apart - low range (manipulation only local!)
Mobile Communication and Mobile Computing164
Bluetooth – security Generic access:Three modes- non-secure- service level enforced security - link level enforced security
For Devices:two modes- trusted- untrusted
for Services:three modes:- services that require authorization and authentication- services that require authentication only - services that are open to all devices
Bluetooth device initiates security procedures before the channel is established
Sources: http://www.niksula.cs.hut.fi, Müller T., Bluetooth Security Architecture
Bluetooth is not secureenough for critical transmissions(billing etc.)
Mobile Communication and Mobile Computing165
Bluetooth – applications (1)
• replaces perhaps infrared in the area of the coupling of peripherals completely
• „Intelligent Shop“– shop informs the buyer about special offers by mobile phone or handles
inquiries for offers in the individual halls
• Bluetooth-capable ticket machine– Payment over mobile telephone is carried out without contacts
• control of home appliances by mobile telephone• lower layers are developed further in the context of the IEEE 802.15
working group (WPAN - Wireless Personal Area Networks)– higher data rates, further frequencies, but possible interferences with
other systems
Mobile Communication and Mobile Computing166
Bluetooth - applications
wireless connectionHeadset Handy
Mobile Communication and Mobile Computing167
HIPERLAN
HIPERLAN/1 wireless LAN (as extension to conventional LANs)5,15 - 5,25 GHz, ca. 20 Mbps, reach > 50 m, mobility < 10m/sdecentralized Ad-hoc net, no QoS-guarantee
HIPERLAN/2 wireless ATM-LAN (as extension to ATM and IP nets)5,15 - 5,25 GHz, ca. 20 Mbps, reach 50 m,
mobility<10m/scellular structure with base stations, ATM service classes
HIPERACCESS point-to-multipoint ATM connections5,15 - 5,25 GHz, ca. 25 Mbps, reach 5000 m, stationary/quasi-stationary, point-to-multipoint, ATM service classes
HIPERLINK point-to-point ATM connection17,1 - 17,3 GHz, 155 MBit/s, reach 150 m, stationary/quasi-stationary, point-to-point, ATM
source: ETSI RES 10, BRAN
Mobile Communication and Mobile Computing168
Assessment of HIPERLAN
• despite of some unique characteristics there are no products available yet, only single prototypes
• is planned as one of the alternatives for BRAN (Broadband Radio Access Network) in the Wireless ATM
• planned frequencies are originally not worldwide available (5,1-53GHz)
Mobile Communication and Mobile Computing169
Requirements:• wireless connection of mobile terminals to ATM-networks• compatibility to existing standards• existing networks should be easily upgradeable• guaranteed service quality properties which other wireless nets
don't offer• UMTS and WLANs don‘t offer any data rates >50 Mbit/sProblems:• ATM is conceived for high data rates• ATM is optimized on reliable media• applications should notice nothing of the wireless mode
Wireless ATM
Mobile Communication and Mobile Computing170
Wireless ATM: review• WATM still is standardization endeavors, no definite standards
approved • the WATM forum has tried to standardize as much as possible,
the WATM standard is relatively complex• WATM supports relatively many configurations:
– wireless Ad-hoc networks– wireless mobile end-devices: access to the network via radio
subsystem, similar to access-points– mobile end-devices: seamless handover between connected
terminals – mobile ATM-Switches (for planes, ships, trains etc.)– fixed ATM-terminals: conventional ATM– fixed terminals with radio access: comparable with line-of-sight
radio links• It is not arranged completely for which configuration also
products will exist
Mobile Communication and Mobile Computing171
Satellite-based systems
Mobile Communication and Mobile Computing172
Sample systemInter-Satellite Link (ISL)
GatewayLink (GWL)
Mobile UserLink (MUL)
Spot beams
Footprint
GatewayGround Station
User
PSTN, ISDN, GSM, ...Internet
Mobile Communication and Mobile Computing173
Basics (1)
• satellites describe elliptical or circular orbit around the earth
• distance to the earth remains constant:
ZG FrmrRgmF 22/
f
ω
g
r
R
m
F
F
Z
G - Appeal of the Earth
- Centrifugal force
- Mass of the satellite
- Earth radius, 6.370km
- Distance of the satellite to the Earth’s center
- Grounding acceleration, g = 9,81 m/s2
- Angular frequency: /2/1,2 fTf- Cycle frequency of the satellite
(1)
Mobile Communication and Mobile Computing174
Basics (2)
Formulae transformation:• F = m . a (by Newton)
• Fgrav = k . M . m / r2 (Gravitation between 2 point masses)
• mg = k . M . m / R2 (Appeal on the Earth surface =
Gravitation) • k . M = gR2
• FG = gR2 m/r2 = gm(R/r)2 (transformed)
• δt = 2 . (r-R) / c
Signal propagation delay
Satellite
Downlinkr-Rr-R
Uplink
Mobile Communication and Mobile Computing175
Basics (3)• (1) resolved to r gives:
• that means, the distance of a satellite to the earth's surface depends only on its cycle duration (special case T = 24h - > synchronous distance r=35.786 km)
3
2
2
2 f
gRr
(2)
Cycle duration [h]
10 20 30 40 x 106 m
4
12
20
velocity [x1000km/h]
Synchronous distance 35.786 km
Mobile Communication and Mobile Computing176
GEO (Geostationary Earth Orbit) ca. 36 000 km
MEO (Medium Earth Orbit) ca. 6000 - 12 000 km
Van-Allen-belts2000 - 6000 km15 000 - 30 000 km(no satellite use possible)
LEO (Low Earth Orbit) ca. 500 - 1500 km
HEO (Highly Elliptical Orbit)
Satellite system classes
Mobile Communication and Mobile Computing177
Base for Inmarsat
Principle:Satellit
Uplink Downlink
Geostationary Satellite systems
• Constant position to the Earth, 3 satellites cover complete earth (with the exception of the polar caps), satellites move synchronously to the Earth
• Simple solution, however large distance (36000 km), therefore high signal propagation delay, long life time of the satellites: ~ 15 years
• low data rates, large transmission power required
• problems:– on the other side of the 60th degree of latitude reception problems
(elevation)– because of a high transmission power unfavorable for mobile telephones– signal propagation delay too high (0.25 s)
Mobile Communication and Mobile Computing178
LEO- Systems• non-stationary satellites (LEO - Low Earth Orbit)• distance to the earth ~ 500 - 2000 km• shorter signal runtimes (5-10 ms), lower transmission power of
the mobile stations sufficing• however more satellites necessary, frequent handover between
satellites, approximately all 10 min.• examples: Teledesic, Globalstar• only low transmission power necessary, suitable for mobile
phone networks• Disadvantages:
– large number is necessary (50 - 200, or more)
– fast handovers within satellites are necessary
– short life time of the satellites because of atmospheric friction (5-8 years)
Mobile Communication and Mobile Computing179
MEO- Systems
• ~ 10000km, lower number of satellites necessary : ~12• slow movement: handover between satellites is hardly
necessary• cycle duration: 6h• high elevation enables coverage large, highly-populated
areas• Problems:
– signal propagation delay: 70 to 80 ms– higher transmission power is necessary– special antennas for small cells are necessary
Mobile Communication and Mobile Computing180
Service transitions in Inmarsat-C-service
Terrestrial stationBuffer memory
X.25Interface
Phone-InterfaceTelefax-Interface
Fixed network
Internet
X.25 Net Email System
modem PAD
data +maps
laptop fax
data +maps
desktop desktop desktop
laptop
Inmarsat - C – End-TerminalGraphic table
Fax-Interface
MailBox
text
600 bit/s
600 bit/sInmarsatSatellite
L-Band 1,5/1,6 GHzRx/Tx (GPS)
Mobile Communication and Mobile Computing181
Satellites Height Data rate
Teledesic (planned) 288 (?) ~ 700 km 64 Mbit/s 2 / 64 Mbit/s
Iridium 66 (+6) ~ 780 km 2,4 / 4,8 kbit/s
Globalstar 48 (+4) ~ 1400 km 9,6 kbit/s
ICO 10 (+2) ~ 10 000 km 4,8 kbit/s
Inmarsat 5 geostationary 2,4 kbit/s
Orbcomm 35 LEO-stationary 57,6 kbit/s
Examples of satellite-based systems
Globalstar can transfer bi-directionally up to 144 Kbit/s, throughcombination of channels
Orbcomm - first commercial LEO–service worldwide http://Globalstar.com/
Mobile Communication and Mobile Computing182
Comparison of satellite-based systemsSatellite-based
systemGEO MEO LEO
Distance, km r = 35.786 km r-R=6000 –12000 km
r-R= 500 – 2000 km
Cycle duration, T 24 h 6 h 95 – 120 min
Signal propagation delay, t
0.25 s 70-80 ms 10 ms
Transmission power, W
10 5 1
Use examples Numerous systems, approx. 2000:•Sputnik (1957)•Intelsat 1-3 (1965, 1967, 1969)•Marisat (1976) •Inmarsat-A (1982)•Inmarsat-C (1988)
ICO 10+2 •Iridium (bankrupt, 2000) 66+6•Globalstar, 48+4/ 144 kBit/s•Teledesic (2003), 288/ 2-64 MBit/s• Orbcomm, 35
Data rate, kBit/s 0.1 – 1 10 1 – 64000
Life time, years 15 10 5-8
Mobile Communication and Mobile Computing183
Global Positioning System, GPS
Mobile Communication and Mobile Computing184
Overview• 24 satellites on the 6 orbits (20200 km, time of circulation =
12h)• 5 earth stations (Hawaii, Ascension Island, Diego Garcia,
Kwajalein, Colorado Springs)• Accuracy:
– so called P-Code for military applications: on ~6m accurately, partially 2,8m
– so called Selective Availability Mode, SAM (artificial degradation) for civil applications: < 100m (1.5.2000 disestablished)
• Functionality principle: Triangulation• GPS-receiver calculates distance to the satellite on the base of
Time of Arrival of the received signals• distances to at least three satellites enables the calculation of
position, a fourth satellite can be used for determination of elevation over zero
• official initiation 1995, testing since 1978
Mobile Communication and Mobile Computing185
Principle: TOA (Time of Arrival) / TDOA (Time Difference of Arrival)
Distance d,Signal Delay T Mobile Object
• synchronized clocks
• measurement of signal delay by speed of light between satellite and receiver, for instance T = 100 ms
• hence calculation of distance:d = T • c = 1 • 10-1s • 3 • 108 m/s = 3 • 107 m = 30.000 km
• calculation of spheres around each satellite
• the position is on the intersection point of three spheres
Mobile Communication and Mobile Computing186
Principles
• satellites send a signal composed of three components 50 times per second:– identification component: PRC (Pseudo Random Code), provides
satellite recognition and status information– position component: exact position of satellite– time component: time point, when signal is transmitted
• the time offset measured by the receiver is corresponding to the Time of Arrival, from TOA the distance is calculated
• for measurement of TOA of signals very accurate clocks are required
• the exact position of the satellites must be known
Mobile Communication and Mobile Computing187
Sources of errorsClocks• highly accurate atom clocks in the satellites• simple clocks in the receivers are calibrated via measurement of
a fourth satelliteSatellite position• satellite orbits are relatively stable and forecastable• deviations are measured by US DoD • deviations are transmitted as correction factor to the satellites
using the PRCMiscellaneous error sources• atmospheric faults• multi-path propagation
Mobile Communication and Mobile Computing188
Differential GPS, DGPS
• use of a stationary receiver as reference• position of this receiver is exactly known• the stationary receiver carries out position determination
and calculates correction factor from the actually obtained position on the base of deviations
• correction factor is delivered to the mobile receiver
Mobile Communication and Mobile Computing189
DGPS accuracy grades
• Accuracy under 10cm:– professional applications, for instance is interesting in
meterology and respectively for user of well-engineered software decisions (machine control systems etc.)
• Accuracy under 1m:– events mapping, control of machines, traffic control
systems, agriculture • Guaranteed accuracy under 10m:
– agriculture/ forestry, railway (wagon search service), car navigation (private/commercial)
Mobile Communication and Mobile Computing190
Galileo
• EU-Project for installation of European satellite navigation system
• initiation: prospective 2008• positioning accuracy: 45cm• 30 satellites• Approx. costs: 3,2 Billion €
Mobile Communication and Mobile Computing191
„ A system that both competes with and complements the American GPS system “ Galileo
ITS (Intelligent Transport System)
•based on a constellation of 30 MEO-satellites •ground stations providing information concerning the positioning of users •in many sectors usable:
─transport (vehicle location, route searching, speed control, etc.)─social services (e.g. aid for the disabled or elderly)─the justice system ( border controls)─public works (geographical information systems)
Mobile Communication and Mobile Computing192
Galileo -architecture
Service centres
GALILEO GLOBAL CONTENT
MEO Constellation
OSSNetwork
TTC
Navigation control & constellation management
OSSNetwork
...
User segment
UHF- S&RI-Band- NAV
Local Components
Local MS
Local MS
.
.
Data link
Data link
UMTS
External complementary systems
Regional Components
BSS network
.
.
COSPAS-SARSATground segment
BSS network
RMS network
GEO
EGNOS
i-bandi-band
Integrity determination
&dissemination
s-bands-band
Mobile Communication and Mobile Computing193
Broadcast Systems, Distribution Networks
Mobile Communication and Mobile Computing194
Overview
• special variants of asymmetric communication systems• HSCSD supports for instance asymmetric connections regarding to
data rate, also ADSL• WWW is the biggest representative of asymmetric communication:
– data volume of uplink (URLs) is much lower than downlink (complete HTML-pages)
• Problem of distribution systems: Sender can be optimized for a large quantity of receivers only, for instance videostreaming
• Examples:– DVB, Digital Video Broadcast
– DAB, Digital Audio Broadcast
Mobile Communication and Mobile Computing195
Principle of Distribution Systems
AC
BA
A
AAB
BBC
CCC
Time information sequence is optimized for expected access behavior of all consumers
t
Individual access sample of diverse consumers can more or less deviate from expected access behavior
Mobile Communication and Mobile Computing196
Digital Audio Broadcast, DAB• Audio-transmission in CD-Quality• Non-sensible towards interferences of multi-path-propagation• Use of SFN (Single Frequency Network) – i.e. all senders of
some broadcast-program are working on the same frequency as a rule
• Frequencies: UHF,VHF, for instance: 174-230 MHz, 1452-1492 MHz
• Modulation methods: DQPSK (Differential Quadrature Phase Shift Keying)
• Optionally COFDM (Coded Orthogonal Frequency Division Multiplexing) is used with several carrier frequencies inside some DAB-channel (its quantity is between 192 and 1536), 1,5MHz bandwidth for each channel
• FEC (Forward Error Correction)-mechanism for fault correction• Up to 6 stereo-programs by 192 kbit/s in the same frequency
band are transmittable• alternatively data can be transmitted with up to 1,5 Mbit/s
(responding to the used code rate etc.)
Mobile Communication and Mobile Computing197
Digital Audio Broadcast, DAB
2 Transport Mechanisms
• Main Service Channel (MSC):– Data, Audio, Multimedia– 2 Transport Modes: Stream Mode, Packet Mode
• Fast Information Channel (FIC):– Transport of Fast Information Blocks (FIB, 32 Byte) – control data for
interpretation of Data in the MSC, can be also used for services such as Traffic Dispatches, Paging etc.
• Audio-converting: PCM 48 kHz & MPEG2-Audiocompression
• High transmission rates by high velocities, up to 250 km/h, responding to distance from sender and error security class, use for instance in high-speed train
• MOT (Multimedia Object Transfer) protocol for data transmission
• Cyclic repeat and caching of data blocks
Mobile Communication and Mobile Computing198
Dynamic channel reconfiguration for DAB
Ensemble-Configuration
Temporarily changed Ensemble-Configuration
Audio 2192 KBit/s
PAD
Audio 3192 KBit/s
PAD
Audio 4160 KBit/s
PAD
Audio 5160 KBit/s
PAD
Audio 6128 KBit/s
PAD
Audio 1192 KBit/s
PAD
DataD2
DataD3
DataD1
DataD6
DataD7
DataD4
DataD8
DataD5
Audio 2192 KBit/s
PAD
Audio 4160 KBit/s
PAD
Audio 5160 KBit/s
PAD
Audio 1192 KBit/s
PAD
Audio 3128 KBit/s
PAD
DataD10
DataD11
DataD2
DataD3
DataD1
DataD6
DataD7
DataD4
DataD8
DataD5
Audio 796 KBit/s
PAD
Audio 896 KBit/s
PAD
Mobile Communication and Mobile Computing199
DVB - Digital Video Broadcasting
• 1991 ELR (European Launching Group) founded• Goal: joint digital Television System for Europe• Specifications: DVB-S, DVB-T, DVB-C• Frequency reaches: 200, 550, 700 MHz• Cell size: up to 60 km• Used data rate: ~38,5 Mbit/s• Velocity of mobile stations: up to 200 km/h• Central Unit: combined DVB-Receiver-Decoder (set-top-box)
– can receive DVB-Data via satellites, B-ISDN, ADSL…
– some transmission systems offer a feedback channel for Video on Demand etc.
Mobile Communication and Mobile Computing200
DVB - Digital Video Broadcasting• Different Quality Levels defined:
– SDTV (Standard Definition TV)
– EDTV (Enhanced DTV)
– HDTV (High DTV)
• Data transport:– User Data: MPEG2-Container (Data Transfer Unit) like DAB,
Container doesn’t define the type of data
• Service Information about MPEG2-Container-content:– NIT (Network Information Table): Information from a provider about
offered services and optional data for the receiver
– SDT (Service Description Table): Description and parameters for each service in the MPEG2-stream
– EIT (Event Information Table): Data about actual transmission status
– TDT (Time and Date Table): e.g. updating of DVB-receiver
Mobile Communication and Mobile Computing201
MPEG2/DVB-Container MPEG2/DVB-Container
MPEG2/DVB-Container MPEG2/DVB-Container
HDTVEDTV
SDTV
Single channel
(High Definition TV)
Several channels (Enhanced DTV)
Several channels (Standard TV)
Multimedia(data broadcasting)
Possible contents of DVB/MPEG2-Container
Mobile Communication and Mobile Computing202
DVB used as medium for asymmetric Internet-access
• Client sends data query to Provider, Provider transmits data to the satellite network, receiver obtains data via DVB-receiver
• Feedback channel can be phone network, for on-demand services
• Data rates:– 6 up to 38 Mbit/s downlink, 33 kbit/s up to over 100 kbit/s (ADSL) uplink
• Advantages:– data can be transmitted in parallel with TV– no additional costs for satellite provider– low priced for low-density populated areas
• Disadvantages:– all users need satellite antennas– only a minor part of the total bandwidth is usable– not suitable for high-density populated areas
Mobile Communication and Mobile Computing203
Internet
DVB–Card in the PC
Satellite provider
dedicated line (user-to-user)
Service Provider
Content Provider
DVB as medium for the asymmetric Internet-access
Mobile Communication and Mobile Computing204
3. Mobile Computing
Mobile Communication and Mobile Computing205
UNIT - IV
Mobile Communication and Mobile Computing206
Layer 3
Mobile IP v4 & v6DHCP
Mobile Communication and Mobile Computing207
Mobile IP (Internet Protocol)
Mobile Communication and Mobile Computing208
Problem situation• computer mobility in heterogenic networks• relocation between different IP-subnets• Goal: transparent migration and localization,
compatibility to IP, no changes of existing routers• Idea: introduction of temporary/ actual IP-addresses
(also “care-of-address”, COA);• mapping of permanent to temporary IP-addresses
using localization technique
Mobile Communication and Mobile Computing209
Requirements to MobileIP according to IETF
Transparency:– mobile computer is permanently reachable via its
previous “home-address”– can change its network access point freely– can also communicate after coupling/uncoupling
Compatibility:– supports each layer below IP (also 1 & 2)– mobile computer can also communicate with each “non-
mobileIP”-computer– no changes to existing computer/routers
Security:– all registering messages must be authenticated
Mobile Communication and Mobile Computing210
IETF Mobile IP Goals/Restrictions
Minimization of overheads: – mobile connections are possibly wireless and have
limited band width– mobile connections have possibly higher error rate
Efficiency and scalability:– support of a large quantities of mobile computers– support of a theoretically Internet-wide mobility
Mobile Communication and Mobile Computing211
GlobalInternet
Home Subnet
Anywhere
Foreign Subnet
Home Agent (HA) Router
Foreign Agent (FA)
Correspondent Node (CN)
Architecture model
Mobile Node
Mobile Communication and Mobile Computing212
TermsMobile Node (MN) with permanent IP-address from Home
Subnet
Home Address permanent address of a mobile computer
Home Agent (HA) with knowledge of actual residence of all MNs from so called Home Subnet, like GSM-HLR
Care of Address temporary address of a mobile computer from Foreign Subnet
Foreign Agent (FA) for assignment of temporary IP-addresses (care of address) and packet forwarding to MNs currently residing in its subnet
Mobile Communication and Mobile Computing213
Log on via Foreign Agent
• Log on with a FA - Care-of Address (address of FA, is just an intermediate target for all MN- related packets, tunnel-end) or
• Application of a co-located Care-of Address (address from Foreign-Subnet, MN is tunnel-end itself), but reception of an Agent Advertisement Message with a set “R”-bit, i.e. the MN is forced to log on with FA itself, although it can operate autonomously
MN
HAForeignSubnet
HomeSubnet
1.) Registration.request
2.) relaying request
4.) Registration reply
FA
3.) relaying.reply
{grant, deny}
Mobile Communication and Mobile Computing214
Log on by Home Agent directly
HA
HomeSubnet
1.) Registration.request
2.) Registration.reply
{grant, deny}
MN
• MN uses co-located Care-of Address• MN is returned to Home Network and would like to log
on/off itself with the HA
Authentication:
• each mobile entity (MN, HA, FA) must be able to support a “mobility security association”, which is indicated via IP-address and SPI (Security Parameter Index).
• Mobile IP provides three different Authentication Extensions:
• Mobile - Home Authentication Ext.
• Mobile - Foreign Authentication Ext.
• Foreign - Home Authentication Ext.
Mobile Communication and Mobile Computing215
Addressing
Problem: For the receivers 2 addresses are necessary (permanent and temporary IP-address respectively home address and COA)
Methods of resolution:• Encapsulation
– IP in IP, standard method in MobileIPv4– minimal Encapsulation
• IP-Option (not supported by all implementations)
Mobile Communication and Mobile Computing216
IP in IP Encapsulation
• IP-source/target address of external/outer IP-Header defines the “end- points” of the tunnel
• IP-source/target address of internal IP-Header represents the actual packet sender respectively receiver
• Internal IP-Header isn't changed using “Encapsulator” (exception:
TTL)
IP HEADER
IP PAYLOAD IP PAYLOAD
IP HEADER
OUTER IP HEADER
Mobile Communication and Mobile Computing217
Routing (unicast)• Mobile Node:
– in Home Network it operates like each other Node– in Foreign Network it must search a Default Router using the
following rules:• FA COA:
– ICMP Router Advertisement-Part; – IP-source address of Agent Advertisements (lower Prior.)
• co-located COA: ICMP Router Advertisement for this address
• Foreign Agent:– FA must check by reception of tunneled packets whether
internal target address corresponds with one of the IP-addresses of Visitor List
– FA must route the received packets of registered MN’s!
Mobile Communication and Mobile Computing218
Routing (unicast) II• Home Agent:
– HA must intercept each packet for absent MN– in addition IP-target address of each incoming
packets is verified – if MN has no mobile coupling presently, the packets
sent to it must not be intercepted, MN is situated in Home Subnet and accepts packets itself or is off-line
Mobile Communication and Mobile Computing219
Routing (necessities)
• ARP (Address Resolution Protocol):– oriented to resolution of IP-addresses in physical (Hardware, Link Layer)
addresses (Ethernet: MAC-addresses of controllers)
• Proxy ARP:– Proxy ARP-reply is an ARP-reply, which can be sent instead of a host A
by other host B (with its hardware address)– Hosts, receiving this reply, associate the hardware-address of node B
with the IP-address of node A and send future packets for A to B
• Gratuitous ARP:– is an ARP-reply, which is sent from a host, to force other hosts to
update the records in their ARP-Caches– this ARP-reply contains the IP-address, which should be changed in the
ARP- Caches, as well as the hardware address which should be updated
Mobile Communication and Mobile Computing220
Routing - Scenario
• MN leaves Home Network• MN decides to register FA Care-of Address• Before Registration Request: MN re-sets a reaction on
future ARP-requests• Registration Request• contains and accepts HA Request, implements
Gratuitous ARP (IP-address MN ===> own hardware-address) and uses Proxy ARP to respond to ARP-requests corresponding to MN hardware address
Mobile Communication and Mobile Computing221
Triangle Routing
HA
FA
MN
CN
Foreign
Network
Home
Network
although CN is in the same Subnet like MN, packets are routed respectively tunneled via FA and primarily HA (possibly over half of terrestrial globe)!!!
CN ===> MN:
MN ===> CN:
Be routed conventionally via Default Router
Special case: Routing (MN & CN are in the same Subnet)
Relief (IPv4): Route Optimization
Mobile Communication and Mobile Computing222
Optimizations: Routing
Terms:• Binding Cache: table with Mobility Bindings of
MNs (on CN, can tunnel itself now)• Binding Update: message, contains up-to-date
Mobility Binding of a MN, particularly the Care-of Address
Procedure:• Update of Binding Caches
• Control seamless Handoffs between FA‘s
Mobile Communication and Mobile Computing223
Updating of Binding Caches
• Binding Cache of a CN: Care-of Address of one/several MN‘s, with respective Lifetime
• No Entry: non-optimal Routing, BUT: HA doesn’t only tunnel a datagram from CN, but also sends a Binding Update to it
• CN should generate/change Binding Cache-Entry only then, when trusted Mobility Binding received (Bind. Upd.) for corresponding MN (ergo: Secure CN <===> HA)
• If FA receives tunneled Packet for a MN that is no longer in Visitor List, then it must care that corresponding CN receives a Binding Update (Binding Warning to HA)
Mobile Communication and Mobile Computing224
Smooth Handoff between FAs
• Problem of Basis-MobileIP: MN is with a new FA, but the packets tunneled to old FA will be lost
• FA Smooth Handoff: MNs are informed via new FA (packet can be forwarded)
• also Packets of hosts with non-up-to-date entries in Binding Cache can be forwarded now from old FA to the new FAs
• Previous Foreign Agent Notification Extension enables to prompt the new FA to inform the old FA (Binding Update Message)
Mobile Communication and Mobile Computing225
MobileIP v4 & v6 in comparisonMobile IPv4 Mobile IPv6
Optimal Routing, only if MNin the Home Network. (Otherwisenon-efficient „Triangle“-Routing)
Optimal Routing is generallypossible, if CN knows the Care-of Address
Routing
HA is a possible bottleneck, because all trafficto the MN is processed over it
HA is load essentially reduced, because CN‘s can just directly communicate with mit MN‘s
Bottle neck
Authentication is prescribed only by Registration and then also between HA and MN only
Authentication and encryption are possible anywhere, becausethey are supported from IPv6
Security
Used FA‘s / HA‘s must not be off-line
Short-time failure/re-configuration of HA is mastered thanks toAutomatic Home Agent Discovery.IPv6 is essentially simpler to upgrade, therewith also Mobile IPv6
Robustness
No good performancedue to IPv4-requirementsand non-optimal Routing
Essentially better due to requirements from IPv6 (uniform Headers, less Over-heads) and optimal Routing
Performance
Mobile Communication and Mobile Computing226
Assessment
• Mobile IP enables the unlimited accessibility/roaming of mobile computers using perpetuation of their addresses and step-less transfer between subnets
• Particularly necessary for applications without “pull”-semantics (for instance, distributed applications with mobile users, videoconferences, VoIP)
• Keeping of permanent addresses are also important corresponding to Firewalls etc. in the case of call semantics
• Successive availability in the form of products
Mobile Communication and Mobile Computing227
Dynamic Host Configuration Protocol (DHCP)
Properties:• permits automatic
configuration (IP-address, subnet-mask, router, DNS-Server, ...) and therewith integration of (mobile) computers
• Client/Server-Model• Lease Concept• Relevant for
management of Care-of-Addresses
Server A Server BClient
DHCPDISCOVER DHCPDISCOVERDeterminationof configuration DHCPOFFER DHCPOFFER
Selection of a configuration
DHCPREQUEST
(reject)
DHCPREQUEST(options)Confirmationof configuration
DHCPACK
Determinationof configuration
Mobile Communication and Mobile Computing228
DHCP Assessment
• no secure mechanisms standardized• no standardized communication (signalization,
for instance information exchange about managed address areas) between DHCP-servers
• good base for allocation of co-located COAs in MobileIP
Mobile Communication and Mobile Computing229
IPsec: Network security
Mobile Communication and Mobile Computing230
IPsec: Security on the network layer (1)
• IPsec - IP Security Protocol – new developed protocol from TCP/IP-Stack, related to the IPng - Group
• IPsec uses: – encryption services -> DES, TripleDES and 40-bit-DES between
hosts at a VPN (virtual private network)– specification for Internet Key Management Protocol (IKMP),
based on ISAKMP/Oakley (1998, Internet Security Association and Key Management Protocol - ISAKMP)
• IPSec-tunnels – encapsulation of TCP/IP-data via the ESP/AH- headers:– Developed by S.Kent, R. Atkinson „IP Encapsulating Security
Payload" (RFC 2406, 1998) and "IP Authentication Header" (RFC 2402, 1998)
– relevant for key assignment to IP-subnets
Mobile Communication and Mobile Computing231
IPsec: Security on the network layer (2)
• Secrecy on the network layer: a sending host encrypts/authenticates data encapsulated in the IP-datagrams
– TCP/UDP-segments– ICMP/SNMP-messages
• Authentication on the network layer: – target host can authenticate source IP-addresses
• Basic protocols:– Authentication Header (AH) Protocol– Encapsulation Security Payload (ESP) Protocol
• AH and ESP both requires target and source Handshake-Routine:– establishment of a logical channel via network layer, called Service Agreement
(SA)– each SA is unidirectional
• Distinctly determined via:– security protocol (AH / ESP)– source IP-address– Con-ID of 32 Bit
Mobile Communication and Mobile Computing232
Encapsulation Security Payload (ESP) Protocol
• offers secrecy, host authentication and data integrity• data, ESP trailers encrypted• next header field is a trailer in the ESP• ESP- authentication field is similar to AH- authentication field;
protocol field = 50
ESP-AuthESP-Auth
Protocol = 50
ESP-TrailerESP-TrailerTCP-/UDP-SegmentTCP-/UDP-Segment
authenticatedencrypted
ESP-HeaderESP-HeaderIP-HeaderIP-Header
Mobile Communication and Mobile Computing233
Authentication Header (AH) Protocol• offers host authentication and data integrity, but no secrecy• AH headers inserted between IP-Header and IP-data field; protocol
field = 51• participated routers process datagrams as usually
AH-Header consists of:• Con-ID• authentication data: signed message digest calculated via original
IP-Datagram, offers authentication of source hosts and data integrity
• next header field is specific data type (TCP, UDP, ICMP etc.)
TCP-/UDP-SegmentTCP-/UDP-SegmentAH-HeaderAH-HeaderIP-HeaderIP-Header
Protocol = 51
Mobile Communication and Mobile Computing234
Layer 4
Mobile Communication and Mobile Computing235
Problems of conventional protocols
Problem:• Loss of packets on the radio channels with higher bit-
error rate (BER) results in frequent retransmissions of packets and therewith in further efficiency loss
• TCP-Protocol uses so called “Slow-Start”-mechanisms: window size is reduced by significant packet losses; this is reasonable for fixed networks, to react on overload, but not for packet losses due to higher BER
• limited suitability of conventional transport protocols for mobile communication!
Mobile Communication and Mobile Computing236
Conventional protocolsCongestion Control:
• packet loss as a rule, in fixed networks occurs only by overload of several components
• reducing of transmission rate
Slow Start:
• sender calculates a traffic window size
• start with window size 1
• exponential growth till to Congestion Threshold
• then linear growth
Fast Retransmit / Fast Recovery:
• If ≥ 3 DUPACK (duplicate ACK) are received
-> sender informs about packet losses and repeats missing packets
Mobile Communication and Mobile Computing237
Resulting problems in mobile environment
• packet losses due to transmission errors are wrongly interpreted as traffic jam (Congestion)!
• > Slow Start is also wrong• > Ideally the packets lost due to transmission
errors are simply repeated (no effects on Congestion Control)
• great variances of Round-Trip-Time
Mobile Communication and Mobile Computing238
Scenario
Mobile Host
Fixed HostAccess Point 1
Access Point 2
Mobile Communication and Mobile Computing239
SolutionsSender- transparent:• to hide the packet losses transparent to the sender• transmission repeat via Access Point
– on layer 2
– on TCP-layer
Wireless-aware sender:• sender understands the reason of packet loss• explicit notification of senders• sender tries to determine the reason of loss
Where will be the modifications carried out?:• only by the sender• only by the receiver• only on the transient node (Access Point)• combinations
Mobile Communication and Mobile Computing240
– Separation between transport functionality in the fixed network respectively in the mobile network:
– MobileTCP is specially optimized (up to 100% of efficiency improvement possible)
– system-internal TCP-Handovers are necessary, however transparent for fixed computer (Workstation)
Work-station MSR
MSR
Mobilenode
Mobile Support Router
TCP
Fixed networkMobile TCP
Mobile network
TCP-Handoverby relocation of mobile node
Solution “Split Connection“
Mobile Communication and Mobile Computing241
UNIT - V
Mobile Communication and Mobile Computing242
Example of I-TCP (indirect TCP)• separation of TCP-connection at the Access Point• optimized TCP over the wireless Link (not absolutely necessary)• no changes of TCP for the fixed network• transparent for Fixed Host • loss of End-to-End-semantics
Mobile Host
Fixed HostAccess Point 1
„wireless TCP“ „standard TCP“
Mobile Communication and Mobile Computing243
Example of I-TCP
• Mobility: status and buffer transfer
Mobile Host
Fixed Host
Access Point 1
Access Point 2
Mobile Communication and Mobile Computing244
I-TCP Assessment
+ no changes in the fixed network+ the errors in the wireless part aren’t propagated to the fixed network+ both parts can be optimized independently + relatively simple: „wireless TCP“ concerns one Hop only+ the properties of wireless networks (bit-error rate, delay time) are
known, therefore fast retransmissions are possible ─ loss of End-to-End-semantics─ additional costs (computation time, storage place) concerning the
Access Point─ high delay times with handover caused by buffering of data by
Access Point─ IT-security mechanisms must be adapted
Mobile Communication and Mobile Computing245
Example of Snoop• transparent extension of Access Point from sender’s viewpoint• Access Point listens to the traffic (snoops) and filters the ACKs• buffering of data, are sent to the mobile computer• after losses of packets in the wireless network a direct
retransmission takes place between Access Point and Mobile Host• Access Points send NACK after packet losses of MH
Mobile Host
Fixed HostAccess Point 1
TCP
Buffer„local retransmission”
Mobile Communication and Mobile Computing246
Snoop Assessment
+ maintenance of End-to-End-semantics+ modifications only at the TCP-Stack of Access Points+ errors in the wireless part can be corrected locally+ Soft State
+ no status transfer at new Access Point is necessary
+ change is possible, also if the new Access Point possesses no Snoop
• no complete transparency of wireless connection• handling of NACK requires the modifications of MH• IT-security: encryption can prevent an access to TCP-Header (most
of the up-to-date approaches use End-to-End-encryption!)
Mobile Communication and Mobile Computing247
Higher Layers and Services
Mobile Communication and Mobile Computing248
Wireless Application Protocol - WAP
Based partially on the materials of WAP-Forum
Mobile Communication and Mobile Computing249
WAP – Standard Overview
• Goal: Fusion of Internet-Technologies and mobile radio, creation of new innovative services
• standardized by WAP-Forum (http://www.wapforum.org), initiated by Ericsson, Nokia, Motorola
• specifies application environment and protocols for mobile end-devices such as radio phones, PDAs, pagers
Mobile Communication and Mobile Computing250
Why WAP?• Mobile radio networks and mobile phones
possess special properties and requirements– Display: sizes and presented colors, numerical
keyboard, lower processor performance and storage capacity ...
– Networks: low data rates, high delays and costs
• WAP offers the use of several carriers– TCP/IP, UDP/IP, USSD, SMS, ...
USSD - unstructured supplementary service data (GSM)SMS - short message service (GSM)
Mobile Communication and Mobile Computing251
Why WAP ?• WAP-architecture has a modular organization• the modules build together a complete Internet-protocol-stack• WML-contents can be queried by HTTP-request-messages• WAP uses XML (eXtensible Markup Language)-Standard as
well as optimized contents and protocols• user interface of conventional end-devices is supported by
WML-components– enhances acceptance by users
• WAP uses conventional HTTP-Servers– existing development strategies are applicable in the
future (common gateway interface - CGI, active server pages - ASP, netscape server API - NSAPI...)
Mobile Communication and Mobile Computing252
Why HTTP/HTML doesn’t suffice?
Big pipe - small pipe syndrome
<HTML><HEAD><TITLE>NNN Interactive</TITLE><META HTTP-EQUIV="Refresh" CONTENT="1800, URL=/index.html"></HEAD><BODY BGCOLOR="#FFFFFF" BACKGROUND="/images/9607/bgbar5.gif" LINK="#0A3990" ALINK="#FF0000" VLINK="#FF0000" TEXT="000000" ONLOAD="if(parent.frames.length!=0)top.location='http://nnn.com';"> <A NAME="#top"></A><TABLE WIDTH=599 BORDER="0"><TR ALIGN=LEFT><TD WIDTH=117 VALIGN=TOP ALIGN=LEFT>
<HTML><HEAD><TITLE>NNN Interactive</TITLE><META HTTP-EQUIV="Refresh" CONTENT="1800, URL=/index.html">
InternetHTTP/HTML
Converting to binary format
Mobile radio networks
<WML><CARD><DO TYPE="ACCEPT"><GO URL="/submit?Name=$N"/></DO>Enter name:<INPUT TYPE="TEXT" KEY="N"/></CARD></WML>
010011010011110110010011011011011101010010011010
WAP
Mobile Communication and Mobile Computing253
WAP-overviewWAP-standard defines:• Environment = Wireless Application Environment
(WAE)– WML (Wireless Markup Language) micro-browser– WMLScript virtual machine– WMLScript standard library– Wireless Telephony Application (WTA) Interface– Contents = WAP Content Types
• Layer architecture– Wireless Session Protocol (WSP)– Wireless Transaction Protocol (WTP)– Wireless Datagram Protocol (WDP)– Interface definitions for mobile network
Mobile Communication and Mobile Computing254
Comparison: Internet/WWW and WAP
HTMLJavaScript
HTTP
TLS - SSL
TCP/IPUDP/IP
Wireless ApplicationEnvironment (WAE)
Session Layer (WSP)
Security Layer (WTLS)
Transport Layer (WDP)
other services andapplications
Transaction Layer (WTP)
Carrier: SMS USSD CDMA CDPD etc..GPRS
InternetWireless Application Protocol
SMS - Short Message Service (GSM), GPRS - General Packet Radio Service (GSM II+), CDMA - Code Division Multiple Access, CDPD - Cellular Digital Packet Data
Mobile Communication and Mobile Computing255
Wireless Application Environment - WAE
• environment for distributed applications with specific reference to low-performance end-devices with limited operation comfort and mobile radio networks
• Goals:– network-independent application environment– optimized for application in mobile radio systems– Internet, i.e. WWW–programming model– high interoperability level
Mobile Communication and Mobile Computing256
WAE – abstract network architecture
GatewayClientNetwork
Application
WSP/HTTP Request {URL}
WSP/HTTP Reply {Content}
Mobile Communication and Mobile Computing257
Constituents• Architecture
– Programming model– Browser, Gateway, Content Server
• WML– as page markup language
• WMLScript– as scripting language
• WTA– offers access to phone services
• Content formats– sets free-defined formats: bitmaps, phonebook records,
dates ...
Mobile Communication and Mobile Computing258
Options
• User Agent Profiling– to user, end-device, ... adapted contents
• Push-model– network initiates delivery of contents
• Options for performance improvement– Caching, ...
Mobile Communication and Mobile Computing259
Sample: WAP-Gateway
Web Server
Contents
CGIScripts
etc.
WM
L D
ecks
,W
ML
-Scr
ipt
WAP Gateway
WML Encoder
WMLScriptCompiler
Protocol adapter
HTTPWSP/WTP
Client
WML
WML-Script
WTAI
etc. WA
E U
ser
Ag
ent
Mobile Communication and Mobile Computing260
Sample: WAP - Application Server
Contents
Applicationlogic
WM
L D
ecks
,W
ML
-Scr
ipt
WAP Application Server
WML Encoder
WMLScriptCompiler
Protocol adapter
WSP/WTP
Client
WML
WML-Script
WTAI
etc. WA
E U
ser
Ag
ent
Mobile Communication and Mobile Computing261
Wireless Markup Language - WML(1)
HDML - Handheld Device Markup Language, W3C - World Wide Web Consortium, XML - eXtensible Markup Language
• HTML-like page markup language– different font styles are available, tables
and graphics too, but limited • based on W3C-XML• uses HTML and HDML-elements• Deck/Card-metaphor
– interactions-/selection possibilities are separated in Cards
– navigation (anchor: #) takes place between Cards
– Deck-stack corresponds to a WML-file
Mobile Communication and Mobile Computing262
Wireless Markup Language - WML(2)
• explicit navigation model between Decks– Hyperlinks– Events from user interface– History
• variables and status-management– variable status can tell about validity of a stack
Mobile Communication and Mobile Computing263
WML– text styles
DeckCard
<wml> <card id=“Card1” title=“Text Styles”> <p align="left">
<i>italic</i>, <b>bold</b>,<br>
<big>big</big>,<small>small</small>,<u>underlined</u> </p> </card></wml>
Mobile Communication and Mobile Computing264
WML-example (1)
Selectedinput
Script call
Variables
Navigation
<wml> <card id=„Card1" title=„Currency" newcontext="true"> <p> Amount: <input format="*N" name=„amount" title=„Amount:"/> From: <select name=“from“ value=" USD“ title=„From:"> <option value="EUR">Euro</option> ... <option value="USD">US Dollar</option> </select> To: <select name= ... <br/> = <u>$(conv)</u> <do type="accept" label=„Calculate"> <go href=“bsp.wmls#convert('conv', '$(from)','$(to)',$(amount))"/> </do> <do type="help" label="Help"> <go href="#card1_help"/> </do> </p> </card> ...
Mobile Communication and Mobile Computing265
WML-example (1): Processing
Mobile Communication and Mobile Computing266
WML-example (2)
Events processing
<card id="card1_help" title="Help"> <onevent type="onenterforward"> <go href="bsp.wmls#getInfoDate('date')"/> </onevent> <p> Currency exchange rates stem from Federal Reserve Bank of New York and are from $(date). <do type="prev" label=„Back"> <prev/> </do> </p> </card></wml>
Mobile Communication and Mobile Computing267
WMLScript-overview (1)
• scripting language, similar to JavaScript– procedures, loops, conditions, ...– optimized for devices with low storage capacity and
CPU-performance
• integrated with WML, enables:– reducing of network workload– validation of inputs– access to vendor-specific APIs– programming of conditional logic
Mobile Communication and Mobile Computing268
WMLScript-overview (2)
• Bytecode-based Virtual Machine– stack-oriented design– ROM-able– designed with regard to simple, less work-expensive
implementation
• Compiler in network– better utilization of network capacity and end-device
storage
• Standard library– basic functionality for processing of strings, URLs, ...
Mobile Communication and Mobile Computing269
WMLScript-example
Procedures
Variables
Statements
extern function getInfoDate(varName){ WMLBrowser.setVar(varName,„June,3,2002"); WMLBrowser.refresh();}extern function convert(varName,from,to,amount){ var multiplier = 0.0; ... if (from == „EUR") { ... if (to == „EUR") multiplier = 1.0; else if (to == „RUR") multiplier = EUR_RUR; ... } else if ... WMLBrowser.setVar(varName,returnString); WMLBrowser.refresh();}
Mobile Communication and Mobile Computing270
Wireless Telephony Application - WTA (1)
• offers mechanisms for applications in field of telephony
• primary focus: operators/providers and vendors
• security and trust are the emphasis• WTA Browser
– using improvements of standard WML/WMLScript- browsers
– own interface WTAI (... Interface)
Mobile Communication and Mobile Computing271
Wireless Telephony Application - WTA (2)
• WTAI contains:– call control, messaging, interface to phonebook,
events processing...
• own Client/Server-interaction model – event signalization...
• security via separation– browser and port separated
• WTAI in WML and WMLScript available
Mobile Communication and Mobile Computing272
WAE content formats
• WAE defines uniform formats– visit cards, so called IMC vCard Standard– dates, IMC vCalendar Standard– graphics, WBMP (Wireless BitMaP)– compiled WML, WMLScript
• Goal: Interoperability
IMC - Internet Mail Consortium
Mobile Communication and Mobile Computing273
WAP layer architecture
Wireless Session Protocol (WSP)
Wireless Transaction Protocol (WTP)
Wireless Datagram Protocol (WDP)
CarrierService A
CarrierService B
CarrierService C
Carrier DService D
Physical Layer Air Link Technology
Carrier AAdaptation
Carrier BAdaptation
Carrier CAdaptation
Wireless Transport Layer Security (WTLS)
Mobile Communication and Mobile Computing274
Wireless Session Protocol
• supports Client/Server context (shared state), optimization of content transmission
• offers semantics and mechanisms, which are based on HTTP
• and improvements for use in mobile radio networks with low-performance end-devices
Mobile Communication and Mobile Computing275
WSP overview (1)• HTTP elements:
– extensible request/reply methods– extensible request/reply headers– uniform contents– composed objects– asynchronous requests
• Improvements:– binary encoding of headers– session headers (Client & Server)– confirmed and unconfirmed network-initiated delivery (Push)
Mobile Communication and Mobile Computing276
WSP overview (2)• Improvements corresponding to HTTP:
– negotiations of supported characteristics– session suspend/resume– multiple complete asynchronous transactions– connectionless service
• Why doesn’t HTTP suffice?– no compact encoding– insufficient negotiations– Push doesn't exist
Mobile Communication and Mobile Computing277
Characteristics
• message size• protocol options
– Confirmed Push Facility/ Push Facility (unconfirmed)– Session Resume …
• maximum outstanding (unanswered) requests• Header Code Pages (known field names in the
protocol headers are separated into pages)• ...
Mobile Communication and Mobile Computing278
Suspend/Resume
• Server knows, when a Client accepts data (Push)• multi-carrier devices• dynamical addressing• enables release of carrier resources
Mobile Communication and Mobile Computing279
Wireless Transaction Protocol (WTP)
• Goal:– efficient request/reply-based transport mechanism for mobile
radio networks and low-performance end-devices
• Properties:– robust data transmission– no explicit connection set up and connection release– data are transmitted already with the first packet– packet oriented– abortion-function for outstanding (unanswered) requests
Mobile Communication and Mobile Computing280
Wireless Transaction Protocol (WTP)
• Properties:– supports concatenation of messages– further WTP features:
• repeated transmission due to packet loss (selective)• fragmentation• port numbers (UDP)• flow control
• Transaction = Interaction between Initiator and Responder
Mobile Communication and Mobile Computing281
WTP – transaction classes (1)• Class 0:
– non-robust datagram-service– for instance for Push during a session– shouldn’t substitute WDP– the transactions are closed after transmission of
Invoke
• Class 1:– robust datagram-service– the transactions are closed after transmission of
Invoke
Mobile Communication and Mobile Computing282
WTP – transaction classes (2)
• Class 2:– robust datagram-service with robust Invoke- and
robust Result-messages– the transactions are closed via the Initiator after
answer confirmation of the Responder
Mobile Communication and Mobile Computing283
Wireless Datagram Protocol (WDP)
• provides connectionless, non-robust datagram-service
• is substituted by UDP, if IP the a carrier• re-adaptation to the carrier takes place in the
Adaptation Layer• supports port numbers
Mobile Communication and Mobile Computing284
Wireless Transport Layer Security (WTLS)
• enables secure connections, uses protocol elements of known, secure Internet-protocols (TLS)
• provides mechanisms for encryption, strong authentication, integrity and key management
• corresponds to guidelines of national authorities
• offers end-to-end security
Mobile Communication and Mobile Computing285
WAP & Security
• WTLS (Wireless Transport Layer Security) offers only security via encryption of transmitted data (Grade #1) presently, similar to TLS, only communication trustiness is protected
• Grade #2 supports Server- and Client-certificates, for instance via additional chip-cards in mobile phones, so called WIM - Wireless Identification Module
Mobile Communication and Mobile Computing286
UBS (Switzerland)• data with WTLS class 2, 128 bit 3DES encrypted• UBS authentication against mobile phone via certificates with a
key size of 1024 bit• participant authentication against UBS via WAP similarly like via
Internet with agreement number, password and list-number• automatic connection release (Timeout) embedded
– after ten minutes without interaction participant is demanded to re-authenticate with password und list-number input
Deutsche Bank (Germany)• WTLS (Wireless Transport Layer Security)• end-to-end-encryption• data encryption already at the mobile phone• decryption at the server
WAP & Security
Sources: UBC.ch,db24.de
Mobile Communication and Mobile Computing287
WAP-Gateway Web-Server
Java-Servlet-APIWML
HTTP
Dir-X-wap
Dir-X-Servlet LDAP-Client
Server
LDAP/X.500-Directory-Service
LDAP
Server
WML-pages Profiles
WAP-example: access to enterprise data
Mobile Communication and Mobile Computing288
WAP-example: access to enterprise data
Example: Siemens Dir-X Meta-Directory Service as a base of a corporate information pool
• software-package consists of Directory Server (Dir-X-Metahub) and several Clients, is completely LDAP v3 compatible, based on X.500
• 2 Gateways outwards: Dir-X-Web and Dir-X-wap• secure access also via WAP available, because all security
properties of Directory-Servers are handed-on to mobile user• registration via phone number and password, the
authorizations/licenses are deposited within the system in user profiles
• Java-Servlets built the kernel components of WAP-connection Dir-X-wap-Server:• Servlet-components undertake communication with the Web-Server• LDAP-Client provides data exchange between the Dir-X-wap-Server
and the directory service
Mobile Communication and Mobile Computing289
WAP-example: access to enterprise data
Dir-X-Wap-Application:• consists of a set of WML-pages containing DSL• Dir-X-Servlet parses DSL-commands• 2 configuration files for an application necessary:
– Global Profile: contains information for the Servlet– Application Profile: stores the data that are necessary to
execution of WAP-application• In principle, each Web-Server is usable with the product,
it must only support the Servlets
DSL: Directory Script Language; Language for processing of directory requests from Web- or WML-pages and for representation of obtained results in WML or HTML, contains the language elements for LDAP-access
Mobile Communication and Mobile Computing290
WAP-examples
• Bond/Security-Order processing: Consors, Advance Bank, Deutsche Bank
• Mobile “Yellow Pages” – Orange Telecom• Mobile Timetable: wap.hafas.de• Mobile Auctioning: wap.yahoo.de, wap.ebay.de• Mobile „Last Minute Bargain “:
– 12snap at Vodafone, presently also with WAP
• Mobile marketplaces/stock exchanges (Mobile Brokerage):– http://www.heizoelboerse.de/– http://www.amazon.de/
Mobile Communication and Mobile Computing291
Bond/Security-Order
•Mobile Banking
•Mobile Brokerage
WAP-example: Bond/Security-Order
Mobile Communication and Mobile Computing292
Private Banking-> Login page
Other services ... Lufthansa, Sixt, etc.
WAP-example: Bond/Security-Order
Mobile Communication and Mobile Computing293
WAP-example: Bond/Security-Order
Main menu• Brokerage ...
Bond/security info
Mobile Communication and Mobile Computing294
WAP-example: Bond/Security-Order
Order book
• Status of bond transactions
• Executed and deleted orders are indicated in the order book for some days more
• Partial execution of some order is presented as one open and one executed partial order in the order book
• Details to an order could be indicated via dial-up of correspondent Links
Mobile Communication and Mobile Computing295
Portfolio review• Bond/security depots
WAP-example: Bond/Security-Order
Mobile Communication and Mobile Computing296
WAP-example: Bond/Security-Order
Brief queries
• exchange rates of Bonds/Securities with a delay of approx. 15Min
• search criteria– Bond/Security-ID and/or
– Bond/Security-name
Mobile Communication and Mobile Computing297
WAP-example: soccer/football score
source: http://www.wapgoal.com
Mobile Communication and Mobile Computing298
Further WAP-examples
soccer/football scores:
http://wap.goal.com
auctioning:
http://wap.12snap.com
miscellaneous:
http://wap.yahoo.com
Mobile Communication and Mobile Computing299
Input the address
...wait ...
WAP-example: timetable service
Input
-> English -> Query...
…wait ...
Mobile Communication and Mobile Computing300
Input the start & target
railway stations
...Dresden,
…Hannover
...scroll …
WAP-example: timetable service
Input
..date, time....
…scroll …
Mobile Communication and Mobile Computing301
After input …
search...
..wait..
WAP-example: timetable service
Selection of train connections with departure platform ...earlier/later...
then probably ->
END
Mobile Communication and Mobile Computing302
For comparison: PC-timetable service
Details
Options
PC-timetable service is still detailed!
Mobile Communication and Mobile Computing303
WAP-result• WML doesn’t bring whole Internet’s diversity to a mobile phone
• there are no satisfactory rate models at the moment; the data-rates are too low even with GPRS
• limited input and selection possibilities require a reconsidering of interaction semantics, WAP isn’t oriented for many applications, for instance catalogs with a large selection -> PDAs, appliances, voice input and -recognition
• with introduction of data services with higher data-rates WAP could lose its relevance possibly -> XHTML
• however WAP means a first step towards independence from PC by access to Internet contents -> multi-dimensional distribution channels for information
• WAP means the start for creation of a formidable user population (potentially all mobile radio participants)!
Mobile Communication and Mobile Computing304
WAP-Improvements: WAP2.0 (1)• New version
– Internet-based data services on mobile phones – approved by WAP Forum mid-2001– oriented to GPRS and 3G cellular/UMTS
• Useful services at WAP2.0 devices– color graphics and Pictograms– location-specific content, navigational functions and user-friendly
menus– animation representations and streaming media– Multimedia Messaging Service (MMS)– large-file downloading (music)– synchronization of user information with personal information
manager software on a desktop PC in a remote location
Source: http://www.wapforum.org
Mobile Communication and Mobile Computing305
WAP-Improvements: WAP2.0 (2)
• WAP 2.0 builds upon the latest Internet standards: – XHTML, TCP/IP, HyperText Transfer Protocol (HTTP/1.1) and
Transport Layer Security (TLS)– uses mostly TCP as transport – optimized for small low-performance end-devices
• WAP 2.0 supports additionally:– Wireless Telephony Application (WTA), Push, and User Agent
Profile (UAPROF) utilize more advanced features in WAP 2.0 than in WAP1.x
Mobile Communication and Mobile Computing306
WAP-Improvements: WAP2.0 (3)
• Application development – easier development of WAP applications
– More comfortable user environment
• Migration aspects– WAP2.0 offers a migration to XHTML (Extensible Hypertext Markup
Language) and TCP (Transmission Control Protocol)
– Supporting XHTML, WAP 2.0 reduces development costs, allowing developers to write applications for both PC and WAP
• Security– offers more secure due to “end-to-end encryption” (from the mobile
device to the server)
Mobile Communication and Mobile Computing307
WAP2.0 and i-mode
• Competition & Fusion– NTT DoCoMo's I-Mode is a serious competitor
of WAP2.0– NTT DoCoMo's I-Mode moves in the direction
of support of XHTML and TCP, too– I-mode and WAP2.0 will probably converge
Mobile Communication and Mobile Computing308
Based partially on the materials of NTT-DoCoMo
i-Mode
An overview
Mobile Communication and Mobile Computing309
Structure
Mobile Communication and Mobile Computing310
Overview• i-Mode is a product and a trademark of NTT-
DoCoMo• The enterprise NTT-DoCoMo started in February
1999 with a proprietary development: i-Mode, although NTT-DoCoMo is the member of WAP-Forum itself
• Meantime i-Mode has got a large number of registered users : over 33 millions
Source: http://www.nttdocomo.com
Mobile Communication and Mobile Computing311
Properties
• i-Mode is packet oriented– always online, no time delays to dial-up– billing regarding data volumes and not regarding to
time• simple page markup language – compact HTML
(cHTML)• End of 2002: change into XHTML (WAP 2.0)• a great success in Japan, because private computers
and private Internet access over fixed networks are infrequent
• In Germany E-plus has started i-Mode on 16th march 2002
Mobile Communication and Mobile Computing312
compact HTML• cHTML or compact HTML is a language subset
of HTML
• very simplified HTML
• Lists, Forms, Selections, Input fields are possible
• no Frames, no Tables, no CSS
• 166 additional pictograms, for instance
Fine
Motor sports WC
Heartbreak
Mobile Communication and Mobile Computing313
compact HTML (2)• Access key-Attribute for direct link activation respectively for direct
selection of input fields
• pictures can be displayed only in GIF-format, max. 5 KB per page. GIF-pictures mustn’t larger than 120*128 dots (little display)
• also animated GIFs
• 256 colours (capable of Display)
• Compact HTML Sites look like “normal” HTML, so also “normal” Browsers like Netscape can work with them
an i-Mode screenshot
i-Mode – on a mobile phone
Mobile Communication and Mobile Computing314
Network Configuration
Mobile Communication and Mobile Computing315
PDC:Personal Digital CellularTelecommunication System
PDC-P:PDC Packet System
BS:Base Station
IP:Information Provider
M-PGW: Mobile Message-Packet Gateway Module
MS:Mobile Station
M-SCP:Mobile-Service Control Point
NSP:Network Service Provider
PGW:Packet Gateway Module
PPM:Packet Processing Module
i-Mode network architecture
http://www.nttdocomo.co.jp/
IP
IP
i-mode Server
Connection Network
[NSP/Corporate LAN]
M-SCP PGW M-PGW
PPM PPM
BS
MS
BS
MS
BS
MS
BS
MS
Internet
PDC-PNetwork
Mobile Communication and Mobile Computing316
i-Mode network architecture (2)• i-Mode Server:
- consists of multiple server systems (B-,C-,M-Max ..), each server system is responsible for special tasks- represents the contents of „Information Providers“, operates Internet-Mail and i-Mode-Mail, enables the connection to Internet
• M-PGW (Mobile Message-Packet Gateway Module):transforms the protocols: TCP with i-Mode-Server and TLP (Transport Layer Protocol) with PPM
• PPM (Packet Processing Module):executes the packet connection with the mobile end-devices/peripherals
Mobile Communication and Mobile Computing317
i-Mode network architecture (3)• M-SCP (Mobile-Service Control Point):
authentication of user data (similar to voice communication)
• PGW (Packet Gateway Module):transition to other networks, for instance to offer the enterprises a Virtual Private Network (VPN)
Mobile Communication and Mobile Computing318
i-Mode protocol stack
RTCC MM
LAPDM
L1
TLP
AL (HTTP)
MS
CCRT MM
LAPDM
L1
PMAP
L2
L1
PPM
PMAP
L2
L1
PMAP
L2
L1
TCP/IP
L2
L1
TLP
UITP/NWMP
M-PGW
TCP/IP
L2
L1
UITP/NWMP
AL HTTP/SMTP
i-Mode ServerTLP:Transfer Layer ProtocolCC:Call ControlMM:Mobility ManagementRT:Radio Frequency Transmission ManagementLAPDM:Link Access Protocol on theD-Channel, modifiedPMAP:Packet Mobile Application Part
HTTP:HyperText Transport ProtocolSMTP:Simple Mail Transport Protocol UITP:User Information Transfer ProtocolNWMP:Network Management Protocol
TCP/IP: Transmission Control Protocol/Internet ProtocolL1:Layer1 (Physical Layer Protocol)L2:Layer2 (Data Link Layer Protocol)
Mobile Communication and Mobile Computing319
i-Mode protocol stack II• UITP (User Information Transfer Protocol):
transmits user information such as, for instance, MSN (Mobile Subscriber Number) to i-Mode-Server
• NWMP (Network Management Protocol):performs i-Mode Service-functions
• TLP (Transfer Layer Protocol): has a simplified transmission procedure and can transmit the signalization and user data together
Mobile Communication and Mobile Computing320
Java for mobile phones
• base: Java 2 micro edition and Java MIDP (Mobile Information Device Profile)
• downloading of Java-programs(ca. 30-50 kByte); color representation; applications, also games etc.
• billing via micro-payment of operator (ca. 1-5 € per application)
• products e.g. of Nokia, Ericsson, Siemens; support through big operators
Mobile Communication and Mobile Computing321
M-Commerce - applications
• Mobile Shopping
• Mobile Banking
• Mobile Brokerage
• Mobile Traveling
Mobile Communication and Mobile Computing322
Pervasive Computing
• Operation as parallel as possible of all users independent of the terminal, it means terminals with different equipment (PC‘s, mobile phones, PDAs, Applicances, etc.) should be supported by most different entrance nets
• It means finding a suitable system architecture for “multidimensional“ Internet communication (e.g. regarding end terminals) over *ML (Markup Languages)
Mobile Communication and Mobile Computing323
System architecture, one-dimensional
WWW-BrowserWeb Server
databases, etc.
Application Server
Thin Clients
Firewall Firewall
Mobile Communication and Mobile Computing324
Browser-Client
ThinClient
Transaction-monitors
businessSoftware
Mainframe-applications
data bases
Out
er F
irew
all
Inne
r F
irew
all
Web-Server
HTML-Dokumente
HTML-DokumenteHTML-
Dokumente
HTML-DokumenteHTML-
documents
HTML-documents
HTML-Dokumente
HTML-DokumenteHTML-
Dokumente
HTML-DokumenteCGI-
scripts
CGI-scripts
Application-Server
proprietaryprotocols
proprietaryprotocols
proprietaryprotocols
HTTP
Stateless-connection
stateful-connection
Internet Inter-ORB ProtocolSOAP (Simple Object Access Protocol)
System architecture, one-dimensional
Mobile Communication and Mobile Computing325
Properties of application servers
main characteristics:• object-oriented communication systems• component- framework• transaction concepts• security concepts• connection of legacy applications• integration of WWW-services• general support of design, deployment and runtime
Mobile Communication and Mobile Computing326
System architecture, two- dimensional
WAP Server
WWW-BrowserWeb Server
Data bases, etc.
Application Server
Thin Clients
WAP-Browser
FirewallFirewall
…e.g.:BEA WebLogic M-Commerce Solution
Mobile Communication and Mobile Computing327
Application Server + WWW Server
XSL-Prozessors
System architecture, two- dimensional
Backend
standardize access to Backend, create business logic
call data from the EJBs and generate e.g. XML
convert XML into HTML, WML
Servlets EJBs
WAP-Server
Mobile Communication and Mobile Computing328
design principles
use in the Internet
more powerful than HTML
separation of content and style
possibility of definition of user-specific document-types
ability of XML-document processing
XML (Extensible Markup Language)
Mobile Communication and Mobile Computing329
specialtags
reference toStyle Sheet File
XML- document „bibliography“
Mobile Communication and Mobile Computing330
XML-Documents can have a DTD (Document Type Definition).The DTD can be contained in the document or can be referenced by a link.
A DTD specifies, which tags are permitted and how these can be combined.It has a special meaning for the processing of documents.
The processing programs can check XML- documents for structural errors with the help of DTD. If there is no error then a document is valid!
Well-formed documents contain no DTD- reference, but fulfill the XML-syntax-rules.
Valid and well-formed documents
Mobile Communication and Mobile Computing331
RULE for root-element
Cycle
Insert of lower elements
Accompanying Style Sheet File
Mobile Communication and Mobile Computing332
Presentation in MS IE 5.0 correspondently IE6.0
Mobile Communication and Mobile Computing333
Other Style Sheet File
Mobile Communication and Mobile Computing334
Other presentation via XSL
Mobile Communication and Mobile Computing335
XML
XSL
XSL-Processor EDI/WML
presentationfor processing
EDI:Electronic Document Interchange
Change of XML- documents
• Conversion of XML- documents into workable formats (with the help of XSL-Style-Sheets)
• e.g. into EDI- formats for commercial data processing
• in the mobile field very interesting for conversion into WML!
Mobile Communication and Mobile Computing336
Application Server + WWW Server
XSL-Processors
System architecture, multidimensional
Backend
call data from EJBs and generate e.g. XML
convert XML into *ML
Servlets EJBs
Access-Server
Standardize access to Backend, create business logic
Mobile Communication and Mobile Computing337
IBM Websphere Transcoding Publisher
• syntax customization of content• easy installation• little administration effort• changeable, expandable architecture of components
Mobile Communication and Mobile Computing338
IBM Websphere Transcoding Publisher
WAP – capable mobile phone
7.Output of contents
1.Request over port xx
Evaluation of used profiles
Text Clipper:transforms HTML into WML
Fragmentation Transcoder:Change into WML-decks
&
Mobile Communication and Mobile Computing339
Oracle Application Server Wireless Edition
• syntactic customization of content• renewable, expandable architecture of components• good customization of specific content
RequestManager
MasterService
Adapter
Trans-former
Request Manager authentifies user and calls Master Service
ClientRequest
the adapter fetches the Information
(via e.g. HTTP, SQL,
etc.)
Master Service configures und starts an
adapter
A transformer converts
information in suitable Client-
format
Mobile Communication and Mobile Computing340
Oracle Application Server Wireless Edition
Expiry of a user request
Mobile Communication and Mobile Computing341
Oracle Application Server Wireless Edition
Adapter and Transformer
Mobile Communication and Mobile Computing342
Contents customization with XML / XSLT
• Separation of content and presentation• content client- independent in XML• XSLT: XSL transformations: a XML- data format is changed into a
new data format (not necessarily XML), this new data format can include platform dependent information about the presentation of data besides the main information
• presentation client- dependent in some XSLTs• XML-Support in many data bases • the server itself needs additional logic
Mobile Communication and Mobile Computing343
server-sided requests:• reconnaissance and classification of the client• choice of the suitable style sheets• parameter handover to XSLT• Processing of other documents (e.g. bitmaps)
Contents customization with XML / XSLT
Mobile Communication and Mobile Computing344
Example application: Pizza ordering service
• content and logic in same XML-document
• no presentation-semantic in XML, so all client- abilities can be used in XSLT
• but stylesheets are not reusable
Mobile Communication and Mobile Computing345
Example application: pizza ordering service
<?xml version='1.0' encoding="ISO-8859-1" standalone="no" ?><?xml-stylesheet type="text/xsl" href="Pizzaservices.xsl"?><?xml-stylesheet type="text/xsl" href="Pizzaservices.lynx.xsl" media="lynx"?><?xml-stylesheet type="text/xsl" href="Pizzaservices.lynx.xsl" media="palm"?><?xml-stylesheet type="text/xsl" href="Pizzaservices.wap.xsl" media="wap"?><?cocoon-process type="xsp"?><?cocoon-process type="xslt"?><xsp:page language="java" xmlns:xsp="http://www.apache.org/1999/XSP/Core"><xsp:logic>
class Item extends Vector {private int[] numbers;
public Item () {super ();numbers= new int[10];
}
public void setNumber (int nr, int a) {numbers[nr]=a;
}
public int getNumber (int nr) {return numbers[nr];
}}
...
Mobile Communication and Mobile Computing346
<services> <service> <name>Hi Pizza</name> <banner>hellopizza.jpg</banner> <description>Hot Ware on Order</description> <location zipcode ="01277"> <address>Bodenbacher Strasse 16b, 01277 Dresden</address> <phone>03512540707</phone> <fax>03512540708</fax> </location > <location zipcode="01127"> <address>Mohnstraße 50, 01127 Dresden</address> <phone>03518485590</phone> <fax>03518485558</fax> </location > <proposal> <category name="Pizza"> <food> <name>Pizza Kentucky</name> <description>Salami</description> <price size="Normal">8.00</price> <price size="Jumbo">15.00</price> <price size="Pan">10.00</price> </food>...
Example application: pizza ordering service
Mobile Communication and Mobile Computing347
Pizza ordering service: PC-presentation
Mobile Communication and Mobile Computing348
Pizza ordering service: presentation on Palmscape and in WAP
Mobile Communication and Mobile Computing349
XHTML
Mobile Communication and Mobile Computing350
XHTML
• XHTML™ 1.0 is Extensible HyperText Markup Language (Second Edition)– reformulation of HTML 4 in XML 1.0– use instead of WML2.0 correspondently cHTML (i-
Mode)– basis for integration between WAP2.0 and i-Mode
WWW: http://www.w3.org/TR/xhtml1/#xhtml
Mobile Communication and Mobile Computing351
XHTML
• supporting via as well as WAP-Browsers also Netscape Navigator and Internet Explorer
• constituents:– DTD (Document Definition)– XSL (Extensible Stylesheet Language)
• large quantity of supported tags in comparison with WML2.0 and cHTML– CSS– frames– tables– forms/input fields– applet calls
Mobile Communication and Mobile Computing352
XHTML vs HTML
• XHTML describes data <-> HTML displays data! • XHTML – combining HTML and XML, and their
strengths• XHTML is oriented to internet/PC and mobile
internet/ mobile phones and hand helds• XHTML - compatibility
– everything has to be marked up correctly -> "well-formed" documents
– pages can be read by all XML enabled devices– upgrading of XML supported browsers– compatibility to all browsers– backward browser compatible
Mobile Communication and Mobile Computing353
Mobile agents
Mobile Communication and Mobile Computing354
The agent- model
• an agent-system consists of the agents themselves and an execution engine for working with agents. The execution engine offers basic services to the agents
• Agent is an independent program generally, it consists of data, code and execution state, it works in interest and order of a third party (e.g. user, application).
Mobile Communication and Mobile Computing355
Hardware
OS
Hardware
Operating systemHardware
Operating System
Agent system
Network
place 4
Place 3
Place 1
place 5
Mobile Communication and Mobile Computing356
Agent model
• migration: transfer of code, data, state• local interactions with server• transfer of the result
migrationClient
create Agentcode,data,
state
simpleServer-
interface
Clientresult Agent
code,data,
state
simpleServer-
interface
Mobile Communication and Mobile Computing357
Properties of mobile agents
Advantages: + reduction of network load
+ autonomy and asynchronity
+ dynamic adapting in environment
+ heterogeneity
+ robustness and error tolerance
+ scalability
+ personalization and individualization
+ dynamic code-installation
+ encapsulation of protocols
Disadvantages: – need of special execution
engine (Middleware)
– high security requirements
– transfer of code, data, state
– Decision: migration vs. remote communication
Mobile Communication and Mobile Computing358
Applications
• E-commerce• database requests• intelligent e-mails• Office applications/workflow• traffic telematic• Web surfing• load balancing • virtual enterprise• Mobile computing
Mobile Communication and Mobile Computing359
Existing agent systems
• Voyager (ObjectSpace)• Aglets (IBM)• Concordia (Mitsubishi Electric)• Grasshopper (IKV++)• Odyssey (General Magic)
• Mole (Stuttgart), Ara (Kaiserslautern)• Agent TCL (Dartmouth University)• MASIF (OMG)• Telescript
Mobile Communication and Mobile Computing360
Middleware for spontaneous Networking
Mobile Communication and Mobile Computing361
Vision
JINI UPnP
• spontaneous networking of electrical devices (but not only computers)
• very simple connection• platform independence
Mobile Communication and Mobile Computing362
JAVA Intelligent Infrastructure, JINI
• „Middleware“ for spontaneous networking; originally developed from Sun
• JINI Connection Technology enables dynamic control of networked services and devices
• Partitioning into so called Lookup Groups: different sets of lookup-services
• basic operations:– Discovery: offers locating of a directory services (lookup
service)– Join: enables acquaintance/ registration of the services
implemented from some device
Mobile Communication and Mobile Computing363
JAVA Intelligent Infrastructure, JINI
• Lookup-Service enables locating of services via other users/devices per lookup-operations
• Leasing offers time-limited allocation of resources (using of services)
• Jini integrates distributed events processing and distributed transactions further on for co-ordination between services
Mobile Communication and Mobile Computing364
Lookup service
JINI device / service
Client
Discovery & join
protocol Discovery lookup
General procedure: step 1
Mobile Communication and Mobile Computing365
Lookup Service
JINI device / service
Client
Proxy uploadProxy download
General procedure: step 2
Mobile Communication and Mobile Computing366
JINI device / service
Client
Direct Connection
General procedure: step 3
• synchronization• data exchange between Device and Client
over own communication protocol
Mobile Communication and Mobile Computing367
JINI - Details
• Proxy hides all details of communication and is executed in the form of Client (dynamic installation of Stubs)
• security over RMI - Security Extension Framework• new versions of JINI Starter Kits include advanced possibilities, for
instance:– Caching of request results by Clients
– unicast-discovery
– comfortable control of using period (lease)
– asynchronous receiving of events among other features
• further development via JINI Community:– for instance JINI Surrogate Architecture: supports devices that do not
have all required resources for JAVA and JINI
– printer working group
Mobile Communication and Mobile Computing368
JINI - Assessment
• suitable to support scenarios from the field of Ubiquitous/Pervasive Computing
• JINI is a part of JAVA 2 Micro Edition
Mobile Communication and Mobile Computing369
Universal Plug and Play, UPnP• reply of Microsoft to JINI• Embedded in UPnP- forum• with this improvement corresponding to Plug- and- Play
Standards, the PC peripheral devices should be connected to a home-network problem-less
• via Universal Plug and Play diverse devices can communicate with each other like with Jini
Mobile Communication and Mobile Computing370
Universal Plug and Play, UPnP
• essentially based on open standards like TCP/IP and therefore is compatible to each network
• in Windows ME integrated• a special toolkit for creation of drivers on the basis of
UPnP developed by INTEL
Mobile Communication and Mobile Computing371
Home application
Universal PnP
Bus attached
(ISA,PCI,USB,
IEEE,1394,IR,..)
Discovery Description Usage
Internet Protocol attached
Network media(Ethernet,HomeRF,
HomePNA,..
IrDA X10
IR PLC
..
..
Common Abstrac-
tions
Common Interfaces
Media Indepen-
dence
UPnP architecture
Mobile Communication and Mobile Computing372
Further approaches
HAVi – Home Audio and Video Interop.• essentially supported by the vendors of consumer-electronics field• UPnP Forum is interlocked however represented more broadly on
the market (specially also in computer-industry)
HomePlug• consortium for standardizing of data communication over (low
voltage) power cable• performance like by IEEE 802.11b
• the members are among others Cisco and Panasonic
Mobile Communication and Mobile Computing373
Services and system support for Mobile Computing
Mobile Communication and Mobile Computing374
Mobile Computing: system support
Essential properties und requirements:
• dynamics, localization
• heterogeneity of networks and end-devices
• security problems
Mobile Communication and Mobile Computing375
Product Data
Main officeCaching
ClientLAN-Access
Maintenance technician
- very different performance and charges: GSM, ISDN, LAN
Software-technical, automatic adaptation to concrete system environmentExample: Access to picture data/compressed picture
data/graphics/text
Mobile Access
Local Resources,Error Protocols
Mobile distributed applications: example
Mobile Communication and Mobile Computing376
Problems and requirements
Problem fields:
• dynamic system and net configuration
• dynamic change of Quality-of-Service-properties
• uncoupling/re-connection
• transparency of resource access
• security aspectsRequirements:
• connection monitoring and selection
• treatment of uncoupling/off-sets and migration; emulation of services
• configuration update
• localization of mobile servers and clients
• advanced security and transaction services
Mobile Communication and Mobile Computing377
Mobile RPC
Goals:• Mobile Binding
– Transparent call to an alternative server by non-accessibility
• Datagram RPC– Queuing of calls in disconnected status
• Queued RPC– intermediate storage and delivery of results after re-coupling
Realization:• Attachment on existent RPC- systems (without new implementation
or internal code changes)
Mobile Communication and Mobile Computing378
Decoupling
Net connection
RPC reaches Server
Return to Client
Time Behavior Datagram RPC
T1 T2 Time T3 T4
•Client
•Server
•DCE RPC
•Datagram RPC
Mobile Communication and Mobile Computing379
Message Queuing: MQ Series example
• Base: Messages, Queues with Queue Manager• dynamic coupling between applications and local Queues via
logon/logoff • using of Queues for transmission or receiving; also mixed using is
possible• coupling of distributed Queue Managers via Message Channels• Internet Gateway, C++- and Java-Support• support of essential operating system platforms
Mobile Communication and Mobile Computing380
Example scenario
• decoupling of application through Queue Manager:– Message forwarding is possible even if application
isn’t running
Computer A
Queue Manager
Queue Manager
App-lication
1 MQPUT
MQGET
Computer B
Queue Manager
Queue Manager
App-lication
2MQGET
MQPUT
MessageChannel
Mobile Communication and Mobile Computing381
N:M - communication
A
B
C
D
EQueue, with
optional support of message priorities
Access to Servervia multiple Clients
• Load balancing (selective delivery) or
• Parallel processing (replicated delivery)
Mobile Communication and Mobile Computing382
Message Queuing: Assessment
Advantages+ simple manageability+ robust message delivery + flexible application fields (for instance load balancing,
parallelization, batch-transmission of branch data etc.)+ relevant for easy coupling of programs, for instance via Internet,
or for Mobile Computing
Disadvantages− limited communication semantics− interaction model is different than with procedures/method
invocations− limited accessibility of higher services− only several proprietary decisions up to now, only step-by-step
standardization
Mobile Communication and Mobile Computing383
Ethernet
Ethernet
Ethernet
E-Fax-OrderE-Fax-Order
ManagementDB-Access
ManagementDB-Access
FirmBranch office
Client X
GSM
xDSL
Application
Resource
Mobile Station
Communication path
DBDistributed Database
Distributed Database
Cache
Application Structure
Mobile Communication and Mobile Computing384
Domain-concept
Mobile Communication and Mobile Computing385
Main functionality: Domain and Station Manager
Domain Manager:• management of all global objects (users, global
available resources, stations, net topology)
Station Manager:• management of all local objects of a station (net
access, running applications etc.)
Mobile Communication and Mobile Computing386
Architecture of Station Manager
Authentication and Encryption Service
Application
Subsystem(Application Programming Interface)
Subsystem
(System Calls)
Location Service
Application Data Mobilizer and Manager
Registry Service
Bandwidth and CostManagement Service
Disconnected Operation Handling Service (CS, QS, CHS, BMC)
Active Database
Resource Broker
Mobile Communication and Mobile Computing387
Mobile Multimedia Email: message transfer
User Agent
Message Store
Email Proxy
Queuing Service
Subsystem
Queuing Service
message transferMobile Enhanced Message Handling
System
em
ail
pro
toc
ol
email protocol
email protocol
Mobile Communication and Mobile Computing388
Mobile Multimedia Email: selection of quality parameters
Cent Cent
Mobile Communication and Mobile Computing389
Mobile File Manager: example CODA
• distributed file system, which offers the unbreakable access to data also in the case of server shut-down or net failure
• developed at the Carnegie Mellon University• based on AFS (Andrew File System, distributed
file system in UNIX-environment)• relatively transparent to the applications
Mobile Communication and Mobile Computing390
CODA overview
• based on the model of „Disconnected Operations”• client keeps Read- and Write-access on the data via
inset of a local buffer (Cache) also during temporary disconnection from net
• with re-connection system forwards changes and recognizes potential conflicts
• for different operating systems available (for instance LINUX, Solaris, Windows)
Mobile Communication and Mobile Computing391
CODA system model
Replicated Server:High availability
Net communicationat file open and close
Client(“Whole-File-Caching”)
Disconnected Client:local data accesson Cache
Mobile Communication and Mobile Computing392
properties of consistence (Coda)
• Callback– logic reference from server to the active client, used for
immediate information about file changes via other client
• after connection failures the file in client cache remains valid till to timeout termination (as a rule several minutes)
• thereby reduced consistency• conflict processing explicitly in interactive form, however
low conflict probability
Mobile Communication and Mobile Computing393
Conflict processing (CODA)
• extensive automation as objective purpose, however isn’t possibly for:– Update/Update-conflict: independent double update of the same
file– Delete/Update-conflict: independent erasure respectively update
of the same file– Name/Name-conflict: generating of two files with the same name
Manual access after user notification
Mobile Communication and Mobile Computing394
Cache management (Coda)
• “Cache-Misses”: searched file isn’t in the Client-Cache– processing failure in the disconnected status
• priority list of important files per user– the highest priority is always kept in the cache (for instance
by system programs, user profiles, address files etc.)– other priorities: exchange strategies correspondent to
importance– dynamic generated files via list of essential operations
referenced (for instance actual test protocol etc.)
Mobile Communication and Mobile Computing395
File synchronization under Windows
- Windows: over System Control -> Management -> Services so called „file replication (server)“ for synchronization of data between different servers
- under Explorer -> Extras -> Synchronization: - Synchronization of own Homepage with PC - Synchronization of Sites in WWW
Mobile Communication and Mobile Computing396
E-Hand
http://www.ehand.com/ehand/
- connects existing Enterprise Systems with mobile end-devices
- platform independent- very simple synchronization and data transfer- supports XML, ODBC and SyncML
Advantages:
- contains Web-similar user interface for application installation and for mobile participants
Mobile Communication and Mobile Computing397
E- Hand
Mobile Communication and Mobile Computing398
Motivation:
• SFA-Sales-force-automation:
-> actual information about clients, competitors and market trends to the field (outside-) workers
• emergent business transactions on the site -> efficiency increasing
Example:
Pharmaceutical Industry
• visit of 6 up to 8 distribution medics per day
• to bring dialogue to the point more quickly– previous information about the medic (contacts, receipt prescription habits)
are recallable from the firm-net
• presently still manually due to dialogue recording and product documentation
• in the future via mobile databases permanently faster access to data without inconvenient storage, connection establishment etc.
Mobile databases support
Mobile Communication and Mobile Computing399
• mobile databases offer principally data synchronization and replication of enterprise servers and for mobile end-devices like PALM etc.
• due to increasingly mobile business processes there is a necessity of databases, which must perform these functionalities among other things:– quickly– compatible to as many as possible mobile systems
• 2 mobile database types:– “asynchronous synchronization”: for instance SQL Remote of Sybase
• data replication between central database and multiple remote databases• also offline-working is possible due to email-queuing principle (sent, if connected)
– “synchronous synchronization”: for instance Sybase Mobilink Synchronization Server
• co-operation with databases of other vendors (via Server Middleware)• permanent connection necessary, for instance via GSM
Mobile databases support
Mobile Communication and Mobile Computing400
IBM DB2 Everyplace
• compatible for instance to Windows CE, PalmOS, EPOC ...• footprint: ~150 k (storage requirements)• for data balancing DB Everyplace Sync Server is necessary
– synchronization with other Handhelds without PC!
• includes so called Mobile Devices Administration Center enables central management of all mobile end-devices of a enterprise
• supports integration of enterprise data from different databases and other sources (DB2 replication technology, JDBC, Adapter API for customized decisions)
• data are encrypted during synchronization (56 or 128 Bit)• supports automatic conflict processing
Mobile Communication and Mobile Computing401
IBM DB2 Everyplace
Source: http.//www.ibm.com
SynchronizationServer
Backend
IBM DB2Microsoft
OracleInformixSybase
Other DBMS (JDBC)
Mobile Devices
Mobile Communication and Mobile Computing402
Oracle Lite
• 3 constituents:– Oracle Lite DBMS
• database with low footprint (storage requirements)• Java-enabled
– iConnect• components for synchronization and creation of messaging-
applications (principle of message queues)
– Web-to-go• components supporting development, deployment and
management of mobile Web-applications
Mobile Communication and Mobile Computing403
Oracle Lite
replication via Internet
File-based replication
Mobile Communication and Mobile Computing404
Sybase SQL Anywhere Studio
• mini-database, can be operated on the PDAs• supports PalmOS, EPOC and WindowsCE• small „footprint“: ~50kByte• developer can adapt the database according to the required SQL-
properties, modular design principle• synchronization enables data balancing with the enterprises
database, all well-known database vendors are supported• only the changed data are transmitted• both local (for instance B. Hotsync (Palm)) and remote
synchronization supported• architecture similar to IBM DB2 Mobile Connect
(Source: http://www.sybase.com/products/anywhere/)
Mobile Communication and Mobile Computing405
Further approaches
• Microsoft Mobile Information Server
• Lotus Everyplace
• numerous further products, mostly similar architecture concepts
Mobile Communication and Mobile Computing406
Further sample applications
• Traffic management• Mobile Information Services• M-Commerce
• Service technician• Customer consultant• Field workers in general• Environmental engineering (measurement data logging)• Medic (visits on site)
Mobile Communication and Mobile Computing407
Traffic management
Services:• Traffic engineering• Travel information• Maintenance service • Mobile Office
Paris
Berlin
Dresden
Service Center
“Local” Provider
“Global” Provider
Mobile Communication and Mobile Computing408
GPSGSM
Internet
PSTN/ISDN
End-user Distributed Service-Center
Distributed Information services
VirtualPrivate
Network
Center A
Center B
Information Provider
Info
InfoInfo
InfoInfo
Info
Traffic management
Mobile Communication and Mobile Computing409
PrinterHost
Notepad HUB PC Terminal
Application scenario: car maintenance
Mobile Communication and Mobile Computing410
Client
Client (mobile)low battery resource
Server for instance WWW
low band width
Online-information services
• Client/Server-access by individual requests• additionally: separate broadcast-channel from Server to the mobile
Clients: transmission and caching of frequently requested information; thereby lower battery consumption (receiving less expensive as sending for the Client)
Mobile Communication and Mobile Computing411
Optimization: basic concept
• information in Publication-Group: regular Broadcast
• information in On-Demand-Group: Client/Server-queries
• exchange between both groups on the basis of:– access frequency (for instance on WWW-pages)– page modification frequency– channel bandwidths– clients storage volumes (Cache)
Mobile Communication and Mobile Computing412
Mobile e-Mail
Quelle: http://www.eudora.com
• Eudora Internet Suite, consists of:– Eudora email for the Palm computing platform– EudoraWeb browser for the Palm Computing platform– Eudora Mail Conduit
• Properties:– Eudora and EudoraWeb browser support SSL (Secure Sockets
Layer) and TLS (Transport Layer Security), i.e. end-to-end security
– synchronization of bookmarks between PC Web-Browser and EudoraWeb browser via Eudora Web Conduit
– synchronization with PC-Email applications– several Email-accounts
Mobile Communication and Mobile Computing413
Alternative M-Commerce applications
• 12snap.de (pronounciation: “one two snap”)– Auctioning channel
• www.paybox.de– Cashless payments
Mobile Communication and Mobile Computing414
Sample: 12snap system architecture
mobile radionet D2
center
Offers viaCellularBroadcast
externalprovider
Internet
Call Center
Automatic processing of the orders whichare incoming viaphone-service; also coupling of WAP and telephony
Users are registered by 12snap and enable direct debit, respectively booking via the credit card;Orders are sent to a Call-Center via keyboard tone, clientidentification takes place via his phone number(CLIP = Calling Line Identification Presentation)
Mobile Communication and Mobile Computing415
Sample: paybox.net
• Client is registered in the Internet by paybox.net and enables direct debit
• Client obtains as a result so called Paybox-PINs; using Paybox-PIN client can unblock the transactions
• purchase payments in the Internet are carried out as follows:– Client selects „Paybox“ as a payment type– Merchant sends transaction to Paybox-provider via secure data
connection – Provider dials up the clients via phone numbers stored in his
master data– then Client can unblock the transaction with his PIN– Paybox transfers money via direct debit and forwards it to the
Merchant