Mobile Communications Wireless Telecommunication Systems · transmit power 5mW to 15W Mobile...

Mobile CommunicationsWireless Telecommunication

SystemsSystems Generation 1 (1G) Generation 3 (3G) Generation 2 (2G) Generation 2.5 (2.5G)

Generation 4 (4G) TETRA

Mobile Communication Wireless Telecommunication 1

History

o Mobile Communication: transmission of signals and b t t ti f hi h t l t i bilmessages between stations from which at least one is mobile

o Goes back to the 1920’s: public wireless radio system operated by the train in Germany (Reichsbahn)p y y ( )

o 1946 first portable mobile telephone in the US: 18kg, 8min. battery life1957 fi t bil t l ti t i Go 1957 first mobile telecommuncation system in Germany (nowadays called PLMTS stands for Public Land Mobile Telecommunications System) so called A-system, manually switched, 137 calling zones

o 1972 start of operation of the B-System, automatic switching, but separate phone number in each calling zone (i.e. one hadbut separate phone number in each calling zone (i.e. one had to know who is where, if that one is to be called)


History

o 1981 first analog cellular system with fixed number for b ib t ti h d b t ll NMT 450 isubscribers, automatic handover between cells. NMT 450 in

Scandinavia. This is sometimes called 1st generation (1G).o 1981 C-Netz in Germany, analog, in operation until 2001y, g, po 1982 work begins on a standard for a pan-European digital

PLMTS which offers new services (SMS, call forwarding, …) by Group Speciale mobile (GSM)by Group Speciale mobile (GSM)

o 1987 "Memorandum of Understanding" signed by 18 countries to deploy „GSM“ (now “Global System for Mobile Communication”). In 1988 the standards were taken over by ETSI (European Telecommunication Standards Institute). This is a system of the 2nd Generation (2G)y ( )

o 1992 first GSM networks in operationo 1993 one million subscribers to GSM


History

o 1998 introduction of GSM 1800o 1999 Wireless Application Protocol (WAP)o 1999 HSCSDo 2000 GPRS Generation 2 5 (2 5G)o 2000 GPRS, Generation 2.5 (2.5G)o 25.9.2002 first operation of a 3rd Generation (3G) network in

Europa (UMTS) in Austriao 2006 NTT DoCoMo starts 4th Generation (4G) trial network in

in Yokosuka in Japan. Maximum transmission rate 2,5 Gigabit pro Sekunde.pro Sekunde.

o 2007 4G trial networks with100 Gigabit/s at 10 km/ho First 4G-Networks on the Basis of LTE (Long Term Evolution)

in 2011


Main characteristics of different generations

o Generation 0 (0G): calling zones, no handover

o Generation 1 (1G): analog, uniform subscriber number handover between cellsnumber, handover between cells

o Generation 2 (2G): fully digitalo Generation 2.5 (2.5G): data transmission

G ti 3 (3G) b d b d di it lo Generation 3 (3G): broad band digital

o Generation 4 (4G): all IP based, broad band, higho Generation 4 (4G): all IP based, broad band, high speed


Generation 1 (1G)

o wasn’t the beginning of mobile communication, but the b i i f ll l ith h d d i b tbeginning of cellular with handover and roaming between some network operators

o analog transmission of user channels, mostly for speech onlyg , y p yo already digital signalling for switching purposeso no dominant standard:

o Nordic Mobile Telephone NMT-450 und NMT-900o Total Access Communication System (TACS), Japan, GBo Advanced Mobile Phone Services (AMPS) in USo Advanced Mobile Phone Services (AMPS) in USo C-Netz (Germany)o Radiocomm 2000 (France)( )


Generation 1 (1G)

Example C-Netz (Germany)

o Technical features:o speech and signalling is transmitted in parallel (in band)o speech and signalling is transmitted in parallel (in band)o speech from 300 to 3400 Hzo downlink 461,30 to 465,74 MHzo uplink 451,30 to 455,74 MHzo duplex separation10 MHzo channel separation 20 kHz (222 channels)o transmit power 5mW to 15W


Generation 1 (1G)

cell radius 2km – 20km

cell around base station

switching system


Generation 1 (1G)

o Sender divides speech signal into blocks of 12 5 msinto blocks of 12,5 ms

o compression of the blocks results in extra time slots of 1 1 ms1,1 ms

o extra time slots are used to transmit signalling information, e.g. handover, …

o Receiver separates signallingdata from speech anddata from speech and decompresses the signal


Generation 1 (1G)

o Already in the first generation the smallest part of the transmission path is done wirelessis done wireless

cellular userair interface

core network

Hand n t erHandynutzer

fixed networkcore network

gateway

Mobile Communication Wireless Telecommunication 10Generation 1 (1G)

Generation 2 (2G)

o digital for user traffics and signallinghi h it id t th 1Go higher capacity, wider spectrum than 1G

o hierarchical cell structure:


Generation 2 (2G)

Main standards

o Global System for Mobile Communication (GSM)o Digital AMPS (D-AMPS)g ( )o IS-95o Personal Digital Cellular (PDC)


Generation 2 (2G) - GSM

o Global System for Mobile Communication (GSM) is the most successful cellular system worldwide >80% market sharecellular system worldwide, >80% market share

o 1988 first trials of GSM, 1991 first network in operationo 1993 first milliono 1993 first implementations outside Europe (Australia, New Zeeland,

Hongkong)o 2011 approx. 5 million subscribers (http://www.gsmworld.com)pp ( p g )o Coverage map (http://www.gsmworld.com/roaming/gsminfo)o Operations in different bands, e.g. 450MHz, 850MHz , 900MHz,

1800MHz 1900MHz1800MHz, 1900MHz, …o Roaming contracts between operators result in a single world wide

network



Coverage by China Mobile

source: GSM Association



Coverage by AT&T Mobile




Coverage by Radiomovil (Mexico)




Coverage by E-Plus (Germany)



Generation 2 (2G) – GSM – system architecture

VLR HLR

fixed network, BSC

VLR HLR

,BSC(G)MSCCore Network

BTS

Core Network(CN)

Base Station Subsystem (BSS) =Radio Access Network (RAN)


( )

Generation 2 (2G) – GSM components

Mobile StationMS

Mobile Station

o max. transmit power is 2-20Wo MS only works with a SIM (Subscriber Identification Module):o MS only works with a SIM (Subscriber Identification Module):

o smart card with memoryo identifies the subscriber in the networko can store personal data such as address booko can be protected by PIN



Base (Transceiver) StationBTS

Base (Transceiver) Station

o is the “opposite” of the MSo is close to the center of a cello is close to the center of a cell



Base Station ControllerBSC

Base Station Controller

o supervises several base stationso frequency allocationo frequency allocationo handover functionality



(Gateway) Mobil Switching Center(G)MSC

( y) g

o Interface to the fixed networko Complete switching system with all necessary routingo Complete switching system with all necessary routing

functionality to switch connections within the system and the outsideContains all relevant data for each of the subscribers of theo Contains all relevant data for each of the subscribers of the network that operates this (G)MSC



Home Location Register

o is the “home” of a subscriber (actually the SIM)

HLRHome Location Register

o s e o e o a subsc be (ac ua y e S )o contains all relevant data of all subscriberso permanent data, e.g.:

o IMSI (International Mobile Subscriber Identification Number)is not identical with phone number

o shared secrets (keys)o shared secrets (keys)o information about supplementary services of each subscriber

o temporal data, e.g.o address of the current VLRo destination for call forwarding



Visitor Location Register

o contains all relevant data of a subscriber currently within a MSC

VLRVisitor Location Register

o co a s a e e a da a o a subsc be cu e y a SCo temporal data are somewhat different from HLR, e.g.

o TMSI (Temporal MSI), use for confidentiality reasons, so that th IMSI d ’t h t t itt d th i i t fthe IMSI doesn’t have to transmitted on the air interface several times


Generation 2 (2G) – GSM frequency

o 35 MHz bandwidth = 175 x 200 Khz channels (FDMA)8 h l (TDMA)o 8 users per channel (TDMA)

880 - 915 Mhz (uplink)

925 - 960 Mhz (downlink)

891,0 Mhz channel 45

891,2 Mhz ...



,

...


Generation 2 (2G) – GSM TDMA

1710 - 1785 Mhz (uplink)

1805 1880 Mh (d li k)1805 - 1880 Mhz (downlink)



o access to a frequency band is only allowed duringcertain times (time slots)certain times (time slots)

o a mobile station may have a slot in a TDMA frame

MS A

6 7 0 1 2 3 4 5 6 7 1 0

MS A

TDMA frame 4,615 ms



o A mobile station is allocated to the same TDMA time slot for uplink and downlink however uplink and downlink are shifted by 3 slotsand downlink, however, uplink and downlink are shifted by 3 slots, advantages:

o no sending and receiving at the same timeo less energy consumptiono less cost

Time Division Duplex0 1 2 3 4 5 6 7 10 2 3 downlink

6 7 0 1 2 3 4 5 6 7 0 5 uplink



o energy built up and down at the antenna (data burst)

dB

+4

6-6

-3030

-70 (148 bits)

28 s 28 s 542.8 s



structure of a „Normal Burst“ in a time slot:

UserData57 Bits

UserData57 Bits

TrainingSequence26 Bits

T3

T3

S1

S1

GP8,25

148 Bits = 546.12 s

T (Tail Bits)S (Signalling/User Data)( g g )GP (Guard Period)



other bursts:other bursts:


Generation 2 (2G) – GSM Hierarchy of frames


Generation 2 (2G) – GSM Physical vs. Logical channels

o Physical channels are formed by all the available time slots in a BTS If the BTS uses 6 frequency bands (carriers) the there areBTS. If the BTS uses 6 frequency bands (carriers), the there are 48 physical channels.

o The logical channels are a structure on top of the physical ones. One physical channel may carry several logical channels. Each logical channel performs a specific task

Logical channels:Logical channels:o Speech traffic channels (TCH)

o Full-rate TCH (TCH/F)o Half-rate TCH (TCH/H)

o Broadcast channels (BCH)Frequency correction channel (FCCH)o Frequency correction channel (FCCH)

o Synchronization channel (SCH)o Broadcast control channel (BCCH)


o oadcast co t o c a e ( CC )

Generation 2 (2G) – GSM Physical vs. Logical channels

Logical channels (cont.):C ll b d t h l (CBCH)o Cell broadcast channel (CBCH)

o Common control channels (CCCH)o Paging channel (PCH)o Paging channel (PCH)o Access grant channel (AGCH)o Random access channel (RACH)

o Dedicated control channel (DCCH)o Slow associated control channel (SACCH)

Stand alone dedicated control channel (SDCCH)o Stand-alone dedicated control channel (SDCCH)o Fast associated control channel (FACCH)


Generation 2 (2G) – GSM Synchronization

Synchronization of an MS with a network (procedure lasts 2-20 sec)BTS FDMA i ( l t 200kH b d)o BTS uses an FDMA carrier (one complete 200kHz band) as a base channel

o On this channel the BTS transmits with maximum power, i.e. pevery single time slot in a frame is filled, most of them with a dummy burst

o The MS looks for a FCCH on this base channelo The MS looks for a FCCH on this base channelo If the FCCH has been found the MS can synchronise on

frequency and time and look for the BCCH in the same frequency band.

o BCCH contains information, e.g. for describing the current control channel structure and other information about the network andchannel structure and other information about the network and how to gain access


Generation 2 (2G) – GSM Location update

MS BTS BSC MSC VLR HLR

Channel request

MS BTS BSC MSC VLR HLR

Channel activation command

Channel Activation k l dacknowledge

Channel assignment

Location update requestLocation update requestAuthentication request

Authentication response p


Generation 2 (2G) – GSM Location update (cont.)

MS BTS BSC MSC VLR HLRMS BTS BSC MSC VLR HLR

Comparison of Authentication parametersp

Assignment of the new area and the TMSI

Acknowledgement of the new area and the TMSI

E t f th dEntry of the new area and TMSI into VLR and HLR

Channel releaseChannel release


Generation 2 (2G) – GSM MOC

Mobil-Originating-Call (MOC)

Channel request

MS BTS

Channel request

Channel assignment

Call establishment request

A th ti ti tAuthentication request

Authentication response

Ciphering command

Ciphering complete (now ciphering)

Setup message, indicating the desired number

Call proceeding, the network routes the call to the desired number


Generation 2 (2G) – GSM MOC (cont.)

Mobil-Originating-Call (MOC)

MS BTS

Assignment of a traffic channel for theAssignment of a traffic channel for the user data

Assignment complete, from now on all messages are exchanged on traffic channelmessages are exchanged on traffic channelAlerting, the called number is not busy and the phone is ringing

Connect the called party accepted the callConnect, the called party accepted the callConnect acknowledge, now the call is active and both parties can talk to each other

Exchange of speech dataExchange of speech data


Generation 2 (2G) – GSM Handover

o If an MS in operation moves from one cell to another, a handover procedure takes placeprocedure takes place

o The BTS tells the MS on the base channel a list of channels of neighbouring cells

o The MS constantly measures the signal levels for these channels of neighbouring base stations

o The signal levels of the own cell and those of the neighbouringo The signal levels of the own cell and those of the neighbouring cells are reported back by the MS to the own BTS

o If handover is necessary, i.e. the signal quality of a neighbouring cell is significantly better than the own one, handover will be performed


Generation 2 (2G) – GSM Handover (cont.)

receive levelBTSold

receive levelBTSnew

HO_MARGIN

MS MS

BTSold BTSnew



Types of handover

MS MS MS MS

12 3 4

MS MS MS MS

BTS BTS BTSBTS

MSC MSC

BSC BSCBSC1 – Intra-Cell2 – Inter-Cell3 – Inter-BSC3 Inter BSC4 – Inter-MSC



Handover procedure

BTS BSCBSC MSCMS BTSBTSold BSCnew

measurementresult

BSCold MSCMSmeasurementreport

HO decision

BTSnew

HO decisionHO required HO request

resource allocation

HO access

ch. activation

ch. activation ackHO request ackHO commandHO commandHO commandHO access

Link establishment

HO completeHO completeclear commandclear commandclear command

clear complete clear complete


Generation 2 (2G) – GSM Services

o GSM offers three service domainsB S io Bearer Services

o Telematic Serviceso Supplementary Serviceso Supplementary Services


Generation 2 (2G) – GSM Bearer Services

o Telecommunication services to transfer data between access pointsS ifi ti f i t th t i l i t f (OSI l 1 3)o Specification of services up to the terminal interface (OSI layers 1-3)

o Different data rates for voice and data (original standard)o data service (circuit switched)o data service (circuit switched)

o synchronous: 2.4, 4.8 or 9.6 kbit/so asynchronous: 300 - 1200 bit/s

o data service (packet switched)o synchronous: 2.4, 4.8 or 9.6 kbit/s

asynchronous: 300 9600 bit/so asynchronous: 300 - 9600 bit/s

o In 2.5G much higher data rates are possible, will be covered latero In 2.5G much higher data rates are possible, will be covered later


Generation 2 (2G) – GSM Tele Services

o Telecommunication services that enable voice communication via mobile phonesmobile phones

o All these basic services have to obey cellular functions, security measurements etc.

o Offered serviceso mobile telephony

primary goal of GSM was to enable mobile telephony offering theprimary goal of GSM was to enable mobile telephony offering the traditional bandwidth of 3.1 kHz

o Emergency numbercommon number throughout Europe (112); mandatory for all service providers; free of charge; connection with the highest priority (preemption of other connections possible)

o SMS (Short Message Service), alphanumerical short messages for the display at the receiver mobile phone


Generation 2 (2G) – GSM Supplementary Services

o Services in addition to the basic services, cannot be offered stand-alonealone

o Similar to ISDN services besides lower bandwidth due to the radio link

o May differ between different service providers, countries and protocol versions

o Important services:o Important services:o identification: forwarding of caller numbero suppression of number forwardinggo automatic call-backo conferencing with up to 7 participantso locking of the mobile terminal (incoming or outgoing calls)o ...


Generation 2 (2G) – Other standards

o IS-95 (CDMAone): a North American standard of 2G that already uses DS CDMA on the Air interface Couldn’t gain much territoryuses DS-CDMA on the Air interface. Couldn t gain much territory against GSM/UMTS and also it’s follow-up CDMA2000.

o Personal Digital Cellular (PDC)o Japanese Standard

Based on TDMAo Based on TDMAo 800 and 1500 MHzo Physical characteristics similar to D-AMPS (the follow up of theo Physical characteristics similar to D AMPS (the follow up of the

North American AMPS standard)o Not successful outside Japano Japan was one of the prime pusher of 3G (UMTS)


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