Mobile Communication Unit1

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Unit I


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Overview What is Mobile Communications?Evolution of mobile radio communicationsMobile radio system around the worldExamples of wireless communication systems

Paging systemCordless telephone systemsCellular telephones

Trends in cellularExisting Mobile NetworksProtocol layer in a 3G wireless networkComparison between 2G+ and 3G wireless networks

2Mobile Communication7/3/2011


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MOBILE COMMUNICATION 3 aspects:

1. Wireless Communication2. Mobility 3. Portability

3

Stay connected anywhere, anytime

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1. Wireless CommunicationTransmitting/receiving voice & data usingelectromagnetic waves in open space

Each channel has a fixed frequency bandwidth & Capacity (bit-rate)

Different channels can be used to transmit information in parallel & independently.

Node A

Channel 3 (20KHz)

Channel 2 (20KHz)

Channel 1 (20KHz)

60KHz 60KHz

Node A



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2. MobilityLocation-independent services

Authentication/Authorization

Privacy to prevent the tracking of mobile users

Security



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3. PortabilityRisks to data

Physical damage, loss, theft, unauthorizedaccess, etc.

Small memory and CPU

Low power Battery operated



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Timeline of Wireless Communications Development...

1991 - (GSM)

1935 - Edwin Armstrong

demonstrated FM

1946 - Firstpublic mobile

telephoneservice



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Classification of mobile radio

transmission system

Simplex : communication in only one direction

Half-duplex : same radio channel for bothtransmission and reception

(push-to-talk, release-to-listen)

Full-duplex : simultaneous radio transmission andreception (FDD, TDD)



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contdFrequency Division Duplexing uses two radiochannel. (analog/digital)

Forward channel: base station to mobile userReverse channel: mobile user to base station

Time Division Duplexing shares a single radiochannel in time. (only for digital )



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ExampleCordless phone

Hand-held walkie-talkiesPagersCellular telephone Wireless LANSatellite-based transmissions



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Cordless Telephone SystemLow mobility, low power, two-way tether less voicecommunicationCordless telephone systems are full duplexcommunication systems.First generation cordless phone

in-home usefew tens of meters

Second generation cordless phoneoutdoorcombine with paging systemfew hundred meters per station



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Paging SystemsConventional paging system send brief messages to asubscriber.Modern paging system: news headline, faxes, etc.

Simultaneously broadcast paging message from eachBS (simulcasting )

Large transmissionpower to cover wide area.



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Cellular Mobile Radio SystemsHigh mobility, wide-ranging, two-way tether less voice

communication.The key point is frequency reuse

Cells" are grouped in clusters of seven cellsTo prevent interference, frequencies are not reused inadjacent cells

The size of the cells varies...



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contdBasic cellular system : mobile stations(MS), basestations(BS) & mobile switching center(MSC).

BS


MS

FCC

RCCFVC

RVC

Channels


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A call from a LL to a Mobile User

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A call initiated by a Mobile



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Satellites in Mobile Communication


EARTH

GEO

MEO

LEO

VAN ALLEN BELT

Height: 35,780KmRotation period: 24hr

Height:5000-12000Km

Rotation period:

6hr

Height: 500-1500Km

Rotation period:~90min

HEO(Non-Circular)


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Satellite- Based Systems (2)Types:Geostationary orbit systems (GEOS):

3 satellites are sufficient, but lower capacity for a givenspectrum

Low-earth-orbit system (LEOS):many satellites in lower orbit, lower latency, higher capacity,less expensive satellites

Medium-earth-orbit system (MEOS):Unlimited user (includes GPS owned by Military), < 10 SatHighly Elliptical orbit System (HEOS):

Used by commercial satellites

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Satellite- Based Systems (3)

Mobile Communication 21

Cell

BS

Foot Print

ISL

GWL

GSMPSTN

Building

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Trends in Cellular Radio and Personal

CommunicationThe concept of the personal systems that combinedthe network intelligence of todays PSTN with digitalsignal processing and RF technology is calledPersonal Communication Services (PCS).

An international standard body, IEEE 802.11, is

developing standards for wireless access betweencomputers inside buildings.



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contdThe technical group TG 8/1 is considering worldwide wireless network and implementation of worldwidefrequency coordination to allow subscriber units to work anywhere in the world.

Worldwide standard also required low earth orbit

(LEO) satellite communication systems.



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Second Generation Wireless Technology

The second generation (2G) of the wireless mobile network wasbased on low-band digital data signaling.

The most popular 2G wireless technology is known as GlobalSystems for Mobile Communications (GSM).

GSM technology is a combination of Frequency DivisionMultiple Access (FDMA) and Time Division Multiple Access(TDMA).

The first GSM systems used a 25MHz frequency spectrum in the900MHz band.

Today, GSM systems operate in the 900MHz and 1.8 GHz bandsthroughout the world with the exception of the Americas wherethey operate in the 1.9 GHz band.



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contdThe Second Generation (2G) wireless networksmentioned above are also mostly based on circuit-switched technology.

2G wireless networks are digital and expand the rangeof applications to more advanced voice services, suchas Called Line Identification.

2G wireless technology can handle some datacapabilities such as fax and short message service atthe data rate of up to 9.6 kbps, but it is not suitable for web browsing and multimedia applications.



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Second Generation (2G+) Wireless Networks

2G+ technology that is packet-based and increases thedata communication speeds to as high as 384kbps.

2G+ systems are based on the following technologies:High Speed Circuit-Switched Data (HSCSD),General Packet Radio Service (GPRS) and

Enhanced Data Rates for Global Evolution (EDGE)technologies.



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contdHSCSD is one step towards 3G wideband mobile data networks.This circuit-switched technology improves the data rates up to57.6kbps by introducing 14.4 kbps data coding and by aggregating 4 radio channels timeslots of 14.4 kbps.

GPRS technology is packet-based and designed to work inparallel with the 2G GSM.GPRS uses a multiple of the 1 to 8 radio channel timeslots in the200kHz-frequency band allocated for a carrier frequency toenable data speeds of up to 115kbps.

EDGE technology is a standard that has been specified toenhance the throughput per timeslot for both HSCSD and GPRS.The enhancement of HSCSD is called ECSD (384kbps).



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Third Generation (3G) Wireless NetworksOne of the most important aspects of 3G wirelesstechnology is its ability to unify existing cellular standards,such as CDMA, GSM, and TDMA, under one umbrella.

3G wireless networks consist of a Radio Access Network(RAN) and a core network.

The core network consists of a packet-switched domain, which includes3G SGSNs and GGSNs, which provide the same functionality that they provide in a GPRS system

The access network provides a core network technology independent access for mobile terminals to different typesof core networks and network services.



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Brief description of each protocol layer in a

3G wireless network infrastructureGlobal Mobility Management (GMM): protocol that includes attach,detach, security, and routing area update functionality.Node B Application Part (NBAP): provides procedures for pagingdistribution, broadcast system information and management of dedicated and logical resources.Packet Data Convergence Protocol (PDCP): maps higher levelcharacteristics onto th e characteristics of the underlying radio-interface protocols. PDCP also provides protocoltransparency for higher layer protocols.Radio Link Control (RLC): provides a logical link control over the

radio interface.Medium Access Control (MAC): controls the access signaling(request and grant) procedures for the radio channel.Radio resource Control (RRC): manages the allocation andmaintenance of radio communication paths.



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contdRadio Access Network Application Protocol (RANAP): encapsulates higher

layer signaling. Manages the signaling and GTP connections between RNC and3G-SGSN, and signaling and circuit-switched connections between RNC and3G MSC.

Radio Network Service Application Part (RNSAP): provides thecommunication between RNCs.

GPRS Tunnel Protocol (GTP): protocol that tunnels the protocol data unitsthrough the IP backbone by adding routing information. GTP operates on topof TCP/UDP over IP.

Mobile Application Part (MAP): supports signaling between SGSN/GGSNand HLR/AuC/EIR.

AAL2 Signaling (Q.2630.1, Q.2150.1, Q.2150.2, AAL2 SSSAR, and AAL2 CPS):protocols suite used to transfer voice over ATM backbone using ATMadaptation layer 2.

Sigtran (SCTP, M3UA): protocols suite used to transfer SCN signalingprotocols over IP network.



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Comparison between 2G+ and 3G wireless

networks



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contd



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Suggested Reading

1. T.S. Rappaport, Wireless Communications, 2ndEdition, Pearson Education. 2002.

2. W.C.Y. Lee, Mobile Cellular Telecommunications,2nd Edition, McGraw Hill, 1995.



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Mobile Communication Unit1

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