Wireless Communication

Wireless CommunicationB.E. (E&TC) Theory :100 MarksT.W. : 25Marks1

Chapter IReview : 2G, 3G wireless networks, WLL, Cellular Concept2 OutlineConcept of 2G,3G wireless networksWorking of 2G and 3G networksWireless in Local Loop (WLL) conceptCellular conceptJuly 18, 201433Learning outcomesAfter studying this chapter students will be able to ..Demonstrate the examples of 2G, 3G networks used in practice.Explain what is WLL? & how it works?Tell the various frequency ranges used in RF frequency bands.Elaborate the Cellular concept.4Types of Waves5TransmitterReceiverEarth Sky waveSpace waveGround wave

Troposphere (0 - 12 km)Stratosphere (12 - 50 km)Mesosphere (50 - 80 km)Ionosphere (80 - 720 km)5Radio Frequency BandsClassification BandInitialsFrequency RangeCharacteristicsExtremely lowELF< 300 HzGround wave

Infra lowILF300 Hz - 3 kHzVery lowVLF3 kHz - 30 kHzLowLF30 kHz - 300 kHzMediumMF300 kHz - 3 MHzGround/Sky waveHighHF3 MHz - 30 MHzSky waveVery highVHF30 MHz - 300 MHzSpace wave

Ultra highUHF300 MHz - 3 GHzSuper highSHF3 GHz - 30 GHzExtremely highEHF30 GHz - 300 GHzTremendously highTHF300 GHz - 3000 GHz661G,2G, wireless networksIn 1G, Narrow band analogue wireless network is used, with this we can have the voice calls and can send text messages1G in this we could contact with in the premises of that particular nationExamples: AMPS family: AMPS (Advanced Mobile Phone System),TACS(Total Access Communications System ),ETACS(Europien Total Access Communications System)2G Narrow Band Wireless Digital Network is used.latest technologies such as GPRS, is not available in these generations71G wireless networksThese are the analog telecommunications standards that were introduced in the 1980s and continued until being replaced by 2G digital telecommunicationsThrough 1G, a voice call gets modulated to a higher frequency of about 150MHz and up as it is transmitted between radio towers.This is done using a technique called Frequency-Division Multiple Access (FDMA).8Disadvantages- 1GHas low capacity, unreliable handoff, poor voice links, No security at all since voice calls were played back in radio towers, making these calls susceptible to unwanted taping somebody's phone by third parties.Analog systems known as Analog Mobile Phone Systems (AMPS) based on circuit-switched technology and designed for voice, not data.

92G Wireless Networks2G systems were first introduced in early 1990s.2G Standard use digital modulation formats and TDMA(Time Division Multiple Access)/FDD(Frequency Division Duplexing) and CDMA (Code division Multiple Access)/FDD multiple access techniques.102G StandardsA) Global system Mobile (GSM) : Widely deployed by service providers in Europe, Asia, Australia, South America and Some part of US. Channel capacity is 200 KHz.B) Interim Standard 136 (IS-136) or North American Digital Cellular (NADC): Popular in North & south America and Australia. Channel capacity is 30KHz.C) Pacific Digital Cellular (PDC): A Japan TDMA Standard similar to IS-136. more than 50 million users. channel capacity is 30KHz.D) IS-95 CDMA: also known as cdmaOne, supports up to 64 users & simultaneously transmitted on each 1.25MHz channel112G2.5G3GGSMIS-136 & PDCIS-95BHSCSDGPRSEDGECdma2000-3xRTTCdma2000-1xEV,DV,DOTD-SCDMAEDGEIS-95CDMA2000-1xRTTW-CDMA3GPP3GPP2122.5GThree upgrade paths:High speed Circuit Switched data (HSCSD)General Packet Radio service (GPRS)Enhanced data Rates for GSM Evolution (EDGE)These options provides improvements in Internet access speed over todays GSM and IS-136 tech.13HSCSD for 2.5G GSMA circuit switched technique that allows single mobile user to use consecutive user time slots in the GSM standardi.e. instead of limiting each user to only one specific time slot in the GSM TDMA standard, HSCSD allows individual data users to grab consecutive time slots in order to obtain higher speed data access on the GSM network.It relaxes the error control coding algorithms.Increases the available application data rate to 14400bps compared to original 9600bps in GSM specification.14GPRS for 2.5G GSM & IS-136General Packet Radio Service is a packet-based data network, well suited for non real time internet usage like retrieval of e-mail, faxes, asymmetric web browsing.Support multiuser network sharing of individual radio channels and time slots (can support many more users than HSCSD).GPRS standard provides a packet network on dedicated GSM or IS-136 radio channels.Peak 21.4kbps per channel data rate specified by GPRS works well with both GSM & IS-136.

15EDGE for 2.5G GSM and IS-136Enhanced data rates for GSM Evolution (EDGE), a more advanced upgrade to the GSM standard .Require new H/W and S/W at existing base stations.EDGE allows for nine different air interface formats, known as multiple modulation and coding schemes (MCS) with varying error control protection.EDGE uses higher order 8-PSK modulation & a family of MCSs for each GSM radio channel slot so that each user can choose best MCS setting for data access16EDGE for 2.5G GSM and IS-136Because of this adaptive capability known as incremental redundancy whereby packets are transmitted first with maximum error protection and maximum data rate throughput.

173G wireless networks26/07/10 AdvantagesMulti-megabits Internet access, communications using Voice over Internet Protocol (VoIP), voice activated calls, unparalleled network capacity n omnipresent, always on access.Ability to receive live music, conduct interactive web sessions and have simultaneous voice and data access with multiple parties at the same time using a single mobile handset, whether driving, walking or standing still in an office setting.183G wireless networks3G Evolution for CDMA systems leads to cdma-2000, currently being developed3G evolution for GSM, IS-136 & PDC systems leads to Wideband-CDMA(W-CDMA) also called Universal Mobile Telecommunications Service (UMTS).ITU IMT-2000 standards organizations are separated into two major organizations reflecting two 3G camps:3GPP (3G partnership Project) for Wideband CDMA standards based on backward compatibility with GSM and IS-136/PDC 3GPP2 (3G partnership Project for cdma-2000 standards based on backward compatibility with IS-95

193G W-CDMA (UMTS)The Universal Mobile Telecommunication System (UMTS) is an air interface standard that has evolved since late 1996.UMTs or W-CDMA assures backward compatibility with the second generation GSM, IS-136 & PDC TDMA technologies also 2.5G TDMA technologies.3G W-CDMA air interface standard had been designed for always on packet based wireless network & be connected to the internet any time any where.W-CDMA will support packet data rates up to 2.048 Mbps per user203G W-CDMA requires a minimum spectrum allocation of 5 MHz.W-CDMA provides public & private network features n also videoconferencing and virtual home entertainment.

21Wireless Local Loop (WLL) (26/7/10) OutlineWhat is WLL?Differences with mobile cellular systemsWhy WLL?System Analysisexamples

22Wireless Local Loop (WLL)What is WLL?- WLL is a system that connects subscribers to the local telephone station wirelessly. Systems WLL is based on:CellularSatellite (specific and adjunct)MicrocellularOther namesRadio In The Loop (RITL) Fixed-Radio Access (FRA).

23A general WLL setup

24Connection SetupPSTNSwitch functionWLLControllerAMHLRTransceiverWASU

TrunkAir InterfaceUWLLTWLL Wireless Access Network Unit(WANU)Interface between underlying telephone network and wireless linkconsists ofBase Station Transceivers (BTS)Radio Controller(RPCU)Access Manager(AM)Home Location Register(HLR)

WANU Wireless Access Subscriber Unit(WASU)located at the subscribertranslates wireless link into a traditional telephone connection25Wireless in Local Loop (WLL)The term used for wireless communication link as the last mile/first mile connection.Used to deliver Plain old Telephone Services (POTS) and/or Broadband Internet to consumer.26ComparisionWLLMobile WirelessWirelineRician fadingRayleigh fadingNo fadingNarrowbeam directed antennasOmnidirectional antennasExpensive wiresHigh Channel reuseLess Channel reuseReuse Limited by wiringSimple design, constant channelExpensive DSPs, power controlExpensive to build and maintainLow in-premises mobility only, easy accessHigh mobility allowed, easy accessLow in-premises mobility, wiring of distant areas cumbersomeWeather conditions effectsNot very reliableVery reliable27WLLAdvantages:Once the wireless equipment is paid, no additional cost is required for transport between central office (CO) and customer premises equipment (CPE)Direct competition with copper-wire based digital subscriber Loop (DSL) technology28LMDSIn 1998, 1300 MHz of unused spectrum in 27-31 GHz band was chosen by US govt. to support LMDS (Local Multipoint Distribution Service).A vast array of services & applications have been proposed & that includes LMDS.The concept of LMDS provides broadband telecommunications access in the local exchange.It is a fixed wireless service which require enormous amount of bandwidth.29Cellular ConceptIt is a system level idea which calls for replacing a single high power transmitter (large cell) with many low power transmitters (small cells) providing coverage to small portion of service area.Each base station is allocated a portion of the total number of channels available to entire system.Neighboring base stations are assigned different groups of channels so interference between base stations is minimized.30By limiting the coverage area to within the boundaries of a cell, the same group of channels may be used to cover different cells separated by distance large to keep interference levels within tolerable limits.The design process of selecting and allocating channel groups for all of the cellular base stations within a system is called frequency reuse or frequency planning.31Frequency reuse conceptBGFEACDBGCDFEAGFBCDAEFigure a) Illustration of cellular frequency reuse concept32Cells with same letter use the same set of frequencies.A cell cluster is outlined in bold and replicated over the coverage area.From the figure, cluster size N, is equal to seven and frequency reuse factor is 1/7 since each cell contains one-seventh of the total number of available channels.33Let,S=total duplex channels available for use.k= no. of channels allocated to each cell (k