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CDMA

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1: Direct sequence and frequency hopped spread spectrum, spreading sequence and their correlation functions, Acquisition and tracking of spread spectrum signals. ...

1: Direct sequence and frequency hopped spread spectrum, spreading sequence and their correlation functions, Acquisition and tracking of spread spectrum signals.
2: Error probability for DS-CDMA, on AWGN channels, DS-CDMA on frequency selective fading, channels, Performance analysis of cellular CDMA.
3: Capacity estimation, Power control, effect of imperfect power control on DS CDMA performance, Soft Handoffs.
4: Spreading /coding tradeoffs, multi-carrier CDMA, IS-95 CDMA system, third generation CDMA systems, multi-user detection.

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CDMA CDMA Presentation Transcript

  • Telecom TutorialsMonday, June 03, 2013www.tempustelcosys.comCDMA SYSTEM
  • 1: Direct sequence and frequency hopped spread spectrum, spreadingsequence and their correlation functions, Acquisition and tracking ofspread spectrum signals.2: Error probability for DS-CDMA, on AWGN channels, DS-CDMA onfrequency selective fading, channels, Performance analysis of cellularCDMA.3: Capacity estimation, Power control, effect of imperfect powercontrol on DS CDMA performance, Soft Handoffs.4: Spreading /coding tradeoffs, multi-carrier CDMA, IS-95 CDMAsystem, third generation CDMA systems, multi-user detection.Monday, June 03, 2013www.tempustelcosys.com
  • • 1G Analog Cellular• 2G TDMA - GSM• 2G CDMA - IS-95• 2.5G• 3G• 4G and BeyondMonday, June 03, 2013www.tempustelcosys.com
  • First Generation (1G) mobile systems were designed tooffer a single service, i.e., speech.Second Generation (2G) mobile systems were alsodesigned primarily to offer speech with a limited capability tooffer data at low rates.Third Generation (3G) mobile systems are expected tooffer high-quality multi-media services and operate indifferent environments.3G systems are referred to as Universal MobileTelecommunications System (UMTS) in Europe andInternational Mobile Telecommunications 2000 (IMT2000)worldwide.Monday, June 03, 2013www.tempustelcosys.com
  • 1G: First generation wireless cellular: Early 1980sAnalog transmission, primarily speech: AMPS (Advanced MobilePhone Systems) and others2G: Second generation wireless cellular: Late 1980sDigital transmissionPrimarily speech and low bit-rate data (9.6 Kbps)High-tier: GSM, IS-95 (CDMA), etcLow-tier (PCS): Low-cost, low-power, low-mobility e.g. PACS2.5G: 2G evolved to medium rate (< 100kbps) data3G: future Broadband multimedia144 kbps - 384 kbps for high-mobility, high coverage2 Mbps for low-mobility and low coverageBeyond 3G: research in 4GMonday, June 03, 2013www.tempustelcosys.com
  • Monday, June 03, 2013www.tempustelcosys.comAAMPSPSIS-95GSMCDMA-20001XRTTGPRSCDMA20003XRTT(UMTS)EDGEW-CDMA(UMTS)1G-2G MigrationTDMA MigrationCDMA Migration1980 1999 2000 2001 2002 20031 Kbps10 Kbps50 Kbps100 Kbps150 Kbps500 kbps2 Mbps
  • Mobile radio telephones were used for military communications in early20th centuryCar-based telephones first introduced in mid 1940sSingle large transmitter on top of a tall buildingSingle channel used for sending and receivingTo talk, user pushed a button, enabled transmission and disabledreceptionBecame known as “push-to-talk” in 1950sCB-radio, taxis, police cars use this technologyIMTS (Improved Mobile Telephone System) introduced in 1960sUsed two channels (one for sending, one for receiving)No need for push-to-talkUsed 23 channels from 150 MHz to 450 MHzMonday, June 03, 2013www.tempustelcosys.com
  • 1G uses analog signals and has 9.6 KHz maximumtransmission speedBased on Advanced Mobile Phone Service (AMPS),1G uses 800-900 MHz frequencyEach channel is 30 KHz wide with 45 KHz passband832 frequencies are available, with 790 used for voicetraffic and 42 for control channelTwo frequencies are required for conversation,so there are actually only 395 voice channels and21 control channelsAnalog cellular phones are insecureMonday, June 03, 2013www.tempustelcosys.com
  • The need for efficient frequency utilization of theradio frequency spectrum and the desire to usedigital encoding of voice and digital modulationof the radio carrier led to the development of thisgeneration of systems.This second generation is considered to be adigital one as opposed to the analogue firstgeneration.Monday, June 03, 2013www.tempustelcosys.com
  • Voice, data and fax can be integrated into a singlesystem.Better compression can lead to better channelutilization.Error correction codes can be used for better quality.Sophisticated encryption can be used.Monday, June 03, 2013www.tempustelcosys.com
  • Digital traffic channels – first-generation systems are almostpurely analog; second-generation systems are digitalEncryption – all second generation systems provide encryptionto prevent eavesdroppingError detection and correction – second-generation digital trafficallows for detection and correction, giving clear voice receptionChannel access – second-generation systems allow channels tobe dynamically shared by a number of usersMonday, June 03, 2013www.tempustelcosys.com
  • Completely designed from scratch (no backwardcompatability)Uses 124 channels per cell, each channel can support 8users through TDM (992 users max)Some channels used for control signals, etcSeveral flavors based on frequency:GSM (900 MHz)GSM 1800 (called DCS 1800)GSM 1900 (called DCS 1900) - used in North AmericaMonday, June 03, 2013www.tempustelcosys.com
  • Monday, June 03, 2013www.tempustelcosys.comPublicSwitchedTelephoneNetwork(PSTN)HLRGatewayMTSCTerminatingMSCVLR1103210541069101. Call made to mobile unit (cellularphone)2. Telephone network recognizes numberand gives to gateway MSC3. MSC can‟t route further, interrogatesuser‟s HLR4. Interrogates VLR currently serving user(roaming number request)5. Routing number returned to HLR andthen to gateway MSC6. Call routed to terminating MSC7. MSC asks VLR to correlate call tothe subscriber8. VLR complies9. Mobile unit is paged10. Mobile unit responds, MSCs conveyinformation back to telephoneLegend: MTSC= Mobile Telephone Service Center, BTS = Base Transceiver StationHLR=Home Location Register, VLR=Visiting Location Register
  •  Code Division Multiple Access (CDMA) is a digital wirelesstechnology that was pioneered and commercially developed byQUALCOMM.CDMA works by converting speech into digital information, which isthen transmitted as a radio signal over a wireless network. Using aunique code to distinguish each different call, CDMA enables manymore people to share the airwaves at the same time - withoutstatic, cross-talk or interference.Commercially introduced in 1995, CDMA quickly became one of theworlds fastest-growing wireless technologies. In 1999, theInternational Telecommunications Union selected CDMA as theindustry standard for new "third-generation" (3G) wireless systems. Today, over 100 million consumers worldwide rely on CDMA forclear, reliable voice communications and leading-edge dataMonday, June 03, 2013www.tempustelcosys.com
  • IS-95 is the best known example of 2G with CDMAAdvantages of CDMA for Cellular Frequency diversity – frequency-dependent transmissionimpairments have less effect on signal Multipath resistance – chipping codes used for CDMAexhibit low cross correlation and low autocorrelation Privacy – privacy is inherent since spread spectrum isobtained by use of noise-like signals Graceful degradation – system only gradually degradesas more users access the systemMonday, June 03, 2013www.tempustelcosys.com
  •  Self-jamming – arriving transmissions frommultiple users not aligned on chip boundariesunless users are perfectly synchronized Near-far problem – signals closer to the receiverare received with less attenuation than signalsfarther away Soft handoff – requires that the mobile acquiresthe new cell before it relinquishes the old; thisis more complex than hard handoff used inFDMA and TDMA schemesMonday, June 03, 2013www.tempustelcosys.com
  •  Pilot (channel 0) - allows the mobile unit to acquiretiming information, provides phase reference andprovides means for signal strength comparison Synchronization (channel 32) - used by mobile stationto obtain identification information about cellular system Paging (channels 1 to 7) - contain messages for one ormore mobile stations Traffic (channels 8 to 31 and 33 to 63) – the forwardchannel supports 55 traffic channelsMonday, June 03, 2013www.tempustelcosys.com
  •  UMTS™ (Universal Mobile Telephone Service) is aThird Generation (3G) Mobile System beingdeveloped by ETSI™ within the ITU‟s IMT-2000framework. It will provide data speeds of up to 2Mbps, making portable videophones a reality.Monday, June 03, 2013www.tempustelcosys.com
  • Fourth generation mobile communicationssystems that are characterised by high-speed data rates at 20 to 100 Mbps, suitablefor high-resolution movies and television.Monday, June 03, 2013www.tempustelcosys.com
  •  Also known as „Mobile Broadband everywhere‟ „MAGIC‟› Mobile Multimedia Communication› Anywhere, Anytime with Anyone› Global Mobility Support› Integrated Wireless Solution› Customized Personal Service.Monday, June 03, 2013www.tempustelcosys.com
  • Higher data rates ~2-20 Mbps.New air interface needs to be developedPotential candidate OFDM.Smart antennas can form directed beams to increase strength of thedesired signal.A new spectrum needs to be assigned.All-IP vision: base stations become an access routerMonday, June 03, 2013www.tempustelcosys.com
  • Transmission at 20 Mbps2000 times faster than mobile data rates10 times faster than top transmission rates planned in finalbuild out of 3G broadband mobile10-20 times faster than standard ADSL services.Companies developing 4G technologyCellular phone companies: Alcatel, Nortel, Motorola,IT Companies: Hughes,HP,LG ElectronicsMonday, June 03, 2013www.tempustelcosys.com
  • Unlike the 3G networks which are a combination of circuitswitched and packet switched networks ,4G will bebased on packet switching only .This will allow lowlatency data transmission .Monday, June 03, 2013www.tempustelcosys.com
  • Monday, June 03, 2013www.tempustelcosys.com
  • Monday, June 03, 2013www.tempustelcosys.comThank You