信息与通信工程专业英语.ppt

Wireless Communication 2Jin WangSubject OutlinenIntroduction to Cellular Mobile CommunicationsnRadio Propagation:Large Scale EffectsqPath loss prediction modelsqShadowingnRadio Propagation:Small Scale EffectsqMulti-path models:Rayleigh,RicianqDoppler effect,power spectra and signal correlationqCoherence time and bandwidth,flat and selective fading channelnModulation TechniquesqConstant envelope and phase modulationqQPSK,/4 QPSK,FSK,GMSK3Subject OutlinenEqualization,Diversity and Coding TechniquesqLinear and non-linear equalizationqSelection,equal-gain and maximal ratio combiningqInterleaving and convolution codingnMultiple Access TechniquesqFDMA,TDMA,CDMA,SDMAqPacket radio and random accessnCellular System ConceptsqFrequency reuseqChannel assignment and controlqCellular trafficqCellular coverageqSystem expansion techniques4Subject OutlinenCDMA Cellular SystemsqPower Control and InterferenceqMulti-user DetectionqCapacity and Enhancementn More Advanced Topics(if time allows)qOrthogonal Frequency Division Mulitplexing(OFDM)qMulti-carrier CDMA SystemnSpeech Coding Fundamentals of quantization,PCM,VocodernBrief Overview of System Standards GSM,IS-95,IMT20005ReferencesnTheodore S.Rappaport,Wireless Communications:Principles&Practice,Prentice-Hall,2nd Edition.nJon W Mark,Weihua Zhuang,Wireless Communications and Networking,Prentice Hall.nSimon R.Saunders,Antennas and Propagation for Wireless Communication Systems,Wiley.nWilliam C.Y.Lee,Mobile Communications Engineering,McGraw-Hill.nJ.D.Parsons,The mobile radio propagation channel,Wiley,2nd Edition.nMichel Daoud Yacoub,Foundations of Mobile Radio Engineering,CRC Press.nWilliam C.Jakes,Microwave Mobile Communications,IEEE Press.6Wireless CommunicationsnSatellite nTVnCordless phonenCellular phonenWireless LAN,WIFInWireless MAN,WIMAXnBluetoothnUltra Wide BandnWireless LasernMicrowavenGPSnAd hoc/Sensor Networks7Europe StandardsnGSMnCT2nDect8Japan Standards9North American Major StandardsnPCSnGSMnCorelessnFDMAnTDMAnCDMAnModulationqFMqQPSKqGMSKqBPSKqQAM10Basic conceptsnSimplex,half-duplex,and full duplexnFrequency division duplexing,FDDqMost of system because of simplicitynTime division duplexing,TDD:qindoor system only,because of delaynDifferent from FDMA and TDMA11Basic concepts12Pager System13Cordless phonenVirtually all telephones now sold in the US use the 900 MHz,2.4 GHz,or 5.8 GHz bands.There is no specific requirement for any particular transmission mode on 900,2.4,and 5.8,but in practice virtually all 900 MHz phones are inexpensive,bare-bones analog models;digital features such as DSSS and FHSS are generally only available on the higher frequencies.nThe recently allocated 1.9 GHz band is used by the popular DECT phone standard from Europe 14Mobile 15Base Station16IntroductionnThe target for mobile communications is to provide communications for anyone,from anywhere,at any time.nA demanding task.Technological challenges include:qTimevarying,hostile communication channel.q Location and tracking complexities due to mobility.q Efficient use of scarce resources such as frequency spectrum cellular structure.The amount of interference generated is critical.q Power restrictions due to health issues.17IntroductionnThe exponential growth of mobile subscribers worldwide is due to the decreasing service charges and diminishing hardware costs.The continuous development of the enabling technologies is the key.18IntroductionRF technologies(such as improved frequency stability in electronics)19IntroductionqIC design(size)qBattery technology(weight and size)qHigher order modulation is made possible due to the use of more sophisticated advanced digital signal processing techniques.qSpeech coding techniques reduces the required bandwidth per channel.20Cellular systemExample:qConsider a system allocated total bandwidth of 12.5MHz and each voice channel requires a 10kHz slot.We can only support 12.5MHz/10kHz or 1250 simultaneous conversations.qSupposing the penetration rate in Singapore is 10%,for a population of 3M+,this is equivalent to 300k users.What happen if 1%of the users making call at the same time?Channels need to be in someway reused or shared?21Cellular systemWhat can we do?qFrequency bands are reused at different locations.With this,higher user capacity in the same frequency spectrum can be achieved.qTechnical challenge:interference issue,location tracking,etc.,needs to be overcome.22Cellular system23Cellular systemnEach cell has a base station(BS),providing the radio interface to the mobile station(MS).nA sophisticated switching technique called a handover enables a call to proceed uninterrupted across cell boundaries.nAll the BSs are connected to a mobile switching center(MSC)which is responsible for connection users to the public switched telephone network(PSTN).nControl channels transmit and receive data messages that carry call initiation and service requests,and are monitored by mobiles when they do not have a call in progress.5%of total available channels.24Cellular systemnCommunication between the BS and the mobiles is defined by a standard common air interface that specifies 4 different physical channelsqForward(Downlink)voice/data channel:BS to MSqReverse(Uplink)voice/data channel:MS to BSqForward(Downlink)control channel:BS to MSqReverse(Uplink)control channel:MS to BSnA MS contains a transceiver,an antenna and control circuitry.A BS consists of several transmitters and receivers.251G 2G Distributions262G Standard272G to 3G evolution28