中英文对照的CDMA95标准

Slide No.1Advanced Learning SolutionsSlide 1Telstra 2001Telstra in confidenceCDMA Technology and Operations for Unicom Senior ManagersIS95 Standards THE IS-95 Standards IS-95 标准标准Slide No.2Advanced Learning SolutionsSlide 2Telstra 2001Telstra in confidenceCDMA Technology and Operations for Unicom Senior ManagersIS95 Standards Overview综述综述THE IS95 Standards IS95 标准Spectrum and Frequency Plans 频谱和频率分配方案A CDMA SystemCDMA 系统Logical Data Channels 逻辑数据信道Forward Link Structure 前向链路结构Reverse Link Structure反向链路结构Codes 编码Power Control 功率控制Handoff 切换CDMA Call Processing CDMA呼叫处理Slide No.3Advanced Learning SolutionsSlide 3Telstra 2001Telstra in confidenceCDMA Technology and Operations for Unicom Senior ManagersIS95 Standards Major IS95 Standards主要的主要的IS95标准标准Cdma2000 1xRTT and packet data.Backwards compatible with IS95B 1xRTT及打包数据，后台与IS95B兼容IS95A/Bradio interface specification(also called TIA/EIA95 无线接口说明也称为TIA/EIA95IS96A8 kbps speech service option 8kbps的语音效劳选项IS97BTS Minimum Performance Standards 基站最低性能标准IS98MS Minimum Performance Standards 最低性能标准IS127EVRC Speech Service Option EVRC语音效劳选项IS634AOpen A Interface(MSC to BSC)开放A接口MSC至BSCIS707APacket Data 打包数据IS-73313 kbps Speech service option 13 kbps的语音效劳选项IS-637Short Message Service 短信息效劳IS-638Over-the-air activation and parameter administration 无线激活和参数管理Slide No.4Advanced Learning SolutionsSlide 4Telstra 2001Telstra in confidenceCDMA Technology and Operations for Unicom Senior ManagersIS95 Standards Spectrum Allocations频谱分配频谱分配Same duplex bands as AMPS与AMPS相同的双波段2x20 MHz(excluding the extension bands A,B and A)2x20 MHz除了扩展波段A、B和A之外A CDMA channel centre frequency is given by:CDMA信道中心频率来自：825+n*0.03 MHz(Reverse Link,MS to BTS)825+n*0.03 MHz 反向连接，到基站870+n*0.03 MHz(Forward Link,BTS to MS)870+n*0.03 MHz前向连接，基站到 Each CDMA Carrier occupies 1.25MHz(x2)每个CDMA载波占用1.25MHz x2 1.25825845MHz1.251.251.25870890MHz1.251.25Reverse Link反向链路反向链路Forward Link前向链路前向链路Slide No.5Advanced Learning SolutionsSlide 5Telstra 2001Telstra in confidenceCDMA Technology and Operations for Unicom Senior ManagersIS95 Standards Primary and Secondary Carriers主要和次要载波主要和次要载波777*691*次要载波384283主要载波B波段A波段PAPB880890870MHzA波段B波段PAPB835845825A波段B波段MS TransmitBTS Receive手机发射，基站接收手机发射，基站接收BTS TransmitMS Receive基站发射，手机接收基站发射，手机接收These channels fall in the AMPS Extension Bands 这些频道在AMPS扩展波段之内Only Primary and Secondary carriers are specified in IS95.Other carrier frequencies are defined by the operator.IS95中只规定了主要和次要载波。其他载波频率由运营商定义。Slide No.6Advanced Learning SolutionsSlide 6Telstra 2001Telstra in confidenceCDMA Technology and Operations for Unicom Senior ManagersIS95 Standards CDMA Frequency PlansCDMA 频率分配方案频率分配方案IS-95 is really CDMA/FDMA.IS-95 是真正的CDMA/FDMA。Each 1.25 MHz“Carrier or Frequency Allocation(FA)can support approx 20-30 simultaneous users(depending on various factors).每1.25兆赫兹的“载波或频率分配FA可同时支持大约20到30个用户取决于各种因素。Codes are used within each carrier to distinguish users 每个载波都用代码识别用户Initially all sectors on all base station use a common 1.25MHz Carrier.开始时，所有基站的所有扇区都共用1.25兆赫兹载波Additional carriers are added per site as traffic increases.随着话务量的增长增加其它载波7/21,4/12 etcN=1GSM/AMPS etcCDMACode 1Code 2Code 3Code 4Code NFrequency 1频率频率1Code 1Code 2Code 3Code 4Code NFrequency 2Slide No.7Advanced Learning SolutionsSlide 7Telstra 2001Telstra in confidenceCDMA Technology and Operations for Unicom Senior ManagersIS95 Standards A CDMA SystemReverse Link反向链路Forward Link前向链路BTSBTSBase Station Controller(BSC)基站控制器基站控制器BSCMobile Station(MS)移动移动 Mobile Switching Center(MSC)移动交换中心移动交换中心MSCPSTNVocoders声码器声码器HLR,VLRSlide No.8Advanced Learning SolutionsSlide 8Telstra 2001Telstra in confidenceCDMA Technology and Operations for Unicom Senior ManagersIS95 Standards Vocoders声码器声码器Vocoders convert analog speech(bandwidth 3 kHz)to a low bit-rate digital signal suitable for transmission over a mobile system(typically,8 kbps or 13 kbps).声码器将模拟语音带宽3千赫兹转换成适合移动系统通常速率为8kbps或13kbps传输的低比特率数字信号。Waveform coders sample a signal and transmit a replica of the signal.Examples include G.703(64 kbps),G.721 32 kbps ADPCM used for PSTN.波形编码器对信号取样并发送一个与该信号相同的复制信号。例如用于PSTN的G.703(64 kbps)、G.721 32 kbps ADPCM。Vocoders perform a parametric modelling of human speech and transmit parameters describing the input signal.These parameters are used to regenerate the original signal.声码器将人类语言进行参数模拟并传输这些参数来描述这些输入信号。这些参数被用来复原原始信号。Slide No.9Advanced Learning SolutionsSlide 9Telstra 2001Telstra in confidenceCDMA Technology and Operations for Unicom Senior ManagersIS95 Standards Speech Vocoders语音声码器语音声码器Vocoder声码器Demodulation解调PSTN8 kbps(或 13 kbps)Modulation调制Vocoder声码器64 kbps PCM 或 32 kbps ADPCM3 kHz 8 kbps(或 13 kbps)BTSCoding and decoding introduce delay 编码和解码导致时延Delays 64Block.EncLong PN code gen.Short PN code gen.28.8 ksps307.2 ksps1.2288 Mcps1.2288 McpsRFW=1.25 MHzESN addressmaskData Coding(x32)x4 spreadingx1 Spreading(randomisation)Slide No.27Advanced Learning SolutionsSlide 27Telstra 2001Telstra in confidenceCDMA Technology and Operations for Unicom Senior ManagersIS95 Standards Detailed Reverse Link Structure反向链路详细构造反向链路详细构造R=1/3 Encoding and RepetitionR=1/3解码和重复Block Inter-leaver块交织器To RF9600,4800,2400,1200 bps19.2 ksps307.2 ksps1.2288 McpsQ Short CodeI Short Code6-64Block.Enc6-64解码19.2 ksps1.2288 Mcps1/2 chip delayLong PN Code Generator长PN编码发生器ESN based Mask(42 bits)基于ESN的掩码42位1.2288 Mcpsx4 spreadingX4扩展Data Coding(x32 to x256)数据编码(x32 to x256)x1 Spreading(randomisation)X扩展随机Punct-ure击穿Decimate分样Slide No.28Advanced Learning SolutionsSlide 28Telstra 2001Telstra in confidenceCDMA Technology and Operations for Unicom Senior ManagersIS95 Standards Reverse Link RF反向链路反向链路RF1.2288 MspsQ Short CodeQ短编码短编码I Short Code1.2288 Mcps1.2288 Mcpscos(wct)sin(wct)HPAI1/2 chip delay集成电路继电器QFIR FilterFIR滤波器FIR FilterFIR滤波器Why Offset QPSK?为何为何QPSK会产生分支会产生分支Using the chip delay,180 phase transitions are avoided.使用使用1/2码片延时可防止码片延时可防止180度相变度相变When passed through a non-linear amplifier(eg a mobile PA),OQPSK exhibits less spectral regrowth than QPSK.当经过一个非线性放大器如移动当经过一个非线性放大器如移动PA后，后，OQPSK的频谱再生比的频谱再生比QPSK小小Slide No.29Advanced Learning SolutionsSlide 29Telstra 2001Telstra in confidenceCDMA Technology and Operations for Unicom Senior ManagersIS95 Standards IS-95 Reverse LinkIS-95反向链路反向链路Rate 1/3 convolutional+rate 6/64 Block data coding is effectively rate 1/32 convolutional encoding1/3率的卷积编码加上6/64率的块编码效果相当于1/32率卷积解码。Block encoding done with Walsh functions 用沃尔什函数完成块解码Each 6 data bits selects 1 of 64 Walsh functions(each 64 symbols long)每6个数据位选择64个沃尔什函数之一每个长64码元Allows non-coherent detection(i.e Wn or+Wn map to the same 6 bit data sequence)可进行非连贯性检测例如Wn或+Wn对应同样的6位数据序列 Long PN performs x4 spreading to final 1.25 MHz bandwidth.长PN实现x4扩展至最终的1.25MHz带宽。Repeats every 42 days!每42天重复一次Unique phase(offset)per mobile 每个受机都有特定的相位偏移Short PN code randomises(but no spreading).短PN编码是随机的但不扩展Repeats every 26.6667 ms每26.6667毫秒重复一次Slide No.30Advanced Learning SolutionsSlide 30Telstra 2001Telstra in confidenceCDMA Technology and Operations for Unicom Senior ManagersIS95 Standards IS95 CodesIS95代码代码Slide No.31Advanced Learning SolutionsSlide 31Telstra 2001Telstra in confidenceCDMA Technology and Operations for Unicom Senior ManagersIS95 Standards The Short Codes短代码短代码Only two short codes are used in IS95(I and Q channels)只有两种短代码用于IS95中I和Q信道Maximal length sequences,with 1 additional bit 最大长度序列，带一个附加位length=215=32,678 chipsThe offset,or phase,of the code is used to discriminate between sector transmissionsAll BTS sectors transmit a pilot,which is unmodulated I and Q short codes代码的偏移或相位用于区分小区传输。所有的BTS小区发送一个导频，该导频为未调制的I和Q短代码used by mobiles to identify sectors for handoff用于 切换时识别扇区There are 512 allowable offsets(i.e every 64 chips)有512个可用的偏移例如每64个芯片Slide No.32Advanced Learning SolutionsSlide 32Telstra 2001Telstra in confidenceCDMA Technology and Operations for Unicom Senior ManagersIS95 Standards Synchronisation 同步同步Pilot signal(short codes only)radiated from each BTS sector 每个BTS扇区播送导频信号仅限于短代码。Typically Pilot power=15%of maximum transmission power通常的导频功率=最大传输功率的15%Same code is used for all sectors but with different offsets,providing discrimination between sectors and BTS.同一个代码 可用于所有的扇区，但带有不同的偏移，以区分不同的扇区和BTS。GPS supplies tight Pilot timing(T_ADDCandidate Pilot Active Pilot+T_COMPNeighbour Pilot相邻引导 T_ADDRemaining剩余集剩余集Candidate Pilot T_DROP and T_TDROP ExpiredActive Pilot MAX_AGESlide No.51Advanced Learning SolutionsSlide 51Telstra 2001Telstra in confidenceCDMA Technology and Operations for Unicom Senior ManagersIS95 Standards Pilot Search Windows导频搜索窗口导频搜索窗口MS initially derives timing from PN30 MS从PN30获得初始时钟Unsure where PN112 and PN172 pilots are due to path differences.由于路径不同，不能确定是PN112还是PN172。Search windows are needed to capture pilot energy,including multi-paths搜索窗口需要捕获导频能量，包括多路径。PN=30PN=112PN=17230112172BTS PN TimingSRCH_WIN_NSRCH_WIN_NSRCH_WIN_ASRCH_WIN_RMS PN Timing30112172NNA“Relative path delays are important “相应的路径延迟非常重要相应的路径延迟非常重要Slide No.52Advanced Learning SolutionsSlide 52Telstra 2001Telstra in confidenceCDMA Technology and Operations for Unicom Senior ManagersIS95 Standards Pilot Search Windows 导频搜索窗口导频搜索窗口MS performs SHO to include PN112 and PN172 in the active setMS执行SHO，将PN112和 PN172纳入有效集Active SCHWIN centred around earliest found multi-paths of PN112 and PN172有效SCHWIN集中与最早发现的PN112和PN172的多径信号。PN=30PN=112PN=17230112172BTS PN TimingSRCH_WIN_ASRCH_WIN_RMS PN Timing30112172CCASRCH_WIN_ASRCH_WIN_ASlide No.53Advanced Learning SolutionsSlide 53Telstra 2001Telstra in confidenceCDMA Technology and Operations for Unicom Senior ManagersIS95 Standards Pilot Search Windows导频搜索窗口导频搜索窗口30112172BTS PN TimingSRCH_WIN_ASRCH_WIN_RMS PN Timing30112172AAAOffset in chips of strongest multi-path is reported to BTS.最强的多径信号的码片偏移被报告给BTS。Mobile centres active SCHWIN with offset.集中在有效SCHWIN，伴有偏移SRCH_WIN_ASRCH_WIN_A0Slide No.54Advanced Learning SolutionsSlide 54Telstra 2001Telstra in confidenceCDMA Technology and Operations for Unicom Senior ManagersIS95 Standards Message信息信息Sent by发送方发送方Contains包含内容包含内容Pilot Strength Measurement Message(PSMM)引导强度测量信息（PSMM）Mobile手机For each pilot:对于每个引导装置：Ec/IoArrival time(relative to expected PN offset)Handoff Drop Timer到达的时间（与期望的PN分支有关）Handoff Direction Message(HDM)切换指示信息（HDM）BTSCDMA Frequency assignment CDMA频率分配Active Set(new and old pilots)有效集（新、旧导频）Walsh Code for each pilot 用于每个导频的沃尔什码SCHWINs for Active and candidate sets有效和候选集的SCHWINsHandoff parameters(T_ADD,T_DROP,T_COMP,T_TDROP切换参数（T_ADD,T_DROP,T_COMP,T_TDROP）Handoff Completion Message(HCM)切换完成信息（HCM）Mobile移动装置AcknowledgmentPN of each pilot in the Active Set对有效集中每个导频PN的确认Neighbour List Update Message(NLUM)邻域列表更新信息（NLUM）BTSComposite Neighbor List混合邻域列表Handoff Messages切换信息切换信息Slide No.55Advanced Learning SolutionsSlide 55Telstra 2001Telstra in confidenceCDMA Technology and Operations for Unicom Senior ManagersIS95 Standards Pilot Strength Measurement Message导频强度测量信息导频强度测量信息This PSMM includes 2 pilots:本PSMM包含2个导频：PN30(reference)PN at 7170 chips offset 在 7170 芯片偏移的PN 7170/64=112.0313 PNs =112 PNs+2 chips(1 PN=64 chips)Pilot Strength Measurement Message导频强度测量信息导频强度测量信息ACK_SEQ:1MSG_SEQ:7ACK_REQ:0REF_PN:30PILOT_STRENGTH:-5.0 dB(Ec/Io)KEEP:1PILOT_PN_PHASE:7170(112+2 chips)PILOT_STRENGTH:-17.0 dB(Ec/Io)KEEP:0Slide No.56Advanced Learning SolutionsSlide 56Telstra 2001Telstra in confidenceCDMA Technology and Operations for Unicom Senior ManagersIS95 Standards Extended Handoff Direction Message其他切换指示信息其他切换指示信息Extended Handoff Direction Message其他的切换信息其他的切换信息ACK_SEQ:5MSG_SEQ:0ACK_REQ:0ENCRYPTION密码密码:0PILOT_PN:112PWR_COMB_IND:0CODE_CHAN:48PILOT_PN:24PWR_COMB_IND:0CODE_CHAN:8Code Channel is the Walsh function to be used编码信道即被采用的沃尔什函数。PWR_COMB_IND is used for softer handoff.PWR_COMB_IND 用语软件移交。Slide No.57Advanced Learning SolutionsSlide 57Telstra 2001Telstra in confidenceCDMA Technology and Operations for Unicom Senior ManagersIS95 Standards Handoff Completion Message切换完成信息切换完成信息Handoff Completion Message切换完成信息切换完成信息ACK_SEQ:0MSG_SEQ:6ACK_REQ:0ENCRYPTION:0LAST_HDM_SEQ:2PILOT_PN:112PILOT_PN:24PRIMARY_PN:112HANDOFF_STATE:SOFTThe Primary PN is the PN with the earliest Arriving Multipath主要的PN是最早到达的多径信号的PN。Slide No.58Advanced Learning SolutionsSlide 58Telstra 2001Telstra in confidenceCDMA Technology and Operations for Unicom Senior ManagersIS95 Standards Neighbor List Update Message邻域列表更新信息邻域列表更新信息This message commands the mobile to put PNs 115,118,27 and 30 in the active state neighbour list本信息命令 将PN115、118、27和30置于有效状态的邻域列表。Neighbour List Update Message邻域列表更新信息邻域列表更新信息ACK_SEQ:6MSG_SEQ:1ACK_REQ:0ENCRYPTION:0PILOT_INC:3NBHBR_PN:115NBHBR_PN:118NBHBR_PN:27NBHBR_PN:30Slide No.59Advanced Learning SolutionsSlide 59Telstra 2001Telstra in confidenceCDMA Technology and Operations for Unicom Senior ManagersIS95 Standards Search Windows搜索窗口搜索窗口 Larger Search windows require more searching time 搜索窗口越大，搜索需要的时间就越长Increases time to acquire new pilots 延长时间以捕获新的导频Some Mobiles do not implement SCHWINs 13 correctly 有些 不能正确实现SCHWINs 13SCHWINWindow Size窗口规格(PN Chips)Window Size窗口尺寸(km)041.0(0.5)161.5(0.75)282.0(1)3102.4(1.2)414 3.4(1.7)5204.9(2.45)6286.8(3.4)7409.8(4.8)86014.6(7.3)98019.5(9.75)1010024.4(12.2)1113031.7(15.65)1216039.1(19.55)1322655.2(27.6)1432078.1(39.05)15452110.4(55.2)Slide No.60Advanced Learning SolutionsSlide 60Telstra 2001Telstra in confidenceCDMA Technology and Operations for Unicom Senior ManagersIS95 Standards Pilot Searching导频搜索导频搜索Example 例如3 Actives PN 12,15 and 183 neighbours 60,63,66Search Order 搜索顺序12,15,18,60,12,15,18,63,12,15,18,66,12,15,18,R,12,15,18,60,12,15,18,63,12,15,18,66,12,15,18,R,Measure all Active Pilots测量所有有效导频Measure next Neighbour测量下一邻域导频All Neighbours Searched?是否搜索了所有邻域Measure next Remainder测量下一剩余导频集NSlide No.61Advanced Learning SolutionsSlide 61Telstra 2001Telstra in confidenceCDMA Technology and Operations for Unicom Senior ManagersIS95 Standards Adding and Removing a Pilot导频的增减导频的增减Ec/Io Pilot Strength(dB)T_ADDT_DROPT_TDROPtimeNeighbour邻域邻域Candidate候选域候选域ActiveMS Send PSMMMS发送PSMMBS Send HDMBS 发送 HDMMS Send HCMMS 发送 HCMNeighbour邻域邻域MS sends HCMMS 发送 HCMMS sends PSMMMS 发送 PSMMBS sends HDMBS 发送 HDMBTS sends NLUMBTS 发送 NLUMSlide No.62Advanced Learning SolutionsSlide 62Telstra 2001Telstra in confidenceCDMA Technology and Operations for Unicom Senior ManagersIS95 Standards Direct and Multipath Signals 直接信号和多径信号直接信号和多径信号I-PNQ-PNW0PilotW32SyncW1PagingW2.31TrafficW33.63TrafficS SQPSKModulatorBSCVocodersToPSTNBTS1-Sector 1F1F2F3SearchRFTrafficMobileBTS1-W2BTS1-W2Uses direct path on one RAKE finger and multipath signals on other fingersResults in a more robust link在一个RAKE指针用直接路径信号，其它的指针用多径信号。链路更强。Helps overcome direct path fades by combining indirect path signals通过合并非直接路径信号，克服直接信道的衰减How does a mobile use multipath?如何使用多径传输如何使用多径传输Slide No.63Advanced Learning SolutionsSlide 63Telstra 2001Telstra in confidenceCDMA Technology and Operations for Unicom Senior ManagersIS95 Standards I-PNQ-PNW0PilotW32SyncW1PagingW2.31TrafficW33.63TrafficQPSKModulatorBTS1-Sector 1S SBSCI-PNQ-PNW0PilotW32SyncW1PagingW2.31TrafficW33.63TrafficQPSKModulatorBTS1-Sector 1S SSoft Handoff 软切换软切换ToPSTNF1F2F3SearchRFTrafficMobileBTS1 Sector 1 W2BTS1 Sector 1-W2Combining is performed in the MobileSelection Diversity in the BSCBTS2 Sector 2 W42VocoderSelectorSlide No.64Advanced Learning SolutionsSlide 64Telstra 2001Telstra in confidenceCDMA Technology and Operations for Unicom Senior ManagersIS95 Standards IS95 Call ProcessingIS95呼叫处理呼叫处理Slide No.65Advanced Learning SolutionsSlide 65Telstra 2001Telstra in confidenceCDMA Technology and Operations for Unicom Senior ManagersIS95 Standards IS95 Call Processing IS95呼叫处理呼叫处理Carrier Selection载波选择Acquire Pilot and Synch捕获导频和同步Acquire Paging.Listen for Pages捕获寻呼等待寻呼MS sends message on Access Channel.BTS responds on PagingMS应答寻呼，在接入信道发送信息Speech on traffic channels.Signalling on Associated Control 业务信道上通话。辅助控制信令。Mobile acquires Primary or secondary carrier.Can then“Hash to other carriers.捕获主用载波或次级载波。然后才能“干扰其他载波。System Initialisation State系统初始状态System Idle State系统空闲状态System Access State系统接入状态Traffic Channel State通业务信道态 Associated control channel carries messaging using Dim&Burst or Blank&Burst.Power control on downlinkSlide No.66Advanced Learning SolutionsSlide 66Telstra 2001Telstra in confidenceCDMA Technology and Operations for Unicom Senior ManagersIS95 Standards Call Origination呼叫发起呼叫发起Mobile is synchronised to a sector and monitoring a Paging Channel 与一个扇区同步并侦测寻呼信道Mobile send one or more sequences of short probes on Reverse Access Channel.Transmit power is estimated using Open Loop Power Control.在反向接入信道发送一个或多个短序列。利用开环功率控制确定发送功率。timepowerBTS responds on PCH and directs mobile to setup call on traffic channelBTS对PCH应答，指示 在业务信道上建立呼叫Forward TCH is established 建立正向TCHMobile demodulates forward TCH and starts transmitting 解调前向TCH并开始发送 SuccessP1P1=-RSSI 73+INIT_PWR+NOM_PWR(dBm)Slide No.67Advanced Learning SolutionsSlide 67Telstra 2001Telstra in confidenceCDMA Technology and Operations for Unicom Senior ManagersIS95 Standards Call Termination 呼叫中止呼叫中止 Mobile is synchronised to a sector and monitoring a Paging Channel 与扇区同步并监测寻呼信道 Mobile detects Page message with its IMSI 用自己的IMSI探测寻呼消息 Send one or more Page Response on Reverse Access Channel.在反向接入信道上发出一个或多个寻照应答 BTS responds on PCH and directs mobile to setup call on traffic channel BTS在PCH应答，指示 在业务信道建立呼叫 Forward TCH is established with Associated Control Channel 通过辅助控制信道建立前向TCH Mobile demodulates forward TCH and starts transmitting.解调前向TCH 并开始发送powertime SuccessSlide No.68Advanced Learning SolutionsSlide 68Telstra 2001Telstra in confidenceCDMA Technology and Operations for Unicom Senior ManagersIS95 Standards Glossary of Terms 术语术语BERBit Error Rate 误比特率CDMACode Division Multiple Access 码分多址DSDirect Sequence 直接序列Eb/NoBit Energy to Noise power spectral density 比特能量对噪声功率谱密度比Eb/ItBit Energy to Noise plus interference power spectral density比特能量对噪声和干扰功率谱密度比FERFrame Error Rate 误帧率FIRFinite Impulse Response.A digital filter implementation.有限脉冲响应GPSGlobal Positioning System 全球定位系统IS95A technical standard for a CDMA cellular system CDMA移动系统技术标准PNPsuedo Noise(applies to PN codes used in CDMA)伪随机噪声QPSKQuadrature Phase Shift Keying 四相位相移键控RTTRadio Transmission Technology 无线传输技术SHOSoft-Handoff 软切换SSSpread Spectrum 扩展频谱