cdma2000_1X基础知识(中国移动)

1,CDMA 原理,2,主要内容,码分多址的基本原理 码分多址的关键技术 CDMA同GSM的比较,3,目标,不同用户是如何用码区分出来的 三种CDMA码的用途 CDMA逻辑信道的划分 编码，软切换和功率控制,4,码分多址的基本原理 码分多址的关键技术 CDMA同GSM的比较,5, N Users / Wideband Channel, C/I is still negative after I.F. filtering but,positive after despreading process, Can consider despreading as the last “filtering“ stage, 3 Users / Narrowband Channel, C/I is negative prior to I.F. filtering and,positive after filtering,1,2,3,1,TDMA,(3 timeslots shown),30 kHz,Frequency,Time, 1 User/ Narrowband Channel, C/I is negative prior to I.F. filtering and,positive after filtering,FDMA,30 kHz,Frequency,Time,DS-CDMA,1.23 MHz,Frequency,Time,CDMA,CDMA基本原理,Walsh Code,6,IS-95 was an interim standard developed by TIA/EIA. IS-95 defined mobile station and base station compatibility for the first application of CDMA technology in cellular systems. TIA/EIA is an accredited standards development organization through the ANSI TIA/EIA: Telecommunications Industries Association/ Electronics Industries Association ANSI: American National Standards Institute,IS-95接口标准,7,MSC,CBSC,PSTN,BTS,CDMA系统网络结构,8,BTS,CBSC,CDMA IS-95A+系统结构实例,开放的网结构Opening Network Architecture CDG IOS,Cell Site,Voice,Control,L Interface,UNO,OMC- R,BTS,BTS,XC,IWU,MM,MSC/VLR,CDG IOS,IN Application,HLR,ANSI-41,9,CDMA 物理信道,Tx: 870-880MHz Rx: 825-835MHz,10,CDMA 首选载波分配,11,联通拥有的频率资源,825,835,845,CDMA Tx,870,880,CDMA Rx,960,CDMA/AMPS,UC CDMA,Spectrum Allocation,GSM Rx,915,GSM Tx,Freq (MHz),CMCC GSM,935,890,909,UC GSM,UC,UC,954,A Band,B Band,A Band,B Band,CMCC,894,CMCC,939,12,CDMA的基本原理：CDMA码,PN码 （伪随机噪声序列） 貌似随机，实际上是有规律的周期性二进制序列。在CDMA中用到两个伪随机序列，长码和短码。 Walsh Code 具有正交特性,13,伪随机码 (PN CODE) 的生成,0,1,0,0 0 1 1 1 0 0 4 0 1 0 2 1 0 1 5 1 1 0 6 1 1 1 7 0 1 1 3 0 0 1 1,1,4,2,5,6,7,3,14,0,1,0,0 0 1 1 1 0 0 4 1 1 0 6 1 1 1 7 0 1 1 3 1 0 1 5 0 1 0 2 0 0 1 1,1,4,6,7,3,5,2,伪随机码 (PN CODE),15,Walsh码递归公式,16,8阶Walsh码,W0 0 0 0 0 0 0 0 0 W1 0 1 0 1 0 1 0 1 W2 0 0 1 1 0 0 1 1 W3 0 1 1 0 0 1 1 0 W4 0 0 0 0 1 1 1 1 W5 0 1 0 1 1 0 1 0 W6 0 0 1 1 1 1 0 0 W7 0 1 1 0 1 0 0 1,17,CDMA Codes,PN short code Length215 1 1 215 32，768 chips Walsh code 64 PN long code Length242-1 4.4 1012 chips,18,CDMA系统中采用的编码,Walsh 码 在CDMA前向逻辑信道中使用,以区分同一小区或扇区 用户,19,PN 短码 区分不同扇区或小区 伪随机序列 215 = 32,768 unit (period 26.67ms) 用于前向及反向物理信道扩频,CDMA系统中采用的编码,20,64 chips,32,768 chips / 64 = 512 PN offsets,.,.,PN chips,PN短码偏置,21,长码 用于反向逻辑信道区分不同用户 伪随机序列 242-1 unit 在前向链路上对业务及寻呼信道进行扰码,CDMA系统中采用的编码,22,CDMA前向信道结构,23,CDMA反向信道结构,24,CDMA前向信道结构,25,CDMA前向信道结构,26,CDMA反向信道结构,27,CDMA反向信道结构,28,Overhead Channels Traffic Channels Carry messaging,Identification and Primarily carry voice and user data timing information traffic Carry some signaling information used to control MS Pilot Sync Forward Forward Traffic Paging Access Reverse Reverse Traffic,CDMA基本原理,29,Pilot Sync Paging Traffic,DSS by Walsh 0,DSS by Walsh 32,DSS by Walsh 1-7,DSS by remaining 55 Walsh codes,64 logical channels are combined Then quadrature spread using pilot PN code,CDMA基本原理,30,Spread by long code (offset),Spread by long code (offset),Access,Traffic,Quadrature spread using pilot PN code without any offset,CDMA基本原理,31,码分多址的基本原理 码分多址的关键技术 CDMA同GSM的比较,32,码激励线性预测编码(CELP) 功率控制 软切换,CDMA关键技术,33,CELP,Code Excited Linear Predictive Compressed digital voice between XC and MS Uses much less data to approximate the original signal 8K or 13K,34,功率控制,反向开环功率控制 反向闭环功率控制 前向闭环功率控制,35,功率控制的重要性,36,Forward,Reverse,远近效应,功率控制,Based on: power measurement (Eb/No) frame error rate(FER),37,Time,Access Probes,Initial Power,Initial Power+open loop correction,Tx Power(dbm),开环功率控制,38,开环功率控制：,Assumes Loss is Similar on Forward and Reverse Paths Receive Power+Transmit Power = -73 All powers in dBm Example: For a Received Power of -85 dBm Transmit Power = (-73) - (-85) Transmit Power = +12 dBm Provides an Estimate of Reverse TX Power for Given Propagation Conditions,39,反向功率控制：,Maximum System Capacity is Achieved if: All Mobiles are Powered Controlled to the Minimum Power for Acceptable Signal Quality As a result, all Mobiles are Received at About Equal Power at the Base Station Independent of Their Location There are Two Types of Reverse Control: Open Loop Power Control Closed Loop Power Control Open & Closed Loop Power Control are Always Both Active,40,闭环功率控制：,Directed by Base Station Updated Every 1.25 msec Commands Mobile to Change TX Power in +/-1 dB Step Size Fine Tunes Open Loop Power Estimate Power Control Bits are “Punctured“ over the Encoded Voice Data Puncture Period is two 19.2 kbps Symbol Periods = 103.6 usec,41,FDMA & TDMA 切换,Break-before-make,42,CDMA软切换,Make-before-break,43,CDMA软切换,更软切换 软切换 CBSC 间软切换,44,Narrow Band,Cells Compete,Mobile Position,Cell A,Cell B,Soft Handoff,Signal Strength,A,B,CDMA,Cells Team up,Break Before Make,Make Before Break,软切换,45,软切换导频集,Active,Active,Active,Neighbor,Neighbor,Neighbor,Neighbor,Neighbor,Neighbor,Neighbor,Remaining,Remaining,有效导频集 相邻导频集 剩余导频集 候选导频集,46,软切换,Threshold & Timer T-Add T-Comp T-Drop T-Tdrop,Search, compare, combine, then Soft handoff,47,软切换参数,Pilot Strength,T-Comp,T-Add,T-drop,T-Tdrop,Time,Active Pilot,Neighbor or Remaining,Neighbor,Active,Candidate,48,分集技术：,信号元素合并(Rake 接收机) 帧选择,49,Rake接收机,50,Path Diversity Improves Voice Quality,Receiver,Receiver,Receiver,Mobile Rake Receiver,Analog TDMA Calls,Fading,D/A,Audio,Fading,D/A,Mobile,Receiver,CDMA Calls,Effects of fading are mitigated through use of,multiple receivers that sum radio signals from,different cells and from reflected rays.,51,Soft Handoff Improves Voice Quality,52,Frequency Diversity Improves Voice Quality,Outgoing Waveform,1.25 Mhz,1.25 Mhz,This 400 Khz fade of 12 db only affects 1/3 of CDMA bandwidth.,Therefore, total fade to CDMA user is 2 db,The entire 30 KHz Channel of TDMA is affected by this same fade.,Therefore, total fade to end user is 12 db.,CDMA Offers More Protection Against Frequency Selective Fading,30 Khz,Outgoing Waveform,-80 db,-90 db,-110 db,-120 db,30 Khz,Received Waveform,12 dB Fade,2 dB Loss,12 dB Fade,12 dB Loss!,CDMA,TDMA,53,码分多址的基本原理 码分多址的关键技术 CDMA同GSM的比较,54,CDMA 10 MHz 8个CDMA载波 每载波、每扇区20个话音信道 每小区3个扇区 频率复用系数=1 支持有效话音信道数=8 * 20 * 3 = 480,CDMA和GSM技术的比较：,CDMA与GSM的小区容量对比：,GSM 10 MHz 50个GSM载波(10MHz/200KHz) 每载波8个时隙(包括控制信道和业务信道) 每小区3个扇区 频率复用系数(通常)=4 可配置的站型为S444 支持有效话音信道数 =48 * 8 * /4 = 96-87,去除BCCH,在相同频谱利用度的情况下，CDMA的容量是GSM的5.5倍,55,CDMA 小区覆盖随负载的变化而变化 在无负载的情况下，小区半径是标准GSM的3倍 在每扇区20信道的负载条件下，半径是标准GSM的2倍 GSM 小区在加载的情况下，覆盖保持不变,与GSM相比：,在反向链路预算上，CDMA比GSM高5dB,反向链路预算比较,在相同覆盖条件下， 基站数量减少,56,CDMA： N=1 频率复用,GSM： N=4 频率复用,2,3,4,4,4,3,2,4,3,CELL 1,CELL 1,CELL 1,2,频率规划,工程设计：GSM 频率规划 CDMA PN Offset 规划,57,减少由于切换产生的掉话,CDMA 小区/扇区切换采用软/更软切换 切换是先接续再中断 服务质量高，有效减低掉话,Cell Site A,H A N D O F F,Cell Site B,MAKE,AMPS GSM,B R E A K,Cell Site A,Cell Site B,Cell Site A,Cell Site B,CDMA,中断,减低掉话，提高服务质量,其它无线系统 小区/扇区切换采用硬切换 切换是先中断再接续 容易产生掉话,58,CDMA特点：,技术,特点,技术特点,59,Cdma2000 1X 技术特点 Motorola cdma2000 1X 网络结构,60,cdma20001X 技术特点,61,Performance Enhancements,Reverse Link Pilot for Each Mobile True QPSK Modulation Continuous Reverse Link Waveform Improved Convolutional Encoding for 14.4 kbps Voice Channels Fast Forward & Reverse Link Power Control Supports Auxiliary Pilots for Beam Forming Forward Link Transmit Diversity - OTD, Multi-Antenna,cdma 2000,62,Reuse of TIA/EIA-95-B,cdma2000 is Fully Backwards Compatible with TIA/EIA-95-B Reused Aspects of TIA/EIA-95-B: TIA/EIA-95-B Radio Interface IS-707 Data Services IS-127 EVRC 8 kbps Vocoder and IS-733 13 kbps Vocoder IS-637 SMS & IS-683 Over the Air Activation IS-98 and IS-97 Minimum Performance Standards Common Broadcast Channels (Pilot, Sync Paging) Allows cdma2000 to be Deployed Sooner,63,cdma2000 Terms & Definitions,Chip A chip is a data bit at the final spreading rate SR - Spreading Rate Defines the final spreading rate in terms of 1.2288 Mcps. So a 3.6864 Mcps system is called a SR3 system. RC - Radio Configuration Defines the physical channel configuration based upon a base channel data rate. RCs contain rates derived from their base rate. For example, RC3 is based on 9.6 kbps and includes 1.5, 2.7, 4.8, 9.6, 19.2, 38.4, 76.8, 153.6, and 307.200 kbps. RCs are coupled to specific Spreading Rates,64,cdma2000 SR1,Is an Improved TIA/EIA-95-B Narrowband System Occupies the Same 1.23 MHz Bandwidth as TIA/EIA-95-B Forward Link: Adds Fast Power Control Uses QPSK Modulation Rather than Dual BPSK to: Use 3/8 Rate Convolutional Encoder instead of 3/4 for 14.4 Service (improves error correction) 128 Walsh Codes to Handle More Soft Handoffs for 9.6 service Reverse Link: Uses Pilot Aided BPSK to Allow Coherent Demodulation Uses 1/4 Rate Convolutional Encode Instead of 1/2 or 1/3 Uses HPSK Spreading Enhance System Capacity,65,cdma2000 1X 要点,技术改善 对数据应用支持 MAC, QoS, 和turbo码 快速前后向功率控制 反向信道相干解调 后向兼容 IS-95A/B Operator Benefits 可支持高达153.6k bps数据速率 与IS-95A/B相比，数据应用能力有4-6倍的提高 与IS-95A/B相比， 话音容量有1.5-1.8倍的提高，减小了运营成本 在保护IS-95A/B投资的前提下，提供了经济有效的过渡策略,66,CDMA2000 1x 原理 可变长度的 Walsh Code 码,67,Walsh Code Length v.s Data Rate,Encoder Rate = r,Interleaver,Repetition Factor = R,+,A(t),Walsh code (Length WL) at 1.2288mcps,Data Rate,Coded Symbols,Repeated Symbols,Modulation Symbols,A(t)=d(t)/r*R*WL,WL=1228800*r/d(t)/R,68,W08 0 0 0 0 0 0 0 0 W18 0 1 0 1 0 1 0 1 W28 0 0 1 1 0 0 1 1 W38 0 1 1 0 0 1 1 0 W48 0 0 0 0 1 1 1 1 W58 0 1 0 1 1 0 1 0 W68 0 0 1 1 1 1 0 0 W78 0 1 1 0 1 0 0 1,Walsh Code:Generation & Use in 95A/B,69,Walsh Code:Generation & Use in CDMA2000,W01 =0,W02 =00,W12 =01,W04 =0000,W24 =0011,W14 =0101,W34 =0110,W08 =00000000,W48 =00001111,W28 =00110011,W68 =00111100,W18 =01010101,W58 =01011010,W38 =01100110,W78 =01101001,( W016 ,W816),( W416 ,W1216 ),( W216 ,W1416 ),( W616 ,W1416 ),( W116 ,W916 ),( W516 ,W1316 ),( W316 ,W1116 ),( W716 ,W1516 ),SF=1,SF=2,SF=4,SF=8,SF=16,70,Effects of Using Variable Length Walsh Codes for Spreading,SF=16,SF=2,SF=4,SF=8,1 1 1 1 1 1 1 1,1 1 1 1 -1 -1 -1 -1,1 1 -1 -1,1 1 1 1,1 1,1 -1,1 -1 1 -1,1 -1 -1 1,1,1 -1 1 -1 1 -1 1 -1,1 -1 1 -1 -1 1 -1 1,1 -1 -1 1 1 -1 -1 1,1 -1 -1 1 -1 1 1 -1,1 1 -1 -1 -1 -1 1 1,1 1 -1 -1 1 1 -1 -1,1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1,1 1 1 1 1 1 1 1 -1 -1 -1 -1 -1 -1 -1 -1,1 1 1 1 -1 -1 -1 -1 1 1 1 1 -1 -1 -1 -1,1 1 1 1 -1 -1 -1 -1 -1 -1 -1 -1 1 1 1 1,Using Shorter Walsh Codes Precludes Using all Longer Codes Derived from the Original Shorter Codes on a Branch map into Longer Codes,1 1 -1 -1 1 1 -1 -1 1 1 -1 -1 1 1 -1 -1,1 1 -1 -1 1 1 -1 -1 -1 -1 1 1 -1 -1 1 1,1 1 -1 -1 -1 -1 1 1 1 1 -1 -1 -1 -1 1 1,1 1 -1 -1 -1 -1 1 1 -1 -1 1 1 1 1 -1 -1,1 -1 1 -1 1 -1 1 -1 1 -1 1 -1 1 -1 1 -1,1 -1 1 -1 1 -1 1 -1 -1 1 -1 1 -1 1 -1 1,1 -1 1 -1 -1 1 -1 1 1 -1 1 -1 -1 1 -1 1,1 -1 1 -1 -1 1 -1 1 -1 1 -1 1 1 -1 1 -1,1 -1 -1 1 1 -1 -1 1 1 -1 -1 1 1 -1 -1 1,1 -1 -1 1 1 -1 -1 1 -1 1 1 -1 -1 1 1 -1,1 -1 -1 1 -1 1 1 -1 1 -1 -1 1 -1 1 1 -1,1 -1 -1 1 -1 1 1 -1 -1 1 1 -1 1 -1 -1 1,71,64,4,8,16,32,1,2,9600,19200,38400,76800,153600,307200,614400,Data rate -bps-,Walsh Code Length -chips-,Walsh Code Length v.s Data Rate,72,Long Code Generator,Bit Selector (Decimator),MUX and Signal Point Mapping 0 +1 1 -1,PC Channel Gain,Data Channel Gain,Data Channel Gain,Puncture PC Sym. (optional),Puncture PC Sym. (optional),Walsh Code,Yq,Yi,MUX Control,I,Q,ds1 (t) Wi (t),ds2 (t) j Wi (t),ds1 (t),ds2 (t),PC Bits 800 bps + or - Values,Complex Walsh Covering,73,X .PN i(t),X . j .PN q(t),= ds1 (t) Wi (t). PN i(t),= ds1 (t) Wi (t). j .PNq(t),S2,Z1,Y . j .PN q(t),= ds2 (t) j Wi (t). j .PNq(t),jPNq (t),S3,S0,S1,Y .PN i(t),= ds2 (t) j Wi (t). PN i(t),PNi (t),S2,S0,S3,S1,Complex PN Spreading and Mapping,Real Sum,Imag Sum,Zo,74,CDMA2000 1x 原理 CDMA2000 1x 前反向信道结构,75,FL SR1/3,Common Assignment,Common Power Control,Pilot,Common Control,Sync,Traffic,Broadcast,Paging (SR1),Quick Paging,F- Pilot,Transmit Diversity Pilot,Auxiliary Pilot,Auxiliary Transmit Diversity Pilot,0-1 Dedicated Control,0-1 Fundamental,Power Control /Reverse Pilot,0-7 Supplemental Code RC 1-2,0-2 Supplemental Code RC 3-9,CDMA2000 Forward Link Channels,76,Tx Data Rates (bps),20ms Frame,RC1,RC2,RC3,RC4,RC5,1200,307200,153600,76800,38400,19200,9600,4800,2400,Rate Set 1 “derived”,F-SCH Walsh Codes vs Data Rates for Radio Configuration 3,77,Tx Data Rates (bps),20ms Frame,RC1,RC2,RC3,RC4,RC5,1200,307200,153600,76800,38400,19200,9600,4800,2400,Rate Set 1 “derived”,F-SCH Walsh Codes vs Data Rates for Radio Configuration 4,78,RL SR1/3,Access,R-TCH RC 1/2,Enhanced Access Ch Operation,R-Common Control Ch Operation,R-TCH Operation RC 3-6,R-FCH,0-7 R-SCCH,R-Pilot Ch,Enhanced Access,R-Pilot Ch,R-CCCH,R-Pilot Ch,0-1 R-DCCH,0-1 R-FCH,0-2 R-SCH,R-Power Control SubCh,CDMA2000 Reverse Link Channels,79,MUX,Pilot (all 0s),PC Bits,PC Bits,Pilot (all 0s),384 chips,A,PC Bits,Pilot (all 0s),Reverse Pilot Channel with Reverse PC subchannel,80,Reverse Link Frame =20ms=16PCGs,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,1 PCG,PC sub-channel,Reverse Pilot CH,Structure of Pilot Symbols and Power Control Bits,81,R-DCCH,I - data,Q - data,82,CDMA2000 1x 原理 增强型软切换,83,Cell A,Cell B,Soft Handoff,Signal Strength,A,B,T1,T2,M1,M2,84,CDMA2000 1x 原理 CDMA2000 OSI结构,85,Signaling Services,IP PPP,TCP,UDP,Packet Data Application,High - Speed Circuit Network Layer Services,Voice Services,Circuit Data Application,MAC,LAC,LAC Protocol,Null LAC,Multiplexing,MAC Control State,Best Effort Delivery RLP,QoS Control,Physical Layer,Link Layer (OSI 2),Upper Layers (OSI 3-7),Physical Layer (OSI 1),Unique to cdma2000,cdma2000,86,LAC function,Length and CRC Fields,Encapsulated LAC-PDU,LAC-PDU Fragments,SAR,SAR