npo培训课件lte ofdm原理介绍

1、 NSN TD-LTE开机过程原理培训Kerry 2014-04-25LTE网络架构介绍OFDM原理介绍帧结构配置手机开机物理层过程下行物理信道和物理信号手机开机注册Attach信令过程小区选择和重选过程及原理随机接入过程S- GW + P-GWGGSNSGSNRNCNode B (NB)Direct tunnelGGSNSGSNI-HSPAMMEHSPA R7HSPA R7LTE R8Node B + RNC FunctionalityEvolved Node B (eNB)GGSNSGSNRNCNode B (NB)HSPAHSPA R6LTEUser planeControl Plane

2、Flat architecture: single network element in user plane in radio network and core networkLTE网络架构的演进LTE-UE 无线部分 (E-UTRAN，无RNC)PDN 核心网部分 (EPC)PCRF:Policy & Charging Rule FunctionMMES10S6aServingGatewayS1-US11PDNGatewayS1-MMEPCRFS7Rx+SGiS5/S8EvolvedNode B(eNB)cellX2LTE-UuHSSMME: Mobility Management Ent

3、itySAEGateway其中：核心网EPC部分需要新增：MME，SGW和PGW共3个网元 无线侧E-UTRAN部分需要新增:eNodeB(增强型基站）LTE/SAE网络架构介绍OFDM 子载波特性时域:66.67us频域带宽:1/66.67us=15kHz，频域带宽定义：峰值到第一个零点 的频率间隔。 每相邻两个零点之间的间隔为子载波的带宽。傅里叶正变换timeamplitudeTsTime Domainfrequency f/fsspectral power densityFrequency Domainfs傅里叶逆变换(1) 、第k个子载波C在t时刻的信号表示为在此(2) 、所有子载波在

4、t时刻的信号表示为(3) 、展开时信号表示为(4) 、最终的LTE子载波符号信号表示公式为：(5) 、子载波解调过程OFDMA-数学模型f0f1f2f3f4No ACI (Adjacent Carrier Interference)多个OFDM 子载波的频谱Rake ReceiverCDMA 所接收到的多径信号: 解扩后可分辨的多径信号IS-95 CDMA 关键技术-Rake 接收多径干扰（符号间ISI干扰）多径干扰（ISI干扰）Time 0 TsInter Symbol InterferenceBTS+d1(Direct path)d3d2d1 d2 d3Time 0 Tt Ts+TtTt第

5、1径第2径第1径的第2个符号与第2径的第1个符号叠加干扰在没有保护间隔的情况下，由于多径的存在，各径之间将在交叠处产生符号间干扰(ISI)保护间隔与循环前缀无保护间隔保护间隔与循环前缀加保护间隔保护间隔为了最大限度地消除符号间干扰，在OFDM符号之间插入保护间隔，保护间隔长度大于无线信道的最大时延扩展，这样一个符号的多径分量不会对下一个符号造成干扰 保护间隔与循环前缀加循环前缀FFT积分区间为了避免空闲保护间隔由于多径传播造成子载波间的正交性破坏，将每个OFDM符号的后时间中的样点复制到OFDM符号的前面，形成循环前缀(cyclic prefix) 只要各径的延迟不超过Tg，都能保正在FFT的

6、积分区间内包含各径各子载波的整数个波形ISI干扰定义:(Inter Symbol Interference)在一个数字传输系统中所接收的信号的失真，该失真是表现在单个信号的暂时分散和随后的重叠，直到接收器无法准确地区分状态之间改变在一个或多个电键间隔中的额外信号能量，该能量干扰了在另外一个电键间隔的信号的接收由于来自一个或多个电键间隔中的额外信号能量所造成的干扰，它妨碍了在另外一个电键间隔内的信号接收ISI干扰定义(符号间干扰)Cyclic Prefix(CP的引入和作用）CPTsTime Domain123Symbol DetectionIntervalCPCPSYMBOLSYMBOLSYM

7、BOL123ttotal symbol time T(s)Guard TimeT(g)CP T(g)Useful symbol time T(b)Last part of the next Symbols is used as Cyclic Prefic (CP)CP作用symbolCPsymbolCPsymbolCPsymbolCPsymbolCPsymbolCPsymbolCPsymbolCPsymbolCP231321获取symbol起始和终止位置，保主symbol间正交，抗符号间干扰抗多径时延，CP长度决定同一信号的最大多径时延LowPasscos(2fct) -sin(2fct) I

8、QModulationMapperIFFTs0ModulationMappers1ModulationMappersN-1b10 ,b11,Serial toParallel Converter(BitDistrib.)b20 ,b21,bN-1 0 BinaryCodedData.D Ax0, x1, , xN-1IQSplitLowPassD ARFfreq.f1f2f0fN-1 s0s1sN-1s2Frequency Domaintimet1t2t0tN-1 x0 x1xN-1x2TimeDomainCP/GuardGenerationIQOFDM TransmitterTime Dom

9、ain SignalApplies different Modulation Schemes:OOK,BPSK,QPSK, 1&QAM, 64QAMFrequency Domain Signal:Collection of Sinusoids)Channel CorrectionDemodulatorBit MappingjIQA DChannelEstimationRFLow Noise Amp.+ BandpassA DAGCAutomaticGain ControlDe-rotatorsignal strengthLNA gainFrequency And Timing Syncsign

10、al autocorreationphase correctiontimeeadjust.s0s1sN-1reference(pilot)channelresponses0Bit Mappings1Bit MappingsN-1.B10 ,B11,B20 ,B21,BN-1 0 Bit DistributionSoft BitCodedDatafreq.f1f2f0fN-1 s0s1sN-1s2Frequency DomainTime Domaintimet1t2t0tN-1 y0y1yN-1x2QPSKImRe10110001skd11d10OFDM ReceiverWindowing +F

11、FTFrequency DomainOFDMA符号最大支持64 QAM通过CP解决多径干扰兼容MIMO Sub-carriers Sub-frame Frequency Time Time frequency resource for User 1 Time frequency resource for User 2 Time frequency resource for User 3 System Bandwidth The OFDM Signal TD-LTE帧结构Name1.4 MHz3.0 MHz5.0 MHz10.0 MHz15.0 MHz20.0 MHzSub frame (TTI

12、)1 ms1 ms1 ms1 ms1 ms1 msSubcarrier15 kHz15 kHz15 kHz15 kHz15 kHz.15 kHzFFT size128256512102415362048Number of subcarriers721803006009001200Symbols per slot7 with normal CP and 6 with extended CPCyclic prefix4.7 (5.2) s with normal CP and 16.7 s with extended CPTD-LTE帧结构 下:上行时隙配比 (参数：tddFrameConf)Up

13、link-downlink ConfigurationDownlink-to-Uplink Switch-point periodicitySubframe number012345678905 msDSUUUDSUUU1(目前使用2:2)5 msDSUUDDSUUD2(支持1:3)5 msDSUDDDSUDD310 msDSUUUDDDDD410 msDSUUDDDDDD510 msDSUDDDDDDD65 msDSUUUDSUUD特殊子帧配置 (参数： tddSpecSubfConf)FormatNormal CPExtend CPDwPTSGPUpPTSDwPTSGPUpPTS03101

14、38119483210392311210141213725(支持）39282693917（目前使用）102-8111-distNametddFrameConftddSpecSubfConf513831_1025513526_4127TD-LTE时隙结构144 Ts = 4.69 s012345678910111213141516171819160 TsCPSymbolCPSymbolCPSymbolCPSymbolCPSymbolCPSymbolCPSymbolRadio frame = 10 mssubframe = 1 msOFDM Symbol (Time Domain Samples)

15、x0, x1, , x2047Cyclic Prefixx2047-Ncp, x2047Symbol Tsym = 2048 Ts = 66.67 sTcp = Ncp TsCPSymbol512 Ts = 16.7 sCPSymbolCPSymbolCPSymbolCPSymbolCPSymbolDf = 15 kHz, UL/DL - Extended PrefixCPSymbol1024 Ts = 33.3 sCPSymbolCPSymbolDf = 7.5 kHz, UL/DL - Extended PrefixDf = 15 kHz, UL/DL - Normal PrefixSlo

16、t = 15360 Ts = 500s Time Structure and CP lengthShort cyclic prefix:Long cyclic prefix:Copy= Cyclic prefix= Data5.21 s16.67 sTs: sampling time of the overall channel. Basic Time Unit.Ts =1 secSubcarrier spacing X max FFT sizeTs = 32.5nsec2048144204814420481442048144204814420481442048160T TS66,74,766,74,766,74