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1、TD-LTE 物理层规范解读,Outline,General descriptions LTE Physical layer,Frame structure related Downlink related Uplink related,Confidential,3GPP(R4)Voice/data2001-2002,3GPP(R8)TD-LTE2005-2008,Basic Version,LTE Version,LTE-A(TDD)2008-2011,4G Version,CDMA based technology,OFDM based Technology,第一阶段,第三阶段,第二阶段,
2、3GPP(R5/6/7/8)HSPA/MBMSHSPA+2003-2008,平滑演进,Enhanced Version,TDTD-LTELTE-Advanced(TDD)标准,Confidential,LTE TDD标准发展历程,3GPP为了保持未来10年在宽带移动系统中的竞争力，从2004年12月开始LTE,项目，2008年12月正式发布标准,Confidential,3GPP Long-term Evolution Target,Significantly increased peak data rate e.g.100 Mbps(downlink)and 50 Mbps(uplink),
3、Increase“cell edge bitrate”whilst maintaining same site locations as deployed today,Significantly improved spectrum efficiency(e.g.2-4 x Rel6),Possibility for a Radio-access network latency(user-plane UE RNC(or correspondingnode above Node B)-UE)below 10 ms,Significantly reduced C-plane latency(e.g.
4、including the possibility to exchange user-planedata starting from camped-state with a transition time of less than 100 ms(excludingdownlink paging delay),Scaleable bandwidth 1.4M,3M,5M,10M,15M,20M Support for inter-working with existing 3G systems andnon-3GPP specified systemsFurther enhanced MBMSR
5、educed CAPEX and OPEX including backhaulCost effective migration from Rel-6 UTRA radio interface and architectureReasonable system and terminal complexity,cost,and power consumption.Support of further enhanced IMS and core networkBackwards compatibility is highly desirable,but the trade off versus p
6、erformance and/orcapability enhancements should be carefully considered.Efficient support of the various types of services,especially from the PS domain(e.g.Voiceover IP,Presence)System should be optimized for low mobile speed but also support high mobile speedOperation in paired and unpaired spectr
7、um should not be precludedPossibility for simplified co-existence between operators in adjacent bands as well ascross-border co-existence,Wireless Access,Mobile Network,Packet,Circuit,Confidential,Services Network,Transport,Switch and Access,SCP,Service,managementlayer,Control layerSwitch layer,Acce
8、ss layer,Softswitch,Softswitch,GERAN,UMTS,WLAN,LTE,IP,ASP Enterprise App Server,HorizontalNetwork,3GPP Long-term Evolution Network Architecture,Confidential,LTE/SAE Overall Architecture,Confidential,3GPP RAN1 Term Reference,Specification of the physical layer of the radio Interface for UEand UTRAN,c
9、overing both modes of UTRAN radio interface,FDD and TDD.The work in RAN WG1 includes especially:,Specification of physical channel structures for UE and UTRANSpecification of the mapping of the transport channels onto physicalchannelsSpecification of the physical layer multiplexing,and channel codin
10、gand error detectionSpecification of the spreading and modulationSpecification of the physical layer proceduresSpecification of definition of measurements and their provision bythe physical layer to the upper layers,RAN WG1 is also carrying out work related to handling of thephysical layer related U
11、E capabilities and to physical layerrelated parameters used in UE test developed in TSG RAN.,WG1TR25.814 V1.3.2Physical layer aspectsfor EUTRA,Editor:NTT DoCoMo,WG2TR25.813 V0.9.2EUTRA and EUTRANRadio interface protocol,aspects,Editor:Nokia,LG,NEC,Motorola,Samsung,WG3TR R3.018 V0.4.0EUTRA and EUTRAN
12、Radio Access,Architecture andInterfaces,Editor:,WG4SI TR:NTT DoCoMoBase Station:EricssonTerminal:Motorola,RRM:NokiaRF System Scenarios:,Siemens,Vodafone,EricssonWG specific TRs,ConfidentialLTE Physical layer documentsPhysical layer specifications:TS 36.211,TS 36.212,TS 36.213,TS 36.214TR25.913 V7.2.
13、0Requirements for EUTRA and UTRANTR25.912 V0.1.4Feasibility Study for EUTRA and EUTRANOutcome,10,-Over 100 Mbps in a 20 MHz carrier bandwidth,1.4MHz,5MHz,10MHz,15MHz,20MHz,Alternative TD(Type 2),for TD-SCDMA compatibility,Confidential3G LTE,Spectrum PerspectiveHigher end-user bitrates by wider carri
14、er bandwidth,Allow for operation in a wide range of different spectrum Current and future 3G spectrum(2GHz,2.6GHz,)Migration of 2G spectrum(e.g.900MHz)Re-farming of other spectrum,e.g.UHF bands Uncertain size of future spectrum assignments Efficient operation in differently-sized spectrum allocation
15、s Up to 20MHz to enable very high data rates Less than 5MHz to enable smooth spectrum migration FDD:Simultaneous downlink/uplinktransmission in separate frequencybands TDD:Non-overlapping downlink/uplinktransmission in the same frequencyband,Confidential,Basic transmission techniques,Multiple Access
16、:the same MA for FDD and TDD,Modulation schemes:,BPSK,QPSK,16QAM,64QAM,MIMO and Beamforming,To use multiple antennas schemes to anti-fadong，to improvechannel capacity and spectrum efficiency,to increase thecoverage,etc.,Uplink:SC-FDMA(DFT-S-OFDM)Low PAPR Higher power efficiency Reduced uplink interf
17、erence(enables intra-cell orthogonality)Downlink:Adaptive OFDM Channel-dependent scheduling and link adaptation in timeand frequency domain,Confidential,LTE multiple Access schemes,Downlink-OFDMA Uplink-SC-FDMA,Confidential,Traditional single carrier system,单载波系统的数据传输形式是串行数据流，符号被连续传输，每个数据符号的频谱可占据整个可
18、利用的带宽。,Confidential,Multiple carriers modulation,多载波系统并行传输数据流，（使高速数据流转换低速数据流），许多符号同时传输，将输入数据符号串并转换到N个并行子信道中。,Confidential,Pulse shape for basic OFDM Tx,Confidential,LTE Physical layer-Frame structure related,Confidential,LTE Frame Structure and Resource Grid,Confidential,LTE numerology,Normal CP:5.2
19、08 for 1st symbol in one slot,4.678for othersExtended CP:16.67usSub-carrier space:15KHzChannel Raster:100KHzRB=12 sub-carrier span 1 slot,7 symbols for normal CP6 symbols for extended CPTotal RBs for UL and DL:6110,TTI=Sub-frame=1ms=2*timeslots(0.5ms),Confidential,TDD UL/DL allocations,Confidential,
20、TDD Special sub-frame structure,Confidential,Configuration of special subframe,Confidential,LTE Physical layer-Downlink related,Confidential,channels to Physical channels,下行物理信道,PBCH（物理广播信道）PDSCH（物理下行共享信道）PMCH（物理多播信道）PDCCH（物理下行控制信道）PCFICH（物理控制格式指示信道）PHICH（物理HARQ指示信道）,Confidential,DL resource allocat
21、ion,A virtual resource block is of the same size as a physicalresource block.Two types of virtual resource blocks aredefined:,-Virtual resource blocks of localized type-Virtual resource blocks of distributed type,Confidential,DL Reference signals,Three types of downlink reference signals aredefined:
22、,-Cell-specific reference signals,associated with non-MBSFN transmission-MBSFN reference signals,associated with MBSFNtransmission-UE-specific reference signals,Confidential,DL CRS-Gold generated PN sequence,Confidential,MBSFN RS-Gold generated PN sequence,freq,Confidential,DL DRS-Gold generated PN
23、sequence,RS Port 0,RS Port 1,RS Port 5,Control,time,Confidential,Overview of physical channel processing with,multiple antennas,The baseband signal representing a downlink physical channel is defined interms of the following steps:,-scrambling of coded bits in each of the code words to be transmitte
24、d ona physical channel-modulation of scrambled bits to generate complex-valued modulationsymbols-mapping of the complex-valued modulation symbols onto one or severaltransmission layers-precoding of the complex-valued modulation symbols on each layer fortransmission on the antenna ports-mapping of co
25、mplex-valued modulation symbols for each antenna portto resource elements-generation of complex-valued time-domain OFDM signal for eachantenna port,Confidential,DL transmission Modes,UE is semi-statically configured via higher layersignalling to receive PDSCH data transmissionssignalled via PDCCH UE
26、 specific search spaces,based on one of the following transmission modes,Single-antenna port;port 0Transmit diversityOpen-loop spatial multiplexingClosed-loop spatial multiplexingMulti-user MIMOClosed-loop Rank=1 precodingSingle-antenna port;port 5,Confidential,Physical multicast channel,No transmit
27、 diversity scheme is specified-Layer mapping and precoding shall be done assuming asingle antenna port and the transmission shall use antennaport 4.-In the subframes where PMCH is transmitted on a carriersupporting a mix of PDSCH and PMCH transmissions,upto two of the first OFDM symbols of a subfram
28、e can bereserved for non-MBSFN transmission and shall not beused for PMCH transmission.In a cell with 4 cell-specificantenna ports,the first two OFDM symbols of a subframeare reserved for non-MBSFN transmission in the subframesin which the PMCH is transmitted.The non-MBSFNsymbols shall use the same
29、cyclic prefix as used forsubframe#0.PMCH shall not be transmitted in subframes0 and 5 on a carrier supporting a mix of PDSCH and PMCHtransmission,Confidential,Multi-cell broadcast,Confidential,PBCH-MIB,SIBs(contained in D-BCH)are transmitted on PDSCH,Modulation:QPSK;Cell-specific scrambling;CRC mask
30、ing for antennanumbers,Transmission period:4 symbols span 4 consecutive radio frames;self-decodedin each radio frameCurrent information:DL bandwidth,SFN,PHICH period and group number,Confidential,PCFICH,The physical control format indicator channel carries information about thenumber of OFDM symbols
31、 used for transmission of PDCCHs in a subframe,Confidential,PCFICH,DLDLDLDL,Confidential,PDCCH,The physical downlink control channel carries UL/DL scheduling assignmentsand other control information including power control command,SI/paging/RA placement on PDSCH etc.A physical control channel is tra
32、nsmitted on an aggregation of one or severalconsecutive control channel elements(CCEs),where a control channelelement corresponds to 9 resource element groups.PDCCH formats,Format 0-UL grant-scrambled by C-RNTIFormat 1-DL grant for one codeword-scrambled by C-RNTI,SPS-RNTIFormat 1A-compact DL grant
33、for one codeword-scrambled by C-RNTI,SI-RNTI,P-RNTI,RA-RNTI,SPS-RNTI,TC-RNTIFormat 1B-compact DL grant for one codeword with pre-coding-scrambled by C-RNTIFormat 1C-very compact DL grant for one codeword-scrambled byRA-RNTI,SI-RNTI,P-RNTIFormat 1D-compact DL grant for one codeword with pre-coding an
34、dpower offset(MU-MIMO)-scrambled by C-RNTIFormat 2/2A-CL/OL SM-scrambled by C-RNTI,SPS-RNTIFormat 3/3A-group TPC-TPC-RNTI,.,Confidential,PDCCH,复用,PDCCH n的编码后数据流,一个subframe中,所有PDCCHs复,用的数据流比特,加扰/QPSK调制,多天线映射,添加16-bit CRC,(MAC id implicitly encoded in CRC),下行控制消息(DCI),（针对一个MAC id）,信道编码,/速率匹配,PDCCH 2的编
35、码后数据流.,Blind decoding for PDCCH:,common search space:4 or 8 CCE from index 0UE specific search space:given by hash function,Confidential,PDCCH Detection,Common search space starts from CCE index 0,UE的专有搜索集起始点产生公式表示专有搜索集的起点；表示PDCCH的级别，也就是PDCCH包含的CCE数量；表示子帧k上CCE总的数量；,l,m 2 i 1 mod 2,/,N ID i,N ID m i
36、3mod ni,cell,cell,N ID m ni 3mod ni i 2,2,Confidential,0,n,i cell m mod n i 0 i 1,inimni,PHICH The PHICH carries the hybrid-ARQ ACK/NAK for UL reception,Confidential,Synchronized signals for cell search,There are 504 unique physical-layer cell identities.The physical-layer cell identities are groupe
37、d into168 unique physical-layer cell-identity groups,eachgroup containing three unique identities.Primary synchronization signal is generated from afrequency-domain Zadoff-Chu sequence.Secondary synchronization signal is an interleavedconcatenation of two length-31 M-sequences.Theconcatenated sequen
38、ce is scrambled with ascrambling sequence given by the primarysynchronization signal.,Confidential,P-SCH/S-SCH location and mapping,Confidential,Cell Search procedure,N RB SCRB,N,Confidential,PSS,DL2,k n 31,DLRB,N,6,un(n 1)63,j,ZCu(n)e,DLRB,N,25,Confidential,SSS,d(2n)s1(m1)(n)c0(n),Segment 1-specifi
39、c 加扰,PSS-specific 加扰,Segment 1-specific 加扰(m0)(m1)直流辅同步信号（72个子载波（DC除外）子帧0上的辅同步信号PSS-specific 加扰,(m0)直流辅同步信号（72个子载波（DC除外）子帧5上的辅同步信号,Confidential,DL Resource allocation for PDSCH,A resource allocation field in each PDCCH includes two parts,a,resource allocation header field and information consisting
40、of theactual resource block assignment.Three types are designed in LTE,RA Type 0 and type 1:support by DCI format 1/2/2A,Distinguished by 1 bit in DCI 1/2/2A when DL RB10Only type 0 is used when DL RB=10,RA type 2:support by DCI format 1A/1B/1C,type 0和Type 1适用于不连续分配场景，,type 2适用于连续分配场景；资源分配主要考虑信令开销和调
41、度灵活性这两个重要因素，为此，在LTE系统中，采用了自适应颗粒度bitmap和离散bitmap的方法，在保证信令开销的前提下兼顾调度的灵活性，其中，type 0使用的是自适应颗粒度bitmap方法，type 1使用的是离散bitmap的方法.,Confidential,Resource allocation type 0,Type 0 resource assignment includes a bitmap indicating the resourceblock groups(RBGs)to be allocated to a scheduled UE.A RBG is a set of
42、consecutive physical resource blocks and the sizecan be 1,2,3,4 depending on DL system bandwidth.type 0就是利用bitmap的方法表示资源组的分配情况，bitmap中的每一个比特位按顺序对应于一个资源组的分配情况，如果比特位为1，表示其对应的资源组（包括该资源组内的所有资源块）分配给该UE，如果比特位为0，表示其对应的资源组（包括该资源组内的所有资源块）没有分配给该UE,且bitmap的比特数量等于资源组的个数。假设，下行系统带宽的资源块总数为25，分配给UE的资源块为PRB 2、PRB 3、
43、PRB 12、PRB 13和PRB 24，则相应的bimap如下图所示,Confidential,Resource allocation type 1,Divide the DL RBs into a set of RBG,the size of which is sameas type 0.,Group RBGs into a set of sub-set(total P RBG subsets).A RBG subset consists of every P-th RBG starting from RBG p,0=pP Three information fields:,First f
44、ield:to indicate the subset among the totol RBG subsets inwhich a scheduled UE has allocated resource block.Second field:one bit is used to indicate a shift of the resourceallocation span within a subset.A bit value of 1 indicates shift istriggered.Shift is not triggered otherwise.Third field:Bitmap
45、 are used to indicate the resource blocks to beallocated to a scheduled UE.,type 1相对于type 0 具有更好的调度灵活性，因为可以实现更小数量不连续资源块的调度，同时，考虑离散资源组构成资源组子集相对于连续资源组构成资源组子集具有频率分集优势。,假设，下行系统带宽的资源块总数为25，分配给UE的资源块为PRB 5、PRB 9、PRB 12、PRB 13和PRB 24，则，相应的Information信令如下页图所示,Confidential,Confidential,Resource allocation ty
46、pe 2,资源分配type 2用于表示连续的LVRB和连续的,DVRB分配,所谓的Compact模式。,在DCI format 1A、1B和1D中，1比特用于标识资,源分配type 2表示的是连续的LVRB，还是连续的DVRB（0表示LVRB，1表示DVRB）分配；而在DCI format 1C中，使用资源分配type 2只表示连续的DVRB分配.,采用树状结构进行资源指示，资源指示RIV由“起点,RB的位置”，以及“连续的RB的长度”共同确定，其中每个资源指示构成树状结构中的一个节点。,例如：假设，下行系统带宽中可用资源块数为6，,当用户分得资源块为、2、3、4、5时，对应的RIV值为16；
47、节点16对应的子节点就是就是用户分得的资源块，同层中的位置为，所在层数为5，表示的资源块起始点为资源块，分得连续资源为5个资源块；,Confidential,LTE Physical layer-Uplink related,Confidential,channels to Physical channels,上行物理信道,PRACH（物理随机接入信道）PUSCH（物理上行共享信道）PUCCH（物理上行控制信道）,UL,RBscRBN N,RBscN,N symb,cell and should be fulfill:6 N RB 110,k N RB N scRB 1,N symb N sc
48、RB,l N symb 1,UL resource grid,The quantity of UL RBs depends on UL,UL system bandwidth is given by SIB2,The number of SC-FDMA symbols in a,slot depends on the UL cyclic prefix:Normal CP:7 SC-FDMA symbols,Extended CP:6 SC-FDMA symbolsSame CP scaling as DL,UL CP type is given by SIB2 while DL CP,type
49、 is detected by blind detection.,Sub-carrier spacing:15Khz,1RB contains 12 sub-carriers in frequency,domain and 7/6 symbols in time domain.,Non DC sub-carrier in UL.,UL,TslotConfidential,l 0,UL,UL,(k,l),k 0,UL,transmission bandwidth configured theUL,Confidential,UL DM RS,Generated from frequency dom
50、ain Zadoff-Chu sequence or CG CAZAC,Associated with transmission of PUSCH or PUCCH,Confidential,UL DM RS,对于解调参考信号，解调参考信号与数据（PUSCH或PUCCH）具有相同的带宽。由于PUSCH的带宽是可配置的，因此，参考信号的序列长度也是可变的。也就是说，不同的长度的参考信号是不同的（这跟下行参考信号不一样，下行参考信号，不同长度的参考信号是通过对同一序列进行截断获得）。LTE规定将所有的上行参考信号分为30个组，每个组里，均包含所有可用上行带宽对应的参考信号的1条或2条根序列.,Co
