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使用SRS和PUCCH的上行链路波形建模

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此示例演示了如何配置用户设备（UE）和特定于单元格的参考信号（SRS）传输。物理上行链路控制通道（PUCCH）也配置为传输。

Introduction

SRS配置分为2个部分 - UE特异性和细胞特异性。特定于UE的部分描述了此UE的实际SRS传输的时间表和内容。特定于单元格的部分描述了电池中任何UE可以传输的时间表 - 特定于UE的时间表必须是此时间表的子集。

在此示例中，细胞特异性的SRS配置具有5ms的周期性，偏移为0（由srs.subframeconfig = 3as indicated in TS36.211, Table 5.5.3.3-1 [1]). The UE-specific SRS configuration has 10ms periodicity with an offset of 0 (signaled bysrs.ConfigIdx = 7如TS36.213中所示，表8.2-1 [2]). The cell-specific configuration means that for this cell, two opportunities for SRS transmission exist within each frame, subframes 0 and 5. All UEs in the cell must shorten their Physical Uplink Control Channel (PUCCH) transmissions during these subframes to allow for SRS reception without interference, even if they are not transmitting SRS themselves. The UE-specific configuration means that this UE is configured to generate SRS only in subframe 0.

输出在the MATLAB® command window when running this example shows PUCCH transmission in all 10 subframes, with shortening in subframes 0 and 5, and an SRS transmission in subframe 0.

UE Configuration

ue = struct;ue.nulrb = 15;资源块数量的％ue.ncellid = 10;％物理层单元身份ue.Hopping ='Off';％禁用频率跳跃ue.CyclicPrefixUL ='普通的';% Normal cyclic prefixue.duplexmode ='fdd';％频分双工（FDD）ue.NTxAnts = 1;% Number of transmit antennasue.NFrame = 0;％帧数

Pucch配置

pucch = struct;% Vector of PUCCH resource indices, one per transmission antennapucch.ResourceIdx = 0:ue.NTxAnts-1; pucch.DeltaShift = 1;％Pucch Delta Shift参数pucch.CyclicShifts = 0;% PUCCH delta offset parameterpucch.ResourceSize = 0;分配给Pucch的资源的百分比

SRS Configuration

srs = struct; srs.NTxAnts = 1;% Number of transmit antennassrs.subframeconfig = 3;% Cell-specific SRS period = 5ms, offset = 0srs.BWConfig = 6;％细胞特异性SRS带宽配置srs.BW = 0;% UE-specific SRS bandwidth configurationsrs.HoppingBW = 0;% SRS frequency hopping configurationsrs.TxComb = 0;百分比梳理传输指标srs.freqposition = 0;% Frequency domain positionsrs.configidx = 7;% UE-specific SRS period = 10ms, offset = 0srs.clicshift = 0;% UE-cyclic shift

Subframe Loop

这processing loop generates a subframe at a time. These are all concatenated to create the resource grid for a frame (10 subframes). The loop performs the following operations:

  • SRS信息: By callingltesrsInfo我们可以获取与给定子框架有关的SR相关的信息。这IsSRSSubframefield of the structureSrsinforeturned from theltesrsInfo呼叫指示当前的副帧（由ue.NSubframe）是一个特异性的SRS子帧（IsSRSSubframe = 1）or not (IsSRSSubframe = 0）。该字段的价值可以复制到ue.Shortened场地。这样可以确保随后的PUCCH生成将正确尊重所有子帧的细胞特异性SRS配置，从而省略了细胞特异性SRS子帧中PUCCH的最后一个符号。

  • PUCCH 1 Demodulation Reference Signal (DRS) Generation and Mapping: The DRS signal is located in the 3rd, 4th and 5th symbols of each slot and therefore never has the potential to collide with the SRS.

  • Pucch 1代和映射: Unlike the DRS, the PUCCH 1 transmission can occupy the last symbol of the subframe unlessue.shortened = 1。在这种情况下，子帧的最后一个符号将空空。

  • SRS Generation and Mapping：在这里，我们根据UE特定的SRS配置生成和映射SRS。这俩ltesrsindicesandltesrs功能使用字段ue.NSubframeandsrs.ConfigIdxto determine if the current subframe is configured for SRS transmission; if not, the output of both functions is empty.

txgrid = [];％创建空资源网格为了i = 1:10％流程10个子帧% Configure subframe number (0-based)ue.nsubframe = i-1;fprintf（'副帧％d：\ n'，ue.nsubframe）;% Establish if this subframe is a cell-specific SRS subframe,% and if so configure the PUCCH for shortened transmissionSrsinfo= lteSRSInfo(ue, srs); ue.Shortened = srsInfo.IsSRSSubframe;% SRS信息复制到问题结构% Create empty uplink subframetxsubframe = lteulresourcegrid（ue）;% Generate and map PUCCH1 DRS to resource griddrsindices = ltepucch1drsindices（ue，pucch）;% DRS indicesdrssymbols = ltepucch1drs（ue，pucch）;％DRS序列txsubframe（drsindices）= drssymbols;% Map to resource grid％生成并映射PUCCH1到资源网格pucchIndices = ltePUCCH1Indices(ue, pucch);％pucch1指数ack = [0;1];% HARQ indicator valuespucchSymbols = ltePUCCH1(ue, pucch, ACK);% PUCCH1 sequencetxsubframe（pucchIndices) = pucchSymbols;% Map to resource gridif(ue.Shortened) disp(“传输缩短的Pucch”）；elsedisp('Transmitting full-length PUCCH'）；结尾% Configure the SRS sequence group number (u) according to TS% 36.211 Section 5.5.1.3 with group hopping disabledsrs.SeqGroup = mod(ue.NCellID,30);％根据TS 36.211配置SRS基本序列编号（V）% Section 5.5.1.4 with sequence hopping disabledsrs.seqidx = 0;% Generate and map SRS to resource grid% (if active under UE-specific SRS configuration)[srsIndices, srsIndicesInfo] = lteSRSIndices(ue, srs);% SRS indicessrsSymbols = lteSRS(ue, srs);％srs seq。if(srs.NTxAnts == 1 && ue.NTxAnts > 1)% Map to resource grid% Select antenna for multiple antenna selection diversitytxsubframe（...HSRSOFFSETINDICES（UE，SRSINDICES，SRSINDICESINFO.PORT））=...srsSymbols;elsetxsubframe（srsindices）= srssymbols;结尾％消息给控制台，指示何时将SRS映射到资源％ 网格。if（〜Isempty（srsindices））disp（'Transmitting SRS'）；结尾％联合子框架以形成框架txGrid = [txGrid txSubframe];％＃好的结尾
Subframe 0: Transmitting shortened PUCCH Transmitting SRS Subframe 1: Transmitting full-length PUCCH Subframe 2: Transmitting full-length PUCCH Subframe 3: Transmitting full-length PUCCH Subframe 4: Transmitting full-length PUCCH Subframe 5: Transmitting shortened PUCCH Subframe 6: Transmitting full-length PUCCH Subframe 7: Transmitting full-length PUCCH Subframe 8: Transmitting full-length PUCCH Subframe 9: Transmitting full-length PUCCH

Results

产生的图显示了每个SC-FDMA符号中140个符号中的活动子载波的数量txGrid。所有SC-FDMA符号都包含12个与PUCCH的单个资源块带宽相对应的活动子载波。

  • symbol 13, the last symbol of subframe 0 which has 48 active subcarriers corresponding to an 8 resource block SRS transmission

  • symbol 83, the last symbol of subframe 5 which has 0 active subcarriers corresponding to the shortened PUCCH (last symbol empty) to allow for potential SRS transmission by another UE in this cell.

figure;为了i = 1：ue.ntxants子图（ue.ntxants，1，i）;绘图（0：size（txgrid，2）-1，sum（abs（txgrid（：，：：：，i））〜= 0），'r：o'）Xlabel（'symbol number'）；ylabel（“主动子载体”）；标题（sprintf（sprintf）（'Antenna %d'，i-1））;结尾

用Pucch在频带边缘和子帧0中的SRS梳子传输绘制资源网格。

figure; pcolor(abs(txGrid)); colormap([1 1 1; 0 0 0.5]) shadingflat;Xlabel（'SC-FDMA symbol'）；ylabel（'subcarrier'）

Further Exploration

SRS发射天线选择可以通过设置来证明ue.ntxants = 2and examining the subplots produced for each antenna; the SRS is transmitted on antenna 0 while the PUCCH is shortened on both (all) antennas. A pattern of antenna selection across this one-frame run can be shown by further configuringsrs.subframeconfig = 0andsrs.ConfigIdx = 0。This configures a cell-specific SRS configuration of 2ms periodicity with an offset of 0 (signaled bysrs.subframeconfig = 0）以及2ms周期性的UE特异性SRS配置，偏移为0（由srs.ConfigIdx = 0）。In this case an SRS is transmitted by this UE on even subframes, and the transmit antenna alternates with each transmission.

使用资源多样性在多个天线上的SRS传输可以通过设置显示ue.ntxants = 2andsrs.ntxants = 2。在这种情况下，SRS始终在每个天线上都具有正交资源的所有天线上传输。

附录

此示例使用此辅助功能。

Selected Bibliography

  1. 3GPP TS 36.211 "Physical channels and modulation"

  2. 3GPP TS 36.213 "Physical layer procedures"