基于mimo的城市信道建模代码

以下是一个基于MIMO的城市信道建模代码示例：

% 定义模拟参数
numTxAntennas = 4;      % 发射天线数目
numRxAntennas = 2;      % 接收天线数目
numSubcarriers = 64;    % 子载波数目
numSymbols = 14;        % 符号数目
numPoints = 1000;       % 采样点数目

% 定义城市衰落参数
delaySpread = 30e-9;    % 时延扩展
maxDopplerShift = 100;  % 最大多普勒频移
numClusters = 6;        % 簇数
numSubpaths = 10;       % 子路径数
clusterDelaySpread = 2e-9;  % 簇时延扩展
subpathGain = -10;          % 子路径增益

% 生成城市信道模型
chan = nrCDLChannel;
chan.NumTransmitAntennas = numTxAntennas;
chan.NumReceiveAntennas = numRxAntennas;
chan.SampleRate = 15.36e6;
chan.DelayProfile = 'CDL-C';
chan.DelaySpread = delaySpread;
chan.MIMOCorrelation = 'Low';
chan.TransmitCorrelationMatrix = eye(numTxAntennas);
chan.ReceiveCorrelationMatrix = eye(numRxAntennas);
chan.RandomStream = 'mt19937ar with seed';
chan.Seed = 73;

% 生成频率响应
[txWaveform,~,gridDims] = helperCDLWaveformGenerator(numSubcarriers,numSymbols,numTxAntennas);
rxWaveform = zeros(numPoints,numRxAntennas);
for i = 1:numPoints
    [rxWaveform(i,:),pathGains] = chan(txWaveform(i,:));
end
rxWaveform = reshape(rxWaveform,numSubcarriers,numSymbols,numPoints,numRxAntennas);

% 生成时域响应
maxClusterDelay = ceil(delaySpread*(numClusters-1)/clusterDelaySpread);
maxSubpathDelay = ceil(delaySpread*(numClusters-1)*(numSubpaths-1)/clusterDelaySpread);
numSamples = numSymbols*gridDims(1)*numSubcarriers;
timeWaveform = zeros(numSamples,numTxAntennas,numRxAntennas);
for i = 1:numPoints
    pathFilters = helperCDLPathFilters(pathGains{i},delaySpread,maxDopplerShift,maxClusterDelay,maxSubpathDelay,numTxAntennas,numRxAntennas,numSubpaths,clusterDelaySpread,subpathGain);
    timeWaveform = timeWaveform + helperCDLTimeDomainFilter(rxWaveform(:,:,:,i),pathFilters);  
end
timeWaveform = reshape(timeWaveform,numSymbols,gridDims(1),numSubcarriers,numTxAntennas,numRxAntennas);

这段代码使用了MATLAB中的NR CDL信道模型生成器，可以生成符合城市衰落特性的多输入多输出信道模型。其中，numTxAntennas和numRxAntennas分别表示发射和接收天线数目，numSubcarriers和numSymbols分别表示子载波和符号数目，numPoints表示采样点数目。delaySpread和maxDopplerShift分别表示时延扩展和最大多普勒频移，numClusters和numSubpaths表示簇数和子路径数，clusterDelaySpread和subpathGain分别表示簇时延扩展和子路径增益。最后，代码生成了频率响应和时域响应。