lms2dchannelestimationalgorithm2.m

程序里面包含各部分算法仿真 可供参考和使用

%----Version1.0: To Zhao for 863 Project.----%
function EstimatedChannelData = LMS2D(   ...
                                ReceivedChannelData,    ... %接收到的帧数据
                                FrameStruct,            ... %信道帧结构参数
                                ChannelParameter,       ... %信道参数
                                DetectionMaximumTapline ... %信道最强径位置
                                )
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%本算法命名为2D-LMS，是基于OFDM蜂窝系统的二维自适应信道估计算法。
%特点：算法复杂度稍高，但性能优于目前已有的各种基于OFDM蜂窝系统
%的信道估计算法。
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
[nSubCarrier, nPilotSymbol] = size(ReceivedChannelData);
nSymbol = FrameStruct.N_ts * FrameStruct.N_sym_ts;
SubCarrierNumber = ChannelParameter.SubCarrierNumber;
TxAntennaNumber = ChannelParameter.TxAntennaNumber;

nPilotinSlot = length(FrameStruct.Pos);

if(nPilotinSlot * FrameStruct.N_ts ~= nPilotSymbol)
    errordlg('输入信道数据和帧结构不一致!');
    EstimatedChannelData = [];
    return
end

%根据导频信道进行线性插值
ReceivedChannelDatabyInterp = zeros(nSubCarrier, nSymbol);
xi = 1:FrameStruct.N_sym_ts;
for index = 1:FrameStruct.N_ts
    yi = interp1(FrameStruct.Pos,transpose(ReceivedChannelData(:,(index-1) * nPilotinSlot + 1:index * nPilotinSlot)),xi);
    ReceivedChannelDatabyInterp(:,(index-1) * FrameStruct.N_sym_ts + 1:index * FrameStruct.N_sym_ts) ...
       = transpose(yi);
end

%最强径检测或LS-DFT
PatternDD = zeros(nSubCarrier, nSymbol);
if nargin == 4 %最强径检测
        L = length(DetectionMaximumTapline);
        for index = 1:L
            PatternDD(DetectionMaximumTapline(index),:) = 1;
        end
elseif nargin == 3 %LSDFT
        PatternDD(1:nSubCarrier/4,:) = 1;
end
ReceivedChannelDataDD = ifft(ReceivedChannelDatabyInterp);
ReceivedChannelDataDD = ReceivedChannelDataDD .* PatternDD;
ReceivedChannelDataDD = fft(ReceivedChannelDataDD);

%算法参数设置
correlateTimeLength = 5;

%算法实现
EstimatedChannelData = zeros(SubCarrierNumber, nSymbol); %放置信道估计的结果

if SubCarrierNumber == nSubCarrier
    EstimatedChannelData(:,1:correlateTimeLength) = ReceivedChannelDatabyInterp(:,1:correlateTimeLength);
else %对参考信号和初始（相关长度）数据进行频域插值
    nTxAntenna = SubCarrierNumber/nSubCarrier;
    x = TxAntennaNumber:nTxAntenna:SubCarrierNumber;
    xi = 1:SubCarrierNumber;
    EstimatedChannelData(:,1:correlateTimeLength) = ...
        interp1(x,ReceivedChannelDatabyInterp(:,1:correlateTimeLength),xi,'spline','extrap');
    ReceivedChannelDataDD = interp1(x,ReceivedChannelDataDD,xi,'spline','extrap');
end

G = ones(SubCarrierNumber, nSubCarrier * correlateTimeLength); %初始化算法迭代过程中需要的变量
G = mk_stochastic(G);

p = ReceivedChannelDatabyInterp(:,1:correlateTimeLength);
p = p(:);

power = p' * p;
step = 1 / power;

for index = correlateTimeLength + 1 : nSymbol %算法迭代过程
    
    hEstimate = G * p;
    
    EstimatedChannelData(:,index) = hEstimate;
    
    e = ReceivedChannelDataDD(:,index) - hEstimate;
    
    G = G + step * e * p';
    
    p = ReceivedChannelDatabyInterp(:,index-correlateTimeLength+1:index);
    p = p(:);
    
    power = power - ...
        ReceivedChannelDatabyInterp(:,index-correlateTimeLength)' * ReceivedChannelDatabyInterp(:,index-correlateTimeLength) ...
        + ReceivedChannelDatabyInterp(:,index)' * ReceivedChannelDatabyInterp(:,index);
    step = 1 / power;
    
end