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⛄ 内容介绍
基于Alamouti提出的BPSK调制下空时分组码在Rayleigh衰落信道中的码性能原理,推导出高阶(M ary)调制下Rician衰落信道中空时分组码的符号差错率的最小距离球界,并进行计算机仿真分析了两信道下引入空时分组码的多天线系统中发射和接收天线的分集增益,发射天线数量的"地板效应"以及Rician因子K对符号差错性能的影响。
⛄ 完整代码
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% from Krishna Pillai.
%使用 Alamouti 空间时间分组编码以百分比瑞利衰落信道计算 BPSK 调制误码率的脚本
% Script for computing the BER for BPSK modulation in a
% Rayleigh fading channel with Alamouti Space Time Block Coding
% Two transmit antenna, 1 Receive antenna
clear
N = 10^6; % number of bits or symbols
Eb_N0_dB = [0:25]; % multiple Eb/N0 values
for ii = 1:length(Eb_N0_dB)
% Transmitter
ip = rand(1,N)>0.5; % generating 0,1 with equal probability
s = 2*ip-1; % BPSK modulation 0 -> -1; 1 -> 0
% Alamouti STBC
sCode = zeros(2,N);
sCode(:,1:2:end) = (1/sqrt(2))*reshape(s,2,N/2); % [x1 x2 ...]
sCode(:,2:2:end) = (1/sqrt(2))*(kron(ones(1,N/2),[-1;1]).*flipud(reshape(conj(s),2,N/2))); % [-x2* x1* ....]
h = 1/sqrt(2)*[randn(1,N) + j*randn(1,N)]; % Rayleigh channel
hMod = kron(reshape(h,2,N/2),ones(1,2)); % repeating the same channel for two symbols
n = 1/sqrt(2)*[randn(1,N) + j*randn(1,N)]; % white gaussian noise, 0dB variance
% Channel and noise Noise addition
y = sum(hMod.*sCode,1) + 10^(-Eb_N0_dB(ii)/20)*n;
% Receiver
yMod = kron(reshape(y,2,N/2),ones(1,2)); % [y1 y1 ... ; y2 y2 ...]
yMod(2,:) = conj(yMod(2,:)); % [y1 y1 ... ; y2* y2*...]
% forming the equalization matrix
hEq = zeros(2,N);
hEq(:,[1:2:end]) = reshape(h,2,N/2); % [h1 0 ... ; h2 0...]
hEq(:,[2:2:end]) = kron(ones(1,N/2),[1;-1]).*flipud(reshape(h,2,N/2)); % [h1 h2 ... ; h2 -h1 ...]
hEq(1,:) = conj(hEq(1,:)); % [h1* h2* ... ; h2 -h1 .... ]
hEqPower = sum(hEq.*conj(hEq),1);
yHat = sum(hEq.*yMod,1)./hEqPower; % [h1*y1 + h2y2*, h2*y1 -h1y2*, ... ]
yHat(2:2:end) = conj(yHat(2:2:end));
% receiver - hard decision decoding
ipHat = real(yHat)>0;
% counting the errors
nErr(ii) = size(find([ip- ipHat]),2);
end
simBer = nErr/N; % simulated ber
EbN0Lin = 10.^(Eb_N0_dB/10);
theoryBer_nRx1 = 0.5.*(1-1*(1+1./EbN0Lin).^(-0.5));
p = 1/2 - 1/2*(1+1./EbN0Lin).^(-1/2);
theoryBerMRC_nRx2 = p.^2.*(1+2*(1-p));
pAlamouti = 1/2 - 1/2*(1+2./EbN0Lin).^(-1/2);
theoryBerAlamouti_nTx2_nRx1 = pAlamouti.^2.*(1+2*(1-pAlamouti));
close all
figure
semilogy(Eb_N0_dB,theoryBer_nRx1,'bp-','LineWidth',2);
hold on
semilogy(Eb_N0_dB,theoryBerMRC_nRx2,'kd-','LineWidth',2);
semilogy(Eb_N0_dB,theoryBerAlamouti_nTx2_nRx1,'c+-','LineWidth',2);
semilogy(Eb_N0_dB,simBer,'mo-','LineWidth',2);
axis([0 25 10^-5 0.5])
grid on
legend('theory (nTx=1,nRx=1)', 'theory (nTx=1,nRx=2, MRC)', 'theory (nTx=2, nRx=1, Alamouti)', 'sim (nTx=2, nRx=1, Alamouti)');
xlabel('Eb/No, dB');
ylabel('Bit Error Rate');
title('BER for BPSK modulation with Alamouti STBC (Rayleigh channel)');
⛄ 运行结果
⛄ 参考文献
[1]张薇. 无线移动通信中空时分组编码的性能分析[D]. 兰州大学.
