【通信】基于matlab的OFDM-MIMO通信建模与仿真

1 简介

交频分复用(OFDM)作为一种多载波数字通信方案,是第四代移动通信的核心技术.本文介绍了OFDM基本原理,建立了其通信系统模型,并利用Matlab实现了整个系统的动态仿真.仿真结果表明,该系统能很好地反映OFDM的性能特点,同时验证了该仿真方法的正确性和可行性.

2 部分代码

function bit_out = demodu_sym(sym, mod_type)
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% 功能: 将输入符号映射回比特.大于0,硬判决为比特1;小于0,硬判决为比特0
% 输入: sym, 输入符号
% mod_type, 调制类型
% 输出: bit_out, 输出比特
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
bit_out = zeros(mod_type ,size(sym,2));
switch mod_type
case 1 % BPSK解调
bit_out = real(sym) > 0;
case 2 % QPSK解调
bit0 = real(sym);
bit1 = imag(sym);
bit_out(1,:) = bit0 > 0;
bit_out(2,:) = bit1 > 0;
case 3 % 8PSK解调
bit0 = -imag(sym*exp(1j*pi/8));
bit1 = -real(sym*exp(1j*pi/8));
bit2 = [];
for k = 1:length(sym)
tmp = sym(k)*exp(-1j*pi/8);
if ((real(tmp) <0)&&(imag(tmp) > 0))||((real(tmp) > 0)&&(imag(tmp) < 0))
bit2 = [bit2 0];
else
bit2 = [bit2 1];
end
end
bit_out(1,:) = bit0 >0;
bit_out(2,:) = bit1 >0;
bit_out(3,:) = bit2 ;
case 4 % 16QAM解调
bit0 = real(sym);
bit2 = imag(sym);
bit1 = 2/sqrt(10)-(abs(real(sym)));
bit3 = 2/sqrt(10)-(abs(imag(sym)));
bit_out(1,:) = bit0 > 0;
bit_out(2,:) = bit1 > 0;
bit_out(3,:) = bit2 > 0;
bit_out(4,:) = bit3 > 0;
case 6 % 64QAM解调
bit0 = real(sym);
bit3 = imag(sym);
bit1 = 4/sqrt(42)-abs(real(sym));
bit4 = 4/sqrt(42)-abs(imag(sym));
for m=1:size(sym,2)
for k=1:size(sym,1)
if abs(4/sqrt(42)-abs(real(sym(k,m)))) <= 2/sqrt(42)
bit2(k,m) = 2/sqrt(42) - abs(4/sqrt(42)-abs(real(sym(k,m))));
elseif abs(real(sym(k,m))) <= 2/sqrt(42)
bit2(k,m) = -2/sqrt(42) + abs(real(sym(k,m)));
else
bit2(k,m) = 6/sqrt(42)-abs(real(sym(k,m)));
end;
if abs(4/sqrt(42)-abs(imag(sym(k,m)))) <= 2/sqrt(42)
bit5(k,m) = 2/sqrt(42) - abs(4/sqrt(42)-abs(imag(sym(k,m))));
elseif abs(imag(sym(k,m))) <= 2/sqrt(42)
bit5(k,m) = -2/sqrt(42) + abs(imag(sym(k,m)));
else
bit5(k,m) = 6/sqrt(42)-abs(imag(sym(k,m)));
end;
end;
end;
bit_out(1,:) = bit0 > 0;
bit_out(2,:) = bit1 > 0;
bit_out(3,:) = bit2 > 0;
bit_out(4,:) = bit3 > 0;
bit_out(5,:) = bit4 > 0;
bit_out(6,:) = bit5 > 0;
otherwise
error('调制方式有误! 子程序demod_sym出错');
end

3 仿真结果

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4 参考文献

[1]魏瑞. 基于MATLAB的OFDM通信系统的仿真[J]. 科技广场, 2011(6):3.

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