【手写数字识别】基于贝叶斯结合线性分类器实现手写数字识别含Matlab源码

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

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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