main_80216e.m

IEEE802.16标准系统的仿真

%--------------------------------------------------------------------------
%  This is the simulation of Wimax(802.16e) downlink and has been simplified
%  to compare the performance of different channel estimation algorithm
%  between Ls and Lmmse,at the end also give the BER of Ls , Lmmse , and no
%  channel estimation effect.
%  Reference: IEEE Std 802.16e-2005
%  Author: quan ningbo (权宁波)
%  E-mail & MSN: [e-mail]
%  Release Data : July 6th, 2007
%  If you have any suggestions and ideas ,don't hesitate to contact me.
%--------------------------------------------------------------------------

clc;
clear;

Num1=576;   % 导频数目 （按照每帧26符号，但可用的为24符号计算分配）
Num2=13824; % 数据数目
Length_fft=1024;
CP=1/8;
GI=Length_fft*CP; % 128 
Ts=1e-7;
% Bw=8.75Hz  
% n=8/7 
% G=1/8  
% fs=Bw*n=1e7Hz  
% f(delta)=fs/Num1=1e7/1024=9.765625kHz 
% Tb=0.1024ms  
% Tg=G*Tb=0.0128ms=12.8us   

%--------------------------------------------------------send part
% 产生导频和数据(导频用BPSK调制，数据用16QAM调制)
[Pilot,Data,Data_bit]=generation(Num1,Num2);


%插入导频于数据中组成帧格式
Frame=Insertpilot(Pilot,Data);

%IFFT调制
D_modulation=ifft(Frame,Length_fft);

%加循环前缀
D_addCP=addCP(D_modulation,GI);

%并串变换
D_send=reshape(D_addCP,1,1152*26); % signal for send  Tx

%循环测试
BER_LS=[];
BER_LMMSE=[];
BER_1=[];
snr_intelv=1;
N_snr=15;
for snr_db=0:snr_intelv:N_snr
    SNR=snr_db;
    error_num_LS=0;
    error_num_LMMSE=0;
    error_num_1=0;
%-------------------------------------------------------channel
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% 1sh channel 通过AWGN信道
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
D_receive=AWGN_channel(D_send,SNR);

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% 2th channel 通过频率选择性多径信道
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%参数设置================
loop_num=1; %共仿真loop_num次 （每个dB下信道的仿真次数）
for l=1:loop_num
    num=5;% 多径数为5条
          % 假设功率延迟谱服从负指数分布~exp(-t/trms),trms=(1/4)*cp时长；
          % t在0~cp时长上均匀分布
          % 取5径延迟如下
    delay=[0 2 4 8 10]*1e-6; 
    trms=3.2e-6;
    var_pow=10*log10(exp(-delay/trms));
    fd=100;            % 最大doppler频率为100Hz
    t_interval=1e-7;   % 采样间隔为0.1us   t_interval为离散信道抽样时间间隔，等于OFDM符号长度/(子载波个数+cp长度lp)；
    counter=200000;    % 各径信道的采样点间隔，应该大于信道采样点数()
    count_begin=(l-1)*(5*counter);%每次仿真信道采样的开始位置
    trms_1=trms/t_interval;
    t_max=10e-6/t_interval;
    snr=10^(SNR/10);
    D_receive_2=multipath_chann(D_receive,num,var_pow,delay,fd,t_interval,counter,count_begin);

    %--------------------------------------------------------receive part
    %串并变换
    D_ps=reshape(D_receive_2,1152,26);

   %去循环前缀
   D_offCP=offCP(D_ps,GI);

   %FFT解调 
   D_demodulation=fft(D_offCP,Length_fft);% 1024*26

   %为了和其他模块统一接口，从这里开始将对矩阵的处理转换为对向量的处理
   %并串转换
   D_demodulation_serial=reshape(D_demodulation,1,1024*26);% 行向量，1*26624 复数

   %==========M-file均衡===================================================
   %=======================================================================
   
   %提取导频
   P1=getpilot(D_demodulation_serial);

   %%%%%%%%%%%%%%%%%%%%%%%%%%
   %        Ls rule         %
   %%%%%%%%%%%%%%%%%%%%%%%%%%
   Hp_LS=channelestimation_LS(P1,Pilot);                                 %信道估计LS（得到导频位置的信道频率响应Hp(k)）
   H_LS=neicha(Hp_LS);                                                   %内插（利用导频位置的信道频响内插而得到数据位置上的频响 H(k)）
   D_after_equalization_LS=equalization(D_demodulation_serial,H_LS);     %均衡（只对数据载频处进行均衡）
   
   %比较
   %H_LS_spline=neicha_spline(Hp_LS);                                    %采用cubic 插值方法
   %D_after_equalization_LS_1=equalization(D_demodulation_serial,H_LS_spline); 
   
   %%%%%%%%%%%%%%%%%%%%%%%%%
   %      LMMSE rule       %
   %%%%%%%%%%%%%%%%%%%%%%%%%
   Hp_LMMSE=channelestimation_LMMSE(P1,Pilot,trms_1,t_max,snr,Hp_LS);           %信道估计LMMSE（得到导频位置的信道频率响应Hp(k)）
   H_LMMSE=neicha(Hp_LMMSE);                                                    %内插（利用导频位置的信道频响内插而得到数据位置上的频响 H(k)）
   D_after_equalization_LMMSE=equalization(D_demodulation_serial,H_LMMSE);      %均衡（只对数据载频处进行均衡）
   
   %比较
   %H_LMMSE_spline=neicha_spline(Hp_LMMSE);                                     %采用cubic 插值方法
   %D_after_equalization_LMMSE_1=equalization(D_demodulation_serial,H_LMMSE_spline);
   %=========均衡结束======================================================
   %=======================================================================

   %从帧中取出数据
   D_getdata_LS=getdata(D_after_equalization_LS);                                %均衡后的数据(Ls均衡)
   D_getdata_LMMSE=getdata(D_after_equalization_LMMSE);                          %均衡后的数据(Lmmse均衡)
   D_getdata_1=getdata(D_demodulation_serial);                                   %均衡前的数据(无均衡)

   %plot星座图
   flag=0;
   if(flag==1)
      I=real(D_getdata_LS);
      Q=imag(D_getdata_LS);
      II=real(D_getdata_LMMSE);
      QQ=imag(D_getdata_LMMSE);
      III=real(D_getdata_1);
      QQQ=imag(D_getdata_1);
      subplot(3,1,1);plot(I,Q,'.r')
      subplot(3,1,2);plot(II,QQ,'.')
      subplot(3,1,3);plot(III,QQQ,'.g')
   end

   %16QAM解调
   D_16qam_demodu_LS=demodu_16qam(D_getdata_LS);       
   D_16qam_demodu_LMMSE=demodu_16qam(D_getdata_LMMSE);  %均衡后的数据
   D_16qam_demodu_1=demodu_16qam(D_getdata_1);          %均衡前的数据


   %-------------------------------------------------------------- counter
   %统计误比特率（解调之后的比特）
   error_num_LS=error_num_LS+length(find(D_16qam_demodu_LS~=Data_bit));                
   error_num_LMMSE=error_num_LMMSE+length(find(D_16qam_demodu_LMMSE~=Data_bit)); %均衡后的数据 
   error_num_1=error_num_1+length(find(D_16qam_demodu_1~=Data_bit));             %均衡前的数据 
end  % loop_num/SNR end

error_ratio_LS=error_num_LS/(length(Data_bit)*loop_num);
error_ratio_LMMSE=error_num_LMMSE/(length(Data_bit)*loop_num);
error_ratio_1=error_num_1/(length(Data_bit)*loop_num); 

BER_LS=[BER_LS,error_ratio_LS];
BER_LMMSE=[BER_LMMSE,error_ratio_LMMSE];
BER_1=[BER_1,error_ratio_1];

end  % SNR end

figure(3)
i=0:snr_intelv:N_snr;
semilogy(i,BER_LS,'r-*');
hold on;

semilogy(i,BER_LMMSE,'b-o')
hold on 

semilogy(i,BER_1,'g-+');
hold on;

grid on;

xlabel('SNR in DB');
ylabel('BER');
title('compare the performance of Ls and Lmmse algorithm');
legend('LS Channel Estimation','LMMSE Channel Estimation','No Channel Estimation');
hold off