%% 測試 ofdm，畫仿真曲線
%%
%% 有無添加CP對系統性能的影響
%% 三條多徑

close all;clear all; clc; tic ; %計時開始
global CP_len;
global nSubC;
global ifft_len;
global bitPerSymbol;
global symbolPerCarrier;
global s_len;
global fade;        %信道衰弱

%% 測試參數
%SNR = 40; % dB
CP_len = 0;
nSubC = 48;
ifft_len = 256;
bitPerSymbol = 2;
symbolPerCarrier = 50;
fade = [0, 0, 0, 0.4, 0.3]; % 信道參數，下標為延時點數，值為衰減系數

% 開始測試
s_len = nSubC*bitPerSymbol* symbolPerCarrier;

SNR = 0:2:30;
ber1 = zeros(1,length(SNR));
ber2 = zeros(1,length(SNR));

for kk = 1:length(SNR)
    max = floor((2^(kk))/50)+10;  
    fprintf('仿真信噪比： %d\n', SNR(kk));
    fprintf('仿真點數：   %d\n', max*nSubC*bitPerSymbol*symbolPerCarrier); 
    CP_len = 0;
    ber = 0;
    for m = 1:max
        % 生成用于測試的隨機比特
        s_in = floor( rand(1, s_len )*2 );    
        sch = ofdm_mod_neq(s_in);
        sch = channel(sch,SNR(kk));
        s_out = ofdm_demod_neq(sch);    
        %計算誤比特率
        err_count = sum(abs(s_in-s_out));
        ber = ber + err_count/s_len ;
    end
    ber1(kk) = ber/max;
    fprintf('cp=0  :%f\n',ber1(kk));
    
    CP_len = 16;
    ber = 0;
    for m = 1:max
        % 生成用于測試的隨機比特
        s_in = floor( rand(1, s_len )*2 );    
        sch = ofdm_mod_neq(s_in);
        sch = channel(sch,SNR(kk));
        s_out = ofdm_demod_neq(sch);    
        %計算誤比特率
        err_count = sum(abs(s_in-s_out));
        ber = ber + err_count/s_len;
    end
    ber2(kk) = ber/max ;
    fprintf('cp=16  :%f\n\n',ber2(kk));
    
end
figure(2);
semilogy(SNR,ber1,'o-');
hold on;
semilogy(SNR,ber2,'r*-');

xlabel('SNR in dB');
ylabel('Bit Error Rate');
legend('no CP','CP');
grid;
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