clear;
clc;
s = rng(211); % 設定RNG狀态的可重複性
numFFT = 1024; % FFT點的數量
numRBs = 50; % 資源塊的數量
rbSize = 12; % 每個資源塊的副載波數量
cpLen = 72; % 樣本中的循環字首長度
bitsPerSubCarrier = 6; % 2: QPSK, 4: 16QAM, 6: 64QAM, 8: 256QAM
snrdB =30; % 以dB為機關的SNR
toneOffset = 2.5; % 音調偏移或超額帶寬(在副載波中)
L = 513; % 濾波器長度(=濾波器次序+ 1)，奇數
numDataCarriers = numRBs*rbSize; % 子帶中資料子載波的數量
halfFilt = floor(L/2);
n = -halfFilt:halfFilt;
% Sinc函數原型濾波器
pb = sinc((numDataCarriers+2*toneOffset).*n./numFFT);
% Sinc截斷視窗
w = (0.5*(1+cos(2*pi.*n/(L-1)))).^0.6;
% 歸一化的低通濾波器系數
fnum = (pb.*w)/sum(pb.*w);
% 過濾脈沖響應
h = fvtool(fnum, 'Analysis', 'impulse', ...
'NormalizedFrequency', 'off', 'Fs', 15.36e6);
h.CurrentAxes.XLabel.String = 'Time (\mus)';
h.FigureToolbar = 'off';
% 使用dsp過濾器對象進行過濾
filtTx = dsp.FIRFilter('Structure', 'Direct form symmetric', ...
'Numerator', fnum);
filtRx = clone(filtTx); % Rx的比對過濾器
% QAM符号映射器
qamMapper = comm.RectangularQAMModulator( ...
'ModulationOrder', 2^bitsPerSubCarrier, 'BitInput', true, ...
'NormalizationMethod', 'Average power');
% 為譜圖設定一個數字
hFig = figure('Position', figposition([46 50 30 30]), 'MenuBar', 'none');
axis([-0.5 0.5 -200 -20]);
hold on;
grid on
xlabel('Normalized frequency');
ylabel('PSD (dBW/Hz)')
title(['F-OFDM, ' num2str(numRBs) ' Resource blocks, ' ...
num2str(rbSize) ' Subcarriers each'])
% 生成資料符号
bitsIn = randi([0 1], bitsPerSubCarrier*numDataCarriers, 1);
symbolsIn = qamMapper(bitsIn);
% 将資料打包成OFDM符号
offset = (numFFT-numDataCarriers)/2; % 為通帶中心
symbolsInOFDM = [zeros(offset,1); symbolsIn; ...
zeros(numFFT-offset-numDataCarriers,1)];
ifftOut = ifft(ifftshift(symbolsInOFDM));
%預先加上循環字首
txSigOFDM = [ifftOut(end-cpLen+1:end); ifftOut];
% 使用零填充過濾器來重新整理尾部。 擷取發射信号
txSigFOFDM = filtTx([txSigOFDM; zeros(L-1,1)]);
%繪制功率譜密度(PSD)
[psd,f] = periodogram(txSigFOFDM, rectwin(length(txSigFOFDM)), ...
numFFT*2, 1, 'centered');
plot(f,10*log10(psd));
% 計算峰均功率比(PAPR)
PAPR = comm.CCDF('PAPROutputPort', true, 'PowerUnits', 'dBW');
[~,~,paprFOFDM] = PAPR(txSigFOFDM);
disp(['Peak-to-Average-Power-Ratio for F-OFDM = ' num2str(paprFOFDM) ' dB']);
% 繪制OFDM信号的功率譜密度(PSD)
[psd,f] = periodogram(txSigOFDM, rectwin(length(txSigOFDM)), numFFT*2, ...
1, 'centered');
hFig1 = figure('Position', figposition([46 15 30 30]));
plot(f,10*log10(psd));
grid on
axis([-0.5 0.5 -200 -20]);
xlabel('Normalized frequency');
ylabel('PSD (dBW/Hz)')
title(['OFDM, ' num2str(numRBs*rbSize) ' Subcarriers'])
%計算峰均功率比(PAPR)
PAPR2 = comm.CCDF('PAPROutputPort', true, 'PowerUnits', 'dBW');
[~,~,paprOFDM] = PAPR2(txSigOFDM);
disp(['Peak-to-Average-Power-Ratio for OFDM = ' num2str(paprOFDM) ' dB']);
%添加AWGN和Rayleigh
chan = rayleighchan(0.00001,100);
rxSig = filter(chan,txSigFOFDM);
rxtSig = awgn(rxSig, snrdB, 'measured');
% 接收比對的過濾器,
rxSigFilt = filtRx(rxtSig);
% 考慮過濾器延遲
rxSigFiltSync = rxSigFilt(L:end);
% 删除循環字首
rxSymbol = rxSigFiltSync(cpLen+1:end);
%執行FFT
RxSymbols = fftshift(fft(rxSymbol));
%選擇資料副載波
dataRxSymbols = RxSymbols(offset+(1:numDataCarriers));
% 繪制接收符号星座圖
switch bitsPerSubCarrier
case 2 % QPSK
refConst = qammod((0:3).', 4, 'UnitAveragePower', true);
case 4 % 16QAM
refConst = qammod((0:15).', 16,'UnitAveragePower', true);
case 6 % 64QAM
refConst = qammod((0:63).', 64,'UnitAveragePower', true);
case 8 % 256QAM
refConst = qammod((0:255).', 256,'UnitAveragePower', true);
end
constDiagRx = comm.ConstellationDiagram( ...
'ShowReferenceConstellation', true, ...
'ReferenceConstellation', refConst, ...
'Position', figposition([20 15 30 40]), ...
'MeasurementInterval', length(dataRxSymbols), ...
'Title', 'F-OFDM Demodulated Symbols', ...
'Name', 'F-OFDM Reception', ...
'XLimits', [-1.5 1.5], 'YLimits', [-1.5 1.5]);
constDiagRx(dataRxSymbols);
% 由于沒有通道模組化，是以通道均衡不是必要的
%解映射和BER計算
qamDemod = comm.RectangularQAMDemodulator('ModulationOrder', ...
2^bitsPerSubCarrier, 'BitOutput', true, ...
'NormalizationMethod', 'Average power');
BER = comm.ErrorRate;
% 執行艱難的決策并測量錯誤
rxBits = qamDemod(dataRxSymbols);
ber = BER(bitsIn, rxBits);
disp(['F-OFDM Reception, BER = ' num2str(ber(1)) ' at SNR = ' ...
num2str(snrdB) ' dB']);
%恢複RNG狀态
rng(s);