【正文】 nstem(carriers1, (180/pi)*angle(IFFT_modulation(2,carriers)),39。b*39。)stem(conjugate_carriers1, (180/pi)*angle(IFFT_modulation(2,conjugate_carriers)),39。b*39。)axis ([0 IFFT_bin_length 200 +200])grid onylabel(39。Phase (degrees)39。)xlabel(39。IFFT Bin39。)title(39。OFDM Carrier Phase39。)% 通過IFFT將頻域轉化為時域，得到時域信號time_wave_matrix = ifft(IFFT_modulation39。)。time_wave_matrix = time_wave_matrix39。%畫出一個符號周期的時域OFDM信號figure (3)plot(0:IFFT_bin_length1,time_wave_matrix(2,:))grid onylabel(39。Amplitude39。)xlabel(39。Time39。)title(39。OFDM Time Signal, One Symbol Period39。)%畫出每一個載波對應的時域信號（分離的OFDM信號）for f = 1:carrier_count temp_bins(1:IFFT_bin_length)=0+0j。 temp_bins(carriers(f))=IFFT_modulation(2,carriers(f))。 temp_bins(conjugate_carriers(f))=IFFT_modulation(2,conjugate_carriers(f))。 temp_time = ifft(temp_bins39。)。 figure(4) plot(0:IFFT_bin_length1, temp_time) hold onendgrid onylabel(39。Amplitude39。)xlabel(39。Time39。)title(39。Separated Time Waveforms Carriers39。)for i = 1:symbols_per_carrier + 1windowed_time_wave_matrix(i,:)=real(time_wave_matrix(i,:)).*hamming(IFFT_bin_length)39。windowed_time_wave_matrix(i,:) = real(time_wave_matrix(i,:))。end%串并轉換ofdm_modulation=reshape(windowed_time_wave_matrix39。,1,IFFT_bin_length*(symbols_per_carrier+1))。% 畫出整個時域OFDMtemp_time = IFFT_bin_length*(symbols_per_carrier+1)。figure (5)plot(0:temp_time1,ofdm_modulation)grid onylabel(39。Amplitude (volts)39。)xlabel(39。Time (samples)39。)title(39。OFDM Time Signal39。)% 畫出頻域OFDM信號symbols_per_average = ceil(symbols_per_carrier/5)。avg_temp_time = IFFT_bin_length*symbols_per_average。averages = floor(temp_time/avg_temp_time)。average_fft(1:avg_temp_time) = 0。for a = 0:(averages1)subset_ofdm=ofdm_modulation(((a*avg_temp_time)+1):((a+1)*avg_temp_time))。 subset_ofdm_f = abs(fft(subset_ofdm))。 average_fft = average_fft + (subset_ofdm_f/averages)。endaverage_fft_log = 20*log10(average_fft)。figure (6)plot((0:(avg_temp_time1))/avg_temp_time, average_fft_log)hold onplot(0:1/IFFT_bin_length:1, 35, 39。rd39。)grid onaxis([0 40 max(average_fft_log)])ylabel(39。Magnitude (dB)39。)xlabel(39。Normalized Frequency ( = fs/2)39。)title(39。OFDM Signal Spectrum39。)% 上變頻，這個模型中我們把經(jīng)過IFFT運算后OFDM直接發(fā)送Tx_data = ofdm_modulation。%信道=======================================================% The channel model is Gaussian (AWGN) +Multipath(時延為1) Tx_signal_power = var(Tx_data)。linear_SNR = 10^(SNR/10)。noise_sigma = Tx_signal_power/linear_SNR。noise_scale_factor = sqrt(noise_sigma)。noise = randn(1, length(Tx_data))*noise_scale_factor。copy1=zeros(1,length(ofdm_modulation))。for i=2:length(ofdm_modulation) copy1(i)=ofdm_modulation(i1)。endRx_Data = Tx_data + noise。%RECEIVE % 根據(jù)符號長度和符號數(shù)將串行的符號轉換為并行的% 每一列是符號周期Rx_Data_matrix = reshape(Rx_Data, IFFT_bin_length, symbols_per_carrier + 1)。%對每一列信號做FFT得到頻域信號Rx_spectrum = fft(Rx_Data_matrix)。% 畫出接收到的OFDM信號頻域代表%12345678figure (7)stem(0:IFFT_bin_length1, abs(Rx_spectrum(1:IFFT_bin_length,2)),39。b*39。)grid onaxis ([0 IFFT_bin_length ])ylabel(39。Magnitude39。)xlabel(39。FFT Bin39。)title(39。OFDM Receive Spectrum, Magnitude39。)figure (8)plot(0:IFFT_bin_length1, (180/pi)*angle(Rx_spectrum(1:IFFT_bin_length,2)), 39。go39。)hold onstem(carriers1, (180/pi)*angle(Rx_spectrum(carriers,2)),39。b*39。)stem(conjugate_carriers1, (180/pi)*angle(Rx_spectrum(conjugate_carriers,2)),39。b*39。)axis ([0 IFFT_bin_length 200 +200])grid onylabel(39。Phase (degrees)39。)xlabel(39。FFT Bin39。)title(39。OFDM Receive Spectrum, Phase39。)% 抽取接收信號中有載波的點Rx_carriers = Rx_spectrum(carriers,:)39。%畫出每個接收符號分布圖figure (9)Rx_phase_P = angle(Rx_carriers)。Rx_mag_P = abs(Rx_carriers)。polar(Rx_phase_P, Rx_mag_P,39。bd39。)。% 計算載波的相位% 弧度轉換為角度% 歸一化相位（0360）Rx_phase = angle(Rx_carriers)*(180/pi)。phase_negative = find(Rx_phase 0)。Rx_phase(phase_negative) = rem(Rx_phase(phase_negative)+360,360)。% 用diff（）計算相位差Rx_decoded_phase = diff(Rx_phase)。phase_negative = find(Rx_decoded_phase 0)。Rx_decoded_phase(phase_negative) = rem(Rx_decoded_phase(phase_negative)+360,360)。%12345678% 相位轉化為符號base_phase = 360/2^bits_per_symbol。delta_phase = base_phase/2。Rx_decoded_symbols= zeros(size(Rx_decoded_phase,1),size(Rx_decoded_phase,2))。for i = 1:(2^bits_per_symbol 1) center_phase = base_phase*i。 plus_delta = center_phase+delta_phase。 minus_delta = center_phasedelta_phase。decoded=find((Rx_decoded_phase=plus_delta)amp。(Rx_decoded_phaseminus_delta))。Rx_decoded_symbols(decoded)=i。end% Convert the matrix into a serial symbol streamRx_serial_symbols=reshape(Rx_decoded_symbols39。,1,size(Rx_decoded_symbols,1)*size(Rx_decoded_symbols,2))。% Convert the symbols to binaryfor i = bits_per_symbol: 1: 1 if i ~= 1 Rx_binary_matrix(i,:) = rem(Rx_serial_symbols,2)。 Rx_serial_symbols = floor(Rx_serial_symbols/2)。 else Rx_binary_matrix(i,:) = Rx_serial_symbols。 endendbaseband_in=reshape(Rx_binary_matrix,1,size(Rx_binary_matrix,1)*size(Rx_binary_matrix,2))。% 查找錯位比特bit_errors = find(baseband_in ~= baseband_out)。bit_error_count = size(bit_errors,2)。