MIMO OFDM MATLAB仿真程序.doc

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MIMO OFDM MATLAB 仿真程序一 OFDM.m: OFDM Simulator (outer function) clear all; A = [1 1/exp(1) 1/exp(2)]; % power delay profile N = 64; % number of symbols in a single OFDM symbol GI = 16; % guard interval Mt = 1; % number of Tx antennas Mr = 1; % number of Rx antennas sig2 = 1e-3; % noise variance M = 8; % max constellation bit number Mgap = 10.^(1:(1.7/10):2.7); % gap Btot = 100*Mt; % total # bits per OFDM symbol TransmitIter = 50; % # iterations of symbol transmissions for each channel instance ChannelIter = 100; % # iterations of independent identically distributed channel instances GapIter = length(Mgap); load ENC2.mat load ENC4.mat load ENC16.mat load ENC64.mat load ENC256.mat TotEbNo = []; Errors =[]; EbNo = []; for lGap = 1:GapIter

lGap gap = Mgap(lGap); totalErrors = 0; for lChan = 1:ChannelIter % create channel [H h_f]=create_channel(Mt, Mr, A, N+GI); % decompose each subchannel in the frequency domain [U S V] = svd_decompose_channel(Mt, Mr, h_f, N); % bitloading [bits_alloc,energy_alloc] = BitLoad(S,Btot,Mt*N,gap,sig2,M); %energy_alloc=energy_alloc/(mean(energy_alloc)); %energy_alloc=ones(1,128); for lTrans = 1:TransmitIter % bits to transmit x = (randn(1,Btot)>0); % modulate x_mod = modulate(x,bits_alloc,energy_alloc, s2,s4,s16,s64,s256); % precode modulated signal x_pre = precode(Mt, x_mod, V, N); % ifft, with cyclic prefix for each antenna ofdm_symbol =[]; for i=1:Mt ofdm_symbol = [ofdm_symbol; ifft_cp_tx_blk(x_pre(i:Mt:Mt*(N- 1)+i),N,GI)]; end

ofdm_symbol2 = reshape(ofdm_symbol,Mt*(N+GI),1); % channel y = transpose(channel(sig2, Mt, Mr, ofdm_symbol2, H, N+GI)); % fft rec_symbol =[]; for i=1:Mt rec_symbol = [rec_symbol; fft_cp_rx_blk(y(i:Mt:Mt*(N+GI-1)+i),N,GI)]; end rec_symbol2 = reshape(rec_symbol,1,Mt*N); % shape received signal shaped_vals = shape(rec_symbol2, Mr, U, N); % demodulate y_demod = demodulate(shaped_vals, bits_alloc, energy_alloc, S, s2,s4,s16,s64,s256, c2,c4,c16,c64,c256); % comparison totalErrors = totalErrors + sum(xor(y_demod,x)); end EbNo = [EbNo sum(energy_alloc)/Btot/sig2]; end Errors = [Errors totalErrors/Btot/ChannelIter/TransmitIter] TotEbNo = [TotEbNo mean(EbNo)] EbNo = []; end semilogx(TotEbNo, Errors);

xlabel('Eb/No'); ylabel('BER'); title('SISO link, adaptive rate and power') save SISO_adaptive2.mat Errors EbNo create_channel.m: Generates a Rayleigh fading frequency-selective channel, parametrized by the antenna configuration, the OFDM configuration, and the power-delay profile. function [H, H_f]=create_channel(Mt, Mr, A, N); % function [H, H_f]=create_channel(Mt, Mr, A, N); % % A - vector containing the power-delay profile (real values) % Mt - number of Tx antennas % Mr - number of Rx antennas % N - number of vector symbols to be sent in a single OFDM symbol Tx % ie: N MIMO transmissions in one OFDM symbol % This is for Rayleigh frequency-selective fading, which assumes complex % Gaussian matrix elements with in-phase and quadrature components independent. % Assume iid matrix channel elements, and further, independent channel taps % define the channel taps

H_int = 1/sqrt(2)*(randn(Mr*length(A),Mt) + j*randn(Mr*length(A),Mt)); H_int2=[]; for i = 1:length(A) H_int2 = [H_int2;sqrt(A(i))*H_int((i-1)*Mr+1:i*Mr,:)]; end %h_f = fft(H_int2',64); %%H = H_int2'; H_int2 = [H_int2;zeros((N-length(A))*Mr,Mt)]; H_f = zeros(Mr,Mt*(N-16)); for i = 1:Mt for j = 1:Mr h_f = fft(H_int2(j:Mr:(N-16-1)*Mr+j,i)); for k = 1:(N-16) H_f(j,i+(k-1)*Mt) = h_f(k); end end end H=[H_int2]; for i = 1:N-1 H=[H,[zeros(Mr*i,Mt);H_int2(1:(N-i)*Mr,:)]]; end svd_decompose_channel.m: Since full channel knowledge is assumed, transmission is across parallel singular value modes. This function decomposes the channel into

these modes. function [U, S, V] = svd_decompose_channel(Mt, Mr, h_f, N); % [U S V] = svd_decompose_channel(Mt, Mr, h_f, N); % % Function decomposes the channel at each subcarrier into its SVD components % % Mt - # Tx antennas % Mr - # Rx antennas % h_f - MIMO impulse response - Mr rows, Mt*L columns, where L is the number of % channel taps % N - # subcarriers U = []; S = []; V = []; for i = 1:N [Utmp Stmp Vtmp] = svd(h_f(:,(i-1)*Mt+1:i*Mt)); U=[U Utmp]; V=[V Vtmp]; S=[S Stmp]; end S = sum(S,1);

BitLoad.m: Apply the bit-loading algorithm to achieve the desired bit and energy allocation for the current channel instance. function [bits_alloc,energy_alloc] = BitLoad(subchan_gains,total_bits,num_subc,gap,noise,M) % Bit Loading Algorithm % --------------------- % % Inputs : % subchan_gains : SubCarrier Gains % total_bits : Total Number of bits % num_subc : Number of Subcarriers % gap : Gap of the system % noise : Noise Power % M : Max Constellation Size % Outputs: % bits_alloc : Bits allocation for each subchannel % power_alloc : Total Power allocation % ----------------------------------------------- ---------------- % Compute SNR's for each channel SNR = ComputeSNR(subchan_gains,noise,gap); % This function just initializes the system with a particular bit % allocation and energy allocation using Chow's Algorithm. This is % further efficientize using Campello's Algorithm

[bits_alloc, energy_alloc] = chow_algo(SNR,num_subc,M); % Form the Energy Increment Table based on the present channel % gains for all the subchannels in order to be used by Campello % Algorithm energytable = EnergyTableInit(SNR,M); % Efficientize the algorithm using the Campello's algorithm [bits_alloc,energy_alloc] = campello_algo(bits_alloc,energy_alloc,energytable,total_bits,num_sub c,M ); ComputeSNR.m: Given the subcarrier gains, this simple function generates the SNR values of each channel (each singular value on each tone is a separate channel). function SNR = ComputeSNR(subcar_gains,noise,gap) SNR = abs((subcar_gains.^2)./(noise*gap)); chow_algo.m: Apply Chow's algorithm to generate a particular bit and energy % Chow's Algorithm allocation. % ---------------- % This is based on the paper by Chow et al titled % % A Practical Discrete Multitone Transceiver Loading Algorithm % for Data Transmission over Spectrally Shaped Channels.IEEE Trans % on Communications. Vol. 43, No 2/3/4, pp. 773-775, Feb/Mar/Apr 1995 function [bits_alloc, energy_alloc] = chow_algo(SNR,num_subc,M)

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