OFDMMATLAB仿真程序

1、OFDM.m : OFDM Simulator (outer function) clear all;A = 1 l/exp(l) 1/exp(2);% power delay profileN = 64;% number of symbols in a single OFDM symbolGI = 16;% guard intervalMt = 1;% number of Tx antennasMr = 1;% number of Rx antennassig2 = le-3;% noise varianceM = 8;% max consteRation bit numberMgap =

2、104(1:(1.7/10)27);% gapBtot = 100*Mt;% total# bits per OFDM symbolTransmitter = 50; % # ite rations of symbol transmissions for each channel instance Channellter = 100; % # iterations of independent identicaDy distributed channel instances Gaplter = length(Mgap);load ENC2.matload ENC4.matload ENC16.

3、matload ENC64.matload ENC256.matTotEbNo =;Errors =;EbNo = 0； for IGap = l:GapIterIGapgap = Mgap(lGap); totalEnors = 0;for IChan = 1:Channellter% create channelH 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);% bit

4、loadingbits_alloc,energy_alloc = BitLoad(S,Btot,Mt*N,gap,s ig2,M); % e nergy_a lloc=e ne rgy_a lloc/(me an(ene rgy_a Hoc); %energy_alloc=ones(l,128);for lTrans = 1 :TransmitIter% bits to transmitx = (randn(l,Btot)0);% modulatex_mod = modulate(x,bits_alloc,energy_aHoc, s2,s4,s 16,s64,s256);% precode

5、modulated signal x_pre = precode(Mt, x_mod, V, N);% ifft, with cyclic pre fix for each antennaofdm_symbol =;for i=l:Mtofdm_symbol = ofUm_symbol; ifft_cp_tx_blk(x_pre(i:Mt:Mt*(N-l)+i),N,GI); endofdm_symbol2 = re shape (ofdm_s ymboLMt*(N+GI), 1);% channely = trans pose (channel(sig2, Mt, Mr, oftim_sym

6、bol2, H, N+GI);% fft rec_symbol =;for i=l:Mtrec_symbol = rec_symbol; fft_cp_rx_blk(y(i:Mt:Mt*(N+GI-l)4-i),N,G; endrec_symbol2 = re s ha p e (re c_s ymb o 1,1 ,Mt*N);% shape received signalshaped_vals = shape(rec_symbo!2, Mr, U, N);% demodulatey_demod = de modulate (shaped_va Is, bits_alloc, energy_a

7、lloc, S, s2,s4,s 16,s64,s256, c2,c4,cl6，c64,c256);% comparisontotalEnors = to ta Errors + sum(xor(y_demod,x); endEbNo = EbNo sum(energy_alloc)/Btot/sig2; endErrors = Errors tota Errors/Btot/Channe liter/Trans mitlter TotEbNo = TotEbNo mean(EbNo)EbNo =;end semilogx(TotEbNo, Errors);xlabel( Eb/No);yla

8、bel( BER);title(*SISO link, adaptive rate and power* ) function H，H_f=create_channel(Mt, Mr, A, N); % function H, H_f=cre a te_cha nne l(Mt, Mr, A, N);save SISO_adaptive2.mat Errors EbNocreate_channel.m : Generates parametrized by the antenna power-delay profile.a Rayleigh configuration,fadingire q

9、u e n c y- s e le c ti vethe OFDM configuration,channel, and the% 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 i

10、s 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 tapsH_int = 1 /s qrt(2)*(ra ndn(Mr*le ngth(A),Mt) + j*randn(M

11、r*length(A),Mt);H_int2=0;for i= l:length(A)H_int2 = H_int2;s qrt(A(i)*H_int(i-l )*Mr+1:i*Mr,:);endH_int2 = H_int2;zeros(N-length(A)*Mr,Mt);H_f = zeros(Mr,Mt*(N-16);for i = l:Mtfor j = 1:Mrh_f = ffi(H_int2(j:Mi*:(N-16-1 尸Mr+j,i)； for k = 1:(N-16)H_f(j,i+(k-l)*Mt) = h_f(k);endendendH=H_int2J;for i = 1

12、:N-1H=HJzeros(Mr*i,Mt);H_int2(l:(N-i)*Mr,:);endsvd decomposc channcLm:Since lull channel knowledge isassumed, transmissiondecomposesthe channel intois across parallel singular value modes. This iunction these modesfunction U, S, V = svd_decompose_channel(Mt, Mr, h_f, N);% U S V = svd_decompose_chann

13、el(Mt, Mr, h_f, N);%S VD componentsL is the number% Function decomposes the channel at each subcarrierinto its% Mt - # Tx antennas% Mr - # Rx antennas% h_f - MIMO impulse response - Mr rows, Mt*L columns, where of% channel taps% N # subcarriersU = ；S = ；v=n；for i= 1:NUtmp Stmp Vtmp = s vd(h_f(:,(i-l

14、)*Mt+l :i*Mt);U=U Utmp;V=V Vtmp;S=S Stmp; endS = sum(S J);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% Inpu

15、ts :% subchan_gains : SubCarrier Gains% total_bits : Total Number of bits% num_subc : Number of Subcarriers% gap: Gap of the sys tem% noise : Noise Power%M: Max Constellation Size% Outputs:% bits_alloc : Bits allocation for each subchannel% power_alloc : Total Power allocation% Compute SNRs for each

16、 channelSNR = Computes NR(subchan_ga ins,noise,gap);% This function just initializes the system with a particular bit% allocation and energy allocation using Chows Algorithm. This is% further efficientize using Campellos Algorithmbits_alloc, energy_alloc = chow_algo(SNR,num_subc,M);% Form the Energy

17、 Increment Table based on the present channel% gains for all the subchannels in order to be used by Campello% Algorithmenergytable = EnergyTableInit(SNR,M);% Effieientize the algorithm using the Campello s algorithmbits_a Hoc ,e ne rgy_a Hoc J =campello_algo(bits_alloc,energy_alloc,energytable,total

18、_bits,num_subc,M );ComDUtcSNR.m : Given the subcarrier gains, this simple lunction generates the SNR values of each channel (each singular value on each tone is a separate channel) function SNR = Computes NR(subcar_ga ins,noise,gap)SNR = abs(subcar_gains.A2)./(noise*gap);chow_algom : Apply Chows alg

19、orithm to generate a particular bit and energy allocation.% Chows Algorithm% This is based on the paper by Chow et al titled% A Practical Discrete Multitone Transceiver Loading Algorithm% for Data Transmission over Spectra lly Shaped Channels .IEEE Trans% on Communications. Vol. 43, No 2/3/4, pp. 77

20、3-775, Feb/Mar/Apr 1995function bits_alloc, energy_alloc = chow_a!go(SNR,num_subc,M)for i = 1:num_subc% Assuming each of the subchannels% of the bits for each subchannelte mpbits= log2(l + abs(SNR(i);roundte mpbits = round(te mpbits);if (roundtempbits 8) roundte mpbits = 8; endhas a flat foding, we

21、get initial% bits per two dimension. % round the bits% Limit them between 2 and 15estimateif (mod(roundtempbits,2)= 1 &roundtempbits = 1) roundtempbits = roundtempbits -1;endif roundte mpbits 0for the subchannelenergy_alloc(i) = (2Aroundtempbits-l)/SNR(i); elseenergy_alloc(i) = 0;end% Calculatethe E

22、nergyrequiredend% end of functionEncrgyTablelnif.m : Given the SNR values, form a table of energy increments for each channel.function energytable = EnergyTablelnit(SNR.M);% Inputs:% subcar_gains : Subcarrier Gains%M : max Constellation Size%Gap : Gap of the system% Noise : Noise Power% Outputs:% en

23、ergytable : Energytable% Based on the Subcarrier Gains, we calculate the energy% increment required by each subcarrier for transmitting% 1,2 ,4 ,6,8 bits.% Energy = 2A(i-l)/subcar_gains;%subcar_gains = (subcar_gains.A2)/(Gap*Noise);energytable = abs(l ./SNR)*(2.A(1:M+l-l);% Increase the energy value

24、 for constellation size of more than M to% a very high value so that it is not assignedenergytable(:,M+l) = Infone s (s ize (e ne rgyta ble (:,M+1);for i= 3:2:Menergytable(:,i) = (energytable(:,i) +e ne rgyta ble (：4+1 )/2;energytable(:,i+l) = energytable(: ,i);end%energytable = one s(l,size (energy

25、table J)1 energytable;campello_algom : Apply Campellos algorithm to converge to the optimal bit and energy allocation for the given channel conditions % campello_algo.m% This function is used by Campellos algorithm to allocate bits and energy for% each subchannel optimallyfunctionbits_aHoc, energy_a

26、llocj =campeIlo_algo(bits_alloc,energy_aHoc,energytable Jotal_bits,num_subc,M )bt = sum(bits_alloc);% We cant transmit more than M*(Number of subchannel) bitsif total_bits M*num_subctotal_bits = M*num_subc;endwhile (bt = total_bits)if (bt total_bits)max_val = 0;max_ind = ceil(rand(l)*num_subc);for i = 1:num_subcif bits_alloc(i) = 0te mp = e ne rgyta b le (i,bits_a lloc (i);elsetemp = 0;endif (temp max_va 1)max_val = te mp;max_ind = i;endendif (bits_alloc(max_ind) 0) bits_alloc(max_ind) = bits_alloc(max