% DSSS, and rate 1/2 LDPC
%
% TODO
-% [ ] Nc carriers, 588 bit frames
-% [ ] FEC
+% [X] Nc carriers, 588 bit frames
+% [X] FEC
+% [X] pilot insertion and removal
% [ ] delay on parity and DSSS carriers
-% [ ] pilot insertion and removal
+% [ ] pilot based phase est
+% [ ] uncoded and coded frame sync
+% [ ] timing estimation, RN filtering, carrier FDM
% reqd to make sure we can repeat tests exactly
bps = 2;
Nsymb = framesize/bps;
Nsymbrow = Nsymb/Nc;
+ Npilotsframe = Nsymbrow/Ns;
+ Nsymbrowpilot = Nsymbrow + Npilotsframe;
+
+ printf("Each frame is %d bits or %d symbols, transmitted as %d symbols by %d carriers.",
+ framesize, Nsymb, Nsymbrow, Nc);
+ printf(" There are %d pilot symbols in each carrier, seperated by %d data/parity symbols.",
+ Npilotsframe, Ns);
+ printf(" Including pilots, the frame is %d symbols long by %d carriers.\n\n",
+ Nsymbrowpilot, Nc);
+
+ assert(Npilotsframe == floor(Nsymbrow/Ns), "Npilotsframe must be an integer");
prev_sym_tx = qpsk_mod([0 0])*ones(1,Nc*Nchip);
prev_sym_rx = qpsk_mod([0 0])*ones(1,Nc*Nchip);
- s_ch_mem = zeros(Np*Ns+1, Nc*Nchip);
+ rx_symb_buf = zeros(3*Nsymbrow, Nc);
+ rx_pilot_buf = zeros(3*Npilotsframe,Nc);
+ tx_bits_buf = zeros(1,2*framesize);
% Init LDPC --------------------------------------------------------------------
spread_2ms = spread_2ms(1000:length(spread_2ms));
% decimate down to Rs
-
+
spread = spread(1:M:length(spread));
spread_2ms = spread_2ms(1:M:length(spread_2ms));
noise_log = [];
errors_log = [];
Nerrs_log = [];
-
+ phi_log = [];
+
Terrsldpc = Tbitsldpc = Ferrsldpc = 0;
% init HF channel
hf_n = 1;
- phi_ = zeros(Ntrials+Np*Ns, Nc*Nchip);
phase_offset = 0;
- w_offset = 0;
+ w_offset = pi/16;
% simulation starts here-----------------------------------
- tx_bits = round(rand(1,framesize));
-
- for nn = 1:Ntrials+Np*Ns
+ for nn = 1:Ntrials+2
- tx_bits = round(rand(1,framesize*rate));
if ldpc_code
+ tx_bits = round(rand(1,framesize*rate));
[tx_bits, tmp] = ldpc_enc(tx_bits, code_param);
+ else
+ tx_bits = round(rand(1,framesize));
end
+ tx_bits_buf(1:framesize) = tx_bits_buf(framesize+1:2*framesize);
+ tx_bits_buf(framesize+1:2*framesize) = tx_bits;
% modulate --------------------------------------------
- tx_symb = zeros(Nsymbrow,Nc*Nchip);
-
% organise symbols into a Nsymbrow rows by Nc cols
% data and parity bits are on separate carriers
+ tx_symb = zeros(Nsymbrow,Nc*Nchip);
+
for c=1:Nc
for r=1:Nsymbrow
i = (c-1)*Nsymbrow + r;
end
end
+ % Optionally insert pilots, one every Ns data symbols
+
+ pilot = ones(Npilotsframe,Nc);
+ tx_symb_pilot = zeros(Nsymbrowpilot, Nc);
+
+ for p=1:Npilotsframe
+ tx_symb_pilot((p-1)*(Ns+1)+1,:) = pilot(p,:); % row of pilots
+ %printf("%d %d %d %d\n", (p-1)*(Ns+1)+2, p*(Ns+1), (p-1)*Ns+1, p*Ns);
+ tx_symb_pilot((p-1)*(Ns+1)+2:p*(Ns+1),:) = tx_symb((p-1)*Ns+1:p*Ns,:); % payload symbols
+ end
+ tx_symb = tx_symb_pilot;
+
% Optionally copy to other carriers (spreading)
for c=Nc+1:Nc:Nc*Nchip
if strcmp(modulation,'dqpsk')
for c=1:Nc*Nchip
- for r=1:Nsymbrow
+ for r=1:Nsymbrowpilot
tx_symb(r,c) *= prev_sym_tx(c);
prev_sym_tx(c) = tx_symb(r,c);
end
hf_model(hf_n, :) = zeros(1,Nc*Nchip);
- for r=1:Nsymbrow
+ for r=1:Nsymbrowpilot
for c=1:Nchip*Nc
- time_shift = floor((c-1)*Nsymbrow);
+ time_shift = floor((c-1)*Nsymbrowpilot);
ahf_model = hf_gain*(spread(hf_n+time_shift) + exp(-j*c*wsep*nhfdelay)*spread_2ms(hf_n+time_shift));
if hf_mag_only
s_ch(r,c) *= abs(ahf_model);
s_ch(r,c) *= ahf_model;
end
hf_model(hf_n, c) = ahf_model;
- hf_fading((c-1)*Nsymbrow+r) = abs(ahf_model);
end
hf_n++;
end
% AWGN noise and phase/freq offset channel simulation
% 0.5 factor ensures var(noise) == variance , i.e. splits power between Re & Im
- noise = sqrt(variance*0.5)*(randn(Nsymbrow,Nc*Nchip) + j*randn(Nsymbrow,Nc*Nchip));
+ noise = sqrt(variance*0.5)*(randn(Nsymbrowpilot,Nc*Nchip) + j*randn(Nsymbrowpilot,Nc*Nchip));
noise_log = [noise_log noise];
s_ch = s_ch + noise;
% demodulate stage 1
- for r=1:Nsymbrow
+ for r=1:Nsymbrowpilot
for c=1:Nc*Nchip
rx_symb(r,c) = s_ch(r, c);
if strcmp(modulation,'dqpsk')
end
end
+ % strip out pilots
+
+ rx_symb_pilot = rx_symb;
+ rx_symb = zeros(Nsymbrow, Nc);
+ rx_pilot = zeros(Npilotsframe, Nc);
+
+ for p=1:Npilotsframe
+ % printf("%d %d %d %d %d\n", (p-1)*Ns+1, p*Ns, (p-1)*(Ns+1)+2, p*(Ns+1), (p-1)*(Ns+1)+1);
+ rx_symb((p-1)*Ns+1:p*Ns,:) = rx_symb_pilot((p-1)*(Ns+1)+2:p*(Ns+1),:);
+ rx_pilot(p,:) = rx_symb_pilot((p-1)*(Ns+1)+1,:);
+ end
+
+ % buffer three frames of symbols (and pilots) for phase recovery
+
+ rx_symb_buf(1:2*Nsymbrow,:) = rx_symb_buf(Nsymbrow+1:3*Nsymbrow,:);
+ rx_symb_buf(2*Nsymbrow+1:3*Nsymbrow,:) = rx_symb;
+ rx_pilot_buf(1:2*Npilotsframe,:) = rx_pilot_buf(Npilotsframe+1:3*Npilotsframe,:);
+ rx_pilot_buf(2*Npilotsframe+1:3*Npilotsframe,:) = rx_pilot;
+
+ % pilot assisted phase estimation and correction of middle frame in rx symb buffer
+
+ rx_symb = rx_symb_buf(Nsymbrow+1:2*Nsymbrow,:);
+ if nn > 2
+ phi_ = zeros(Nsymbrow, Nc);
+ for c=1:Nc
+ if verbose > 2
+ printf("phi_ : ");
+ end
+ for r=1:Nsymbrow
+ st = Npilotsframe+1+floor((r-1)/Ns) - floor(Np/2) + 1;
+ en = st + Np - 1;
+ phi_(r,c) = angle(sum(rx_pilot_buf(st:en,c)));
+ if verbose > 2
+ printf("% 4.3f ", phi_(r,c))
+ end
+ rx_symb(r,c) *= exp(-j*phi_(r,c));
+ end
+ if verbose > 2
+ printf("\nrx_symb: ");
+ for r=1:Nsymbrow
+ printf("% 4.3f ", angle(rx_symb(r,c)))
+ end
+ printf("\nindexes: ");
+ for r=1:Nsymbrow
+ st = Npilotsframe+1+floor((r-1)/Ns) - floor(Np/2) + 1;
+ en = st + Np - 1;
+ printf("%2d,%2d ", st,en)
+ end
+ printf("\npilots : ");
+ for p=1:3*Npilotsframe
+ printf("% 4.3f ", angle(rx_pilot_buf(p,c)));
+ end
+ printf("\n\n");
+ end
+ end
+ phi_log = [phi_log ; phi_];
+ end
+
% de-spread
- for r=1:Nsymbrow
+ for r=1:Nsymbrowpilot
for c=Nc+1:Nc:Nchip*Nc
rx_symb(r,1:Nc) = rx_symb(r,1:Nc) + rx_symb(r,c:c+Nc-1);
end
% demodulate stage 2
- rx_bits = zeros(1, framesize);
rx_symb_linear = zeros(1,Nsymb);
+ rx_bits = zeros(1, framesize);
for c=1:Nc
for r=1:Nsymbrow
i = (c-1)*Nsymbrow + r;
- rx_bits((2*(i-1)+1):(2*i)) = qpsk_demod(rx_symb(r,c));
rx_symb_linear(i) = rx_symb(r,c);
- rx_symb_log = [rx_symb_log rx_symb(r,c)];
+ rx_bits((2*(i-1)+1):(2*i)) = qpsk_demod(rx_symb(r,c));
end
end
-
- % Measure BER
- error_positions = xor(rx_bits, tx_bits);
- Nerrs = sum(error_positions);
- Terrs += Nerrs;
- Tbits += length(tx_bits);
- errors_log = [errors_log error_positions];
- Nerrs_log = [Nerrs_log Nerrs];
+ % Wait until we have 3 frames to do pilot assisted phase estimation
+
+ if nn > 2
+ rx_symb_log = [rx_symb_log rx_symb_linear];
- % Optionally LDPC decode
+ % Measure BER
+
+ error_positions = xor(rx_bits, tx_bits_buf(1:framesize));
+ Nerrs = sum(error_positions);
+ Terrs += Nerrs;
+ Tbits += length(tx_bits);
+ errors_log = [errors_log error_positions];
+ Nerrs_log = [Nerrs_log Nerrs];
+
+ % Optionally LDPC decode
- if ldpc_code
+ if ldpc_code
detected_data = ldpc_dec(code_param, max_iterations, demod_type, decoder_type, ...
rx_symb_linear, min(100,EsNo), hf_fading);
- error_positions = xor( detected_data(1:framesize*rate), tx_bits(1:framesize*rate) );
+ error_positions = xor( detected_data(1:framesize*rate), tx_bits_buf(1:framesize*rate) );
Nerrs = sum(error_positions);
ldpc_Nerrs_log = [ldpc_Nerrs_log Nerrs];
ldpc_errors_log = [ldpc_errors_log error_positions];
end
Terrsldpc += Nerrs;
Tbitsldpc += framesize*rate;
+ end
end
- end
-
- TERvec(ne) = Terrs;
- BERvec(ne) = Terrs/Tbits;
- if verbose
- av_tx_pwr = (s_ch_tx_log * s_ch_tx_log')/length(s_ch_tx_log);
+ end
+
+ TERvec(ne) = Terrs;
+ BERvec(ne) = Terrs/Tbits;
- printf("EsNo (dB): %3.1f Terrs: %d BER %4.2f QPSK BER theory %4.2f av_tx_pwr: %3.2f", EsNodB, Terrs,
- Terrs/Tbits, 0.5*erfc(sqrt(EsNo/2)), av_tx_pwr);
- if ldpc_code
- printf("\n LDPC: Terrs: %d BER: %4.2f Ferrs: %d FER: %4.2f",
- Terrsldpc, Terrsldpc/Tbitsldpc, Ferrsldpc, Ferrsldpc/Ntrials);
+ if verbose
+ av_tx_pwr = (s_ch_tx_log * s_ch_tx_log')/length(s_ch_tx_log);
+
+ printf("EsNo (dB): %3.1f Terrs: %d BER %4.2f QPSK BER theory %4.2f av_tx_pwr: %3.2f", EsNodB, Terrs,
+ Terrs/Tbits, 0.5*erfc(sqrt(EsNo/2)), av_tx_pwr);
+ if ldpc_code
+ printf("\n LDPC: Terrs: %d BER: %4.2f Ferrs: %d FER: %4.2f",
+ Terrsldpc, Terrsldpc/Tbitsldpc, Ferrsldpc, Ferrsldpc/Ntrials);
+ end
+ printf("\n");
end
- printf("\n");
- end
end
Ebvec = Esvec - 10*log10(bps);
figure(5);
clf
subplot(211)
- [m n] = size(hf_model);
+ [m n] = size(hf_model)
plot(angle(hf_model(1:m,1)),'g;HF channel phase;')
hold on;
- lphi_ = length(phi_);
- plot(phi_(1+floor(Ns*Np/2):lphi_),'r+;Estimated HF channel phase;')
+ lphi_log = length(phi_log)
+ plot(phi_log(1+floor(Ns*Np/2):lphi_log),'r+;Estimated HF channel phase;')
ylabel('Phase (rads)');
subplot(212)
plot(abs(hf_model(1:m,1)))
sim_in.framesize = 576;
sim_in.Nc = 2;
- sim_in.Rs = 200;
+ sim_in.Rs = 250;
sim_in.Ns = 8;
- sim_in.Np = 0;
+ sim_in.Np = 4;
sim_in.Nchip = 1;
sim_in.ldpc_code_rate = 0.5;
sim_in.ldpc_code = 1;
sim_in.Ntrials = 20;
- sim_in.Esvec = 2;
+ sim_in.Esvec = 3;
sim_in.hf_sim = 0;
- sim_in.hf_mag_only = 1;
+ sim_in.hf_mag_only = 0;
sim_qpsk_hf = ber_test(sim_in, 'qpsk');
endfunction
projects / freetel-svn-tracking.git / commitdiff