sim_in.Nsymb = Nsymb = framesize/bps;
sim_in.Nsymbrow = Nsymbrow = Nsymb/Nc;
- sim_in.Npilotsframe = Npilotsframe = Nsymbrow/Ns;
- sim_in.Nsymbrowpilot = Nsymbrowpilot = Nsymbrow + Npilotsframe + 1;
+ sim_in.Npilotsframe = Npilotsframe = Nsymbrow/Ns+1;
+ sim_in.Nsymbrowpilot = 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);
+ printf("Each frame contains %d data bits or %d data symbols, transmitted as %d symbols by %d carriers.", framesize, Nsymb, Nsymbrow, Nc);
+ printf(" There are %d pilot symbols in each carrier together at the start of each frame, then %d data 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");
+ %assert(Npilotsframe == floor(Nsymbrow/Ns), "Npilotsframe must be an integer");
sim_in.prev_sym_tx = qpsk_mod([0 0])*ones(1,Nc*Nchip);
sim_in.prev_sym_rx = qpsk_mod([0 0])*ones(1,Nc*Nchip);
write_pilot_file(pilot, Nsymbrowpilot, Ns, Np, Nsymbrow, Npilotsframe, Nc);
end
+ % we use first 2 pilots of next frame to help with frame sync and fine freq
+
+ sim_in.Nct_sym_buf = 2*Nsymbrowpilot + 2;
+ sim_in.ct_symb_buf = zeros(sim_in.Nct_sym_buf, Nc);
+
% Init LDPC --------------------------------------------------------------------
if ldpc_code
tx_symb(r,c) = qpsk_mod(tx_bits(2*(i-1)+1:2*i));
end
end
- %tx_symb = zeros(Nsymbrow,Nc);
-
- % insert pilots, one every Ns data symbols
-
- 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;
-
- % Append extra col of pilots at the start
-
- tx_symb = [ pilot(1,:); tx_symb_pilot];
+
+ % insert pilots at start of frame
+
+ tx_symb = [pilot(1,:); pilot(2,:); tx_symb;];
% Optionally copy to other carriers (spreading)
% Frequency offset estimation --------------------------------------------------
+% This function was used in initial Nov 2014 experiments
+
function [f_max s_max] = freq_off_est(rx_fdm, tx_pilot, offset, n)
Fs = 8000;
endfunction
+% Set of functions to implement latest and greatest freq offset
+% estimation, March 2015 ----------------------
+
+% returns an estimate of frequency offset, advances to next sync state
+
+function [next_sync cohpsk] = coarse_freq_offset_est(cohpsk, fdmdv, ch_fdm_frame, sync, next_sync)
+ Fcentre = fdmdv.Fcentre;
+ Nc = fdmdv.Nc;
+ Fsep = fdmdv.Fsep;
+ M = fdmdv.M;
+ Fs = fdmdv.Fs;
+ Ndft = cohpsk.Ndft;
+
+ if sync == 0
+ f_start = Fcentre - ((Nc/2)+2)*Fsep;
+ f_stop = Fcentre + ((Nc/2)+2)*Fsep;
+ T = abs(fft(ch_fdm_frame(1:6*M).* hanning(6*M)', Ndft)).^2;
+ sc = Ndft/Fs;
+ bin_start = floor(f_start*sc+0.5)+1;
+ bin_stop = floor(f_stop*sc+0.5)+1;
+ x = bin_start-1:bin_stop-1;
+ bin_est = x*T(bin_start:bin_stop)'/sum(T(bin_start:bin_stop));
+ cohpsk.f_est = bin_est/sc;
+ printf("coarse freq est: %f\n", cohpsk.f_est);
+ next_sync = 1;
+ end
+
+endfunction
+
+
+% returns index of start of frame and fine freq offset
+
+function [next_sync cohpsk] = frame_sync_fine_timing_est(cohpsk, ch_symb, sync, next_sync)
+ ct_symb_buf = cohpsk.ct_symb_buf;
+ Nct_sym_buf = cohpsk.Nct_sym_buf;
+ Rs = cohpsk.Rs;
+ Nsymbrowpilot = cohpsk.Nsymbrowpilot;
+ Nc = cohpsk.Nc;
+
+ % update memory in symbol buffer
+
+ for r=1:Nct_sym_buf-Nsymbrowpilot
+ ct_symb_buf(r,:) = ct_symb_buf(r+Nsymbrowpilot,:);
+ end
+ i = 1;
+ for r=Nct_sym_buf-Nsymbrowpilot+1:Nct_sym_buf
+ ct_symb_buf(r,:) = ch_symb(i,:);
+ i++;
+ end
+ cohpsk.ct_symb_buf = ct_symb_buf;
+
+ % sample pilots at start of this frame and start of next frame
+
+ sampling_points = [1 2 7 8];
+ pilot2 = [ cohpsk.pilot(1,:); cohpsk.pilot(2,:); cohpsk.pilot(1,:); cohpsk.pilot(2,:);];
+
+ if sync == 2
+
+ % sample correlation over 2D grid of time and fine freq points
+
+ max_corr = 0;
+ for f_fine=-20:1:20
+ f_fine_rect = exp(-j*f_fine*2*pi*sampling_points/Rs)';
+ for t=0:cohpsk.Nsymbrowpilot-1
+ corr = 0; mag = 0;
+ for c=1:Nc
+ f_corr_vec = f_fine_rect .* ct_symb_buf(t+sampling_points,c);
+ for p=1:length(sampling_points)
+ corr += pilot2(p,c) * f_corr_vec(p);
+ mag += abs(f_corr_vec(p));
+ end
+ end
+ %printf(" f: %f t: %d corr: %f %f\n", f_fine, t, real(corr), imag(corr));
+ if corr > max_corr
+ max_corr = corr;
+ max_mag = mag;
+ cohpsk.ct = t;
+ cohpsk.f_fine_est = f_fine;
+ end
+ end
+ end
+
+ printf(" fine freq f: %f max_corr: %f max_mag: %f ct: %d\n", cohpsk.f_fine_est, abs(max_corr), max_mag, cohpsk.ct);
+ if max_corr/max_mag > 0.9
+ printf("in sync!\n");
+ next_sync = 4;
+ else
+ next_sync = 0;
+ printf(" back to coarse freq offset ets...\n");
+ end
+ end
+endfunction
+
+
% Rate Rs BER tests ------------------------------------------------------------------------------
function sim_out = ber_test(sim_in)
randn('state',1);
n = 2000;
-frames = 35;
-framesize = 160
-foff = 50;
+frames = 35*4;
+framesize = 32;
+foff = -80;
-EsNodB = 18;
+EsNodB = 8;
EsNo = 10^(EsNodB/10);
variance = 1/EsNo;
load ../build_linux/unittest/tcohpsk_out.txt
sim_in = standard_init();
-sim_in.framesize = 160;
+sim_in.framesize = framesize;
sim_in.ldpc_code = 0;
sim_in.ldpc_code_rate = 1;
sim_in.Nc = Nc = 4;
freq_hz = Fsep*( -Nc/2 - 0.5 + (1:Nc) );
fdmdv.freq_pol = 2*pi*freq_hz/Fs;
fdmdv.freq = exp(j*fdmdv.freq_pol);
-Fcentre = 1500;
+fdmdv.Fcentre = 1500;
+
+cohpsk.Ndft = 1024;
+cohpsk.f_est = fdmdv.Fcentre;
fdmdv.fbb_rect = exp(j*2*pi*Fcentre/Fs);
fdmdv.fbb_phase_tx = 1;
% Coarse Freq offset estimation
- if sync == 0
- f_start = Fcentre - ((Nc/2)+2)*Fsep; f_stop = Fcentre + ((Nc/2)+2)*Fsep;
- T = abs(fft(ch_fdm_frame(1:8*M).* hanning(8*M)',Fs)).^2;
- T = T(f_start:f_stop);
- x = f_start:f_stop;
- f_est = x*T'/sum(T);
- f_off_est = f_est - Fcentre;
- f_err = f_off_est - foff;
- if abs(f_err) > 5
- f_err_fail++;
- end
- f_err_log = [f_err_log f_err];
- printf("coarse freq est: %f offset: %f f_err: %f\n", f_est, f_off_est, f_err);
- fdmdv.fbb_rect_rx = exp(j*2*pi*(f_est)/Fs);
- sync = 1;
- end
+ next_sync = sync;
+
+ [next_sync cohpsk] = coarse_freq_offset_est(cohpsk, fdmdv, ch_fdm_frame, sync, next_sync);
nin = M;
% shift frame down to complex baseband
-
+
+ fdmdv.fbb_rect_rx = exp(j*2*pi*cohpsk.f_est/fdmdv.Fs);
rx_fdm_frame_bb = zeros(1, sim_in.Nsymbrowpilot*M);
for r=1:sim_in.Nsymbrowpilot*M
fbb_phase_rx = fbb_phase_rx*fdmdv.fbb_rect_rx';
fbb_phase_rx /= mag;
rx_fdm_log = [rx_fdm_log rx_fdm_frame_bb];
+ % sample rate demod processing
+
ch_symb = zeros(sim_in.Nsymbrowpilot, Nc);
for r=1:sim_in.Nsymbrowpilot
ch_symb_log = [ch_symb_log; ch_symb];
% coarse timing (frame sync) and initial fine freq est ---------------------------------------------
-
- ct_symb_buf(1:sim_in.Nsymbrowpilot,:) = ct_symb_buf(sim_in.Nsymbrowpilot+1:2*sim_in.Nsymbrowpilot,:);
- ct_symb_buf(sim_in.Nsymbrowpilot+1:2*sim_in.Nsymbrowpilot,:) = ch_symb;
-
- sampling_points = [1 (2:sim_in.Ns+1:1+sim_in.Npilotsframe*sim_in.Ns+1)];
- pilot2 = [ sim_in.pilot(1,:); sim_in.pilot];
+
+ [next_sync sim_in] = frame_sync_fine_timing_est(sim_in, ch_symb, sync, next_sync);
if sync == 1
- max_corr = 0;
- for f_fine=-15:1:15
- f_fine_rect = exp(-j*f_fine*2*pi*sampling_points/Rs)';
- for t=0:sim_in.Nsymbrowpilot-1
- corr = 0; mag = 0;
- for c=1:Nc
- f_corr_vec = f_fine_rect .* ct_symb_buf(t+sampling_points,c);
- for p=1:sim_in.Npilotsframe+1
- corr += pilot2(p,c) * f_corr_vec(p);
- mag += abs(f_corr_vec(p));
- end
- end
- %printf(" f: %f t: %d corr: %f %f\n", f_fine, t, real(corr), imag(corr));
- if corr > max_corr
- max_corr = corr;
- max_mag = mag;
- ct = t;
- f_fine_est = f_fine;
- end
- end
- end
-
- printf(" fine freq f: %f max_corr: %f max_mag: %f ct: %d\n", f_fine_est, abs(max_corr), max_mag, ct);
- if max_corr/max_mag > 0.8
- sync = 2;
- end
+ next_sync = 2;
end
-
- if (i==50)
- figure(8)
- f_fine_rect = exp(-j*f_fine_est*2*pi*sampling_points/Rs)';
- plot(f_fine_rect,'+');
- hold on;
- plot(ct_symb_buf(ct+sampling_points,1),'b+');
- hold off;
+
+ printf("i: %d sync: %d next_sync: %d\n", i, sync, next_sync);
+ sync = next_sync;
+
+ if (i==10)
xx
end
+ if 0
[rx_symb rx_bits rx_symb_linear amp_linear amp_ phi_ EsNo_ prev_sym_rx sim_in] = qpsk_symbols_to_bits(sim_in, ct_symb_buf(ct+1:ct+sim_in.Nsymbrowpilot,:), []);
rx_symb_log = [rx_symb_log; rx_symb];
rx_amp_log = [rx_amp_log; amp_];
end
prev_tx_bits2 = prev_tx_bits;
prev_tx_bits = tx_bits;
+ end
end
projects / freetel-svn-tracking.git / commitdiff