sim_in.Nct_sym_buf = 2*Nsymbrowpilot + 2;
sim_in.ct_symb_buf = zeros(sim_in.Nct_sym_buf, Nc);
+ sim_in.ff_phase = 1;
+
% Init LDPC --------------------------------------------------------------------
if ldpc_code
% Symbol rate processing for rx side (demodulator) -------------------------------------------------------
-function [rx_symb rx_bits rx_symb_linear amp_linear amp_ phi_ EsNo_ prev_sym_rx sim_in] = qpsk_symbols_to_bits(sim_in, s_ch, prev_sym_rx)
- framesize = sim_in.framesize;
- Nsymb = sim_in.Nsymb;
- Nsymbrow = sim_in.Nsymbrow;
- Nsymbrowpilot = sim_in.Nsymbrowpilot;
- Nc = sim_in.Nc;
- Npilotsframe = sim_in.Npilotsframe;
- Ns = sim_in.Ns;
- Np = sim_in.Np;
- Nchip = sim_in.Nchip;
- modulation = sim_in.modulation;
- pilot = sim_in.pilot;
- rx_symb_buf = sim_in.rx_symb_buf;
- rx_pilot_buf = sim_in.rx_pilot_buf;
- tx_pilot_buf = sim_in.tx_pilot_buf;
- verbose = sim_in.verbose;
-
- % demodulate stage 1
-
- for r=1:Nsymbrowpilot
- for c=1:Nc*Nchip
- rx_symb(r,c) = s_ch(r, c);
- if strcmp(modulation,'dqpsk')
- tmp = rx_symb(r,c);
- rx_symb(r,c) *= conj(prev_sym_rx(c)/abs(prev_sym_rx(c)));
- prev_sym_rx(c) = tmp;
- end
- end
- end
-
- % strip out pilots
-
- rx_symb_pilot = rx_symb;
- rx_symb = zeros(Nsymbrow, Nc*Nchip);
- rx_pilot = zeros(Npilotsframe, Nc*Nchip);
+function [rx_symb rx_bits amp_ phi_ EsNo_ cohpsk] = qpsk_symbols_to_bits(cohpsk, ct_symb_buf)
+ framesize = cohpsk.framesize;
+ Nsymb = cohpsk.Nsymb;
+ Nsymbrow = cohpsk.Nsymbrow;
+ Nsymbrowpilot = cohpsk.Nsymbrowpilot;
+ Nc = cohpsk.Nc;
+ Npilotsframe = cohpsk.Npilotsframe;
+ pilot = cohpsk.pilot;
+ verbose = cohpsk.verbose;
+
+ % average pilots to get phase and amplitude estimates
+ % we assume there are two samples at the start of each frame and two at the end
+
+ sampling_points = [1 2 7 8];
+ pilot2 = [cohpsk.pilot(1,:); cohpsk.pilot(2,:); cohpsk.pilot(1,:); cohpsk.pilot(2,:);];
+ phi_ = zeros(Nsymbrow, Nc);
+ amp_ = zeros(Nsymbrow, Nc);
+
+ for c=1:Nc
+ corr = pilot2(:,c)' * ct_symb_buf(sampling_points,c);
+ mag = sum(abs(ct_symb_buf(sampling_points,c)));
- 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,:);
+ phi_(:, c) = angle(corr);
+ amp_(:, c) = mag/length(sampling_points);
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;
- sim_in.rx_symb_buf = rx_symb_buf;
- sim_in.rx_pilot_buf = rx_pilot_buf;
-
- % pilot assisted phase estimation and correction of middle frame in rx symb buffer
+ % now correct phase of data symbols and make decn on bits
- rx_symb = rx_symb_buf(Nsymbrow+1:2*Nsymbrow,:);
-
- phi_ = zeros(Nsymbrow, Nc*Nchip);
- amp_ = ones(Nsymbrow, Nc*Nchip);
-
- for c=1:Nc*Nchip
-
- 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;
- ch_est = tx_pilot_buf(st:en,c)'*rx_pilot_buf(st:en,c)/Np;
- phi_(r,c) = angle(ch_est);
- amp_(r,c) = abs(ch_est);
- %amp_(r,c) = abs(rx_symb(r,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
-
- % de-spread
-
- for r=1:Nsymbrow
- for c=Nc+1:Nc:Nchip*Nc
- rx_symb(r,1:Nc) = rx_symb(r,1:Nc) + rx_symb(r,c:c+Nc-1);
- amp_(r,1:Nc) = amp_(r,1:Nc) + amp_(r,c:c+Nc-1);
- end
- end
-
- % demodulate stage 2
-
- rx_symb_linear = zeros(1,Nsymb);
- amp_linear = zeros(1,Nsymb);
+ rx_symb = zeros(Nsymbrow, Nc);
+ rx_symb_linear = zeros(1, Nsymbrow*Nc);
rx_bits = zeros(1, framesize);
for c=1:Nc
for r=1:Nsymbrow
i = (c-1)*Nsymbrow + r;
- rx_symb_linear(i) = rx_symb(r,c);
- amp_linear(i) = amp_(r,c);
+ rx_symb(i) = ct_symb_buf(2+r,c)*exp(-j*phi_(c));
+ rx_symb_linear(i) = rx_symb(i);
rx_bits((2*(i-1)+1):(2*i)) = qpsk_demod(rx_symb(r,c));
end
end
% Estimate signal power
- Es_ = mean(amp_linear .^ 2);
+ Es_ = mean(amp_ .^ 2);
EsNo_ = Es_/No_;
%printf("Es_: %f No_: %f Es/No: %f Es/No dB: %f\n", Es_, No_, Es_/No_, 10*log10(EsNo_));
-
- % LDPC decoder requires some amplitude normalisation
- % (AGC), was found to break ow. So we adjust the symbol
- % amplitudes so that they are an averge of 1
-
- rx_symb_linear /= mean(amp_linear);
- amp_linear /= mean(amp_linear);
-
+
endfunction
max_mag = mag;
cohpsk.ct = t;
cohpsk.f_fine_est = f_fine;
+ cohpsk.ff_rect = exp(-j*f_fine*2*pi/Rs);
end
end
end
n = 2000;
frames = 35*4;
framesize = 32;
-foff = -80;
+foff = 0;
EsNodB = 8;
EsNo = 10^(EsNodB/10);
% coarse timing (frame sync) and initial fine freq est ---------------------------------------------
[next_sync acohpsk] = frame_sync_fine_timing_est(acohpsk, ch_symb, sync, next_sync);
+ %acohpsk.ff_rect = exp(j*2*pi*(-1.0)/Rs);
if sync == 1
next_sync = 2;
end
- printf("i: %d sync: %d next_sync: %d\n", i, sync, next_sync);
+ %printf("i: %d sync: %d next_sync: %d\n", i, sync, next_sync);
sync = next_sync;
- if (i==10)
+ if (i==1000)
xx
end
- if 0
- [rx_symb rx_bits rx_symb_linear amp_linear amp_ phi_ EsNo_ prev_sym_rx acohpsk] = qpsk_symbols_to_bits(acohpsk, ct_symb_buf(ct+1:ct+acohpsk.Nsymbrowpilot,:), []);
- rx_symb_log = [rx_symb_log; rx_symb];
- rx_amp_log = [rx_amp_log; amp_];
- rx_phi_log = [rx_phi_log; phi_];
- rx_bits_log = [rx_bits_log rx_bits];
+ % We can decode first that we get sync on. Need to fine freq correct all of it's symbols,
+ % including pilots. From then on, just correct new symbols into frame.
+ % make copy, so if we lose sync we havent fine freq corrected ct_symb_buf
+ % if next_sync == 4 correct all 8
+ % if sync == 2 correct latest 6
- % BER stats
+ if (next_sync == 4) || (sync == 4)
- if i > 3
- error_positions = xor(prev_tx_bits2, rx_bits);
- Nerrs += sum(error_positions);
- nerr_log = [nerr_log sum(error_positions)];
- Tbits += length(error_positions);
+ if next_sync == 4
+
+ % first frame, we've just gotten sync so fine freq correct all Nsymbrowpilot+2 samples
+
+ ct_symb_ff_buf = acohpsk.ct_symb_buf(acohpsk.ct+1:acohpsk.ct+acohpsk.Nsymbrowpilot+2,:);
+ for r=1:acohpsk.Nsymbrowpilot+2
+ acohpsk.ff_phase *= acohpsk.ff_rect';
+ ct_symb_ff_buf(r,:) *= acohpsk.ff_phase;
+ end
+
+ else
+
+ % second and subsequent frames, just fine freq correct the latest Nsymbrowpilot
+
+ ct_symb_ff_buf(1:2,:) = ct_symb_ff_buf(Nsymbrowpilot+1:Nsymbrowpilot+2,:);
+ ct_symb_ff_buf(3:Nsymbrowpilot+2,:) = acohpsk.ct_symb_buf(acohpsk.ct+3:acohpsk.ct+acohpsk.Nsymbrowpilot+2,:);
+ for r=3:acohpsk.Nsymbrowpilot+2
+ afdmdv.ff_phase *= afdmdv.ff_rect';
+ ct_symb_ff_buf(r,:) *= afdmdv.ff_phase;
+ end
+
+ end
+
+ mag = abs(acohpsk.ff_phase);
+ acohpsk.ff_phase /= mag;
+
+ [rx_symb rx_bits amp_ phi_ EsNo_] = qpsk_symbols_to_bits(acohpsk, ct_symb_ff_buf);
+ rx_symb_log = [rx_symb_log; rx_symb];
+ rx_amp_log = [rx_amp_log; amp_];
+ rx_phi_log = [rx_phi_log; phi_];
+ rx_bits_log = [rx_bits_log rx_bits];
+
+ % BER stats
+
+ if i > 2
+ error_positions = xor(prev_tx_bits2, rx_bits);
+ Nerrs += sum(error_positions);
+ nerr_log = [nerr_log sum(error_positions)];
+ Tbits += length(error_positions);
+ end
end
+
prev_tx_bits2 = prev_tx_bits;
prev_tx_bits = tx_bits;
- end
end
stem_sig_and_error(6, 212, imag(rx_symb_log_c(1:n)), imag(rx_symb_log(1:n) - rx_symb_log_c(1:n)), 'rx symb im', [1 n -1.5 1.5])
stem_sig_and_error(7, 111, rx_bits_log_c(1:n), rx_bits_log(1:n) - rx_bits_log_c(1:n), 'rx bits', [1 n -1.5 1.5])
+if 0
check(tx_bits_log, tx_bits_log_c, 'tx_bits');
check(tx_symb_log, tx_symb_log_c, 'tx_symb');
check(tx_fdm_log, tx_fdm_log_c, 'tx_fdm');
check(rx_phi_log, rx_phi_log_c, 'rx_phi_log');
check(rx_symb_log, rx_symb_log_c, 'rx_symb',0.01);
check(rx_bits_log, rx_bits_log_c, 'rx_bits');
+end
% Determine bit error rate
projects / freetel-svn-tracking.git / commitdiff