diff options
Diffstat (limited to 'octave/ofdm_ldpc_rx.m')
| -rw-r--r-- | octave/ofdm_ldpc_rx.m | 279 |
1 files changed, 279 insertions, 0 deletions
diff --git a/octave/ofdm_ldpc_rx.m b/octave/ofdm_ldpc_rx.m new file mode 100644 index 0000000..6ef15aa --- /dev/null +++ b/octave/ofdm_ldpc_rx.m @@ -0,0 +1,279 @@ +% ofdm_ldpc_rx.m +% David Rowe April 2017 +% +% OFDM file based rx, with LDPC and interleaver, Octave version of src/ofdm_demod.c + +#{ + 1. Streaming mode operation: + + ofdm_ldpc_rx("test_700d.raw","700D") + + 2. Burst mode, tell state machine there is one packet in each burst: + + ofdm_ldpc_rx("test_datac0.raw","datac0","packetsperburst",1) + +#} + +function ofdm_ldpc_rx(filename, mode="700D", varargin) + ofdm_lib; + ldpc; + gp_interleaver; + more off; + pkg load signal; + + % init modem + + config = ofdm_init_mode(mode); + states = ofdm_init(config); + ofdm_load_const; + states.verbose = 1; + pass_packet_count = 0; + + i=1; + while i <= length(varargin) + if strcmp(varargin{i},"packetsperburst") + states.data_mode = "burst"; % use pre/post amble based sync + states.packetsperburst = varargin{i+1}; i++; + states.postambledetectoren = 1; + elseif strcmp(varargin{i},"passpacketcount") + pass_packet_count = varargin{i+1}; i++; + else + printf("\nERROR unknown argument: [%d] %s \n", i ,varargin{i}); + return; + end + i++; + end + + % some constants used for assembling modem frames + + [code_param Nbitspercodecframe Ncodecframespermodemframe] = codec_to_frame_packing(states, mode); + + % load real samples from file + + Ascale= states.amp_scale/2.0; % /2 as real signal has half amplitude + frx=fopen(filename,"rb"); rx = fread(frx, Inf, "short")/Ascale; fclose(frx); + Nsam = length(rx); + prx = 1; + + % Generate tx frame for BER calcs + + payload_bits = round(ofdm_rand(code_param.data_bits_per_frame)/32767); + tx_bits = fec_encode(states, code_param, mode, payload_bits, Ncodecframespermodemframe, Nbitspercodecframe); + + % Some handy constants + + Nsymsperframe = Nbitsperframe/bps; + Nsymsperpacket = Nbitsperpacket/bps; + Ncodedbitsperpacket = code_param.coded_bits_per_frame; + Ncodedsymsperpacket = code_param.coded_syms_per_frame; + + % init logs and BER stats + + rx_bits = []; rx_np_log = []; timing_est_log = []; delta_t_log = []; foff_est_hz_log = []; + channel_est_pilot_log = []; snr_log = []; mean_amp_log = []; + Terrs = Tbits = Terrs_coded = Tbits_coded = Perrs_coded = 0; + Nerrs_coded_log = Nerrs_log = []; + error_positions = []; + Nerrs_coded = Nerrs_raw = 0; + paritychecks = [0]; + EsNo = 1; + rx_uw = zeros(1,states.Nuwbits); + + rx_syms = zeros(1,Nsymsperpacket); rx_amps = zeros(1,Nsymsperpacket); + packet_count = frame_count = 0; + + % main loop ---------------------------------------------------------------- + + rx = ofdm_rx_filter(states, mode, rx); + + f = 1; + while(prx < Nsam) + + % insert samples at end of buffer, set to zero if no samples + % available to disable phase estimation on future pilots on last + % frame of simulation + + lnew = min(Nsam-prx,states.nin); + rxbuf_in = zeros(1,states.nin); + + if lnew + rxbuf_in(1:lnew) = rx(prx:prx+lnew-1); + end + prx += states.nin; + + if states.verbose + printf("f: %3d nin: %4d st: %-6s ", f, states.nin, states.sync_state); + end + + if strcmp(states.sync_state,'search') + [timing_valid states] = ofdm_sync_search(states, rxbuf_in); + else + % accumulate a buffer of data symbols for this packet + rx_syms(1:end-Nsymsperframe) = rx_syms(Nsymsperframe+1:end); + rx_amps(1:end-Nsymsperframe) = rx_amps(Nsymsperframe+1:end); + [states rx_bits achannel_est_pilot_log arx_np arx_amp] = ofdm_demod(states, rxbuf_in); + rx_syms(end-Nsymsperframe+1:end) = arx_np; + rx_amps(end-Nsymsperframe+1:end) = arx_amp; + + rx_uw = extract_uw(states, rx_syms(end-Nuwframes*Nsymsperframe+1:end), rx_amps(end-Nuwframes*Nsymsperframe+1:end)); + + % We need the full packet of symbols before disassembling and checking for bit errors + if (states.modem_frame == (states.Np-1)) + packet_count++; + + % unpack, de-interleave PSK symbols and symbol amplitudes + [rx_uw_unused payload_syms payload_amps txt_bits] = disassemble_modem_packet(states, rx_syms, rx_amps); + payload_syms_de = gp_deinterleave(payload_syms); + payload_amps_de = gp_deinterleave(payload_amps); + + % Count uncoded (raw) errors + rx_bits = zeros(1,Ncodedbitsperpacket); + for s=1:Ncodedsymsperpacket + if bps == 2 rx_bits(2*s-1:2*s) = qpsk_demod(payload_syms_de(s)); end + if bps == 4 rx_bits(bps*(s-1)+1:bps*s) = qam16_demod(states.qam16,payload_syms_de(s), payload_amps_de(s)); end + end + errors = xor(tx_bits, rx_bits); + Nerrs = sum(errors); + Nerrs_log = [Nerrs_log Nerrs]; Nerrs_raw = Nerrs; + Terrs += Nerrs; + Tbits += Nbitsperpacket; + + % LDPC decode + + % keep earlier mean amplitude estimator for compatibility with 700D + if states.amp_est_mode == 0 + mean_amp = states.mean_amp; + else + mean_amp = mean(payload_amps_de)+1E-12; + end + mean_amp_log = [mean_amp_log mean_amp]; + + % used fixed EsNo est, as EsNo estimator for QAM not working very well at this stage + EsNo = 10^(states.EsNodB/10); + + % TODO 2020 support for padding with known data bits + + [rx_bits paritychecks] = fec_decode(states, code_param, payload_syms_de,... + payload_amps_de, mean_amp, EsNo); + errors = xor(payload_bits, rx_bits); + Nerrs_coded = sum(errors); + + if Nerrs_coded Perrs_coded++; end + Terrs_coded += Nerrs_coded; + Tbits_coded += code_param.data_bits_per_frame; + Nerrs_coded_log = [Nerrs_coded_log Nerrs_coded]; + + % per-packet SNR estimate + EsNo_estdB = esno_est_calc(rx_syms); + SNR_estdB = snr_from_esno(states, EsNo_estdB); + snr_log = [snr_log SNR_estdB]; + end + + % we are in sync so log modem states + + rx_np_log = [rx_np_log arx_np]; + timing_est_log = [timing_est_log states.timing_est]; + delta_t_log = [delta_t_log states.delta_t]; + foff_est_hz_log = [foff_est_hz_log states.foff_est_hz]; + channel_est_pilot_log = [channel_est_pilot_log; achannel_est_pilot_log]; + frame_count++; + end + + states = sync_state_machine(states, rx_uw); + + if states.verbose + if strcmp(states.last_sync_state,'search') == 0 + pcc = max(paritychecks); + iter = 0; + for i=1:length(paritychecks) + if paritychecks(i) iter=i; end + end + % complete logging line + if (states.modem_frame == 0) && (strcmp(states.last_sync_state, "trial") == 0) + printf("euw: %3d %d mf: %2d pbw: %s foff: %4.1f eraw: %3d ecod: %3d iter: %3d pcc: %3d snr: %5.2f", + states.uw_errors, states.sync_counter, states.modem_frame, states.phase_est_bandwidth(1), states.foff_est_hz, + Nerrs_raw, Nerrs_coded, iter, pcc, SNR_estdB); + else + printf("euw: %3d %d mf: %2d pbw: %s foff: %4.1f", + states.uw_errors, states.sync_counter, states.modem_frame, states.phase_est_bandwidth(1), states.foff_est_hz); + end + end + printf("\n"); + end + + % reset stats if in streaming mode, don't reset if in burst mode + if strcmp(states.data_mode, "streaming") && states.sync_start + Nerrs_raw = Nerrs_coded = 0; + Nerrs_log = []; + Terrs = Tbits = 0; + Tpacketerrs = Tpackets = 0; + Terrs_coded = Tbits_coded = 0; + error_positions = Nerrs_coded_log = []; + end + f++; + end + Nframes = f; + + printf("Raw BER..: %5.4f Tbits: %5d Terrs: %5d SNR3k: %5.2f\n", Terrs/(Tbits+1E-12), Tbits, Terrs, mean(snr_log)); + printf("Coded BER: %5.4f Tbits: %5d Terrs: %5d\n", Terrs_coded/(Tbits_coded+1E-12), Tbits_coded, Terrs_coded); + printf("Coded PER: %5.4f Pckts: %5d Perrs: %5d Npre: %d Npost: %d\n", + Perrs_coded/(packet_count+1E-12), packet_count, Perrs_coded, states.npre, states.npost); + + if length(rx_np_log) + figure(1); clf; + plot(exp(j*pi/4)*rx_np_log(floor(end/4):floor(end-end/8)),'+'); + mx = 2*mean(abs(channel_est_pilot_log(:))); + axis([-mx mx -mx mx]); + title('Scatter'); + + figure(2); clf; + plot(angle(channel_est_pilot_log),'g+', 'markersize', 5); + title('Phase est'); + axis([1 length(channel_est_pilot_log) -pi pi]); + + figure(3); clf; + amp_est = abs(channel_est_pilot_log); + plot(amp_est,'g+', 'markersize', 5); + title('Amp est'); + axis([1 length(channel_est_pilot_log) min(amp_est(:)) max(amp_est(:))]); + + figure(4); clf; + subplot(211); plot(snr_log); ylabel('SNR3kdB'); + subplot(212); plot(mean_amp_log); ylabel('mean amp'); + + figure(5); clf; + subplot(211) + stem(delta_t_log) + title('delta t'); + subplot(212) + plot(timing_est_log); + title('timing est'); + + figure(6); clf; + plot(foff_est_hz_log) + mx = max(max(abs(foff_est_hz_log)),1); + axis([1 max(Nframes,2) -mx mx]); + title('Fine Freq'); + ylabel('Hz') + end + + if length(Nerrs_log) > 1 + figure(7); clf; + subplot(211) + stem(Nerrs_log); + title('Uncoded errors/modem frame') + axis([1 length(Nerrs_log) 0 Nbitsperpacket*0.2]); + if length(Nerrs_coded_log) + subplot(212) + stem(Nerrs_coded_log); + title('Coded errors/mode frame') + axis([1 length(Nerrs_coded_log) 0 Nbitsperpacket*0.2]); + end + end + + figure(9); clf; plot_specgram(rx, Fs=8000, 0, 3000); + + if pass_packet_count > 0 + if packet_count >= pass_packet_count printf("Pass!\n"); else printf("Fail!\n"); end; + end +endfunction |