102 lines
3.2 KiB
Matlab
102 lines
3.2 KiB
Matlab
% fsk_lib_demo.m
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% Uncoded FSK modem demo
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fsk_lib;
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% set up waveform
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function [states M bits_per_frame] = modem_init(Rs,Fs,df)
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M = 4;
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states = fsk_init(Fs,Rs,M,P=8,nsym=100);
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bits_per_frame = 512;
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states.tx_real = 0; % complex signal
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states.tx_tone_separation = 250;
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states.ftx = -2.5*states.tx_tone_separation + states.tx_tone_separation*(1:M);
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states.fest_fmin = -Fs/2;
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states.fest_fmax = +Fs/2;
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states.fest_min_spacing = Rs/2;
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states.df = df;
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states.ber_valid_thresh = 0.1;
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states.ber_invalid_thresh = 0.2;
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end
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% Run a complete modem (freq and timing estimators running) at a
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% single Eb/No point. At low Eb/No the estimators occasionally fall
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% over so we get complete junk, we consider that case a packet error
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% and exclude it from the BER estimation.
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function [states ber per] = modem_run_test(EbNodB = 10, num_frames=10, Fs=8000, Rs=100, df=0, plots=0)
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randn('state',1); rand('state',1);
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[states M bits_per_frame] = modem_init(Rs, Fs, df);
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N = states.N;
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if plots; states.verbose = 0x4; end
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EbNo = 10^(EbNodB/10);
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variance = states.Fs/(states.Rs*EbNo*states.bitspersymbol);
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nbits = bits_per_frame*num_frames;
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test_frame = round(rand(1,bits_per_frame)); tx_bits = [];
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for f=1:num_frames
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tx_bits = [tx_bits test_frame];
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end
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tx = fsk_mod(states, tx_bits);
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noise = sqrt(variance/2)*randn(length(tx),1) + j*sqrt(variance/2)*randn(length(tx),1);
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rx = tx + noise;
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run_frames = floor(length(rx)/N)-1;
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st = 1; f_log = []; f_log2 = []; rx_bits = []; rx_bits2 = [];
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for f=1:run_frames
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% extract nin samples from input stream
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nin = states.nin;
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en = st + states.nin - 1;
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% due to nin variations it's possible to overrun buffer
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if en < length(rx)
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sf = rx(st:en);
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states = est_freq(states, sf, states.M); states.f = states.f2;
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[arx_bits states] = fsk_demod(states, sf);
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rx_bits = [rx_bits arx_bits];
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f_log = [f_log; states.f];
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st += nin;
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end
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end
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num_frames=floor(length(rx_bits)/bits_per_frame);
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log_nerrs = []; num_frames_rx = 0;
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for f=1:num_frames-1
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st = (f-1)*bits_per_frame + 1; en = (f+1)*bits_per_frame;
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states = ber_counter(states, test_frame, rx_bits(st:en));
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log_nerrs = [log_nerrs states.nerr];
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if states.ber_state; num_frames_rx++; end
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end
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if states.Terrs
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printf("Fs: %d Rs: %d df % 3.2f EbNo: %4.2f ftx: %3d frx: %3d nbits: %4d nerrs: %3d ber: %4.3f\n",
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Fs, Rs, df, EbNodB, num_frames, num_frames_rx, states.Tbits, states.Terrs, states.Terrs/states.Tbits);
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ber = states.Terrs/states.Tbits;
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else
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ber = 0.5;
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end
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if plots
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figure(1); clf;
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ideal=ones(length(f_log),1)*states.ftx;
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plot((1:length(f_log)),ideal(:,1),'bk;ideal;')
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hold on; plot((1:length(f_log)),ideal(:,2:states.M),'bk'); hold off;
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hold on;
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plot(f_log(:,1), 'linewidth', 2, 'b;peak;');
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plot(f_log(:,2:states.M), 'linewidth', 2, 'b');
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hold off;
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xlabel('Time (frames)'); ylabel('Frequency (Hz)');
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figure(2); clf; plot(log_nerrs); title('Errors per frame');
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end
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per = 1 - num_frames_rx/num_frames;
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end
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[states ber per] = modem_run_test(EbNodB=6);
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BER_theory=0.01579; % for Eb/No = 6dB
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if ber < 1.5*BER_theory
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printf("PASS\n");
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end
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