Exemplo n.º 1
0
int main(int argc, char*argv[])
{
    srand( time(NULL) );

    // options
    float SNRdB       =  20.0f; // signal-to-noise ratio
    float noise_floor = -20.0f; // noise floor
    float dphi        =  0.01f; // carrier frequency offset
    float theta       =  0.0f;  // carrier phase offset
    float dt          =  -0.2f;  // fractional sample timing offset

    crc_scheme check         =  LIQUID_CRC_32;     // data validity check
    fec_scheme fec0          =  LIQUID_FEC_NONE;   // fec (inner)
    fec_scheme fec1          =  LIQUID_FEC_NONE;   // fec (outer)
    unsigned int payload_len =  200;               // payload length

    int debug_enabled = 0;

    // get options
    int dopt;
    while((dopt = getopt(argc,argv,"hdS:F:P:T:")) != EOF){
        switch (dopt) {
        case 'h': usage();              return 0;
        case 'd': debug_enabled = 1;    break;
        case 'S': SNRdB = atof(optarg); break;
        case 'F': dphi  = atof(optarg); break;
        case 'P': theta = atof(optarg); break;
        case 'T': dt    = atof(optarg); break;
        default:
            exit(-1);
        }
    }

    // derived values
    float nstd  = powf(10.0f, noise_floor/20.0f);         // noise std. dev.
    float gamma = powf(10.0f, (SNRdB+noise_floor)/20.0f); // channel gain

    // create frame generator
    fskframegen fg = fskframegen_create();
    fskframegen_print(fg);

    // create frame synchronizer using default properties
    fskframesync fs = fskframesync_create(callback,NULL);
    fskframesync_print(fs);
    if (debug_enabled)
        fskframesync_debug_enable(fs);

    // data payload
    unsigned int i;
    // initialize header and payload data
    for (i=0; i<8; i++)
        header[i] = i;
    for (i=0; i<200; i++)
        payload[i] = rand() & 0xff;

    // allocate memory for the frame samples
    unsigned int  buf_len = 64;
    float complex buf_tx[buf_len];  // receive buffer
    float complex buf_rx[buf_len];  // transmit buffer
    
    // assemble the frame
    fskframegen_assemble(fg, header, payload, payload_len, check, fec0, fec1);

    // spectral periodogram
    unsigned int nfft  = 4200;
    spgramcf periodogram = spgramcf_create_default(nfft);

    // write frame in blocks
    int frame_complete = 0;
    while (!frame_complete)
    {
        frame_complete = fskframegen_write_samples(fg, buf_tx, buf_len);

        // add noise, channel gain
        for (i=0; i<buf_len; i++)
            buf_rx[i] = buf_tx[i]*gamma + nstd*(randnf() + randnf()*_Complex_I)*M_SQRT1_2;

        // synchronize/receive the frame
        fskframesync_execute_block(fs, buf_rx, buf_len);
        
        // estimate power spectral density
        spgramcf_write(periodogram, buf_rx, buf_len);
    }

    // compute power spectral density of received signal
    float psd[nfft];
    spgramcf_get_psd(periodogram, psd);

    // clean up allocated objects
    spgramcf_destroy(periodogram);
    fskframegen_destroy(fg);
    fskframesync_destroy(fs);

    // 
    // export results
    //
    FILE * fid = fopen(OUTPUT_FILENAME,"w");
    fprintf(fid,"%% %s : auto-generated file\n", OUTPUT_FILENAME);
    fprintf(fid,"clear all\n");
    fprintf(fid,"close all\n");
    fprintf(fid,"nfft        = %u;\n", nfft);

    // save power spectral density
    fprintf(fid,"psd = zeros(1,nfft);\n");
    for (i=0; i<nfft; i++)
        fprintf(fid,"psd(%4u) = %12.8f;\n", i+1, psd[i]);

    // plot PSD
    fprintf(fid,"figure('Color','white');\n");
    fprintf(fid,"f = [0:(nfft-1)]/nfft - 0.5;\n");
    fprintf(fid,"plot(f,psd,'LineWidth',1.5,'Color',[0.5 0 0]);\n");
    fprintf(fid,"axis([-0.5 0.5 -30 30]);\n");
    fprintf(fid,"xlabel('Normalized Frequency [f/F_s]');\n");
    fprintf(fid,"ylabel('PSD [dB]');\n");
    fprintf(fid,"grid on;\n");

    fclose(fid);
    printf("results written to '%s'\n", OUTPUT_FILENAME);

    printf("done.\n");
    return 0;
}
Exemplo n.º 2
0
int main(int argc, char*argv[])
{
    // options
    int          ftype       = LIQUID_FIRFILT_ARKAISER;
    int          ms          = LIQUID_MODEM_QPSK;
    unsigned int k           = 2;       // samples per symbol
    unsigned int m           = 7;       // filter delay (symbols)
    float        beta        = 0.20f;   // filter excess bandwidth factor
    unsigned int num_symbols = 4000;    // number of data symbols
    unsigned int hc_len      =   4;     // channel filter length
    float        noise_floor = -60.0f;  // noise floor [dB]
    float        SNRdB       = 30.0f;   // signal-to-noise ratio [dB]
    float        bandwidth   =  0.02f;  // loop filter bandwidth
    float        tau         = -0.2f;   // fractional symbol offset
    float        rate        = 1.001f;  // sample rate offset
    float        dphi        =  0.01f;  // carrier frequency offset [radians/sample]
    float        phi         =  2.1f;   // carrier phase offset [radians]

    unsigned int nfft        =   2400;  // spectral periodogram FFT size
    unsigned int num_samples = 200000;  // number of samples

    int dopt;
    while ((dopt = getopt(argc,argv,"hk:m:b:s:w:n:t:r:")) != EOF) {
        switch (dopt) {
        case 'h':   usage();                        return 0;
        case 'k':   k           = atoi(optarg);     break;
        case 'm':   m           = atoi(optarg);     break;
        case 'b':   beta        = atof(optarg);     break;
        case 's':   SNRdB       = atof(optarg);     break;
        case 'w':   bandwidth   = atof(optarg);     break;
        case 'n':   num_symbols = atoi(optarg);     break;
        case 't':   tau         = atof(optarg);     break;
        case 'r':   rate        = atof(optarg);     break;
        default:
            exit(1);
        }
    }

    // validate input
    if (k < 2) {
        fprintf(stderr,"error: k (samples/symbol) must be greater than 1\n");
        exit(1);
    } else if (m < 1) {
        fprintf(stderr,"error: m (filter delay) must be greater than 0\n");
        exit(1);
    } else if (beta <= 0.0f || beta > 1.0f) {
        fprintf(stderr,"error: beta (excess bandwidth factor) must be in (0,1]\n");
        exit(1);
    } else if (bandwidth <= 0.0f) {
        fprintf(stderr,"error: timing PLL bandwidth must be greater than 0\n");
        exit(1);
    } else if (num_symbols == 0) {
        fprintf(stderr,"error: number of symbols must be greater than 0\n");
        exit(1);
    } else if (tau < -1.0f || tau > 1.0f) {
        fprintf(stderr,"error: timing phase offset must be in [-1,1]\n");
        exit(1);
    } else if (rate > 1.02f || rate < 0.98f) {
        fprintf(stderr,"error: timing rate offset must be in [1.02,0.98]\n");
        exit(1);
    }

    unsigned int i;

    // buffers
    unsigned int    buf_len = 400;      // buffer size
    float complex   x   [buf_len];      // original signal
    float complex   y   [buf_len*2];    // channel output (larger to accommodate resampler)
    float complex   syms[buf_len];      // recovered symbols
    // window for saving last few symbols
    windowcf sym_buf = windowcf_create(buf_len);

    // create stream generator
    symstreamcf gen = symstreamcf_create_linear(ftype,k,m,beta,ms);

    // create channel emulator and add impairments
    channel_cccf channel = channel_cccf_create();
    channel_cccf_add_awgn          (channel, noise_floor, SNRdB);
    channel_cccf_add_carrier_offset(channel, dphi, phi);
    channel_cccf_add_multipath     (channel, NULL, hc_len);
    channel_cccf_add_resamp        (channel, 0.0f, rate);

    // create symbol tracking synchronizer
    symtrack_cccf symtrack = symtrack_cccf_create(ftype,k,m,beta,ms);
    symtrack_cccf_set_bandwidth(symtrack,0.05f);

    // create spectral periodogram for estimating spectrum
    spgramcf periodogram = spgramcf_create_default(nfft);

    unsigned int total_samples = 0;
    unsigned int ny;
    unsigned int total_symbols = 0;
    while (total_samples < num_samples)
    {
        // write samples to buffer
        symstreamcf_write_samples(gen, x, buf_len);

        // apply channel
        channel_cccf_execute(channel, x, buf_len, y, &ny);

        // push resulting sample through periodogram
        spgramcf_write(periodogram, y, ny);

        // run resulting stream through synchronizer
        unsigned int num_symbols_sync;
        symtrack_cccf_execute_block(symtrack, y, ny, syms, &num_symbols_sync);
        total_symbols += num_symbols_sync;

        // write resulting symbols to window buffer for plotting
        windowcf_write(sym_buf, syms, num_symbols_sync);

        // accumulated samples
        total_samples += buf_len;
    }
    printf("total samples: %u\n", total_samples);
    printf("total symbols: %u\n", total_symbols);

    // write accumulated power spectral density estimate
    float psd[nfft];
    spgramcf_get_psd(periodogram, psd);

    //
    // export output file
    //

    FILE * fid = fopen(OUTPUT_FILENAME,"w");
    fprintf(fid,"%% %s, auto-generated file\n\n", OUTPUT_FILENAME);
    fprintf(fid,"clear all;\n");
    fprintf(fid,"close all;\n");

    // read buffer and write last symbols to file
    float complex * rc;
    windowcf_read(sym_buf, &rc);
    fprintf(fid,"syms = zeros(1,%u);\n", buf_len);
    for (i=0; i<buf_len; i++)
        fprintf(fid,"syms(%3u) = %12.8f + j*%12.8f;\n", i+1, crealf(rc[i]), cimagf(rc[i]));

    // power spectral density estimate
    fprintf(fid,"nfft = %u;\n", nfft);
    fprintf(fid,"f=[0:(nfft-1)]/nfft - 0.5;\n");
    fprintf(fid,"psd = zeros(1,nfft);\n");
    for (i=0; i<nfft; i++)
        fprintf(fid,"psd(%3u) = %12.8f;\n", i+1, psd[i]);

    fprintf(fid,"figure('Color','white','position',[500 500 1400 400]);\n");
    fprintf(fid,"subplot(1,3,1);\n");
    fprintf(fid,"plot(real(syms),imag(syms),'x','MarkerSize',4);\n");
    fprintf(fid,"  axis square;\n");
    fprintf(fid,"  grid on;\n");
    fprintf(fid,"  axis([-1 1 -1 1]*1.6);\n");
    fprintf(fid,"  xlabel('In-phase');\n");
    fprintf(fid,"  ylabel('Quadrature');\n");
    fprintf(fid,"  title('Last %u symbols');\n", buf_len);
    fprintf(fid,"subplot(1,3,2:3);\n");
    fprintf(fid,"  plot(f, psd, 'LineWidth',1.5,'Color',[0 0.5 0.2]);\n");
    fprintf(fid,"  grid on;\n");
    fprintf(fid,"  pmin = 10*floor(0.1*min(psd - 5));\n");
    fprintf(fid,"  pmax = 10*ceil (0.1*max(psd + 5));\n");
    fprintf(fid,"  axis([-0.5 0.5 pmin pmax]);\n");
    fprintf(fid,"  xlabel('Normalized Frequency [f/F_s]');\n");
    fprintf(fid,"  ylabel('Power Spectral Density [dB]');\n");

    fclose(fid);
    printf("results written to %s.\n", OUTPUT_FILENAME);

    // destroy objects
    symstreamcf_destroy  (gen);
    spgramcf_destroy     (periodogram);
    channel_cccf_destroy (channel);
    symtrack_cccf_destroy(symtrack);
    windowcf_destroy     (sym_buf);

    // clean it up
    printf("done.\n");
    return 0;
}
Exemplo n.º 3
0
int main(int argc, char*argv[])
{
    // options
    unsigned int m           =   3;     // number of bits/symbol
    unsigned int k           =   0;     // filter samples/symbol
    unsigned int num_symbols = 8000;    // number of data symbols
    float        SNRdB       = 40.0f;   // signal-to-noise ratio [dB]
    float        bandwidth   = 0.20;    // frequency spacing
    unsigned int nfft        = 1200;    // FFT size for compute spectrum

    int dopt;
    while ((dopt = getopt(argc,argv,"hm:k:b:n:s:")) != EOF) {
        switch (dopt) {
        case 'h': usage();                      return 0;
        case 'm': m           = atoi(optarg);   break;
        case 'k': k           = atoi(optarg);   break;
        case 'b': bandwidth   = atof(optarg);   break;
        case 'n': num_symbols = atoi(optarg);   break;
        case 's': SNRdB       = atof(optarg);   break;
        default:
            exit(1);
        }
    }

    unsigned int i;
    unsigned int j;

    // derived values
    if (k == 0)
        k = 2 << m; // set samples per symbol if not otherwise specified
    unsigned int M    = 1 << m;
    float        nstd = powf(10.0f, -SNRdB/20.0f);

    // validate input
    if (k < M) {
        fprintf(stderr,"errors: %s, samples/symbol must be at least modulation size (M=%u)\n", __FILE__,M);
        exit(1);
    } else if (k > 2048) {
        fprintf(stderr,"errors: %s, samples/symbol exceeds maximum (2048)\n", __FILE__);
        exit(1);
    } else if (M > 1024) {
        fprintf(stderr,"errors: %s, modulation size (M=%u) exceeds maximum (1024)\n", __FILE__, M);
        exit(1);
    } else if (bandwidth <= 0.0f || bandwidth >= 0.5f) {
        fprintf(stderr,"errors: %s, bandwidht must be in (0,0.5)\n", __FILE__);
        exit(1);
    }

    // create modulator/demodulator pair
    fskmod mod = fskmod_create(m,k,bandwidth);
    fskdem dem = fskdem_create(m,k,bandwidth);
    fskdem_print(dem);

    // 
    float complex buf_tx[k];    // transmit buffer
    float complex buf_rx[k];    // transmit buffer
    
    // spectral periodogram
    spgramcf periodogram = spgramcf_create_default(nfft);

    // modulate, demodulate, count errors
    unsigned int num_symbol_errors = 0;
    for (i=0; i<num_symbols; i++) {
        // generate random symbol
        unsigned int sym_in = rand() % M;

        // modulate
        fskmod_modulate(mod, sym_in, buf_tx);

        // add noise
        for (j=0; j<k; j++)
            buf_rx[j] = buf_tx[j] + nstd*(randnf() + _Complex_I*randnf())*M_SQRT1_2;

        // demodulate
        unsigned int sym_out = fskdem_demodulate(dem, buf_rx);

        // count errors
        num_symbol_errors += (sym_in == sym_out) ? 0 : 1;

        // estimate power spectral density
        spgramcf_write(periodogram, buf_rx, k);
    }

    printf("symbol errors: %u / %u\n", num_symbol_errors, num_symbols);

    // compute power spectral density of received signal
    float psd[nfft];
    spgramcf_get_psd(periodogram, psd);
    spgramcf_destroy(periodogram);

    // 
    // export results
    //
    
    FILE * fid = fopen(OUTPUT_FILENAME,"w");
    fprintf(fid,"%% %s : auto-generated file\n", OUTPUT_FILENAME);
    fprintf(fid,"clear all\n");
    fprintf(fid,"close all\n");
    fprintf(fid,"k = %u;\n", k);
    fprintf(fid,"M = %u;\n", M);
    fprintf(fid,"num_symbols = %u;\n", num_symbols);
    fprintf(fid,"nfft        = %u;\n", nfft);

    // save power spectral density
    fprintf(fid,"psd = zeros(1,nfft);\n");
    for (i=0; i<nfft; i++)
        fprintf(fid,"psd(%4u) = %12.8f;\n", i+1, psd[i]);

    // plot PSD
    fprintf(fid,"figure('Color','white');\n");
    fprintf(fid,"f = [0:(nfft-1)]/nfft - 0.5;\n");
    fprintf(fid,"plot(f,psd,'LineWidth',1.5,'Color',[0.5 0 0]);\n");
    fprintf(fid,"axis([-0.5 0.5 -40 20]);\n");
    fprintf(fid,"xlabel('Normalized Frequency [f/F_s]');\n");
    fprintf(fid,"ylabel('PSD [dB]');\n");
    fprintf(fid,"grid on;\n");

    fclose(fid);
    printf("results written to '%s'\n", OUTPUT_FILENAME);

    return 0;
}