root/vtcross/trunk/src/cognitive_radio_test.c @ 27

//
// Cognitive radio simulator
//

#include "cognitive_radio_test.h"

// transmitter thread
void execute_tx(
        metadata _md,
        char *_msg_in,
        unsigned int _msg_len,
        float * _I,
        float *_Q,
        unsigned int *_sym_len)
{
    // symbols buffer
    char sym[_msg_len];

    // pack bits into symbols
    repack_bytes(
        _msg_in,        // input buffer
        1,              // input symbol size (number bits)
        _msg_len,       // input buffer size
        sym,            // output buffer
        _md->mod_bps,   // output symbol size (number of bits)
        _msg_len,       // output buffer size
        _sym_len        // number of symbols written to output
        );

    // run modulator
    unsigned int i, s;
    modem * mod = modem_create(_md->mod_scheme, _md->mod_bps);
    for (i=0; i<(*_sym_len); i++) {
        s = (unsigned int)(sym[i]);
        modulate(mod, s, &_I[i], &_Q[i]);
    }
}

// channel thread
void execute_channel(metadata _md, float _std, float * _I, float *_Q, unsigned int _len)
{
    // add noise
    float noise_i, noise_q;
    unsigned int i;
    for (i=0; i<_len; i++) {
        // generate random noise values
        randnf(&noise_i, &noise_q);

        // TODO scale by appropriate amount
        _I[i] += noise_i * _std;
        _Q[i] += noise_q * _std;
    }
}

// receiver thread
void execute_rx(
        metadata _md,
        float * _I,
        float *_Q,
        unsigned int _sym_len,
        char *_msg_out,
        unsigned int *_msg_len)
{
    char msg[_sym_len];

    // create demodulator and demodulate
    modem * demod = modem_create(_md->mod_scheme, _md->mod_bps);
    unsigned int i, s;
    for (i=0; i<_sym_len; i++) {
        demodulate(demod, _I[i], _Q[i], &s);
        msg[i] = (char) s;
    }

    // unpack bytes
    repack_bytes(
        msg,            // input buffer
        _md->mod_bps,   // input symbol size (number of bits)
        _sym_len,       // num input symbols
        _msg_out,       // output buffer
        1,              // output symbol size (number of bits)
        999999,         // output buffer size
        _msg_len        // number of output symbols written
        );

}

unsigned int count_errors(char * _msg_in, char * _msg_out, unsigned int _num_bits)
{
    unsigned int i, num_errors=0;
    for (i=0; i<_num_bits; i++)
        num_errors += (_msg_in[i]==_msg_out[i]) ? 0 : 1;

    return num_errors;
}