// create least mean-squares (LMS) equalizer object
// _h : initial coefficients [size: _p x 1], default if NULL
// _p : equalizer length (number of taps)
EQLMS() EQLMS(_create)(T * _h,
unsigned int _p)
{
EQLMS() eq = (EQLMS()) malloc(sizeof(struct EQLMS(_s)));
// set filter order, other params
eq->p = _p;
eq->mu = 0.5f;
eq->h0 = (T*) malloc((eq->p)*sizeof(T));
eq->w0 = (T*) malloc((eq->p)*sizeof(T));
eq->w1 = (T*) malloc((eq->p)*sizeof(T));
eq->buffer = WINDOW(_create)(eq->p);
eq->x2 = wdelayf_create(eq->p);
// copy coefficients (if not NULL)
if (_h == NULL) {
// initial coefficients with delta at first index
unsigned int i;
for (i=0; i<eq->p; i++)
eq->h0[i] = (i==0) ? 1.0 : 0.0;
} else {
// copy user-defined initial coefficients
memmove(eq->h0, _h, (eq->p)*sizeof(T));
}
// reset equalizer object
EQLMS(_reset)(eq);
return eq;
}
// create least mean-squares (LMS) equalizer object
// _h : initial coefficients [size: _h_len x 1], default if NULL
// _p : equalizer length (number of taps)
EQLMS() EQLMS(_create)(T * _h,
unsigned int _h_len)
{
EQLMS() q = (EQLMS()) malloc(sizeof(struct EQLMS(_s)));
// set filter order, other params
q->h_len = _h_len;
q->mu = 0.5f;
q->h0 = (T*) malloc((q->h_len)*sizeof(T));
q->w0 = (T*) malloc((q->h_len)*sizeof(T));
q->w1 = (T*) malloc((q->h_len)*sizeof(T));
q->buffer = WINDOW(_create)(q->h_len);
q->x2 = wdelayf_create(q->h_len);
// copy coefficients (if not NULL)
if (_h == NULL) {
// initial coefficients with delta at first index
unsigned int i;
for (i=0; i<q->h_len; i++)
q->h0[i] = (i==0) ? 1.0 : 0.0;
} else {
// copy user-defined initial coefficients
memmove(q->h0, _h, (q->h_len)*sizeof(T));
}
// reset equalizer object
EQLMS(_reset)(q);
// return main object
return q;
}
// create LMS EQ initialized with low-pass filter
// _h_len : filter length
// _fc : filter cut-off, _fc in (0,0.5]
EQLMS() EQLMS(_create_lowpass)(unsigned int _h_len,
float _fc)
{
// validate input
if (_h_len == 0) {
fprintf(stderr,"error: eqlms_%s_create_lowpass(), filter length must be greater than 0\n", EXTENSION_FULL);
exit(1);
} else if (_fc <= 0.0f || _fc > 0.5f) {
fprintf(stderr,"error: eqlms_%s_create_rnyquist(), filter cutoff must be in (0,0.5]\n", EXTENSION_FULL);
exit(1);
}
// generate low-pass filter prototype
float h[_h_len];
liquid_firdes_kaiser(_h_len, _fc, 40.0f, 0.0f, h);
// copy coefficients to type-specific array (e.g. float complex)
unsigned int i;
T hc[_h_len];
for (i=0; i<_h_len; i++)
hc[i] = h[i];
// return equalizer object
return EQLMS(_create)(hc, _h_len);
}
// create symtrack object with basic parameters
// _ftype : filter type (e.g. LIQUID_FIRFILT_RRC)
// _k : samples per symbol
// _m : filter delay (symbols)
// _beta : filter excess bandwidth
// _ms : modulation scheme (e.g. LIQUID_MODEM_QPSK)
SYMTRACK() SYMTRACK(_create)(int _ftype,
unsigned int _k,
unsigned int _m,
float _beta,
int _ms)
{
// validate input
if (_k < 2) {
fprintf(stderr,"error: symtrack_%s_create(), filter samples/symbol must be at least 2\n", EXTENSION_FULL);
exit(1);
} else if (_m == 0) {
fprintf(stderr,"error: symtrack_%s_create(), filter delay must be greater than zero\n", EXTENSION_FULL);
exit(1);
} else if (_beta <= 0.0f || _beta > 1.0f) {
fprintf(stderr,"error: symtrack_%s_create(), filter excess bandwidth must be in (0,1]\n", EXTENSION_FULL);
exit(1);
} else if (_ms == LIQUID_MODEM_UNKNOWN || _ms >= LIQUID_MODEM_NUM_SCHEMES) {
fprintf(stderr,"error: symtrack_%s_create(), invalid modulation scheme\n", EXTENSION_FULL);
exit(1);
}
// allocate memory for main object
SYMTRACK() q = (SYMTRACK()) malloc( sizeof(struct SYMTRACK(_s)) );
// set input parameters
q->filter_type = _ftype;
q->k = _k;
q->m = _m;
q->beta = _beta;
q->mod_scheme = _ms == LIQUID_MODEM_UNKNOWN ? LIQUID_MODEM_BPSK : _ms;
// create automatic gain control
q->agc = AGC(_create)();
// create symbol synchronizer (output rate: 2 samples per symbol)
if (q->filter_type == LIQUID_FIRFILT_UNKNOWN)
q->symsync = SYMSYNC(_create_kaiser)(q->k, q->m, 0.9f, 16);
else
q->symsync = SYMSYNC(_create_rnyquist)(q->filter_type, q->k, q->m, q->beta, 16);
SYMSYNC(_set_output_rate)(q->symsync, 2);
// create equalizer as default low-pass filter with integer symbol delay (2 samples/symbol)
q->eq_len = 2 * 4 + 1;
q->eq = EQLMS(_create_lowpass)(q->eq_len,0.45f);
// nco and phase-locked loop
q->nco = NCO(_create)(LIQUID_VCO);
// demodulator
q->demod = MODEM(_create)(q->mod_scheme);
// set default bandwidth
SYMTRACK(_set_bandwidth)(q, 0.9f);
// reset and return main object
SYMTRACK(_reset)(q);
return q;
}
// create square-root Nyquist interpolator
// _type : filter type (e.g. LIQUID_RNYQUIST_RRC)
// _k : samples/symbol _k > 1
// _m : filter delay (symbols), _m > 0
// _beta : excess bandwidth factor, 0 < _beta < 1
// _dt : fractional sample delay, 0 <= _dt < 1
EQLMS() EQLMS(_create_rnyquist)(int _type,
unsigned int _k,
unsigned int _m,
float _beta,
float _dt)
{
// validate input
if (_k < 2) {
fprintf(stderr,"error: eqlms_%s_create_rnyquist(), samples/symbol must be greater than 1\n", EXTENSION_FULL);
exit(1);
} else if (_m == 0) {
fprintf(stderr,"error: eqlms_%s_create_rnyquist(), filter delay must be greater than 0\n", EXTENSION_FULL);
exit(1);
} else if (_beta < 0.0f || _beta > 1.0f) {
fprintf(stderr,"error: eqlms_%s_create_rnyquist(), filter excess bandwidth factor must be in [0,1]\n", EXTENSION_FULL);
exit(1);
} else if (_dt < -1.0f || _dt > 1.0f) {
fprintf(stderr,"error: eqlms_%s_create_rnyquist(), filter fractional sample delay must be in [-1,1]\n", EXTENSION_FULL);
exit(1);
}
// generate square-root Nyquist filter
unsigned int h_len = 2*_k*_m + 1;
float h[h_len];
liquid_firdes_rnyquist(_type,_k,_m,_beta,_dt,h);
// copy coefficients to type-specific array (e.g. float complex)
// and scale by samples/symbol
unsigned int i;
T hc[h_len];
for (i=0; i<h_len; i++)
hc[i] = h[i] / (float)_k;
// return equalizer object
return EQLMS(_create)(hc, h_len);
}
struct EQLMS(_s) {
unsigned int p; // filter order
float mu; // LMS step size
// internal matrices
T * h0; // initial coefficients
T * w0, * w1; // weights [px1]
unsigned int n; // input counter
WINDOW() buffer; // input buffer
wdelayf x2; // buffer of |x|^2 values
float x2_sum; // sum{ |x|^2 }
};
// update sum{|x|^2}
void EQLMS(_update_sumsq)(EQLMS() _eq, T _x);
// create least mean-squares (LMS) equalizer object
// _h : initial coefficients [size: _p x 1], default if NULL
// _p : equalizer length (number of taps)
EQLMS() EQLMS(_create)(T * _h,
unsigned int _p)
{
EQLMS() eq = (EQLMS()) malloc(sizeof(struct EQLMS(_s)));
// set filter order, other params
eq->p = _p;
eq->mu = 0.5f;
eq->h0 = (T*) malloc((eq->p)*sizeof(T));
eq->w0 = (T*) malloc((eq->p)*sizeof(T));
