void LiquidOfdmModComponent::initialize()
{
// print capabilities of liquid
if (debug_x) {
liquid_print_modulation_schemes();
liquid_print_fec_schemes();
liquid_print_crc_schemes();
}
// initialize subcarrier allocation
unsigned char p[noSubcarriers_x];
ofdmframe_init_default_sctype(noSubcarriers_x, p);
// create frame generator properties object and initialize to default
ofdmflexframegenprops_s fgProps;
ofdmflexframegenprops_init_default(&fgProps);
modulation_scheme ms = liquid_getopt_str2mod(modulationScheme_x.c_str());
fec_scheme fec0 = liquid_getopt_str2fec(fecZero_x.c_str());
fec_scheme fec1 = liquid_getopt_str2fec(fecOne_x.c_str());
crc_scheme check = liquid_getopt_str2crc(crcScheme_x.c_str());
fgProps.mod_scheme = ms;
fgProps.fec0 = fec0;
fgProps.fec1 = fec1;
fgProps.check = check;
gain_factor_ = powf(10.0f, gain_x/20.0f);
// create frame generator object
try {
frameGenerator_ = ofdmflexframegen_create(noSubcarriers_x, cyclicPrefixLength_x, taperLength_x, p, &fgProps);
ofdmflexframegen_print(frameGenerator_);
}
catch(...)
{
LOG(LERROR) << "Unexpected exception caught during frame generator generation";
}
}
void LiquidOfdmModComponent::process()
{
DataSet< uint8_t >* in = NULL;
getInputDataSet("input1", in);
unsigned int payloadSize = (unsigned int)in->data.size();
unsigned char* payload = &in->data[0];
unsigned char header[8];
for (int i = 0; i < 8; i++)
header[i] = frameHeader_x.c_str()[i] & 0xff;
ofdmflexframegen_assemble(frameGenerator_, header, payload, payloadSize);
unsigned int symbols = ofdmflexframegen_getframelen(frameGenerator_);
unsigned int symbolSize = noSubcarriers_x + cyclicPrefixLength_x;
unsigned int frameSize = symbols * symbolSize;
if (debug_x)
ofdmflexframegen_print(frameGenerator_);
//Allocate memory for single symbol and whole frame
DataSet< complex<float> >* out = NULL;
getOutputDataSet("output1", out, frameSize);
std::complex<float> buffer[symbolSize];
// generate frame, one OFDM symbol at a time
unsigned int bytesWritten = 0;
while (symbols--) {
ofdmflexframegen_writesymbol(frameGenerator_, buffer);
std::transform(buffer, buffer + symbolSize, out->data.begin() + bytesWritten, _1 * gain_factor_);
bytesWritten += symbolSize;
}
out->timeStamp = in->timeStamp; // copy meta data of the frame
releaseInputDataSet("input1", in);
releaseOutputDataSet("output1", out);
}
int main(int argc, char*argv[])
{
//srand(time(NULL));
// options
unsigned int M = 64; // number of subcarriers
unsigned int cp_len = 16; // cyclic prefix length
unsigned int taper_len = 4; // taper length
unsigned int payload_len = 120; // length of payload (bytes)
modulation_scheme ms = LIQUID_MODEM_QPSK; // modulation scheme
fec_scheme fec0 = LIQUID_FEC_NONE; // inner code
fec_scheme fec1 = LIQUID_FEC_HAMMING128; // outer code
crc_scheme check = LIQUID_CRC_32; // validity check
float noise_floor = -80.0f; // noise floor [dB]
float SNRdB = 20.0f; // signal-to-noise ratio [dB]
float dphi = 0.02f; // carrier frequency offset
int debug = 0; // enable debugging?
// get options
int dopt;
while((dopt = getopt(argc,argv,"uhds:F:M:C:n:m:v:c:k:")) != EOF){
switch (dopt) {
case 'u':
case 'h': usage(); return 0;
case 'd': debug = 1; break;
case 's': SNRdB = atof(optarg); break;
case 'F': dphi = atof(optarg); break;
case 'M': M = atoi(optarg); break;
case 'C': cp_len = atoi(optarg); break;
case 'n': payload_len = atol(optarg); break;
case 'm': ms = liquid_getopt_str2mod(optarg); break;
case 'v': check = liquid_getopt_str2crc(optarg); break;
case 'c': fec0 = liquid_getopt_str2fec(optarg); break;
case 'k': fec1 = liquid_getopt_str2fec(optarg); break;
default:
exit(-1);
}
}
unsigned int i;
// TODO : validate options
// derived values
unsigned int buf_len = 256;
float complex buf[buf_len]; // time-domain buffer
// allocate memory for header, payload
unsigned char header[8];
unsigned char payload[payload_len];
// create frame generator
ofdmflexframegenprops_s fgprops;
ofdmflexframegenprops_init_default(&fgprops);
fgprops.check = check;
fgprops.fec0 = fec0;
fgprops.fec1 = fec1;
fgprops.mod_scheme = ms;
ofdmflexframegen fg = ofdmflexframegen_create(M, cp_len, taper_len, NULL, &fgprops);
// create frame synchronizer
ofdmflexframesync fs = ofdmflexframesync_create(M, cp_len, taper_len, NULL, callback, (void*)payload);
if (debug)
ofdmflexframesync_debug_enable(fs);
// initialize header/payload and assemble frame
for (i=0; i<8; i++)
header[i] = i & 0xff;
for (i=0; i<payload_len; i++)
payload[i] = rand() & 0xff;
ofdmflexframegen_assemble(fg, header, payload, payload_len);
ofdmflexframegen_print(fg);
ofdmflexframesync_print(fs);
// create channel and add impairments
channel_cccf channel = channel_cccf_create();
channel_cccf_add_awgn(channel, noise_floor, SNRdB);
channel_cccf_add_carrier_offset(channel, dphi, 0.0f);
// generate frame, push through channel
int last_symbol=0;
while (!last_symbol) {
// generate symbol
last_symbol = ofdmflexframegen_write(fg, buf, buf_len);
// apply channel to buffer (in place)
channel_cccf_execute_block(channel, buf, buf_len, buf);
// push samples through synchronizer
ofdmflexframesync_execute(fs, buf, buf_len);
}
// export debugging file
if (debug)
ofdmflexframesync_debug_print(fs, "ofdmflexframesync_debug.m");
// destroy objects
ofdmflexframegen_destroy(fg);
ofdmflexframesync_destroy(fs);
channel_cccf_destroy(channel);
printf("done.\n");
return 0;
}
int main(int argc, char*argv[])
{
srand(time(NULL));
// options
unsigned int M = 64; // number of subcarriers
unsigned int cp_len = 16; // cyclic prefix length
unsigned int taper_len = 4; // taper length
unsigned int payload_len = 120; // length of payload (bytes)
modulation_scheme ms = LIQUID_MODEM_QPSK;
fec_scheme fec0 = LIQUID_FEC_NONE;
fec_scheme fec1 = LIQUID_FEC_HAMMING128;
crc_scheme check = LIQUID_CRC_32;
float noise_floor = -30.0f; // noise floor [dB]
float SNRdB = 20.0f; // signal-to-noise ratio [dB]
float dphi = 0.02f; // carrier frequency offset
int debug_enabled = 0; // enable debugging?
// get options
int dopt;
while((dopt = getopt(argc,argv,"uhds:F:M:C:n:m:v:c:k:")) != EOF){
switch (dopt) {
case 'u':
case 'h': usage(); return 0;
case 'd': debug_enabled = 1; break;
case 's': SNRdB = atof(optarg); break;
case 'F': dphi = atof(optarg); break;
case 'M': M = atoi(optarg); break;
case 'C': cp_len = atoi(optarg); break;
case 'n': payload_len = atol(optarg); break;
case 'm':
ms = liquid_getopt_str2mod(optarg);
if (ms == LIQUID_MODEM_UNKNOWN) {
fprintf(stderr,"error: %s, unknown/unsupported mod. scheme: %s\n", argv[0], optarg);
exit(-1);
}
break;
case 'v':
// data integrity check
check = liquid_getopt_str2crc(optarg);
if (check == LIQUID_CRC_UNKNOWN) {
fprintf(stderr,"error: unknown/unsupported CRC scheme \"%s\"\n\n",optarg);
exit(1);
}
break;
case 'c':
// inner FEC scheme
fec0 = liquid_getopt_str2fec(optarg);
if (fec0 == LIQUID_FEC_UNKNOWN) {
fprintf(stderr,"error: unknown/unsupported inner FEC scheme \"%s\"\n\n",optarg);
exit(1);
}
break;
case 'k':
// outer FEC scheme
fec1 = liquid_getopt_str2fec(optarg);
if (fec1 == LIQUID_FEC_UNKNOWN) {
fprintf(stderr,"error: unknown/unsupported outer FEC scheme \"%s\"\n\n",optarg);
exit(1);
}
break;
default:
exit(-1);
}
}
unsigned int i;
// TODO : validate options
// derived values
unsigned int frame_len = M + cp_len;
float complex buffer[frame_len]; // time-domain buffer
float nstd = powf(10.0f, noise_floor/20.0f);
float gamma = powf(10.0f, (SNRdB + noise_floor)/20.0f);
// allocate memory for header, payload
unsigned char header[8];
unsigned char payload[payload_len];
// initialize subcarrier allocation
unsigned char p[M];
ofdmframe_init_default_sctype(M, p);
// create frame generator
ofdmflexframegenprops_s fgprops;
ofdmflexframegenprops_init_default(&fgprops);
fgprops.check = check;
fgprops.fec0 = fec0;
fgprops.fec1 = fec1;
fgprops.mod_scheme = ms;
ofdmflexframegen fg = ofdmflexframegen_create(M, cp_len, taper_len, p, &fgprops);
// create frame synchronizer
ofdmflexframesync fs = ofdmflexframesync_create(M, cp_len, taper_len, p, callback, (void*)payload);
if (debug_enabled)
ofdmflexframesync_debug_enable(fs);
// initialize header/payload and assemble frame
for (i=0; i<8; i++)
header[i] = i & 0xff;
for (i=0; i<payload_len; i++)
payload[i] = rand() & 0xff;
ofdmflexframegen_assemble(fg, header, payload, payload_len);
ofdmflexframegen_print(fg);
ofdmflexframesync_print(fs);
// initialize frame synchronizer with noise
for (i=0; i<1000; i++) {
float complex noise = nstd*( randnf() + _Complex_I*randnf())*M_SQRT1_2;
ofdmflexframesync_execute(fs, &noise, 1);
}
// generate frame, push through channel
int last_symbol=0;
nco_crcf nco = nco_crcf_create(LIQUID_VCO);
nco_crcf_set_frequency(nco, dphi);
while (!last_symbol) {
// generate symbol
last_symbol = ofdmflexframegen_writesymbol(fg, buffer);
// apply channel
for (i=0; i<frame_len; i++) {
float complex noise = nstd*( randnf() + _Complex_I*randnf())*M_SQRT1_2;
buffer[i] *= gamma;
buffer[i] += noise;
nco_crcf_mix_up(nco, buffer[i], &buffer[i]);
nco_crcf_step(nco);
}
// receive symbol
ofdmflexframesync_execute(fs, buffer, frame_len);
}
nco_crcf_destroy(nco);
// export debugging file
if (debug_enabled)
ofdmflexframesync_debug_print(fs, "ofdmflexframesync_debug.m");
// destroy objects
ofdmflexframegen_destroy(fg);
ofdmflexframesync_destroy(fs);
printf("done.\n");
return 0;
}
