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authorpiotr <Piotr Krysik pkrysik@elka.pw.edu.pl>2014-02-05 22:44:30 +0100
committerpiotr <Piotr Krysik pkrysik@elka.pw.edu.pl>2014-02-05 22:44:30 +0100
commit7e3b0dbfc8e415190b13b6c3efbc314a43a0f3bc (patch)
treeff456d9692c192a6ed213731d3c23331d56603e3 /lib
parent5f1e1d38f828cd761bcacbf3e812c87af03f910a (diff)
Changed differentiation between dummy and normal bursts to a metod based on correlation of training sequences
Diffstat (limited to 'lib')
-rw-r--r--lib/receiver_impl.cc69
-rw-r--r--lib/receiver_impl.h2
2 files changed, 32 insertions, 39 deletions
diff --git a/lib/receiver_impl.cc b/lib/receiver_impl.cc
index bd3d3e4..f11290c 100644
--- a/lib/receiver_impl.cc
+++ b/lib/receiver_impl.cc
@@ -121,11 +121,11 @@ receiver_impl::general_work(int noutput_items,
{
//bootstrapping
case first_fcch_search:
- COUT("FCCH search");
+ DCOUT("FCCH search");
if (find_fcch_burst(input, ninput_items[0])) //find frequency correction burst in the input buffer
{
//set_frequency(d_freq_offset); //if fcch search is successful set frequency offset
- COUT("Freq offset " << d_freq_offset);
+ DCOUT("Freq offset " << d_freq_offset);
//produced_out = 0;
d_state = next_fcch_search;
}
@@ -138,14 +138,14 @@ receiver_impl::general_work(int noutput_items,
case next_fcch_search: //this state is used because it takes some time (a bunch of buffered samples)
{
- COUT("NEXT FCCH search");
+ DCOUT("NEXT FCCH search");
float prev_freq_offset = d_freq_offset; //before previous set_frequqency cause change
if (find_fcch_burst(input, ninput_items[0]))
{
if (abs(prev_freq_offset - d_freq_offset) > FCCH_MAX_FREQ_OFFSET)
{
//set_frequency(d_freq_offset); //call set_frequncy only frequency offset change is greater than some value
- COUT("Freq offset " << d_freq_offset);
+ DCOUT("Freq offset " << d_freq_offset);
}
//produced_out = 0;
d_state = sch_search;
@@ -173,8 +173,8 @@ receiver_impl::general_work(int noutput_items,
detect_burst(input, &channel_imp_resp[0], burst_start, output_binary); //detect bits using MLSE detection
if (decode_sch(&output_binary[3], &t1, &t2, &t3, &d_ncc, &d_bcc) == 0) //decode SCH burst
{
- COUT("sch burst_start: " << burst_start);
- COUT("bcc: " << d_bcc << " ncc: " << d_ncc << " t1: " << t1 << " t2: " << t2 << " t3: " << t3);
+ //COUT("sch burst_start: " << burst_start);
+ //COUT("bcc: " << d_bcc << " ncc: " << d_ncc << " t1: " << t1 << " t2: " << t2 << " t3: " << t3);
d_burst_nr.set(t1, t2, t3, 0); //set counter of bursts value
//configure the receiver - tell him where to find which burst type
@@ -220,7 +220,7 @@ receiver_impl::general_work(int noutput_items,
double freq_offset = compute_freq_offset(input, first_sample, last_sample); //extract frequency offset from it
d_freq_offset_vals.push_front(freq_offset);
- process_normal_burst(d_burst_nr, fc_fb);
+ //process_normal_burst(d_burst_nr, fc_fb);
if (d_freq_offset_vals.size() >= 10)
{
double sum = std::accumulate(d_freq_offset_vals.begin(), d_freq_offset_vals.end(), 0);
@@ -230,8 +230,8 @@ receiver_impl::general_work(int noutput_items,
{
d_freq_offset -= mean_offset; //and adjust frequency if it have changed beyond
//set_frequency(d_freq_offset); //some limit
- COUT("mean_offset: " << mean_offset);
- COUT("Adjusting frequency, new frequency offset: " << d_freq_offset << "\n");
+ DCOUT("mean_offset: " << mean_offset);
+ DCOUT("Adjusting frequency, new frequency offset: " << d_freq_offset << "\n");
}
}
}
@@ -241,7 +241,7 @@ receiver_impl::general_work(int noutput_items,
int t1, t2, t3, d_ncc, d_bcc;
burst_start = get_sch_chan_imp_resp(input, &channel_imp_resp[0]); //get channel impulse response
detect_burst(input, &channel_imp_resp[0], burst_start, output_binary); //MLSE detection of bits
- process_normal_burst(d_burst_nr, output_binary);
+ //process_normal_burst(d_burst_nr, output_binary);
if (decode_sch(&output_binary[3], &t1, &t2, &t3, &d_ncc, &d_bcc) == 0) //and decode SCH data
{
// d_burst_nr.set(t1, t2, t3, 0); //but only to check if burst_start value is correct
@@ -266,26 +266,25 @@ receiver_impl::general_work(int noutput_items,
}
break;
- case normal_burst: //if it's normal burst
- burst_start = get_norm_chan_imp_resp(input, &channel_imp_resp[0], d_bcc); //get channel impulse response for given training sequence number - d_bcc
+ case normal_burst:
+ {
+ float normal_corr_max; //if it's normal burst
+ burst_start = get_norm_chan_imp_resp(input, &channel_imp_resp[0], &normal_corr_max, d_bcc); //get channel impulse response for given training sequence number - d_bcc
detect_burst(input, &channel_imp_resp[0], burst_start, output_binary); //MLSE detection of bits
process_normal_burst(d_burst_nr, output_binary); //TODO: this shouldn't be here - remove it when gsm receiver's interface will be ready
break;
-
+ }
case dummy_or_normal:
{
- burst_start = get_norm_chan_imp_resp(input, &channel_imp_resp[0], TS_DUMMY);
- detect_burst(input, &channel_imp_resp[0], burst_start, output_binary);
-
- std::vector<unsigned char> v(20);
- std::vector<unsigned char>::iterator it;
- it = std::set_difference(output_binary + TRAIN_POS, output_binary + TRAIN_POS + 16, &train_seq[TS_DUMMY][5], &train_seq[TS_DUMMY][21], v.begin());
- int different_bits = (it - v.begin());
-
- if (different_bits > 2)
+ unsigned int normal_burst_start;
+ float dummy_corr_max, normal_corr_max;
+ get_norm_chan_imp_resp(input, &channel_imp_resp[0], &dummy_corr_max, TS_DUMMY);
+ normal_burst_start = get_norm_chan_imp_resp(input, &channel_imp_resp[0], &normal_corr_max, d_bcc);
+
+ //COUT("normal_corr_max: " << normal_corr_max << " dummy_corr_max:" << dummy_corr_max);
+ if (normal_corr_max > dummy_corr_max)
{
- burst_start = get_norm_chan_imp_resp(input, &channel_imp_resp[0], d_bcc);
- detect_burst(input, &channel_imp_resp[0], burst_start, output_binary);
+ detect_burst(input, &channel_imp_resp[0], normal_burst_start, output_binary);
//if (!output_binary[0] && !output_binary[1] && !output_binary[2]) {
// COUT("Normal burst");
process_normal_burst(d_burst_nr, output_binary); //TODO: this shouldn't be here - remove it when gsm receiver's interface will be ready
@@ -293,19 +292,13 @@ receiver_impl::general_work(int noutput_items,
}
else
{
- process_normal_burst(d_burst_nr, dummy_burst);
+ //process_normal_burst(d_burst_nr, dummy_burst);
}
}
case rach_burst:
- //implementation of this channel isn't possible in current gsm_receiver
- //it would take some realtime processing, counter of samples from USRP to
- //stay synchronized with this device and possibility to switch frequency from uplink
- //to C0 (where sch is) back and forth
-
break;
- case dummy: //if it's dummy
- burst_start = get_norm_chan_imp_resp(input, &channel_imp_resp[0], TS_DUMMY); //read dummy
- detect_burst(input, &channel_imp_resp[0], burst_start, output_binary); // but as far as I know it's pointless
+ case dummy:
+ //process_normal_burst(d_burst_nr, dummy_burst);
break;
case empty: //if it's empty burst
break; //do nothing
@@ -316,8 +309,6 @@ receiver_impl::general_work(int noutput_items,
to_consume += TS_BITS * d_OSR + d_burst_nr.get_offset(); //consume samples of the burst up to next guard period
//and add offset which is introduced by
//0.25 fractional part of a guard period
- //burst_number computes this offset
- //but choice of this class to do this was random
consume_each(to_consume);
}
break;
@@ -721,7 +712,7 @@ inline void receiver_impl::mafi(const gr_complex * input, int nitems, gr_complex
//TODO: get_norm_chan_imp_resp is similar to get_sch_chan_imp_resp - consider joining this two functions
//TODO: this is place where most errors are introduced and can be corrected by improvements to this fuction
//especially computations of strongest_window_nr
-int receiver_impl::get_norm_chan_imp_resp(const gr_complex *input, gr_complex * chan_imp_resp, int bcc)
+int receiver_impl::get_norm_chan_imp_resp(const gr_complex *input, gr_complex * chan_imp_resp, float *corr_max, int bcc)
{
vector_complex correlation_buffer;
vector_float power_buffer;
@@ -756,7 +747,6 @@ int receiver_impl::get_norm_chan_imp_resp(const gr_complex *input, gr_complex *
for (int ii = 0; ii < (d_chan_imp_length - 2)*d_OSR; ii++, iter_ii++)
{
- // for (int ii = 0; ii < (d_chan_imp_length)*d_OSR; ii++, iter_ii++) {
if (iter_ii == power_buffer.end())
{
loop_end = true;
@@ -788,7 +778,9 @@ int receiver_impl::get_norm_chan_imp_resp(const gr_complex *input, gr_complex *
// d_channel_imp_resp.push_back(correlation);
chan_imp_resp[ii] = correlation;
}
- // We want to use the first sample of the impulseresponse, and the
+
+ *corr_max = max_correlation;
+ // We want to use the first sample of the impulse response, and the
// corresponding samples of the received signal.
// the variable sync_w should contain the beginning of the used part of
// training sequence, which is 3+57+1+6=67 bits into the burst. That is
@@ -842,6 +834,7 @@ void receiver_impl::configure_receiver()
// d_channel_conf.set_burst_types(TIMESLOT6, TRAFFIC_CHANNEL_F, sizeof(TRAFFIC_CHANNEL_F) / sizeof(unsigned), dummy_or_normal);
// d_channel_conf.set_multiframe_type(TIMESLOT7, multiframe_26);
// d_channel_conf.set_burst_types(TIMESLOT7, TRAFFIC_CHANNEL_F, sizeof(TRAFFIC_CHANNEL_F) / sizeof(unsigned), dummy_or_normal);
+
d_channel_conf.set_multiframe_type(TIMESLOT1, multiframe_51);
d_channel_conf.set_burst_types(TIMESLOT1, TEST51, sizeof(TEST51) / sizeof(unsigned), dummy_or_normal);
d_channel_conf.set_multiframe_type(TIMESLOT2, multiframe_51);
diff --git a/lib/receiver_impl.h b/lib/receiver_impl.h
index 17dec98..6fb1778 100644
--- a/lib/receiver_impl.h
+++ b/lib/receiver_impl.h
@@ -184,7 +184,7 @@ namespace gr {
* @param bcc base station color code - number of a training sequence
* @return first sample number of normal burst
*/
- int get_norm_chan_imp_resp(const gr_complex * input, gr_complex * chan_imp_resp, int bcc);
+ int get_norm_chan_imp_resp(const gr_complex *input, gr_complex * chan_imp_resp, float *corr_max, int bcc);
/**
*