receiver: fixes of synchronization
Correcting and making sense of some magic constants
relating to synchronization. Some magic constants
of unknown origin still stay.
Change-Id: I5a45ce1c8bceded70d34302a5b136da5f92fd902
diff --git a/lib/receiver/receiver_impl.cc b/lib/receiver/receiver_impl.cc
index dcf6533..c88740a 100644
--- a/lib/receiver/receiver_impl.cc
+++ b/lib/receiver/receiver_impl.cc
@@ -48,7 +48,8 @@
#include <iomanip>
#endif
-#define SYNC_SEARCH_RANGE 30
+#define SYNC_SEARCH_RANGE 50
+#define SYNC_START (BURST_SIZE/2-(SYNC_SEARCH_RANGE/2)-(N_SYNC_BITS/2) + 8)
namespace gr
{
@@ -285,7 +286,7 @@
d_burst_nr++;
/* Consume samples up to the next guard period */
- unsigned int to_consume = burst_start + BURST_SIZE * d_OSR + 4 * d_OSR;
+ unsigned int to_consume = burst_start + BURST_SIZE * d_OSR + 4 * d_OSR + 2 * d_OSR + 1; //TODO: figure out where + 2 * d_OSR + 1 comes from
// consume_each(to_consume);
d_samples_consumed += to_consume;
@@ -341,7 +342,7 @@
/* Extract frequency offset */
const unsigned first_sample =
- ceil((GUARD_PERIOD + 2 * TAIL_BITS) * d_OSR) + 1;
+ ceil((GUARD_PERIOD/2 + TAIL_BITS) * d_OSR) + 1;
const unsigned last_sample =
first_sample + USEFUL_BITS * d_OSR - TAIL_BITS * d_OSR;
double freq_offset_tmp =
@@ -383,25 +384,23 @@
pmt::from_double(0.0),pmt::mp("sync_loss"));
message_port_pub(pmt::mp("measurements"), msg);
}
+ } else {
+ /* Compose a message with GSMTAP header and bits */
+ send_burst(d_burst_nr, output_binary,
+ GSMTAP_BURST_SCH, input_nr, d_c0_burst_start);
- break;
+ /**
+ * Decoding was successful, now
+ * compute offset from burst_start,
+ * burst should start after a guard period.
+ */
+ offset = d_c0_burst_start - 2 * d_OSR; //TODO: figure out the -2 * d_OSR part
+ to_consume += offset;
+ d_failed_sch = 0;
}
- /* Compose a message with GSMTAP header and bits */
- send_burst(d_burst_nr, output_binary,
- GSMTAP_BURST_SCH, input_nr, d_c0_burst_start);
-
- /**
- * Decoding was successful, now
- * compute offset from burst_start,
- * burst should start after a guard period.
- */
- offset = d_c0_burst_start - floor((GUARD_PERIOD) * d_OSR);
- to_consume += offset;
- d_failed_sch = 0;
-
- break;
}
+ break;
case normal_burst:
{
@@ -785,8 +784,10 @@
int burst_start;
float energy = 0;
- int len = (SYNC_POS + SYNC_SEARCH_RANGE) * d_OSR;
- for (int ii = SYNC_POS * d_OSR; ii < len; ii++) {
+ int len = (SYNC_SEARCH_RANGE) * d_OSR;
+ int start = (SYNC_START) * d_OSR;
+ int stop = start + len;
+ for (int ii = start; ii < stop; ii++) {
gr_complex correlation = correlate_sequence(&d_sch_training_seq[5],
N_SYNC_BITS - 10, &input[ii]);
correlation_buffer.push_back(correlation);
@@ -839,7 +840,7 @@
}
burst_start = strongest_window_nr + chan_imp_resp_center
- - 48 * d_OSR - 2 * d_OSR + 2 + SYNC_POS * d_OSR;
+ - 48 * d_OSR - 2 * d_OSR + 2 + SYNC_START * d_OSR;
return burst_start;
}