1 files changed, 148 insertions, 0 deletions
diff --git a/Transceiver52M/fbsb.cpp b/Transceiver52M/fbsb.cpp
new file mode 100644
index 0000000..870b28c
--- /dev/null
+++ b/Transceiver52M/fbsb.cpp
@@ -0,0 +1,148 @@
+#include <atomic>
+#include "radioInterface.h"
+#include "Interthread.h"
+#include "GSMCommon.h"
+//#include "Sockets.h"
+
+#include <sys/types.h>
+#include <sys/socket.h>
+
+
+static const auto tssize = 156.25;
+static const auto framee_to_read = 12;
+static const auto ts_to_read = framee_to_read * 8;
+static const int fbsb_chunk_len = ts_to_read * 2 * tssize; // contiguous fcch+sch guaranteed
+static const auto corr_offset = 0;
+
+struct fbsb_par {
+
+    enum class fbsb_state {
+	IDLE,
+	INIT,
+        ACQ,
+        WAIT,
+	ACQ_COMPL,
+        DONE
+    };
+
+    int pos;
+    int time_idx;
+    std::atomic<fbsb_state> s;
+    GSM::Time rcvClock[ts_to_read];
+    complex fbsb_buf[fbsb_chunk_len+corr_offset];
+    complex conjbuf[fbsb_chunk_len+corr_offset];
+    complex avgbuf[fbsb_chunk_len+corr_offset];
+    void addclk(GSM::Time c) { rcvClock[time_idx] = c; time_idx++; return;}
+public:
+    fbsb_par() : s(fbsb_state::IDLE) {
+	reset();
+    };
+    bool done() {return !(time_idx < ts_to_read);}
+    void take(void* addr, int num_cplx_sps, GSM::Time c) {
+        memcpy(fbsb_buf+pos+corr_offset,addr, num_cplx_sps * sizeof(complex));
+	pos += num_cplx_sps;
+	assert(pos < fbsb_chunk_len);
+	rcvClock[time_idx] = c;
+	time_idx++;
+    }
+    void reset() {pos = 0;
+		  time_idx = 0;
+//		s = fbsb_state::IDLE;
+		  memset(fbsb_buf, 0, sizeof(fbsb_buf));
+		  memset(conjbuf, 0, sizeof(conjbuf));
+		  memset(avgbuf, 0, sizeof(avgbuf));
+		 }
+    int sz () {return fbsb_chunk_len;}
+    int off () {return corr_offset;}
+
+    // from osmotrx sigproc
+    complex fastPeakDetect(complex* rxBurst, float* index, int N)
+    {
+	    float val, max = 0.0f;
+	    complex amp;
+	    int _index = -1;
+
+	    for (size_t i = 0; i < N; i++) {
+		    val = rxBurst[i].abs();
+		    if (val > max) {
+			    max = val;
+			    _index = i;
+			    amp = rxBurst[i];
+		    }
+	    }
+
+	    if (index)
+		    *index = (float)_index;
+
+	    return amp;
+    }
+
+    void conj_with_lag(complex* in, complex* out, int lag, int offset, int N) {
+	    int total_offset = offset + lag;
+	    for (int s = 0; s < N; s++)
+		    out[s] = in[s + total_offset] * in[s + total_offset - lag].conj();
+    }
+
+    auto ac_sum_with_lag(complex* in, int lag, int offset, int N) {
+	    complex v(0,0);
+	    auto total_offset = offset + lag;
+	    for (auto s = 0; s < N; s++)
+		    v += in[s + total_offset] * in[s + total_offset - lag].conj();
+	    return atan2(v.imag(), v.real());
+    }
+
+
+    bool running_avg_opt(complex* in, complex* out, int avg_window, int val_to_find, int* idx, int N) {
+	    bool found = false;
+	    complex avg0 = 0;
+	    complex scale(avg_window, avg_window);
+	    for (auto i = 0; i < avg_window; i++)
+		    avg0 += in[i];
+	    out[0] = avg0 / scale;
+
+	    //skip first
+	    for (auto i = 1; i < N - avg_window; i++) {
+		    avg0 += in[i-1] - in[i+avg_window];
+		    auto tmp = avg0 / scale;
+		    out[i] = tmp;
+		    if (!found && tmp.abs() > val_to_find) {
+			    found = !found;
+			    *idx = i;
+			    return true;
+		    }
+	    }
+	    return false;
+    }
+
+    int fcch(complex* amp, int* found_idx, bool dump) {
+	conj_with_lag(fbsb_buf, conjbuf, 3, off(), sz());
+
+	running_avg_opt(conjbuf, avgbuf, 48, 1.5e6, found_idx, sz()-off());
+	float pos;
+	auto r = fastPeakDetect(avgbuf, &pos, sz()-off());
+	*found_idx = *found_idx+off();
+	std::cerr << "fcch found at " << pos << " amp: " << r.abs() << std::endl;
+	*amp = r;
+
+	if(dump) {
+		{
+		    auto f = fopen("inbuf.cfile", "wb");
+		    fwrite(fbsb_buf, sz(), 1, f);
+		    fclose(f);
+		}
+		{
+		    auto f = fopen("conjbuf.cfile", "wb");
+		    fwrite(conjbuf, sz(), 1, f);
+		    fclose(f);
+		}
+		{
+		    auto f = fopen("schfcch.cfile", "wb");
+		    fwrite(avgbuf, sz(), 1, f);
+		    fclose(f);
+		}
+		exit(0);
+	    }
+	return pos;
+    }
+};
+