1 files changed, 332 insertions, 0 deletions
diff --git a/Transceiver52M/radioInterfaceResamp.cpp b/Transceiver52M/radioInterfaceResamp.cpp
new file mode 100644
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+++ b/Transceiver52M/radioInterfaceResamp.cpp
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+/*
+ * Radio device interface with sample rate conversion
+ * Written by Thomas Tsou <ttsou@vt.edu>
+ *
+ * Copyright 2011 Free Software Foundation, Inc.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ * See the COPYING file in the main directory for details.
+ */
+
+#include <radioInterface.h>
+#include <Logger.h>
+
+/* New chunk sizes for resampled rate */
+#ifdef INCHUNK
+  #undef INCHUNK
+#endif
+#ifdef OUTCHUNK
+  #undef OUTCHUNK
+#endif
+
+/* Resampling parameters */
+#define INRATE       65 * SAMPSPERSYM
+#define INHISTORY    INRATE * 2
+#define INCHUNK      INRATE * 9
+
+#define OUTRATE      96 * SAMPSPERSYM
+#define OUTHISTORY   OUTRATE * 2
+#define OUTCHUNK     OUTRATE * 9
+
+/* Resampler low pass filters */
+signalVector *tx_lpf = 0;
+signalVector *rx_lpf = 0;
+
+/* Resampler history */
+signalVector *tx_hist = 0;
+signalVector *rx_hist = 0;
+
+/* Resampler input buffer */
+signalVector *tx_vec = 0;
+signalVector *rx_vec = 0;
+
+/*
+ * High rate (device facing) buffers
+ *
+ * Transmit side samples are pushed after each burst so accomodate
+ * a resampled burst plus up to a chunk left over from the previous
+ * resampling operation.
+ *
+ * Receive side samples always pulled with a fixed size.
+ */
+short tx_buf[INCHUNK * 2 * 4];
+short rx_buf[OUTCHUNK * 2 * 2];
+
+/* 
+ * Utilities and Conversions 
+ *
+ * Manipulate signal vectors dynamically for two reasons. For one,
+ * it's simpler. And two, it doesn't make any reasonable difference
+ * relative to the high overhead generated by the resampling.
+ */
+
+/* Concatenate signal vectors. Deallocate input vectors. */
+signalVector *concat(signalVector *a, signalVector *b)
+{
+	signalVector *vec = new signalVector(*a, *b);
+	delete a;
+	delete b;
+
+	return vec;
+}
+
+/* Segment a signal vector. Deallocate the input vector. */
+signalVector *segment(signalVector *a, int indx, int sz)
+{
+	signalVector *vec = new signalVector(sz);
+	a->segmentCopyTo(*vec, indx, sz);
+	delete a;
+
+	return vec;
+}
+
+/* Create a new signal vector from a short array. */
+signalVector *short_to_sigvec(short *smpls, size_t sz)
+{
+	int i;
+	signalVector *vec = new signalVector(sz);
+	signalVector::iterator itr = vec->begin();
+
+	for (i = 0; i < sz; i++) {
+		*itr++ = Complex<float>(smpls[2 * i + 0], smpls[2 * i + 1]);
+	}
+
+	return vec;
+}
+
+/* Convert and deallocate a signal vector into a short array. */
+int sigvec_to_short(signalVector *vec, short *smpls)
+{
+	int i;
+	signalVector::iterator itr = vec->begin();
+
+	for (i = 0; i < vec->size(); i++) {
+		smpls[2 * i + 0] = itr->real();
+		smpls[2 * i + 1] = itr->imag();
+		itr++;
+	}
+	delete vec;
+
+	return i;
+}
+
+/* Create a new signal vector from a float array. */
+signalVector *float_to_sigvec(float *smpls, int sz)
+{
+	int i;
+	signalVector *vec = new signalVector(sz);
+	signalVector::iterator itr = vec->begin();
+
+	for (i = 0; i < sz; i++) {
+		*itr++ = Complex<float>(smpls[2 * i + 0], smpls[2 * i + 1]);
+	}
+
+	return vec;
+}
+
+/* Convert and deallocate a signal vector into a float array. */
+int sigvec_to_float(signalVector *vec, float *smpls)
+{
+	int i;
+	signalVector::iterator itr = vec->begin();
+
+	for (i = 0; i < vec->size(); i++) {
+		smpls[2 * i + 0] = itr->real();
+		smpls[2 * i + 1] = itr->imag();
+		itr++;
+	}
+	delete vec;
+
+	return i;
+}
+
+/* Initialize resampling signal vectors */
+void init_resampler(signalVector **lpf,
+	   	    signalVector **buf,
+		    signalVector **hist,
+		    int tx)
+{
+	int P, Q, taps, hist_len;
+	float cutoff_freq;
+
+	if (tx) {
+		LOG(INFO) << "Initializing Tx resampler";
+		P = OUTRATE;
+		Q = INRATE;
+		taps = 651;
+		hist_len = INHISTORY;
+	} else {
+		LOG(INFO) << "Initializing Rx resampler";
+		P = INRATE;
+		Q = OUTRATE;
+		taps = 961;
+		hist_len = OUTHISTORY;
+	}
+
+	if (!*lpf) {
+		cutoff_freq = (P < Q) ? (1.0/(float) Q) : (1.0/(float) P);
+		*lpf = createLPF(cutoff_freq, taps, P);
+	}
+
+	if (!*buf) {
+		*buf = new signalVector();
+	}
+
+	if (!*hist);
+		*hist = new signalVector(hist_len);
+}
+
+/* Resample a signal vector
+ *
+ * The input vector is deallocated and the pointer returned with a vector
+ * of any unconverted samples.
+ */
+signalVector *resmpl_sigvec(signalVector *hist, signalVector **vec,
+			    signalVector *lpf, double in_rate,
+			    double out_rate, int chunk_sz)
+{
+	signalVector *resamp_vec;
+	int num_chunks = (*vec)->size() / chunk_sz;
+
+	/* Truncate to a chunk multiple */
+	signalVector trunc_vec(num_chunks * chunk_sz);
+	(*vec)->segmentCopyTo(trunc_vec, 0, num_chunks * chunk_sz);
+
+	/* Update sample buffer with remainder */
+	*vec = segment(*vec, trunc_vec.size(), (*vec)->size() - trunc_vec.size());
+
+	/* Add history and resample */
+	signalVector input_vec(*hist, trunc_vec);
+	resamp_vec = polyphaseResampleVector(input_vec, in_rate,
+					     out_rate, lpf);
+
+	/* Update history */
+	trunc_vec.segmentCopyTo(*hist, trunc_vec.size() - hist->size(),
+				hist->size());
+	return resamp_vec;
+}
+
+/* Wrapper for receive-side integer-to-float array resampling */
+ int rx_resmpl_int_flt(float *smpls_out, short *smpls_in, int num_smpls)
+{
+	int num_resmpld, num_chunks;
+	signalVector *convert_vec, *resamp_vec, *trunc_vec;
+
+	if (!rx_lpf || !rx_vec || !rx_hist)
+		init_resampler(&rx_lpf, &rx_vec, &rx_hist, false);
+
+	/* Convert and add samples to the receive buffer */
+	convert_vec = short_to_sigvec(smpls_in, num_smpls);
+	rx_vec = concat(rx_vec, convert_vec);
+
+	num_chunks = rx_vec->size() / OUTCHUNK;
+	if (num_chunks < 1)
+		return 0;
+
+	/* Resample */ 
+	resamp_vec = resmpl_sigvec(rx_hist, &rx_vec, rx_lpf,
+				   INRATE, OUTRATE, OUTCHUNK);
+	/* Truncate */
+	trunc_vec = segment(resamp_vec, INHISTORY,
+                            resamp_vec->size() - INHISTORY);
+	/* Convert */
+	num_resmpld = sigvec_to_float(trunc_vec, smpls_out);
+
+	return num_resmpld; 
+}
+
+/* Wrapper for transmit-side float-to-int array resampling */
+int tx_resmpl_flt_int(short *smpls_out, float *smpls_in, int num_smpls)
+{
+	int num_resmpl, num_chunks;
+	signalVector *convert_vec, *resamp_vec;
+
+	if (!tx_lpf || !tx_vec || !tx_hist)
+		init_resampler(&tx_lpf, &tx_vec, &tx_hist, true);
+
+	/* Convert and add samples to the transmit buffer */
+	convert_vec = float_to_sigvec(smpls_in, num_smpls);
+	tx_vec = concat(tx_vec, convert_vec);
+
+	num_chunks = tx_vec->size() / INCHUNK;
+	if (num_chunks < 1)
+		return 0;
+
+	/* Resample and convert to an integer array */
+	resamp_vec = resmpl_sigvec(tx_hist, &tx_vec, tx_lpf,
+				   OUTRATE, INRATE, INCHUNK);
+	num_resmpl = sigvec_to_short(resamp_vec, smpls_out);
+
+	return num_resmpl; 
+}
+
+RadioInterfaceResamp::RadioInterfaceResamp(RadioDevice *wRadio,
+					   int wReceiveOffset,
+					   int wSPS,
+					   GSM::Time wStartTime)
+	: RadioInterface(wRadio, wReceiveOffset, wSPS, wStartTime)
+{
+}
+
+/* Receive a timestamped chunk from the device */ 
+void RadioInterfaceResamp::pullBuffer()
+{
+	int num_cv, num_rd;
+	bool local_underrun;
+
+	/* Read samples. Fail if we don't get what we want. */
+	num_rd = mRadio->readSamples(rx_buf, OUTCHUNK, &overrun,
+				     readTimestamp, &local_underrun);
+
+	LOG(DEBUG) << "Rx read " << num_rd << " samples from device";
+	assert(num_rd == OUTCHUNK);
+
+	underrun |= local_underrun;
+	readTimestamp += (TIMESTAMP) num_rd;
+
+	/* Convert and resample */
+	num_cv = rx_resmpl_int_flt(rcvBuffer + 2 * rcvCursor,
+				   rx_buf, num_rd);
+
+	LOG(DEBUG) << "Rx read " << num_cv << " samples from resampler";
+
+	rcvCursor += num_cv;
+}
+
+/* Send a timestamped chunk to the device */ 
+void RadioInterfaceResamp::pushBuffer()
+{
+	int num_cv, num_wr;
+
+	if (sendCursor < INCHUNK)
+		return;
+
+	LOG(DEBUG) << "Tx wrote " << sendCursor << " samples to resampler";
+
+	/* Resample and convert */
+	num_cv = tx_resmpl_flt_int(tx_buf, sendBuffer, sendCursor);
+	assert(num_cv > sendCursor);
+
+	/* Write samples. Fail if we don't get what we want. */
+	num_wr = mRadio->writeSamples(tx_buf + OUTHISTORY * 2,
+				      num_cv - OUTHISTORY,
+				      &underrun,
+				      writeTimestamp);
+
+	LOG(DEBUG) << "Tx wrote " << num_wr << " samples to device";
+	assert(num_wr == num_wr);
+
+	writeTimestamp += (TIMESTAMP) num_wr;
+	sendCursor = 0;
+}