1 files changed, 90 insertions, 0 deletions
diff --git a/src/host/layer23/src/transceiver/demod.c b/src/host/layer23/src/transceiver/demod.c
new file mode 100644
index 00000000..45b0570a
--- /dev/null
+++ b/src/host/layer23/src/transceiver/demod.c
@@ -0,0 +1,90 @@
+/*
+ * demod.c
+ *
+ * Demodulation routines for tranceiver
+ *
+ * Copyright (C) 2013  Sylvain Munaut <tnt@246tNt.com>
+ *
+ * All Rights Reserved
+ *
+ * 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/>.
+ */
+
+#include <stdio.h>
+#include <stdint.h>
+#include <string.h>
+
+#include <osmocom/dsp/cxvec.h>
+#include <osmocom/dsp/cxvec_math.h>
+
+#include <l1ctl_proto.h>
+
+#include "app.h"
+#include "gmsk.h"
+#include "gsm_ab.h"
+
+int
+gsm_ab_ind_process(struct app_state *as,
+                   struct l1ctl_bts_burst_ab_ind *bi,
+                   sbit_t *data, float *toa_p)
+{
+	struct osmo_cxvec *burst = NULL;
+	sbit_t *bits = NULL;
+	float complex chan;
+	float toa;
+	int i, rv;
+
+	/* Load burst */
+	burst = osmo_cxvec_alloc(88);
+	burst->len = 88;
+
+	for (i=0; i<88; i++) {
+		float f[2];
+		f[0] = ((float)((char)bi->iq[(i<<1)  ])) / 128.0f;
+		f[1] = ((float)((char)bi->iq[(i<<1)+1])) / 128.0f;
+		burst->data[i] = f[0] + f[1] * I;
+	}
+
+	/* Normalize burst */
+	osmo_cxvec_sig_normalize(burst, 1, 0.0f, burst);
+
+	/* Detect potential RACH */
+	rv = gsm_ab_detect(as->gs, as->train_ab, burst, 2.0f, &chan, &toa);
+	if (rv)
+		goto err;
+
+	printf("TOA  : %f\n", toa);
+	printf("chan : (%f %f) => %f\n", crealf(chan), cimagf(chan), cabsf(chan));
+
+	/* Demodulate */
+	bits = gsm_ab_demodulate(as->gs, burst, chan, toa);
+	if (!bits)
+		goto err;
+
+	/* Copy */
+	memset(data, 0x00, 148);
+	memcpy(data, bits, GSM_AB_BITS);
+
+	/* Print result */
+	for (i=0; i<GSM_AB_BITS; i++)
+		printf("%d", !!(bits[i] & 0x80));
+	printf("\n");
+
+	*toa_p = toa;
+
+	return 0;
+
+err:
+	return -1;
+}