TRX: Implementation of MS power and timing advance loops

1 files changed, 251 insertions, 0 deletions

diff --git a/src/osmo-bts-trx/loops.c b/src/osmo-bts-trx/loops.c
new file mode 100644
index 00000000..c8815286
--- /dev/null
+++ b/src/osmo-bts-trx/loops.c
@@ -0,0 +1,251 @@
+/* Loop control for OsmoBTS-TRX */
+
+/* (C) 2013 by Andreas Eversberg <jolly@eversberg.eu>
+ *
+ * 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 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 <stdint.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <errno.h>
+
+#include <osmo-bts/gsm_data.h>
+#include <osmo-bts/logging.h>
+#include <osmo-bts/l1sap.h>
+#include <osmocom/core/bits.h>
+
+#include "trx_if.h"
+#include "l1_if.h"
+#include "loops.h"
+
+#define MS_PWR_DBM(lvl) ms_pwr_dbm(gsm_arfcn2band(l1h->config.arfcn), lvl)
+
+/*
+ * MS Power loop
+ */
+
+int trx_ms_power_loop = 0;
+int8_t trx_target_rssi = -10;
+
+/* how much power levels do we raise/lower as maximum (1 level = 2 dB) */
+#define MS_RAISE_MAX 4
+#define MS_LOWER_MAX 4
+
+static int ms_power_diff(struct trx_l1h *l1h, struct gsm_lchan *lchan,
+	uint8_t chan_nr, struct trx_chan_state *chan_state, int8_t diff)
+{
+	int8_t new_power;
+	
+	new_power = lchan->ms_power - (diff >> 1);
+
+	if (diff == 0)
+		return 0;
+
+	if (new_power < 0)
+		new_power = 0;
+
+	// FIXME: to go above 1W, we need to know classmark of MS
+	if (l1h->config.arfcn >= 512 && l1h->config.arfcn <= 885) {
+		if (new_power > 15)
+			new_power = 15;
+	} else {
+		if (new_power > 19)
+			new_power = 19;
+	}
+
+	/* a higher value means a lower level (and vice versa) */
+	if (new_power > lchan->ms_power + MS_LOWER_MAX)
+		new_power = lchan->ms_power + MS_LOWER_MAX;
+	else if (new_power < lchan->ms_power - MS_RAISE_MAX)
+		new_power = lchan->ms_power - MS_RAISE_MAX;
+
+	if (lchan->ms_power == new_power) {
+		LOGP(DLOOP, LOGL_INFO, "Keeping MS new_power of trx=%u "
+			"chan_nr=0x%02x at control level %d (%d dBm)\n",
+			l1h->trx->nr, chan_nr, new_power,
+			MS_PWR_DBM(new_power));
+
+		return 0;
+	}
+
+	LOGP(DLOOP, LOGL_INFO, "%s MS new_power of trx=%u chan_nr=0x%02x from "
+		"control level %d (%d dBm) to %d (%d dBm)\n",
+		(diff > 0) ? "Raising" : "Lowering",
+		l1h->trx->nr, chan_nr, lchan->ms_power,
+		MS_PWR_DBM(lchan->ms_power), new_power, MS_PWR_DBM(new_power));
+
+	lchan->ms_power = new_power;
+
+	return 0;
+}
+
+static int ms_power_val(struct trx_l1h *l1h, struct gsm_lchan *lchan,
+	uint8_t chan_nr, struct trx_chan_state *chan_state, int8_t rssi)
+{
+	/* ignore inserted dummy frames, treat as lost frames */
+	if (rssi < -127)
+		return 0;
+
+	LOGP(DLOOP, LOGL_DEBUG, "Got RSSI value of %d\n", rssi);
+
+	chan_state->meas.rssi_count++;
+
+	/* check if the current L1 header compares to the current ordered TA */
+//	if ((lchan->meas.l1_info[0] >> 3) != lchan->ms_power)
+//		return 0;
+
+	chan_state->meas.rssi_got_burst = 1;
+
+	/* store and process RSSI */
+	if (chan_state->meas.rssi_valid_count
+					== ARRAY_SIZE(chan_state->meas.rssi))
+		return 0;
+	chan_state->meas.rssi[chan_state->meas.rssi_valid_count++] = rssi;
+	chan_state->meas.rssi_valid_count++;
+
+	return 0;
+}
+
+static int ms_power_clock(struct trx_l1h *l1h, struct gsm_lchan *lchan,
+	uint8_t chan_nr, struct trx_chan_state *chan_state)
+{
+	int rssi;
+	int i;
+
+	/* skip every second clock, to prevent oscillating due to roundtrip
+	 * delay */
+	if (!(chan_state->meas.clock & 1))
+		return 0;
+
+	LOGP(DLOOP, LOGL_DEBUG, "Got SACCH master clock at RSSI count %d\n",
+		chan_state->meas.rssi_count);
+
+	/* wait for initial burst */
+	if (!chan_state->meas.rssi_got_burst)
+		return 0;
+
+	/* if no burst was received from MS at clock */
+	if (chan_state->meas.rssi_count == 0) {
+		LOGP(DLOOP, LOGL_NOTICE, "LOST SACCH frame of trx=%u "
+			"chan_nr=0x%02x, so we raise MS power\n",
+			l1h->trx->nr, chan_nr);
+		return ms_power_diff(l1h, lchan, chan_nr, chan_state,
+			MS_RAISE_MAX);
+	}
+
+	/* reset total counter */
+	chan_state->meas.rssi_count = 0;
+
+	/* check the minimum level received after MS acknowledged the ordered
+	 * power level */
+	if (chan_state->meas.rssi_valid_count == 0)
+		return 0;
+	for (rssi = 999, i = 0; i < chan_state->meas.rssi_valid_count; i++) {
+		if (rssi > chan_state->meas.rssi[i])
+			rssi = chan_state->meas.rssi[i];
+	}
+
+	/* reset valid counter */
+	chan_state->meas.rssi_valid_count = 0;
+
+	/* change RSSI */
+	LOGP(DLOOP, LOGL_DEBUG, "Lowest RSSI: %d Target RSSI: %d Current "
+		"MS power: %d (%d dBm) of trx=%u chan_nr=0x%02x\n", rssi,
+		trx_target_rssi, lchan->ms_power, MS_PWR_DBM(lchan->ms_power),
+		l1h->trx->nr, chan_nr);
+	ms_power_diff(l1h, lchan, chan_nr, chan_state, trx_target_rssi - rssi);
+
+	return 0;
+}
+
+
+/*
+ * Timing Advance loop
+ */
+
+int trx_ta_loop = 1;
+
+int ta_val(struct trx_l1h *l1h, struct gsm_lchan *lchan, uint8_t chan_nr,
+	struct trx_chan_state *chan_state, float toa)
+{
+	/* check if the current L1 header acks to the current ordered TA */
+	if (lchan->meas.l1_info[1] != lchan->rqd_ta)
+		return 0;
+
+	/* sum measurement */
+	chan_state->meas.toa_sum += toa;
+	if (++(chan_state->meas.toa_num) < 16)
+		return 0;
+
+	/* complete set */
+	toa = chan_state->meas.toa_sum / chan_state->meas.toa_num;
+
+	/* check for change of TOA */
+	if (toa < -0.9F && lchan->rqd_ta > 0) {
+		LOGP(DLOOP, LOGL_INFO, "TOA of trx=%u chan_nr=0x%02x is too "
+			"early (%.2f), now lowering TA from %d to %d\n",
+			l1h->trx->nr, chan_nr, toa, lchan->rqd_ta,
+			lchan->rqd_ta - 1);
+		lchan->rqd_ta--;
+	} else if (toa > 0.9F && lchan->rqd_ta < 63) {
+		LOGP(DLOOP, LOGL_INFO, "TOA of trx=%u chan_nr=0x%02x is too "
+			"late (%.2f), now raising TA from %d to %d\n",
+			l1h->trx->nr, chan_nr, toa, lchan->rqd_ta,
+			lchan->rqd_ta + 1);
+		lchan->rqd_ta++;
+	} else
+		LOGP(DLOOP, LOGL_INFO, "TOA of trx=%u chan_nr=0x%02x is "
+			"correct (%.2f), keeping current TA of %d\n",
+			l1h->trx->nr, chan_nr, toa, lchan->rqd_ta);
+
+	chan_state->meas.toa_num = 0;
+	chan_state->meas.toa_sum = 0;
+
+	return 0;
+}
+
+int trx_loop_input(struct trx_l1h *l1h, uint8_t chan_nr,
+	struct trx_chan_state *chan_state, int8_t rssi, float toa)
+{
+	struct gsm_lchan *lchan = &l1h->trx->ts[L1SAP_CHAN2TS(chan_nr)]
+					.lchan[l1sap_chan2ss(chan_nr)];
+
+	if (trx_ms_power_loop)
+		ms_power_val(l1h, lchan, chan_nr, chan_state, rssi);
+
+	if (trx_ta_loop)
+		ta_val(l1h, lchan, chan_nr, chan_state, toa);
+
+	return 0;
+}
+
+int trx_loop_sacch_clock(struct trx_l1h *l1h, uint8_t chan_nr,
+	struct trx_chan_state *chan_state)
+{
+	struct gsm_lchan *lchan = &l1h->trx->ts[L1SAP_CHAN2TS(chan_nr)]
+					.lchan[l1sap_chan2ss(chan_nr)];
+
+	if (trx_ms_power_loop)
+		ms_power_clock(l1h, lchan, chan_nr, chan_state);
+
+	/* count the number of SACCH clocks */
+	chan_state->meas.clock++;
+
+	return 0;
+}
+