move openbsc/* to repos root

This is the first step in creating this repository from the legacy openbsc.git.

Like all other Osmocom repositories, keep the autoconf and automake files in
the repository root. openbsc.git has been the sole exception, which ends now.

Change-Id: I9c6f2a448d9cb1cc088cf1cf6918b69d7e69b4e7

1 files changed, 304 insertions, 0 deletions

diff --git a/src/libbsc/handover_decision.c b/src/libbsc/handover_decision.c
new file mode 100644
index 000000000..0f07bcac6
--- /dev/null
+++ b/src/libbsc/handover_decision.c
@@ -0,0 +1,304 @@
+/* Handover Decision making for Inter-BTS (Intra-BSC) Handover.  This
+ * only implements the handover algorithm/decision, but not execution
+ * of it */
+
+/* (C) 2009 by Harald Welte <laforge@gnumonks.org>
+ *
+ * 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 <stdlib.h>
+#include <errno.h>
+
+#include <osmocom/core/msgb.h>
+#include <openbsc/debug.h>
+#include <openbsc/gsm_data.h>
+#include <openbsc/meas_rep.h>
+#include <openbsc/signal.h>
+#include <osmocom/core/talloc.h>
+#include <openbsc/handover.h>
+#include <osmocom/gsm/gsm_utils.h>
+
+/* issue handover to a cell identified by ARFCN and BSIC */
+static int handover_to_arfcn_bsic(struct gsm_lchan *lchan,
+				  uint16_t arfcn, uint8_t bsic)
+{
+	struct gsm_bts *new_bts;
+
+	/* resolve the gsm_bts structure for the best neighbor */
+	new_bts = gsm_bts_neighbor(lchan->ts->trx->bts, arfcn, bsic);
+	if (!new_bts) {
+		LOGP(DHO, LOGL_NOTICE, "unable to determine neighbor BTS "
+		     "for ARFCN %u BSIC %u ?!?\n", arfcn, bsic);
+		return -EINVAL;
+	}
+
+	/* and actually try to handover to that cell */
+	return bsc_handover_start(lchan, new_bts);
+}
+
+/* did we get a RXLEV for a given cell in the given report? */
+static int rxlev_for_cell_in_rep(struct gsm_meas_rep *mr,
+				 uint16_t arfcn, uint8_t bsic)
+{
+	int i;
+
+	for (i = 0; i < mr->num_cell; i++) {
+		struct gsm_meas_rep_cell *mrc = &mr->cell[i];
+
+		/* search for matching report */
+		if (!(mrc->arfcn == arfcn && mrc->bsic == bsic))
+			continue;
+
+		mrc->flags |= MRC_F_PROCESSED;
+		return mrc->rxlev;
+	}
+	return -ENODEV;
+}
+
+/* obtain averaged rxlev for given neighbor */
+static int neigh_meas_avg(struct neigh_meas_proc *nmp, int window)
+{
+	unsigned int i, idx;
+	int avg = 0;
+
+	idx = calc_initial_idx(ARRAY_SIZE(nmp->rxlev),
+				nmp->rxlev_cnt % ARRAY_SIZE(nmp->rxlev),
+				window);
+
+	for (i = 0; i < window; i++) {
+		int j = (idx+i) % ARRAY_SIZE(nmp->rxlev);
+
+		avg += nmp->rxlev[j];
+	}
+
+	return avg / window;
+}
+
+/* find empty or evict bad neighbor */
+static struct neigh_meas_proc *find_evict_neigh(struct gsm_lchan *lchan)
+{
+	int j, worst = 999999;
+	struct neigh_meas_proc *nmp_worst = NULL;
+
+	/* first try to find an empty/unused slot */
+	for (j = 0; j < ARRAY_SIZE(lchan->neigh_meas); j++) {
+		struct neigh_meas_proc *nmp = &lchan->neigh_meas[j];
+		if (!nmp->arfcn)
+			return nmp;
+	}
+
+	/* no empty slot found. evict worst neighbor from list */
+	for (j = 0; j < ARRAY_SIZE(lchan->neigh_meas); j++) {
+		struct neigh_meas_proc *nmp = &lchan->neigh_meas[j];
+		int avg = neigh_meas_avg(nmp, MAX_WIN_NEIGH_AVG);
+		if (!nmp_worst || avg < worst) {
+			worst = avg;
+			nmp_worst = nmp;
+		}
+	}
+
+	return nmp_worst;
+}
+
+/* process neighbor cell measurement reports */
+static void process_meas_neigh(struct gsm_meas_rep *mr)
+{
+	int i, j, idx;
+
+	/* for each reported cell, try to update global state */
+	for (j = 0; j < ARRAY_SIZE(mr->lchan->neigh_meas); j++) {
+		struct neigh_meas_proc *nmp = &mr->lchan->neigh_meas[j];
+		unsigned int idx;
+		int rxlev;
+
+		/* skip unused entries */
+		if (!nmp->arfcn)
+			continue;
+
+		rxlev = rxlev_for_cell_in_rep(mr, nmp->arfcn, nmp->bsic);
+		idx = nmp->rxlev_cnt % ARRAY_SIZE(nmp->rxlev);
+		if (rxlev >= 0) {
+			nmp->rxlev[idx] = rxlev;
+			nmp->last_seen_nr = mr->nr;
+		} else
+			nmp->rxlev[idx] = 0;
+		nmp->rxlev_cnt++;
+	}
+
+	/* iterate over list of reported cells, check if we did not
+	 * process all of them */
+	for (i = 0; i < mr->num_cell; i++) {
+		struct gsm_meas_rep_cell *mrc = &mr->cell[i];
+		struct neigh_meas_proc *nmp;
+
+		if (mrc->flags & MRC_F_PROCESSED)
+			continue;
+
+		nmp = find_evict_neigh(mr->lchan);
+
+		nmp->arfcn = mrc->arfcn;
+		nmp->bsic = mrc->bsic;
+
+		idx = nmp->rxlev_cnt % ARRAY_SIZE(nmp->rxlev);
+		nmp->rxlev[idx] = mrc->rxlev;
+		nmp->rxlev_cnt++;
+		nmp->last_seen_nr = mr->nr;
+
+		mrc->flags |= MRC_F_PROCESSED;
+	}
+}
+
+/* attempt to do a handover */
+static int attempt_handover(struct gsm_meas_rep *mr)
+{
+	struct gsm_network *net = mr->lchan->ts->trx->bts->network;
+	struct neigh_meas_proc *best_cell = NULL;
+	unsigned int best_better_db = 0;
+	int i, rc;
+
+	/* find the best cell in this report that is at least RXLEV_HYST
+	 * better than the current serving cell */
+
+	for (i = 0; i < ARRAY_SIZE(mr->lchan->neigh_meas); i++) {
+		struct neigh_meas_proc *nmp = &mr->lchan->neigh_meas[i];
+		int avg, better;
+
+		/* skip empty slots */
+		if (nmp->arfcn == 0)
+			continue;
+
+		/* caculate average rxlev for this cell over the window */
+		avg = neigh_meas_avg(nmp, net->handover.win_rxlev_avg_neigh);
+
+		/* check if hysteresis is fulfilled */
+		if (avg < mr->dl.full.rx_lev + net->handover.pwr_hysteresis)
+			continue;
+
+		better = avg - mr->dl.full.rx_lev;
+		if (better > best_better_db) {
+			best_cell = nmp;
+			best_better_db = better;
+		}
+	}
+
+	if (!best_cell)
+		return 0;
+
+	LOGP(DHO, LOGL_INFO, "%s: Cell on ARFCN %u is better: ",
+		gsm_ts_name(mr->lchan->ts), best_cell->arfcn);
+	if (!net->handover.active) {
+		LOGPC(DHO, LOGL_INFO, "Skipping, Handover disabled\n");
+		return 0;
+	}
+
+	rc = handover_to_arfcn_bsic(mr->lchan, best_cell->arfcn, best_cell->bsic);
+	switch (rc) {
+	case 0:
+		LOGPC(DHO, LOGL_INFO, "Starting handover\n");
+		break;
+	case -ENOSPC:
+		LOGPC(DHO, LOGL_INFO, "No channel available\n");
+		break;
+	case -EBUSY:
+		LOGPC(DHO, LOGL_INFO, "Handover already active\n");
+		break;
+	default:
+		LOGPC(DHO, LOGL_ERROR, "Unknown error\n");
+	}
+	return rc;
+}
+
+/* process an already parsed measurement report and decide if we want to
+ * attempt a handover */
+static int process_meas_rep(struct gsm_meas_rep *mr)
+{
+	struct gsm_network *net = mr->lchan->ts->trx->bts->network;
+	enum meas_rep_field dlev, dqual;
+	int av_rxlev;
+
+	/* we currently only do handover for TCH channels */
+	switch (mr->lchan->type) {
+	case GSM_LCHAN_TCH_F:
+	case GSM_LCHAN_TCH_H:
+		break;
+	default:
+		return 0;
+	}
+
+	if (mr->flags & MEAS_REP_F_DL_DTX) {
+		dlev = MEAS_REP_DL_RXLEV_SUB;
+		dqual = MEAS_REP_DL_RXQUAL_SUB;
+	} else {
+		dlev = MEAS_REP_DL_RXLEV_FULL;
+		dqual = MEAS_REP_DL_RXQUAL_FULL;
+	}
+
+	/* parse actual neighbor cell info */
+	if (mr->num_cell > 0 && mr->num_cell < 7)
+		process_meas_neigh(mr);
+
+	av_rxlev = get_meas_rep_avg(mr->lchan, dlev,
+				    net->handover.win_rxlev_avg);
+
+	/* Interference HO */
+	if (rxlev2dbm(av_rxlev) > -85 &&
+	    meas_rep_n_out_of_m_be(mr->lchan, dqual, 3, 4, 5))
+		return attempt_handover(mr);
+
+	/* Bad Quality */
+	if (meas_rep_n_out_of_m_be(mr->lchan, dqual, 3, 4, 5))
+		return attempt_handover(mr);
+
+	/* Low Level */
+	if (rxlev2dbm(av_rxlev) <= -110)
+		return attempt_handover(mr);
+
+	/* Distance */
+	if (mr->ms_l1.ta > net->handover.max_distance)
+		return attempt_handover(mr);
+
+	/* Power Budget AKA Better Cell */
+	if ((mr->nr % net->handover.pwr_interval) == 0)
+		return attempt_handover(mr);
+
+	return 0;
+
+}
+
+static int ho_dec_sig_cb(unsigned int subsys, unsigned int signal,
+			   void *handler_data, void *signal_data)
+{
+	struct lchan_signal_data *lchan_data;
+
+	if (subsys != SS_LCHAN)
+		return 0;
+
+	lchan_data = signal_data;
+	switch (signal) {
+	case S_LCHAN_MEAS_REP:
+		process_meas_rep(lchan_data->mr);
+		break;
+	}
+
+	return 0;
+}
+
+void on_dso_load_ho_dec(void)
+{
+	osmo_signal_register_handler(SS_LCHAN, ho_dec_sig_cb, NULL);
+}