dyn PDCH: Add algorithm to defragment shared TCH/F+PDCH channelsjolly/dyn_pdch

This algorithm ensures that gaps between active TCH/F+PDCH channels are
removed, by assigning active connections to standard TCH/F or by assigning
them to consecutive TCH/F+PDCH channels.

1 files changed, 183 insertions, 0 deletions

diff --git a/openbsc/src/libbsc/pdch_defrag.c b/openbsc/src/libbsc/pdch_defrag.c
new file mode 100644
index 000000000..5f075f65d
--- /dev/null
+++ b/openbsc/src/libbsc/pdch_defrag.c
@@ -0,0 +1,183 @@
+/* (C) 2013 by Andreas Eversberg <andreas@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 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 <openbsc/debug.h>
+#include <openbsc/gsm_data.h>
+#include <openbsc/handover.h>
+#include <openbsc/pdch_defrag.h>
+#include <openbsc/chan_alloc.h>
+
+static struct gsm_lchan *find_shared_forward(struct gsm_bts *bts)
+{
+	struct gsm_bts_trx *trx;
+	struct gsm_lchan *lc;
+	int j;
+
+	llist_for_each_entry(trx, &bts->trx_list, list) {
+		for (j = 0; j < 8; j++) {
+			/* find first TCH/F+PDCH */
+			if (trx->ts[j].pchan == GSM_PCHAN_TCH_F_PDCH) {
+				lc = &trx->ts[j].lchan[0];
+				if (lc->state == LCHAN_S_ACTIVE)
+					return lc;
+			}
+		}
+	}
+
+	return NULL;
+}
+
+static struct gsm_lchan *find_shared_reverse(struct gsm_bts *bts)
+{
+	struct gsm_bts_trx *trx;
+	struct gsm_lchan *lc;
+	int j;
+
+	llist_for_each_entry_reverse(trx, &bts->trx_list, list) {
+		for (j = 7; j >= 0; j--) {
+			/* find last TCH/F+PDCH */
+			if (trx->ts[j].pchan == GSM_PCHAN_TCH_F_PDCH) {
+				lc = &trx->ts[j].lchan[0];
+				if (lc->state == LCHAN_S_ACTIVE)
+					return lc;
+			}
+		}
+	}
+
+	return NULL;
+}
+
+static void debug_bts_trx_ts(struct gsm_bts_trx_ts *ts)
+{
+	LOGPC(DHODEC, LOGL_DEBUG, " (BTS %u, TRX %u, TS %u)\n",
+		ts->trx->bts->nr, ts->trx->nr, ts->nr);
+}
+
+/* Try to move a TCH/F+PDCH candidate to maintain as much free and consecutive
+ * GSM_PCHAN_TCH_F_PDCH slots as possible.
+ *
+ * This algorithm is triggered whenever a channel has been released.
+ *
+ * The last (highest TRX/TS number) and active TCH/F+PDCH is searched. If there
+ * is a TCH/F or a free TCH/F+PDCH on a lower TRX/TS number, assignment is
+ * triggered. (When allocation order is reversed, this algorithm handles TRX/TS
+ * numbers in reversed order also.
+ *
+ * This algorithm ensures that gaps between active TCH/F+PDCH channels are
+ * removed, by assigning active connections to standard TCH/F or by assigning
+ * them to consecutive TCH/F+PDCH channels.
+ */
+void do_pdch_defrag(struct gsm_bts *bts)
+{
+	struct gsm_lchan *old_lchan = NULL, *new_lchan;
+	int rc;
+
+	/* search TCH/F+PDCH in reverse order of allocation */
+	if (bts->chan_alloc_reverse) {
+		/* search from first to last TRX/TS */
+		old_lchan = find_shared_forward(bts);
+	} else {
+		/* search from last to first TRX/TS */
+		old_lchan = find_shared_reverse(bts);
+	}
+
+	/* if there is no candidate on GSM_PCHAN_TCH_F_PDCH, we are done */
+	if (!old_lchan)
+		return;
+
+	LOGP(DHODEC, LOGL_DEBUG, "A shared TCH/F+PDCH is in use, check if we "
+		"can move connection.");
+	debug_bts_trx_ts(old_lchan->ts);
+
+	/* allocate new lchan */
+	new_lchan = lchan_alloc(bts, GSM_LCHAN_TCH_F, 0);
+	/* no free destination for candidate */
+	if (!new_lchan) {
+		LOGP(DHODEC, LOGL_DEBUG, "-> Cannot move, no other TCH/F "
+			"available.\n");
+		return;
+	}
+
+	/* if new TS is also a GSM_PCHAN_TCH_F_PDCH */
+	if (new_lchan->ts->pchan == GSM_PCHAN_TCH_F_PDCH) {
+		LOGP(DHODEC, LOGL_DEBUG, "-> New channel for candidate is also "
+			"a TCH/F+PDCH.");
+		debug_bts_trx_ts(new_lchan->ts);
+		/* be sure to move down (or up at reverse allocation) */
+		if (bts->chan_alloc_reverse) {
+			/* new TS is lower */
+			if (new_lchan->ts->trx->nr < old_lchan->ts->trx->nr) {
+				LOGP(DHODEC, LOGL_DEBUG, "-> Move does not "
+					"lower fragmentation, new TRX has "
+					"lower number.\n");
+				goto free_lchan;
+			}
+			if (new_lchan->ts->trx->nr == old_lchan->ts->trx->nr
+			 && new_lchan->ts->nr < old_lchan->ts->nr) {
+				LOGP(DHODEC, LOGL_DEBUG, "-> Move does not "
+					"lower fragmentation, new TS has "
+					"lower number.\n");
+				goto free_lchan;
+			}
+		} else {
+			/* new TS is higher */
+			if (new_lchan->ts->trx->nr > old_lchan->ts->trx->nr) {
+				goto free_lchan;
+				LOGP(DHODEC, LOGL_DEBUG, "-> Move does not "
+					"lower fragmentation, new TRX has "
+					"higher number.\n");
+			}
+			if (new_lchan->ts->trx->nr == old_lchan->ts->trx->nr
+			 && new_lchan->ts->nr > old_lchan->ts->nr) {
+				LOGP(DHODEC, LOGL_DEBUG, "-> Move does not "
+					"lower fragmentation, new TS has "
+					"higher number.\n");
+				goto free_lchan;
+			}
+		}
+	} else {
+		LOGP(DHODEC, LOGL_DEBUG, "-> New channel for candidate is a "
+			"TCH/F.");
+		debug_bts_trx_ts(new_lchan->ts);
+	}
+
+	rc = bsc_handover_start(old_lchan, new_lchan, new_lchan->ts->trx->bts,
+		1);
+	if (rc) {
+		LOGP(DHODEC, LOGL_NOTICE, "Cannot trigger assignment to "
+			"defragment TCH/F+PDCH slots.\n");
+	} else {
+		LOGP(DHODEC, LOGL_NOTICE, "Triggered assignment to defragment "
+			"TCH/F+PDCH slots.\n");
+	}
+
+	/* We do not need to check, if assignment is ongoing or if it fails,
+	 * because in both cases a channel is freed, so this defragmentation
+	 * is triggered again.
+	 */
+
+	return;
+
+free_lchan:
+	lchan_free(new_lchan);
+}
+