[layer23/mobile] Improvement and fixes of idle mode process

This patch introduces cell re-relection. When camping on a cell, it
scanns neighbour cells. If a 'better' cell is found, the cell is selected.
If the cell is in a different location area, a location upating is
performed under certain conditions.

The 'better' cell depends on various informations that are broadcasted on
the BCCH of a neihbour cell and of course the RX level. Most operators
don't set these informations, so the 'better' cell depend on a better
RX level for the same location area, or a much better RX level (6 dBm)
at a different location area.

There were many issues at the idle mode process that has been fixed.
Expecially when moving, the state machines got stuck, so no more cell search
was possible, or no further calls / location updating was possible.

In order to see the process of cell selection, enter the VTY interface and
enable the network monitor:

enable
monitor network 1  (where '1' is the instance of the MS)

In order to see the current state of the processes, enter:

show ms

1 files changed, 48 insertions, 10 deletions

diff --git a/src/host/layer23/src/mobile/gsm48_rr.c b/src/host/layer23/src/mobile/gsm48_rr.c
index d199aacb..9d014d63 100644
--- a/src/host/layer23/src/mobile/gsm48_rr.c
+++ b/src/host/layer23/src/mobile/gsm48_rr.c
@@ -585,14 +585,16 @@ static void timeout_rr_meas(void *arg)
 	uint8_t ch_type, ch_subch, ch_ts;
 	char text[256];
 
-	if (!cs->selected) {
+	/* don't monitor if no cell is selcted or if we scan neighbour cells */
+	if (!cs->selected || cs->neighbour) {
+		sprintf(text, "MON: not camping on serving cell");
 		goto restart;
 	} else if (!meas->frames) {
 		sprintf(text, "MON: no cell info");
 	} else {
-		rxlev = meas->rxlev / meas->frames;
-		berr = meas->berr / meas->frames;
-		snr = meas->snr / meas->frames;
+		rxlev = (meas->rxlev + meas->frames / 2) / meas->frames;
+		berr = (meas->berr + meas->frames / 2) / meas->frames;
+		snr = (meas->snr + meas->frames / 2) / meas->frames;
 		sprintf(text, "MON: f=%d lev=%s snr=%2d ber=%3d "
 			"LAI=%s %s %04x ID=%04x", cs->sel_arfcn,
 			gsm_print_rxlev(rxlev), berr, snr, 
@@ -608,7 +610,8 @@ static void timeout_rr_meas(void *arg)
 			if (ch_type == RSL_CHAN_SDCCH8_ACCH
 			 || ch_type == RSL_CHAN_SDCCH4_ACCH)
 				sprintf(text + strlen(text), "/%d", ch_subch);
-		}
+		} else
+			gsm322_meas(rr->ms, rxlev);
 	}
 	LOGP(DRR, LOGL_INFO, "%s\n", text);
 	if (rr->monitor)
@@ -1256,6 +1259,14 @@ static int gsm48_rr_chan_req(struct osmocom_ms *ms, int cause, int paging)
 	 	return -EINVAL;
 	}
 
+	/* ignore channel request while not camping on a cell */
+	if (!cs->selected) {
+		LOGP(DRR, LOGL_INFO, "Channel request rejected, we did not "
+			"properly select the serving cell.\n");
+
+		goto rel_ind;
+	}
+
 	/* tell cell selection process to leave idle mode
 	 * NOTE: this must be sent unbuffered, because the state may not
 	 * change until idle mode is left
@@ -1415,6 +1426,7 @@ static int gsm48_rr_chan_req(struct osmocom_ms *ms, int cause, int paging)
 		undefined:
 		LOGP(DSUM, LOGL_INFO, "Requesting channel failed\n");
 
+rel_ind:
 		nmsg = gsm48_rr_msgb_alloc(GSM48_RR_REL_IND);
 		if (!nmsg)
 			return -ENOMEM;
@@ -1683,6 +1695,12 @@ static int gsm48_new_sysinfo(struct osmocom_ms *ms, uint8_t type)
 	em->sysinfo = type;
 	gsm322_cs_sendmsg(ms, nmsg);
 
+	/* if not camping, we don't care about SI */
+	if (ms->cellsel.neighbour
+	 || (ms->cellsel.state != GSM322_C3_CAMPED_NORMALLY
+	  && ms->cellsel.state != GSM322_C7_CAMPED_ANY_CELL))
+		return 0;
+
 	/* send timer info to location update process */
 	nmsg = gsm48_mmevent_msgb_alloc(GSM48_MM_EVENT_SYSINFO);
 	if (!nmsg)
@@ -2078,7 +2096,8 @@ static int gsm48_rr_rx_pag_req_1(struct osmocom_ms *ms, struct msgb *msg)
 	/* 3.3.1.1.2: ignore paging while not camping on a cell */
 	if (rr->state != GSM48_RR_ST_IDLE || !cs->selected
 	 || (cs->state != GSM322_C3_CAMPED_NORMALLY
-	  && cs->state != GSM322_C7_CAMPED_ANY_CELL)) {
+	  && cs->state != GSM322_C7_CAMPED_ANY_CELL)
+	 || cs->neighbour) {
 		LOGP(DRR, LOGL_INFO, "PAGING ignored, we are not camping.\n");
 
 		return 0;
@@ -2130,7 +2149,8 @@ static int gsm48_rr_rx_pag_req_2(struct osmocom_ms *ms, struct msgb *msg)
 	/* 3.3.1.1.2: ignore paging while not camping on a cell */
 	if (rr->state != GSM48_RR_ST_IDLE || !cs->selected
 	 || (cs->state != GSM322_C3_CAMPED_NORMALLY
-	  && cs->state != GSM322_C7_CAMPED_ANY_CELL)) {
+	  && cs->state != GSM322_C7_CAMPED_ANY_CELL)
+	 || cs->neighbour) {
 		LOGP(DRR, LOGL_INFO, "PAGING ignored, we are not camping.\n");
 
 		return 0;
@@ -2195,7 +2215,8 @@ static int gsm48_rr_rx_pag_req_3(struct osmocom_ms *ms, struct msgb *msg)
 	/* 3.3.1.1.2: ignore paging while not camping on a cell */
 	if (rr->state != GSM48_RR_ST_IDLE || !cs->selected
 	 || (cs->state != GSM322_C3_CAMPED_NORMALLY
-	  && cs->state != GSM322_C7_CAMPED_ANY_CELL)) {
+	  && cs->state != GSM322_C7_CAMPED_ANY_CELL)
+	 || cs->neighbour) {
 		LOGP(DRR, LOGL_INFO, "PAGING ignored, we are not camping.\n");
 
 		return 0;
@@ -2312,6 +2333,14 @@ static int gsm48_rr_rx_imm_ass(struct osmocom_ms *ms, struct msgb *msg)
 	uint8_t *st, st_len;
 #endif
 
+	/* ignore imm.ass. while not camping on a cell */
+	if (!cs->selected || cs->neighbour || !s) {
+		LOGP(DRR, LOGL_INFO, "IMMEDIATED ASSGINMENT ignored, we are "
+			"have not proper selected the serving cell.\n");
+
+		return 0;
+	}
+
 	memset(&cd, 0, sizeof(cd));
 	cd.ind_tx_power = rr->cd_now.ind_tx_power;
 
@@ -2412,6 +2441,14 @@ static int gsm48_rr_rx_imm_ass_ext(struct osmocom_ms *ms, struct msgb *msg)
 	uint8_t *st, st_len;
 #endif
 
+	/* ignore imm.ass.ext while not camping on a cell */
+	if (!cs->selected || cs->neighbour || !s) {
+		LOGP(DRR, LOGL_INFO, "IMMEDIATED ASSGINMENT ignored, we are "
+			"have not proper selected the serving cell.\n");
+
+		return 0;
+	}
+
 	memset(&cd1, 0, sizeof(cd1));
 	cd1.ind_tx_power = rr->cd_now.ind_tx_power;
 	memset(&cd2, 0, sizeof(cd2));
@@ -2651,7 +2688,8 @@ static int gsm48_rr_tx_meas_rep(struct osmocom_ms *ms)
 	/* check for valid measurements, any frame must exist */
 	if (meas->frames) {
 		meas_valid = 1;
-		serv_rxlev_full = serv_rxlev_sub = meas->rxlev / meas->frames;
+		serv_rxlev_full = serv_rxlev_sub =
+			(meas->rxlev + (meas->frames / 2)) / meas->frames;
 		serv_rxqual_full = serv_rxqual_sub = 0; // FIXME
 	}
 
@@ -4335,7 +4373,7 @@ static int gsm48_rr_est_req(struct osmocom_ms *ms, struct msgb *msg)
 {
 	struct gsm48_rrlayer *rr = &ms->rrlayer;
 	struct gsm322_cellsel *cs = &ms->cellsel;
-	struct gsm48_sysinfo *s = cs->si;
+	struct gsm48_sysinfo *s = &cs->sel_si;
 	struct gsm_subscriber *subscr = &ms->subscr;
 	struct gsm48_rr_hdr *rrh = (struct gsm48_rr_hdr *) msg->data;
 	struct gsm48_hdr *gh = msgb_l3(msg);