Clarify and refactor link quality (C/I) handling

The radio link quality is defined by C/I (Carrier-to-Interference
ratio), which is computed from the training sequence of each
received burst, by comparing the "ideal" training sequence with
the actual (received) one.

Link quality measurements are used by L1SAP to filter out "ghost"
Access Bursts, and by the link quality adaptation algorithms. One
can define minimum link quality values using the VTY interface.

On the VTY interface we expect integer C/I values in centiBels
(cB, 10e-2 B), while the internal structures are using float
values in deciBels (dB, 10e-1 B). Some PHYs (sysmo, octphy,
oc2g, and litecell15) expose C/I measurements in deciBels,
while on the L1SAP interface we finally send then in centiBels.

Let's avoid this confusion and stick to a single format, that
will be used by the internal logic of OsmoBTS - integer values
(int16_t) in centiBels. This will give us the range of:

  -32768  .. 32767  centiBels, or
  -3276.8 .. 3276.7 deciBels,

which is certainly sufficient.

Change-Id: If624d6fdc0270e6813af8700d95f1345903c8a01

7 files changed, 16 insertions, 16 deletions

diff --git a/src/common/bts.c b/src/common/bts.c
index f582ebd1..5c415e86 100644
--- a/src/common/bts.c
+++ b/src/common/bts.c
@@ -51,8 +51,8 @@
 #include <osmo-bts/dtx_dl_amr_fsm.h>
 #include <osmo-bts/cbch.h>
 
-#define MIN_QUAL_RACH    5.0f   /* at least  5 dB C/I */
-#define MIN_QUAL_NORM   -0.5f   /* at least -1 dB C/I */
+#define MIN_QUAL_RACH	 50 /* minimum link quality (in centiBels) for Access Bursts */
+#define MIN_QUAL_NORM	 -5 /* minimum link quality (in centiBels) for Normal Bursts */
 
 static void bts_update_agch_max_queue_length(struct gsm_bts *bts);
 
diff --git a/src/common/l1sap.c b/src/common/l1sap.c
index b730b853..79af8e21 100644
--- a/src/common/l1sap.c
+++ b/src/common/l1sap.c
@@ -1218,7 +1218,7 @@ static int l1sap_tch_ind(struct gsm_bts_trx *trx, struct osmo_phsap_prim *l1sap,
 	 * the content is not available due to decoding issues. Content not
 	 * available is expected as empty payload. We also check if quality is
 	 * good enough. */
-	if (msg->len && tch_ind->lqual_cb / 10 >= bts->min_qual_norm) {
+	if (msg->len && tch_ind->lqual_cb >= bts->min_qual_norm) {
 		/* hand msg to RTP code for transmission */
 		if (lchan->abis_ip.rtp_socket)
 			osmo_rtp_send_frame_ext(lchan->abis_ip.rtp_socket,
diff --git a/src/common/pcu_sock.c b/src/common/pcu_sock.c
index 1d9fa72f..36cc6edf 100644
--- a/src/common/pcu_sock.c
+++ b/src/common/pcu_sock.c
@@ -330,8 +330,8 @@ int pcu_tx_data_ind(struct gsm_bts_trx_ts *ts, uint8_t sapi, uint32_t fn,
 	LOGP(DPCU, LOGL_DEBUG, "Sending data indication: sapi=%s arfcn=%d block=%d data=%s\n",
 	     sapi_string[sapi], arfcn, block_nr, osmo_hexdump(data, len));
 
-	if (lqual / 10 < bts->min_qual_norm) {
-		LOGP(DPCU, LOGL_DEBUG, "Link quality %"PRId16" is below threshold %f, dropping packet\n",
+	if (lqual < bts->min_qual_norm) {
+		LOGP(DPCU, LOGL_DEBUG, "Link quality %"PRId16" is below threshold %d, dropping packet\n",
 			lqual, bts->min_qual_norm);
 		return 0;
 	}
diff --git a/src/common/vty.c b/src/common/vty.c
index f4fc1815..e4f5a16c 100644
--- a/src/common/vty.c
+++ b/src/common/vty.c
@@ -300,9 +300,9 @@ static void config_write_bts_single(struct vty *vty, struct gsm_bts *bts)
 		sapi_buf = osmo_str_tolower(get_value_string(gsmtap_sapi_names, GSMTAP_CHANNEL_ACCH));
 		vty_out(vty, " gsmtap-sapi %s%s", sapi_buf, VTY_NEWLINE);
 	}
-	vty_out(vty, " min-qual-rach %.0f%s", bts->min_qual_rach * 10.0f,
+	vty_out(vty, " min-qual-rach %d%s", bts->min_qual_rach,
 		VTY_NEWLINE);
-	vty_out(vty, " min-qual-norm %.0f%s", bts->min_qual_norm * 10.0f,
+	vty_out(vty, " min-qual-norm %d%s", bts->min_qual_norm,
 		VTY_NEWLINE);
 	vty_out(vty, " max-ber10k-rach %u%s", bts->max_ber10k_rach,
 		VTY_NEWLINE);
@@ -618,24 +618,24 @@ DEFUN(cfg_bts_ul_power_target, cfg_bts_ul_power_target_cmd,
 
 DEFUN(cfg_bts_min_qual_rach, cfg_bts_min_qual_rach_cmd,
 	"min-qual-rach <-100-100>",
-	"Set the minimum quality level of RACH burst to be accpeted\n"
-	"C/I level in tenth of dB\n")
+	"Set the minimum link quality level of Access Bursts to be accepted\n"
+	"C/I (Carrier-to-Interference) ratio in centiBels (10e-2 B or 10e-1 dB)\n")
 {
 	struct gsm_bts *bts = vty->index;
 
-	bts->min_qual_rach = strtof(argv[0], NULL) / 10.0f;
+	bts->min_qual_rach = atoi(argv[0]);
 
 	return CMD_SUCCESS;
 }
 
 DEFUN(cfg_bts_min_qual_norm, cfg_bts_min_qual_norm_cmd,
 	"min-qual-norm <-100-100>",
-	"Set the minimum quality level of normal burst to be accpeted\n"
-	"C/I level in tenth of dB\n")
+	"Set the minimum link quality level of Normal Bursts to be accepted\n"
+	"C/I (Carrier-to-Interference) ratio in centiBels (10e-2 B or 10e-1 dB)\n")
 {
 	struct gsm_bts *bts = vty->index;
 
-	bts->min_qual_norm = strtof(argv[0], NULL) / 10.0f;
+	bts->min_qual_norm = atoi(argv[0]);
 
 	return CMD_SUCCESS;
 }
diff --git a/src/osmo-bts-litecell15/l1_if.c b/src/osmo-bts-litecell15/l1_if.c
index 3710fa80..77b72bd0 100644
--- a/src/osmo-bts-litecell15/l1_if.c
+++ b/src/osmo-bts-litecell15/l1_if.c
@@ -1004,7 +1004,7 @@ static int handle_ph_ra_ind(struct lc15l1_hdl *fl1, GsmL1_PhRaInd_t *ra_ind,
 	struct ph_rach_ind_param rach_ind_param;
 
 	/* FIXME: this should be deprecated/obsoleted as it bypasses rach.busy counting */
-	if (ra_ind->measParam.fLinkQuality < bts->min_qual_rach) {
+	if (ra_ind->measParam.fLinkQuality * 10 < bts->min_qual_rach) {
 		msgb_free(l1p_msg);
 		return 0;
 	}
diff --git a/src/osmo-bts-oc2g/l1_if.c b/src/osmo-bts-oc2g/l1_if.c
index d9c8da0d..9affc89b 100644
--- a/src/osmo-bts-oc2g/l1_if.c
+++ b/src/osmo-bts-oc2g/l1_if.c
@@ -1060,7 +1060,7 @@ static int handle_ph_ra_ind(struct oc2gl1_hdl *fl1, GsmL1_PhRaInd_t *ra_ind,
 	struct ph_rach_ind_param rach_ind_param;
 
 	/* FIXME: this should be deprecated/obsoleted as it bypasses rach.busy counting */
-	if (ra_ind->measParam.fLinkQuality < bts->min_qual_rach) {
+	if (ra_ind->measParam.fLinkQuality * 10 < bts->min_qual_rach) {
 		msgb_free(l1p_msg);
 		return 0;
 	}
diff --git a/src/osmo-bts-sysmo/l1_if.c b/src/osmo-bts-sysmo/l1_if.c
index c431e49e..58fc24ef 100644
--- a/src/osmo-bts-sysmo/l1_if.c
+++ b/src/osmo-bts-sysmo/l1_if.c
@@ -998,7 +998,7 @@ static int handle_ph_ra_ind(struct femtol1_hdl *fl1, GsmL1_PhRaInd_t *ra_ind,
 	struct ph_rach_ind_param rach_ind_param;
 
 	/* FIXME: this should be deprecated/obsoleted as it bypasses rach.busy counting */
-	if (ra_ind->measParam.fLinkQuality < bts->min_qual_rach) {
+	if (ra_ind->measParam.fLinkQuality * 10 < bts->min_qual_rach) {
 		msgb_free(l1p_msg);
 		return 0;
 	}