Change in osmo-pcu[master]: Update MCS selection for retransmission

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Max gerrit-no-reply at lists.osmocom.org
Mon Mar 25 16:09:01 UTC 2019 

Max has uploaded this change for review. ( https://gerrit.osmocom.org/13402


Change subject: Update MCS selection for retransmission
......................................................................

Update MCS selection for retransmission

In 3GPP TS 44.060 the selection of MCS for retransmissions is defined as
separate tables (8.1.1.1 and 8.1.1.2) depending on the value of
resegmentation bit (which is opposite to the way EGPRS_ARQ are defined
in the source code). Let's follow the same idea and explicitly check for
resegmentation bit value and use separate tables. This also makes it
easier to add proper support for special cases (MCS-6-9 and MCS-5-7) and
padding in future independently for different ARQ types. The code is
also moved to c to avoid unnecessary conversions to and from cpp class.

Change-Id: Ia73baeefee7a58834f0fc50e3b8bf8d5e3eb7815
---
M src/coding_scheme.c
M src/coding_scheme.h
M src/gprs_coding_scheme.cpp
M src/gprs_coding_scheme.h
M src/tbf_dl.cpp
5 files changed, 40 insertions(+), 50 deletions(-)



  git pull ssh://gerrit.osmocom.org:29418/osmo-pcu refs/changes/02/13402/1

diff --git a/src/coding_scheme.c b/src/coding_scheme.c
index a4ae882..48a74cd 100644
--- a/src/coding_scheme.c
+++ b/src/coding_scheme.c
@@ -127,3 +127,39 @@
 const char *mode_name(enum mcs_kind val) {
 	return get_value_string(mode_names, val);
 }
+
+/* FIXME: take into account padding and special cases of commanded MCS (MCS-6-9 and MCS-5-7) */
+enum CodingScheme get_retx_mcs(enum CodingScheme initial_mcs, enum CodingScheme demanded_mcs, bool resegment_bit)
+{
+	OSMO_ASSERT(mcs_is_edge(initial_mcs));
+	OSMO_ASSERT(mcs_is_edge(demanded_mcs));
+	OSMO_ASSERT(NUM_SCHEMES - MCS1 == 9);
+
+	if (resegment_bit) { /* 3GPP TS 44.060 Table 8.1.1.1, reflected over antidiagonal */
+		enum CodingScheme egprs_reseg[NUM_SCHEMES - MCS1][NUM_SCHEMES - MCS1] = {
+			{ MCS1, MCS1, MCS1, MCS1, MCS1, MCS1, MCS1, MCS1, MCS1 },
+			{ MCS2, MCS2, MCS2, MCS2, MCS2, MCS2, MCS2, MCS2, MCS2 },
+			{ MCS3, MCS3, MCS3, MCS3, MCS3, MCS3, MCS3, MCS3, MCS3 },
+			{ MCS1, MCS1, MCS1, MCS4, MCS4, MCS4, MCS4, MCS4, MCS4 },
+			{ MCS2, MCS2, MCS2, MCS2, MCS5, MCS5, MCS7, MCS7, MCS7 },
+			{ MCS3, MCS3, MCS3, MCS3, MCS3, MCS6, MCS6, MCS6, MCS9 },
+			{ MCS2, MCS2, MCS2, MCS2, MCS5, MCS5, MCS7, MCS7, MCS7 },
+			{ MCS3, MCS3, MCS3, MCS3, MCS3, MCS6, MCS6, MCS8, MCS8 },
+			{ MCS3, MCS3, MCS3, MCS3, MCS3, MCS6, MCS6, MCS6, MCS9 },
+		};
+		return egprs_reseg[mcs_chan_code(initial_mcs)][mcs_chan_code(demanded_mcs)];
+	} else { /* 3GPP TS 44.060 Table 8.1.1.2, reflected over antidiagonal */
+		enum CodingScheme egprs_no_reseg[NUM_SCHEMES - MCS1][NUM_SCHEMES - MCS1] = {
+			{ MCS1, MCS1, MCS1, MCS1, MCS1, MCS1, MCS1, MCS1, MCS1 },
+			{ MCS2, MCS2, MCS2, MCS2, MCS2, MCS2, MCS2, MCS2, MCS2 },
+			{ MCS3, MCS3, MCS3, MCS3, MCS3, MCS3, MCS3, MCS3, MCS3 },
+			{ MCS4, MCS4, MCS4, MCS4, MCS4, MCS4, MCS4, MCS4, MCS4 },
+			{ MCS5, MCS5, MCS5, MCS5, MCS5, MCS5, MCS7, MCS7, MCS7 },
+			{ MCS6, MCS6, MCS6, MCS6, MCS6, MCS6, MCS6, MCS6, MCS9 },
+			{ MCS5, MCS5, MCS5, MCS5, MCS5, MCS5, MCS7, MCS7, MCS7 },
+			{ MCS6, MCS6, MCS6, MCS6, MCS6, MCS6, MCS6, MCS8, MCS8 },
+			{ MCS6, MCS6, MCS6, MCS6, MCS6, MCS6, MCS6, MCS6, MCS9 },
+		};
+		return egprs_no_reseg[mcs_chan_code(initial_mcs)][mcs_chan_code(demanded_mcs)];
+	}
+}
diff --git a/src/coding_scheme.h b/src/coding_scheme.h
index aac4bba..f93a4a2 100644
--- a/src/coding_scheme.h
+++ b/src/coding_scheme.h
@@ -32,6 +32,7 @@
 
 extern const struct value_string mcs_names[];
 const char *mcs_name(enum CodingScheme val);
+enum CodingScheme get_retx_mcs(enum CodingScheme initial_mcs, enum CodingScheme demanded_mcs, bool resegment_bit);
 
 bool mcs_is_gprs(enum CodingScheme cs);
 bool mcs_is_edge(enum CodingScheme cs);
diff --git a/src/gprs_coding_scheme.cpp b/src/gprs_coding_scheme.cpp
index a149f81..0c22670 100644
--- a/src/gprs_coding_scheme.cpp
+++ b/src/gprs_coding_scheme.cpp
@@ -21,41 +21,6 @@
 
 #include "gprs_coding_scheme.h"
 
-#define MAX_NUM_ARQ           2     /* max. number of ARQ */
-#define MAX_NUM_MCS           9     /* max. number of MCS */
-
-/*
- * 44.060 Table 8.1.1.1 and Table 8.1.1.2
- * It has 3 level indexing. 0th level is ARQ type
- * 1st level is Original MCS( index 0 corresponds to MCS1 and so on)
- * 2nd level is MS MCS (index 0 corresponds to MCS1 and so on)
- */
-static enum CodingScheme egprs_mcs_retx_tbl[MAX_NUM_ARQ]
-			[MAX_NUM_MCS][MAX_NUM_MCS] = {
-		{
-			{MCS1, MCS1, MCS1, MCS1, MCS1, MCS1, MCS1, MCS1, MCS1},
-			{MCS2, MCS2, MCS2, MCS2, MCS2, MCS2, MCS2, MCS2, MCS2},
-			{MCS3, MCS3, MCS3, MCS3, MCS3, MCS3, MCS3, MCS3, MCS3},
-			{MCS1, MCS1, MCS1, MCS4, MCS4, MCS4, MCS4, MCS4, MCS4},
-			{MCS2, MCS2, MCS2, MCS2, MCS5, MCS5, MCS7, MCS7, MCS7},
-			{MCS3, MCS3, MCS3, MCS3, MCS3, MCS6, MCS6, MCS6, MCS9},
-			{MCS2, MCS2, MCS2, MCS2, MCS5, MCS5, MCS7, MCS7, MCS7},
-			{MCS3, MCS3, MCS3, MCS3, MCS3, MCS6, MCS6, MCS8, MCS8},
-			{MCS3, MCS3, MCS3, MCS3, MCS3, MCS6, MCS6, MCS6, MCS9}
-		},
-		{
-			{MCS1, MCS1, MCS1, MCS1, MCS1, MCS1, MCS1, MCS1, MCS1},
-			{MCS2, MCS2, MCS2, MCS2, MCS2, MCS2, MCS2, MCS2, MCS2},
-			{MCS3, MCS3, MCS3, MCS3, MCS3, MCS3, MCS3, MCS3, MCS3},
-			{MCS4, MCS4, MCS4, MCS4, MCS4, MCS4, MCS4, MCS4, MCS4},
-			{MCS5, MCS5, MCS5, MCS5, MCS5, MCS5, MCS7, MCS7, MCS7},
-			{MCS6, MCS6, MCS6, MCS6, MCS6, MCS6, MCS6, MCS6, MCS9},
-			{MCS5, MCS5, MCS5, MCS5, MCS5, MCS5, MCS7, MCS7, MCS7},
-			{MCS6, MCS6, MCS6, MCS6, MCS6, MCS6, MCS6, MCS8, MCS8},
-			{MCS6, MCS6, MCS6, MCS6, MCS6, MCS6, MCS6, MCS6, MCS9}
-		}
-	};
-
 enum Family {
 	FAMILY_INVALID,
 	FAMILY_A,
@@ -63,13 +28,6 @@
 	FAMILY_C,
 };
 
-CodingScheme GprsCodingScheme::get_retx_mcs(const GprsCodingScheme mcs,
-							const GprsCodingScheme demanded_mcs,
-							const unsigned arq_type)
-{
-	return egprs_mcs_retx_tbl[arq_type][mcs_chan_code(mcs)][mcs_chan_code(demanded_mcs)];
-}
-
 static struct {
 	struct {
 		uint8_t bytes;
diff --git a/src/gprs_coding_scheme.h b/src/gprs_coding_scheme.h
index d5604fb..c31f58f 100644
--- a/src/gprs_coding_scheme.h
+++ b/src/gprs_coding_scheme.h
@@ -73,9 +73,6 @@
 	static GprsCodingScheme getGprsByNum(unsigned num);
 	static GprsCodingScheme getEgprsByNum(unsigned num);
 
-	static CodingScheme get_retx_mcs(const GprsCodingScheme mcs,
-				const GprsCodingScheme retx_mcs,
-				const unsigned arq_type);
 private:
 	GprsCodingScheme(int s); /* fail on use */
 	GprsCodingScheme& operator =(int s); /* fail on use */
diff --git a/src/tbf_dl.cpp b/src/tbf_dl.cpp
index 08df05a..c97436a 100644
--- a/src/tbf_dl.cpp
+++ b/src/tbf_dl.cpp
@@ -378,11 +378,9 @@
 
 		if (is_egprs_enabled()) {
 			/* Table 8.1.1.2 and Table 8.1.1.1 of 44.060 */
-			m_rlc.block(bsn)->cs_current_trans =
-				GprsCodingScheme::get_retx_mcs(
-					m_rlc.block(bsn)->cs_init,
-					ms()->current_cs_dl(),
-					bts->bts_data()->dl_arq_type);
+			m_rlc.block(bsn)->cs_current_trans = get_retx_mcs(m_rlc.block(bsn)->cs_init,
+									  ms()->current_cs_dl(),
+									  !bts->bts_data()->dl_arq_type);
 
 			LOGPTBFDL(this, LOGL_DEBUG,
 				  "initial_cs_dl(%s) last_mcs(%s) demanded_mcs(%s) cs_trans(%s) arq_type(%d) bsn(%d)\n",

-- 
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Gerrit-Project: osmo-pcu
Gerrit-Branch: master
Gerrit-MessageType: newchange
Gerrit-Change-Id: Ia73baeefee7a58834f0fc50e3b8bf8d5e3eb7815
Gerrit-Change-Number: 13402
Gerrit-PatchSet: 1
Gerrit-Owner: Max <msuraev at sysmocom.de>
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