Fix: Don't use TIMING_ADVANCE_INDEX in assignment messages, if not used

Some MS will leave packet transfer mode, if TAI is given, but no timing
advance control messages are sent on PTCCH. This could results in
permanent loss of larger packets.

1 files changed, 30 insertions, 10 deletions

diff --git a/src/gprs_rlcmac.cpp b/src/gprs_rlcmac.cpp
index b5e0f352..1f981933 100644
--- a/src/gprs_rlcmac.cpp
+++ b/src/gprs_rlcmac.cpp
@@ -1290,7 +1290,7 @@ int write_immediate_assignment(bitvec * dest, uint8_t downlink, uint8_t ra,
 	uint32_t ref_fn, uint8_t ta, uint16_t arfcn, uint8_t ts, uint8_t tsc,
 	uint8_t tfi, uint8_t usf, uint32_t tlli,
 	uint8_t polling, uint32_t fn, uint8_t single_block, uint8_t alpha,
-	uint8_t gamma)
+	uint8_t gamma, int8_t ta_idx)
 {
 	unsigned wp = 0;
 	uint8_t plen;
@@ -1353,8 +1353,12 @@ int write_immediate_assignment(bitvec * dest, uint8_t downlink, uint8_t ra,
 		bitvec_write_field(dest, wp,gamma,5);   // GAMMA power control parameter
 		bitvec_write_field(dest, wp,polling,1);   // Polling Bit
 		bitvec_write_field(dest, wp,!polling,1);   // TA_VALID ???
-		bitvec_write_field(dest, wp,0x1,1);   // switch TIMING_ADVANCE_INDEX = on
-		bitvec_write_field(dest, wp,0x0,4);   // TIMING_ADVANCE_INDEX
+		if (ta_idx < 0) {
+			bitvec_write_field(dest, wp,0x0,1);   // switch TIMING_ADVANCE_INDEX = off
+		} else {
+			bitvec_write_field(dest, wp,0x1,1);   // switch TIMING_ADVANCE_INDEX = on
+			bitvec_write_field(dest, wp,ta_idx,4);   // TIMING_ADVANCE_INDEX
+		}
 		if (polling) {
 			bitvec_write_field(dest, wp,0x1,1);   // TBF Starting TIME present
 			bitvec_write_field(dest, wp,(fn / (26 * 51)) % 32,5); // T1'
@@ -1381,7 +1385,12 @@ int write_immediate_assignment(bitvec * dest, uint8_t downlink, uint8_t ra,
 			} else
 				bitvec_write_field(dest, wp,0x0,1);   // ALPHA = not present
 			bitvec_write_field(dest, wp,gamma,5);   // GAMMA power control parameter
-			bitvec_write_field(dest, wp, 0, 1);    // TIMING_ADVANCE_INDEX_FLAG
+			if (ta_idx < 0) {
+				bitvec_write_field(dest, wp,0x0,1);   // switch TIMING_ADVANCE_INDEX = off
+			} else {
+				bitvec_write_field(dest, wp,0x1,1);   // switch TIMING_ADVANCE_INDEX = on
+				bitvec_write_field(dest, wp,ta_idx,4);   // TIMING_ADVANCE_INDEX
+			}
 			bitvec_write_field(dest, wp, 1, 1);    // TBF_STARTING_TIME_FLAG
 			bitvec_write_field(dest, wp,(fn / (26 * 51)) % 32,5); // T1'
 			bitvec_write_field(dest, wp,fn % 51,6);               // T3
@@ -1402,7 +1411,8 @@ int write_immediate_assignment(bitvec * dest, uint8_t downlink, uint8_t ra,
 			} else
 				bitvec_write_field(dest, wp,0x0,1);   // ALPHA = not present
 			bitvec_write_field(dest, wp,gamma,5);   // GAMMA power control parameter
-			bitvec_write_field(dest, wp, 0, 1);    // TIMING_ADVANCE_INDEX_FLAG
+			/* note: there is no choise for TAI and no starting time */
+			bitvec_write_field(dest, wp, 0, 1);   // switch TIMING_ADVANCE_INDEX = off
 			bitvec_write_field(dest, wp, 0, 1);    // TBF_STARTING_TIME_FLAG
 		}
 	}
@@ -1414,7 +1424,7 @@ int write_immediate_assignment(bitvec * dest, uint8_t downlink, uint8_t ra,
 void write_packet_uplink_assignment(bitvec * dest, uint8_t old_tfi,
 	uint8_t old_downlink, uint32_t tlli, uint8_t use_tlli,
 	struct gprs_rlcmac_tbf *tbf, uint8_t poll, uint8_t alpha,
-	uint8_t gamma)
+	uint8_t gamma, int8_t ta_idx)
 {
 	// TODO We should use our implementation of encode RLC/MAC Control messages.
 	struct gprs_rlcmac_bts *bts = gprs_rlcmac_bts;
@@ -1442,10 +1452,14 @@ void write_packet_uplink_assignment(bitvec * dest, uint8_t old_tfi,
 	bitvec_write_field(dest, wp,0x0,1); // Message escape
 	bitvec_write_field(dest, wp,bts->initial_cs_ul-1, 2); // CHANNEL_CODING_COMMAND 
 	bitvec_write_field(dest, wp,0x1,1); // TLLI_BLOCK_CHANNEL_CODING 
-
 	bitvec_write_field(dest, wp,0x1,1); // switch TIMING_ADVANCE_VALUE = on
 	bitvec_write_field(dest, wp,tbf->ta,6); // TIMING_ADVANCE_VALUE
-	bitvec_write_field(dest, wp,0x0,1); // switch TIMING_ADVANCE_INDEX = off
+	if (ta_idx < 0) {
+		bitvec_write_field(dest, wp,0x0,1);   // switch TIMING_ADVANCE_INDEX = off
+	} else {
+		bitvec_write_field(dest, wp,0x1,1);   // switch TIMING_ADVANCE_INDEX = on
+		bitvec_write_field(dest, wp,ta_idx,4);   // TIMING_ADVANCE_INDEX
+	}
 
 #if 1
 	bitvec_write_field(dest, wp,0x1,1); // Frequency Parameters information elements = present
@@ -1489,7 +1503,7 @@ void write_packet_uplink_assignment(bitvec * dest, uint8_t old_tfi,
 /* generate downlink assignment */
 void write_packet_downlink_assignment(RlcMacDownlink_t * block, uint8_t old_tfi,
 	uint8_t old_downlink, struct gprs_rlcmac_tbf *tbf, uint8_t poll,
-	uint8_t alpha, uint8_t gamma)
+	uint8_t alpha, uint8_t gamma, int8_t ta_idx, uint8_t ta_ts)
 {
 	// Packet downlink assignment TS 44.060 11.2.7
 
@@ -1520,7 +1534,13 @@ void write_packet_downlink_assignment(RlcMacDownlink_t * block, uint8_t old_tfi,
 
 	block->u.Packet_Downlink_Assignment.Packet_Timing_Advance.Exist_TIMING_ADVANCE_VALUE = 0x1; // TIMING_ADVANCE_VALUE = on
 	block->u.Packet_Downlink_Assignment.Packet_Timing_Advance.TIMING_ADVANCE_VALUE       = tbf->ta;  // TIMING_ADVANCE_VALUE
-	block->u.Packet_Downlink_Assignment.Packet_Timing_Advance.Exist_IndexAndtimeSlot     = 0x0; // TIMING_ADVANCE_INDEX = off
+	if (ta_idx < 0) {
+		block->u.Packet_Downlink_Assignment.Packet_Timing_Advance.Exist_IndexAndtimeSlot     = 0x0; // TIMING_ADVANCE_INDEX = off
+	} else {
+		block->u.Packet_Downlink_Assignment.Packet_Timing_Advance.Exist_IndexAndtimeSlot     = 0x1; // TIMING_ADVANCE_INDEX = on
+		block->u.Packet_Downlink_Assignment.Packet_Timing_Advance.TIMING_ADVANCE_INDEX       = ta_idx; // TIMING_ADVANCE_INDEX
+		block->u.Packet_Downlink_Assignment.Packet_Timing_Advance.TIMING_ADVANCE_TIMESLOT_NUMBER = ta_ts; // TIMING_ADVANCE_TS
+	}
 
 	block->u.Packet_Downlink_Assignment.Exist_P0_and_BTS_PWR_CTRL_MODE = 0x0;   // POWER CONTROL = off