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authorJacob Erlbeck <jerlbeck@sysmocom.de>2015-06-12 10:52:34 +0200
committerJacob Erlbeck <jerlbeck@sysmocom.de>2015-06-22 10:39:06 +0200
commit70b96aa232bd9784a94247bf7b193cb2147ada9d (patch)
treed5abe0611be1107b6cabe58d8ba7195f5acda6d3 /src/bts.h
parent07eb655244bd973a9bdf69ef958ee06cf867a0bb (diff)
ms: Reduce DL CS level if only a few LLC bytes are left
If just a few bytes are left to send to the MS, it makes sense to reduce the coding scheme level to increase the throughput. This has been shown by Chen and Goodman in their paper "Theoretical Analysis of GPRS Throughput and Delay". See their throughput over C/I measurement graphs (figures 4 and 5 in the paper) for details. This commit implements a simplified CS downgrade feature for the downlink. The coding scheme will be downgraded if there are only a few octets are left to be send over the TBF (see the downgrade-threshold command below) and the NACK rate is not low (the CS will not get degraded on a high quality RF link). As an exception, CS-3 will be degraded to CS-1, since CS-2 does not improve the throughput in general when a few small packets are sent and the signal fades slowly (see Chen/Goodman). The following VTY command is added to the config-pcu node: - cs downgrade-threshold <1-10000> - cs no downgrade-threshold to set the threshold of the number of remaining bytes to be RLC/MAC encoded. The CS will only be reduced, if the number is below the threshold. The 'no' command disables this feature completely. The default value is 200 octets. Sponsored-by: On-Waves ehf
Diffstat (limited to 'src/bts.h')
-rw-r--r--src/bts.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/src/bts.h b/src/bts.h
index 0c5b47a..2ed5030 100644
--- a/src/bts.h
+++ b/src/bts.h
@@ -149,6 +149,7 @@ struct gprs_rlcmac_bts {
uint8_t cs_adj_upper_limit;
uint8_t cs_adj_lower_limit;
struct {int16_t low; int16_t high;} cs_lqual_ranges[4];
+ uint16_t cs_downgrade_threshold; /* downgrade if less packets left (DL) */
/* TBF handling, make private or move into TBFController */
/* list of uplink TBFs */