tbf: Add adaptive DL CS adjustment

To cope with transmission failures due to bad radio conditions, a
different coding scheme with more redundance can be used.

This commit adds an implemenation that is based on the Ack/Nack
ratio per PACKET DOWNLINK ACK/NACK message received from the MS.

Basically the CS level is decreased, if the block error rate goes
above cs_adj_upper_limit (default 33%), and it is increased, if the
rate drops below cs_adj_lower_limit (default 10%). Only blocks that
have been encoded with the current CS are taken into account.

Note that this approach doesn't measure the MS->BTS conditions and
that the measurement values reported by the MS are not taken into
account.

Ticket: #1739
Sponsored-by: On-Waves ehf

1 files changed, 2 insertions, 0 deletions

diff --git a/src/rlc.h b/src/rlc.h
index 55cae3ff..313f3c72 100644
--- a/src/rlc.h
+++ b/src/rlc.h
@@ -59,6 +59,8 @@ struct gprs_rlc_data {
 	uint8_t block[RLC_MAX_LEN];
 	/* block len of history */
 	uint8_t len;
+
+	uint8_t cs;
 };
 
 /*