PERFORMANCE STUDY OF LAMS & TYPE - I LAMS - DLC PROTOCOLS

Abstract

The conventional go-back-N ARQ is inadequate for error control on satellite channels due to the large round trip delay and high bit rate. The throughput efficiency of the system drops rapidly as the channel error rate increases. Even HDLC-SREJ is also not suitable for satellite channels due to its waiting time at the end of window for RR signal from receiver. A new Data link layer protocol, LAMS-DLC, suited to the low earth orbit (LEO) environment offering service class known as reliable datagram was proposed by Christopher ward et al. This protocol provides zero-loss, zero-duplicate packet transmission with a minimum delay by relaxing reliability constraint, in-sequence delivery. This dissertation deals with simulation studies to compare it's performance characteristics with the existing HDLC-SREJ protocol. A new data link control protocol named Type-I LAMS which performs very well even in a degraded channel is also suggested. This was accomplished by combining the existing forward error correction (FEC) schemes with the LAMS-DLC protocol. FEC schemes use error-correcting codes for combating transmission errors. The merits and demerits of the two protocols were highlighted by the study. Results show that LAMS-DLC performs well at low bit error rates, and Type-I LAMS performs well at high bit error rates, but looses throughput efficiency in low bit error region.