Improving TCP performance in TDMA-based satellite access networks

In TDMA-based MAC (media access control) protocols for satellite network access, slotted ALOHA which has been widely deployed in Very Small Aperture Terminal (VSAT) systems. More recently, Generalized Retransmission Announcement Protocol (GRAP) was proposed in [5], which regroups the immediate access by contention at low loads and the reservation access at higher loads to achieve a better efficiency. Inspired by GRAP, we propose a new MAC protocol (CA-GRAP) using cumulative acknowledgment (CA) technique to further improve the success probability of reservation request. Furthermore, the efficiency of random access in CA-GRAP is improved by introducing contention index. Our proposal does not require collision or error detection but is based only on correctly received packets, dramatically simplifying the procedure. The impact of all these protocols on TCP traffic is investigated and an upper bound of TCP throughput at high loads is derived for GRAP-based protocols. Simulation results show that our new method significantly outperforms GRAP.