The cross-layer adaptation of TCP-Friendly rate control to 3G wireless links

Existing transmission control protocol (TCP) and TCP-Friendly flows suffer from unpredictable losses and delay over wireless links because such factors may cause sending rate throttling and lower the reactivity of transmission control. This paper presents a cross-layer approach to adapt TCP-Friendly rate control (TFRC) to these two factors of 3-rd generation (3G) wireless links. For effective adaptation, we classify the causes of packet losses and delay observed in transport layer as: Capacity-related and Erroneous-channel-related, and recognize them by using layer 2 automatic repeat-request (ARQ) information. The proposed approach takes into account hybrid ARQ (HARQ), adaptive modulation and coding (AMC), and layer 2 ARQ and is simulated over the high-speed downlink packet access (HSDPA) links. Simulation results show that our approach outperform the standard TFRC and one other improved TFRC scheme. Besides, it is shown that erroneous-channel-related delay adaptation makes it possible to increase the throughput of TFRC effectively even in cases where no erroneous-channel-related loss occurs.