Performance Enhancement of TFRC in Wireless Networks

The TCP-Friendly Rate Control (TFRC) is used as a streaming media transport protocol. Using the TCP congestion response function and current network conditions, TFRC adjusts its transmission rate to yield the maximum TCP-Friendly throughput when sharing capacity with TCP flows. Since TFRC was designed for wired networks, it does not achieve the maximum TCP-Friendly throughput in multihop ad hoc wireless networks. The reduced wireless spatial channel reuse due to hidden terminals in multihop wireless networks induces TFRC throughput reductions. Specifically, TFRC is unaware of MAC layer transmission delays due to collisions, retransmissions and MAC layer congestion. This paper illustrates that an unmodified TFRC’s sending rate overloads the multihop wireless MAC layer, leading to increased round-trip times, higher loss event rates, and lower throughput. We propose an enhancement to TFRC, called RE TFRC, that uses measurements of the current round-trip time and a model of wireless delay to restrict TFRC bitrates from overloading the MAC layer, while retaining desirable TCP-Friendly characteristics. RE TFRC requires minimal changes to TFRC and no changes to the MAC layer and evaluation of RE TFRC show substantial improvements over TFRC for some wireless scenarios