Performance Enhancement of TFRC in Wireless Ad Hoc Networks

The TCP-Friendly Rate Control (TFRC) is a rate-based transport protocol designed for streaming multimedia applications to provide smooth, low delay and TCP-Friendly packet transmission. However, as TFRC was designed for wired networks, it does not perform well in multihop ad hoc wireless networks. Specifically, MAC layer contention effects, such as retransmission and exponential backoff mislead TFRC’s congestion control mechanism, resulting in an inaccurate sending rate adjustment. 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 roundtrip time and a model of wireless delay to restrict TFRC bitrates from overloading the MAC layer, while retaining the desirable TCP-Friendly characteristics. RE TFRC requires minimal changes to TFRC and no changes to the MAC layer and evaluation of RE TFRC shows substantial improvements over TFRC for some wireless scenarios. Keywords—Wireless, Multimedia, IEEE 802.11, TFRC, Ad Hoc