Challenges for TFRC as a Real-Time Protocol Over Multihop Wireless Ad Hoc Networks

Abstract

Multihop wireless networks are emerging as a natural extension of the global Internet for scenarios where wired connections are unfeasible, impossible, or undesired. In these networks,nodes cooperate among themselves by relaying data to each other and generally can move at random. The topology of these networks can change rapidly and unpredictably as the mobile nodes change position or the wireless channel condition fluctuates. Such features require robust, adaptive communication protocols that can handle the unique challenges of these multihop networks smoothly. TCP Friendly Rate Control (TFRC) is a new congestion control scheme for the Internet, intended for use in video streaming and multimedia applications. It aims to send traffic at the same average rate as a TCP/IP sender, but without the sudden variations. However, TFRC is originally tuned to perform well in wired networks and assumes that any loss is due to congestion. Upon any loss, the congestion avoidance algorithm is used to backoff and increase the retransmission timer such that it will not overload the network.

The TFRC response function is not well suited for multihop networks, where most packet losses are due to the features of these networks. Therefore, for TFRC to be successfully deployed over multihop wireless networks it must be adapted to handle the unique challenges of these networks. The novelty of this thesis comes from the realization that TFRC must be adapted in such a way that it faces the challenges in combination and not individually.

This thesis details the key challenges for the TCP Friendly Rate Control (TFRC) in multihop wireless networks and outlines the proposed algorithm to solve the involved problems.The result is an adaptive rate estimation TFRC protocol, ARETFRC.