TCP-friendly streaming protocols in mobile computing environment

Abstract

Explosive growth in wireless communication technology has made it possible for mobile wireless devices to access multimedia resources over the Internet. However, a major problem in supporting multimedia streaming in the Internet is that the streaming protocol used tends to take bandwidth away from competing TCP traffic streams. Thus it is important to devise rate based protocols that are TCP-friendly. Since TCP congestion control is mainly based on the well-known Additive Increase Multiplicative Decrease (AIMD) mechanism for transmission rate adjustment, a protocol that simulates this behavior can share network resources with TCP traffic fairly. There are two main approaches in the design of TCP-friendly congestion control, one is AWID based and the other is equation based. The former uses AIMD directly for transmission rate control and reduces transmission rate in response to a single congestion control indication. Equation based congestion control, on the other hand, predicts the transmission rate of TCP traffic by a model. In this dissertation, we will evaluate both AIMD rate based and formula rate based congestion in a wireless network based on a number of performance measures including TCP friendliness and ability to maintain a steady data rate. We examine the problems of a well known AIMD based protocol, RAP, based on extensive simulation experiments and proposed some remedies. We construct rate based protocols based on two widely used TCP models and show that one model underestimates while the other overestimates TCP bandwidth in the presence of errors, thus affecting the TCP friendliness of the protocol. We propose simple modifications to one of these models and demonstrate the effectiveness of the modification.