Flow Control for Heterogeneous Packet Data Networks

The demand for wireless connectivity to the Internet is increasing. As the network grows and assimilates an increasing range of both wireless and wire line link technologies, it is becoming increasingly heterogeneous. Compared to wire line transmission technologies, practical radio data transmission technologies are far more limited in capacity and reliability. This has lead to the development of a range of mechanisms to improve the efficiency and reliability of radio data transmission. However, physical phenomena, both exogenous and endogenous to the radio link hardware, will ultimately lead to random fluctuations in the radio link capacity. User satisfaction will depend on the user’s application, and what requirements the application demands on the latency, reliability, and rate of data delivery over the network. In this thesis it is argued that a flow control mechanism is required, which takes into account the capacity, and reliability of the underlying network. It should endeavour to simultaneously satisfy the application’s requirements, as well as maximise the overall performance of the wireless component of the network. The goal of this thesis is to design such a flow control mechanism. Based around meeting this goal, the structure of this thesis is organised as follows. Packet data transmissions over a radio link are modelled. These models provide a technique to determine the effect of channel conditions on the distribution of packet transmission times and packet loss probability. These models are then applied to model static window flow control over a heterogeneous network. By applying this model, the performance of rate based flow control is critically compared to window based flow control. Conclusions drawn from studying these models, lead