A MAC protocol for wireless networks with QoS guarantees.

Abstract

Mobile communications are becoming integrated into society at an explosive rate. While 2nd generation (2G) systems limit the user to basic services such as voice and low-bit rate data, 3G networks are characterized by their ability to accommodate wideband multi-media traffic with Quality of Service (QoS) guarantees. In the design of a system the Medium Access Control (MAC) layer is responsible for multiplexing heterogeneous traffic onto a common transmission link and its design is critical to the overall performance of a system. A number of MAC protocols for wireless networks have been proposed in the literature - the majority having time division multiple access (TDMA) at the MAC layer. However in 3G systems there is a trend towards the use of code division multiple access (CDMA) due to its proven advantages in a wireless environment. Although several papers on CDMA based MAC protocols have been published, virtually none of them tackle the analysis aspect of the protocols. Those papers that do perform analyses of CDMA protocols don't often consider heterogeneous traffic, and even fewer support QoS. The thesis addresses these shortcomings by proposing a MAC protocol that supports QoS in the form of Bit Error Rate (BER) and packet delay guarantees. The thesis begins by giving an overview of proposed wireless ATM and 3G CDMA protocols and then details how power control may be used to support BER guarantees. Various Markov based analyses are presented along with Monte-Carlo Simulations. An Equilibrium Point Analysis is then performed and the work discusses how such analyses are generally infeasible for systems supporting heterogeneous traffic. After an overview of conventional scheduling algorithms the thesis proceeds to outline a novel approach by which delay guarantees may be offered using packet dropping rates as the QoS metric. Using a stochastic source model as opposed to the conventional leaky bucket traffic regulator the thesis diverges significantly from conventional literature. The thesis also details how to calculate the probability of QoS violation and concludes with suggestions on further research avenues. As a whole the work is unique in its approach to analyse heterogeneous traffic and the methods it uses to construct session admission zones for QoS guarantees.