Performance analysis and improvement of wireless networks

Abstract

In the recent years, wireless communications have received an explosion of interests. Early adopters of the wireless networks are primarily in the military and emergency services areas. With the development of wireless communication technologies, it becomes common in peoples' daily life. We use wireless devices, such as mobile phones and laptops to get access to the worldwide Internet. By using wireless networks, we can share the information in our small building group or over the world at anytime and anywhere. There are different types of wireless networks. Our research focus on the performance analysis and improvement of existing wireless networks, i.e., wireless metropolitan area networks (WMANs) which is described by the IEEE 802.16 standard and wireless local area networks (WLANs) which is based on the IEEE 802.11 standard. We first introduce the background and previous modeling work of IEEE 802.16 and 802.11 networks in detail, respectively. Then we investigate the network performance of an unsaturated IEEE 802.16 network with the contention-based access mechanism. To capture the bursty characteristics of BE traffic, we model packet arrivals at each subscriber station as a Markov modulated Poisson process (MMPP). Based on the MMPP arrivals assumption, we derive analytical expressions for the network throughput and packet delay. We validate our analytical model by comparing with simulation results under various operating parameters. To demonstrate the benefit of adopting the MMPP arrival process, our analytical model is compared with previous work in which the arrival of packets is modeled by a Poisson process. Finally, we consider improving the throughput of IEEE 802.11 network by randomization of transmission power levels. Successive interference cancellation can resolve collisions involving multiple packets and significantly improve the throughput of an 802.11 network. This technique, however, requires packets to be sent with different power levels. We first develop a detailed analytical model to determine the resulting network throughput with the above multiple-packet reception capability. We then study the problem of determining the optimal probability distribution associating with these power levels when the network is operated in infrastructure and ad hoc modes, respectively. In the infrastructure mode, the problem is formulated as an optimization problem with solution to be broadcast to all the nodes by the access point. In the ad hoc mode, the same problem is formulated as a mixed strategy game where individual node strategically chooses the probability distribution of the transmitting power levels so to maximize its own throughput. We show that the Nash equilibrium of this game is Pareto optimal and fair. Furthermore, the resulting throughput of the distributed approach is close to the optimal performance of the infrastructure mode studied earlier.

Date of Award	2 Oct 2013
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Lin DAI (Supervisor) & Chi Hung Sammy CHAN (Supervisor)