Protocol design and system optimization in wireless communications and networks
Student thesis: Doctoral Thesis
Related Research Unit(s)
Wireless communications have recently been recognized as one of the most significant technologies in nowadays. With the vast majority of end-users supporting mobile applications and devices, such as smart phones and tablet personal computers, the needs of wireless technologies will continue to grow tremendously so that information can be accessed by these mobile users any time at anywhere. Because of the high demands, ongoing research in analyzing and designing advanced protocols to optimize the performances in various wireless systems remains a primary focus in computer networking. In this thesis, our aim is to investigate the fundamental issues in wireless networking such as routing and scheduling, and develop new frameworks and protocols to enhance the Quality of Services (QoS) in different types of systems. Smart antennas are an emerging technology that exploits spatial diversity and allows an access point (AP) to simultaneously transmit downlink packets to multiple stations (STAs). To enhance the system performance, we propose a new AP scheduling scheme for hybrid TDMA (Time Division Multiple Access) and SDMA (Spatial Division Multiple Access). Our scheduling scheme aims at maximizing the system throughput while maintaining the fairness among STAs and guaranteeing Quality of Service (QoS) of different traffic classes. On the other hand, joint power control, rate adaptation, and link scheduling schemes have been previously studied in multihop wireless networks with the objective to maximize the throughput or to minimize the communication latency. Recently, the physical interference model has started to receive more attentions from the wireless communication communities. Yet, the link scheduling problem under this physical interference model is hard, and little work in the literature addresses this issue. For this purpose, we formulate the power controlled rate adaptive scheduling problem (PRSP) as a mixed integer nonlinear programming (MINLP) with the objective of maximizing the minimal traffic delivery ratio of nodes in the multihop wireless network. Furthermore, routing in disconnected delay-tolerant mobile ad hoc networks (MANETs) continues to be a challenging issue. Several works have been done to address the routing issues using the social behaviors of each node. Yet, these algorithms rely purely on the mobility models without considering the social network characteristics. Thus, we introduce the social relations and profiles among nodes as the key metrics, and our objective is to compute the best forwarding node in routing such that the packet delivery probability is maximized. We propose the Social Relation Opportunistic Routing (SROR) distributed protocol to solve the routing issue based on these metrics. Finally, we conclude the thesis with insights for future works and the trends in the wireless networking and communication research. We believe that this research has a high impact to the applied research in general computer networks grounded with rigorous mathematical analysis and theory, which can potentially be applied in data and multimedia applications with wireless communications technology.
- Wireless Application Protocol (Computer network protocol), Wireless communication systems