Exploiting the Benefits of Cooperation in Wireless Networks

Given scarce spectrum resources and the ever-increasing data demands of the mobile users, methods to improve the spectrum efficiency is an active research area. Cooperation is one of the promising solutions that can lead to a significant performance improvement of the wireless system. The main objective of this thesis is to leverage the advanced cooperation techniques in typical wireless systems.;Cellular networks are viewed as the most successful deployment of wireless networks to provide ubiquitous voice and data communications to the mobile users. Video broadcast/multicast service over cellular networks is a popular application, but supporting this is a challenging task, which requires high-bandwidth and low latency. We propose a novel scheme using scalable video coding (SVC) and user cooperation to improve the system-wide user video quality of experience. The users receiving more layers of video can forward the extra layers to the users with fewer layers. Practical protocols for discovering the helpers and efficiently distributing video content are designed. The cellular base station conducts a centralized resource allocation to maximize the overall video quality among all users in the multicast session.;Cognitive radio networks have recently been proposed as a new solution to the spectrum scarcity problem. It allows more efficient utilization of the licensed spectrum by allowing the unlicensed secondary users (SUs), equipped with frequency-agile cognitive radios, to dynamically access the licensed spectrum held by the primary users (PUs). We propose to utilize multiple antennas on the SUs to cooperatively relay the traffic for the PUs while concurrently accessing the same channel to transmit their own traffic. Our scheme, named MIMO-CCRN, is designed by considering both the temporal and spatial domains to improve spectrum efficiency. We also consider two practical network scenarios. One scenario has a single primary link and multiple secondary relays, which we analyze using a Stackelberg game model. Another scenario, with multiple PUs and SUs, is analyzed by finding an optimal matching. In all scenarios, MIMO-CCRN is verified to achieve higher utility for both PUs and SUs.;Cross-layer designs are used in the above work to identify the benefits of cooperation. Either physical layer cooperation based on multiple antennas or network layer cooperation by multi-hop forwarding improves system performance. Additionally, we investigate cooperation among different wireless service providers. Specifically, we study the benefits of sharing infrastructure and spectrum among multiple cellular operators. A multi-cell analytical model using stochastic geometry is provided to analyze the average user throughput under cellular operator cooperation. With both analytical and simulation results, we show large capacity gains exist, providing a strong incentive for operators to cooperate.