Research On Scheduling Algorithm With Cross Layer Design For Wireless Networks

With the development of mobile communications, mobile users and Internet users are increasing dramatically, and the conflict between the limited wireless resource and the increasing Quality of Service (QoS) requirement of multimedia traffics is becoming more and more serious. People expect that next generation mobile communication systems can provide larger capacity and support mobile multimedia services. Besides providing real-time speech service, next generation mobile communication systems are required to support other services such as low/high rate data, pictures etc. Heterogeneous services have different QoS requirements, for example, the requirements of time delay, error bit rate, and transmitting rate for heterogeneous services are differentiated. In many circumstances, packet scheduling policies designed for wired networks and wireless static channels are inadequate for wireless networks because of the limited and time-varying wireless channel capacity. As a result, it is a hot topic in the area of wireless communications to design the packet scheduling algorithms by considering the characteristics of wireless time-varying channels with the objectives of providing QoS guarantees to users as well as increasing the capacities of the wireless networks.In this dissertation, the cross-layer resource scheduling techniques in the typical two emerging types of wireless networks, IEEE 802.16 based Wireless Metropolitan Area Networks(WMAN) and Cognitive Radio Networks, are intensively studied. Economics theories are introduced into the design of wireless scheduling algorithms in order to improve the system performance and user perceived QoS. The research results provide next generation wireless communication networks reference cross-layer optimization strategies and are helpful for the standardization studied. The contents of this work are listed as follows:1. Based on the careful research of IEEE 802.16 protocol, we propose a novel cross-layer scheduling algorithm at the IEEE 802.16 WMAN MAC layer for multiple connections with diverse QoS requirements, where each connection employs AMC scheme at the PHY layer. Based on the specified QoS parameters, our scheduler will first satisfy all the QoS requirements; at the same time, it uses the wireless bandwidth efficiently by exploiting multiuser diversity among connections with different kinds of services and finally makes an optimum trade off between throughput and fairness.2. For cross layer resource scheduling in cognitive radio networks. In cognitive radio systems, one more aspect should be considered to protect the primary user from harmful interference when cognitive users are working in the vicinity of the primary user. Providing individual QoS guarantees and hybrid fairness for multimedia services is also a challenging issue, especially exploiting the synergy between the PHY layer and the MAC layer. The design essence of opportunistic scheduling are exploited here. The scheduler can use the channel state information and interference power information opportunistically. As a result, the user whose interference power is larger will be scheduled when its channel condition is in good state. Our scheduler can decrease the average interference to the primary user with efficient bandwidth utilization and without significantly dropping the QoS.3. We present novel cross-Layer scheduling strategies based on portfolio optimization for multiple connections in wireless access networks and cognitive radio networks, find the way to incorporate the portfolio theory in the design of wireless resource scheduling, and investigate the application and performance of portfolio optimization based scheduling algorithm. Each connection admitted in the system is assigned a priority, which is updated dynamically based on its channel quality, QoS status, system specific considerations and user preferences. The proposed schemes can achieve a desired QoS level and provide flexibility in setting user preference levels.4. For cross layer resource scheduling base on user perceived quality of service, we incorporate the tolerance region based QoS model and the analysis theory of user perceived quality of service into the design of wireless resource scheduling. User perceived QoS in wireless environment is well investigated, and the corresponding policy is given. We regard user perceived QoS as a novel QoS parameter, and make it as the optimize objective to design the cross layer scheduling algorithm. The proposed schemes can clearly improve the degree of user satisfaction, and at the same time use the wireless resource efficiently.