Research On Packet Scheduling Algorithms In Wireless Networks

With the development of mobile communications, mobile users and Internet users are increasing dramatically. 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 quality of service (QoS) requirements, for example, the requirements of time delay, error bit rate, and transmitting rate for heterogeneous services are differentiated. There are two main objects for wireless network design, one is to guarantee QoS requirements of heterogeneous services, and the other is to make resource utilization maximized. This recurs to radio resource management (RRM). Radio resource management for the third generation mobile communication systems includes call admission control, handoff control, power control, load control and packet scheduling. This dissertation pays attention to packet scheduling in wireless multimedia packet networks. Chapter 2 discusses the key issues in how to adapt packet scheduling algorithms in wireline networks to wireless networks, and proposes a wireless fair scheduling algorithm named leading flows giving proportional compensation. The algorithm is capable of supporting differentiate application-level services and uses different queuing strategies for each class of services. Based on the unique characteristics of wireless communication channels, a compensation mechanism and a resource re-allocation method are introduced to achieve fairness. The compensation that a leading flow given up is proportional to the original transmission speed of the flow, while bandwidth is only extracted from flows that have received extra service. The resource re-allocation mechanism also took into consideration some special post-compensation scenarios. The proposed algorithm can be regarded as a combination of traditional scheduling algorithms and weight-adjusting algorithms. The weight-adjusting algorithm realizes the function of compensation. Chapter 3 proposes a wireless fair scheduling algorithm named lagging flow getting proportional compensation. Compared with the algorithm in chapter 2, this algorithm changes the compensation mechanism. The compensation that a lagging flow receives is proportional to the original transmission speed of the flow, while bandwidth is only extracted from flows that have received extra service.Chapter 4 proposes a wireless fair scheduling algorithm named changing the weights of the lagging flow. Compared with the algorithm in chapter 2, this algorithm also changes the compensation mechanism. The compensation mechanism only needs to change the weights of the lagging flows, and can achieve the compensation to the lagging flows. The three algorithms in chapter 2 to chapter 4 are compared.Chapter 5 proposes a wireless fair scheduling algorithm combined with reservation resource compensation. When there are few handoff calls, part of reservation resource is used for compensation, this method can increase resource utilization. When there are a lot of handoff calls, any compensation mechanism of chapter 2 to 4 can be used, and the compensation bandwidth is only extracted from flows that have received extra service.Chapter 6 proposes an idea of using the wireless fair scheduling algorithms in GPRS networks. The simulation results prove that using the wireless fair scheduling algorithm mentioned above can improve the system fairness performance.Chapter 7 is the summarization of the dissertation.