Research And Implementation Of Diffserv Based Adaptive Scheduling Algorithm In The Wireless Multi-hop Networks

With the development of wireless communications, the number of mobile users is increasing dramatically. Supporting multi-traffics has been the trend in the future wireless communication networks. People expect that next generation mobile communication systems can provide larger capacity and support mobile multimedia services. Besides providing real-time audio service, next generation mobile communication systems are required to support other services such as low/high rate data, images, etc. There is different quality of service (QoS) requirement for different heterogeneous services, 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 another is to make resource utilization maximized which leads to the development of wireless resource management (RRM). Wireless resource management includes call-admission control, handoff control, power control, load control and packet scheduling, etc. This dissertation pays attention to packet scheduling in wireless muli-hop networks, and proposes a DiffServ based adaptive scheduling algorithm.It is essential to study self-adaptive packet scheduling algorithm for Diffserv in wireless networks based on the ground that the analysis and research of key technologies of self-adaptive forwarding in wireless networks. Firstly, a scheduling algorithm employing forwarding ratio,FRA (Forwarding Rate Algorithm) is proposed in the paper, which aims at solving the problem in wireless networks that time-critical service would be disrupted by delay accumulation due to single forwarding node. Then, self-adaptive control theory is exploited to adjust forwarding factor adaptively in the algorithm aforementioned. AFRA (Adaptive Forwarding Rate Algorithm) is proposed based on the self-adaptive theory. The impact on forwarding factor caused by network load and length of queue buffer is analyzed comprehensively in wireless network. Furthermore, the self-adaptive setting based on judgment of queue length ratio is proposed to eliminate the negative affect aforementioned. The policy that the sampling of queue length exploits round-rabin scheme in the process of judging queue length ratio and the thought of algorithm that employs retreat scheme to adjust forwarding ratio in time succeed in shortening time, minimizing instability and optimizing ratio in adjust process.Moreover, two queues are modeled and analyzed respectively, which proved the reasonability of the adaptive algorithm. The forwarding latency and loss rates are analyzed through simulation in systems with different loads, and the simulation results validate the correctness and efficiency of our algorithms.