The Study Of Scheduling Algorithms In Mobile Multimedia Communications

With the rapid growth of wireless networks and great success of Internet multimedia, wireless multimedia services are expected to be widely deployed in the near future. In the mobile multimedia communication system, How to according to user need provide QOS(quality of service) that is confronted with more challenging. In computer networks system, the Packet queue scheduling algorithms is among kernel mechanism of implement quality of service. That is importance content of networks resource management, by control allocation link bandwidth to different traffic, case different traffic gain different service. Hence, investigate packet queue scheduling algorithms is important meaning for the mobile multimedia communication system.The main contents of this thesis are as follows:Firstly, the scheduling algorithm of MDRS is proposed, which is based on rate-control. The rate controller shapes the input traffic from each connection into the desired traffic pattern by assigning an eligibility time to each packet. The scheduler orders the transmission of eligible packets from all the connections. The proposed algorithm changes the feedback information from the scheduler to the regulator compared to the traditional algorithms, which makes it become a work-conserving version without increasing its complexities. MDRS improves the performance of throughput, delay and delay jitter. It also has an excellent ability of flow isolation and rate control.Secondly, the scheduling algorithm of WDRS is put forward, which uses MDRS in error-free service models. It has three components: queue regulator, time-slot token scheduler and compensation queue scheduler. MDRS is used to control the time-slot token allocation from regulator to time-slot token scheduler. The compensation token is sent to compensation scheduler after the lagging-flowperceives a good channel condition. When each time-slot scheduler send a token, it will check whether the state of corresponding channel condition is good or bad. If it is good, time-slot token scheduler will send a packet from the corresponding queue in the regulator. Otherwise, the token will be abandoned and the LAG mark will be updated. This algorithm can ensure the data flow in correct order even if the channel is in bad condition and guarantee the QoS parameters of delay and delay-jitter. It has good abilities of flow isolation as well as rate control when the tag-flow is in error channel condition. It also ensures a smooth reduce to a lower rank while the leading-flow replenishes time-slots to compensate the lagging-flow.