Pre-allocation of unused bandwidth algorithm: A QoS control protocol for 802.16 network

In the IEEE 802.16 system, the bandwidth is allocated by the Downlink and Uplink scheduler. All Subscriber Stations know when they should send or receive from the DL_MAP and UP_MAP information. For most existing schedulers, the bandwidth is allocated with the maximum sustained rate. If the allocated bandwidth of one queue has reached the maximum sustained rate, there will be no more bandwidth for it. However, for some lightly loaded system, there may be some slots left after the scheduler assigns slots to all packets in queues. Although there are slots available in this frame, the packets arriving after the scheduling have to wait for the next frame. So, we propose to allocate the available slots to these packets before they may arrive. For this, we propose a new allocation method in this paper. With it, the allocation work is partitioned into three rounds. In the first round, the slots are allocated sequentially based on the maximal sustained rate of each queue. In the second round, the left slots are allocated with the Weighted Round Robin. If there are slots left, the packets in all queues have been scheduled after this round. Then, the third round can be continued. For this round, a method for forecasting the arrival rate of the arriving packets in each queue is proposed. Then, the left slots are assigned according to the forecasted arrival rate of each queue. Comparing to the other protocols, those packets sent in this round can be delivered almost one frame earlier. This can decrease the average delay of the network and improve the performance for the WiMAX system.