Adaptive Slot Allocation to Control Queuing Delay in TDMA Wireless Base Station

An Adaptive Slot Allocation (ASA) scheme for controlling the queueing delay of packet delivery in a TDMA base station is presented in this paper. ASA utilizes the multi-queue architecture in a base station to support differentiated services for mobile hosts. The services required by each host are divided into quality-guaranteed type and best-effort type, which are served by separate queues. Another mechanism to realize service differentiation is the scaling factors used to differentially affect the determination of the outgoing rate for each queue in ASA. Also, the queue status is used as another parameter to determine the outgoing rate so that the adaptation of ASA can be achieved. Based on the allocated data rate and real channel quality, ASA further allocates time slots among the mobile hosts to control their packet delay. Such an adaptive slot allocation scheme can track the variation of input traffic and channel capacity adequately but still controls the queueing delay of target packets. In this analysis, we illustrate how the proposed ASA controls the queue dynamics. Then we investigate the relationship between queue dynamics and queueing delay. As a result, we can conclude that the queueing delay of services for each host is effectively controlled by the parameters of the ASA queuing model. Moreover, the controllability of the service queues relieves the task of buffer management in a base station. A simulation of real streaming traffic traveling across hops is made to evaluate the queue dynamics and delay performance of ASA. The simulation results confirm the expected properties, even under heavy traffic variation.