Determination of optimal PER for real-time traffic in adaptive modulation combined with queuing over rayleigh fading channels

Abstract

In this thesis, we develop a determination method of optimum target packet error rate (PER) for real-time traffic in adaptive modulation (AM) combined with finite-length queuing over Rayleigh fading channels. Considering the packet delay, the limited buffer size in the queue, and channel conditions, the optimization problem for target PER is formulated in a sense of maximizing the average throughput. Discrete-time finite-state Markov chain (DT-FSMC) model is employed for the dynamic behavior of the queue. Through DT-FSMC, we derive the statistics of packet loss caused by both buffer overflow and delay violation according to PER. The statistics of packet loss enables us to obtain the closed-form expression of the average throughput, which is a function of PER. The optimum target PER to maximize the average throughput can be determined by solving one-dimensional optimization problem, with Golden section method (GSM). Simulation results confirm that the performance of the proposed scheme considering the delay effect in the queue is better for delay-sensitive traffic than that of the conventional scheme which does not consider the queuing delay. In addition, it is shown that the performance of the proposed scheme is improved as the packet delay bound decreases and the buffer size in the queue becomes larger.