Distributed MAC protocols and priority oriented scheduling for a PLC access network

In this paper, we propose a distributed channel allocation scheme for the uplink data traffic and implement a priority oriented scheduling for the downlink data traffic for a powerline access type network. We study the performance of the uplink and downlink protocols in terms of the buffering probability, mean delay, statistical dropping probability and the number of subscriber stations supported. The distributed channel allocation scheme uses a modified carrier sensing mechanism and a centralized collision resolution scheme. We model the channel occupancy of uplink data calls using a continuous time Markov chain (CTMC). We derive the expressions for mean delay, statistical dropping probability, and utilization by solving the CTMC. We also perform extensive simulations to complement our analytical results. Our results indicate that, the distributed channel allocation approach achieves 10% improvement in spectrum utilization compared to a centralized reservation protocol. We also implement a priority oriented scheduling policy for the downlink data traffic. In the system we consider, the downlink channels are adaptively modulated based on their signal strength. We maximize the instantaneous link utilization by using MaxFlow algorithm. Simulation results for downlink scheduling show that the mean buffering delay for the real-time variable bit rate traffic is zero and that the system supports 170 access stations. We also show that system with adaptive modulation achieves 26% savings in transmitted power compared to the system without adaptive modulation. Copyright # 2003 John Wiley & Sons, Ltd.