A fuzzy logics based scheduling for downlink OFDMA/SDMA systems with multimedia traffic

In this paper, we propose a fuzzy logics based scheduling (FLBS) scheme for downlink orthogonal frequency division multiple access (OFDMA)/space division multiple access (SDMA) systems with multimedia traffic. The challenge in the scheduling problem of OFDMA/SDMA systems with multimedia traffic is how to effectively utilize the scarce radio resource as well as maximize the system throughput and guarantee the quality of services (QoS) and fairness. Traditionally, the user information and the channel information are used to assist the scheduler to allocate the radio resource. However, these two information can not be simultaneously modeled on a mathematical function to provide a clear scheduling policy. By using fuzzy logics, the proposed FLBS scheme assigns an urgency value to user based on the user information and the channel information. According to the assigned urgency value, each user gets a suitable radio resource region to maximize the system throughput while guarantee QoS requirement and fairness. Simulation results show that, compared to the most recently proposed algorithms, the proposed scheduling algorithm can improve the packet drop ratio by more than 63 % and the fairness performance by more than 75 % when the traffic load is greater than 0.5.