Performance measures of CAC mechanism in OFDMA system using shadow server approximation

We study in this paper the problem of queueing theoretic of OFDMA-based WiMAX with two classes of connections, connections with High Priority (HP) and connections with Low Priority (LP). The key idea to solve the problem of the mixed priority strategy is the technique of the Shadow server approximation. Specifically, we present a single-cell WiMAX environment in which the base station allocates subchannels to the subscriber stations in its coverage area. The subchannels allocated to a subscriber station are shared by multiple connections at that subscriber station. To ensure the Quality of Service (QoS) performances, a Connection Admission Control (CAC) mechanism is considered at a subscriber station. Then, based on the queueing model, both the connection-level and the packet-level performances are studied and compared with their analogues in the case without CAC. The connection arrival is modeled by a Poisson process and the packet arrival for a connection by a Markov Modulated Poisson Process (MMPP). Several performance measures are derived.