  This paper presents a problem of queuing theoretic performance modeling and
analysis of Orthogonal Frequency Division Multiple Access (OFDMA) under
broad-band wireless networks. We consider a single-cell WiMAX environment in
which the base station allocates sub channels to the subscriber stations in its
coverage area. The sub channels allocated to a subscriber station are shared by
multiple connections at that subscriber station. To ensure the Quality of
Service (QoS) performances, two Connection Admission Control (CAC) schemes,
namely, threshold-based and queue-aware CAC schemes are considered at a
subscriber station. A queuing analytical framework for these admission control
schemes is presented considering OFDMA-based transmission at the physical
layer. Then, based on the queuing model, both the connection-level and the
packetlevel 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). We determine analytically and numerically different performance
parameters, such as connection blocking probability, average number of ongoing
connections, average queue length, packet dropping probability, queue
throughput and average packet delay.
