In this paper, a multicell OFDMA WiMAX network is considered for uating the performance analysis both in uplink and downlink .The QOS parameters like blocking time, download time and BER of the network are discussed on various physical layer conditions like modulation techniques, channel models and different MIMO structures. The Erlang capacity of the system is formulated and based on this the optimum admission control and modulation technique is chosen. -In this paper, a multicell OFDMA WiMAX network is considered for　uating the performance analysis both in uplink and downlink .The QOS parameters like blocking time, download time and BER of the network are discussed on various physical layer conditions like modulation techniques, channel models and different MIMO structures. The Erlang capacity of the system is formulated and based on this the optimum admission control and modulation technique is chosen.