IEEE 802.16 standard suite defines two main polling mode: unicast polling and contention-base polling including multicast and broadcast polling. Unicast polling completely overcomes the request collision and is suitable for real-time application. Contention-based polling suffers from collisions and is suitable for non-real-time applications. Though the standard defined different service classes for implementing the polling mechanisms, it does not define exactly an adaptation polling mechanism to efficiently allocate bandwidth. In this paper we evaluate the performance of different polling mechanisms defined in IEEE 802.16 by simulation. We also propose a new optimal unicast and contention-based mixed polling mechanism and show that this optimal mixed polling mechanism could always achieve better performance than any polling mechanisms defined in IEEE 802.16.