The IEEE 802.16 standard (commonly known as WiMAX) which has emerged as a broadband wireless access technology, is capable of delivering very high data rates. However, providing performance guarantees to delay sensitive applications like streaming media is still a challenge. In this paper, we study the media access control (MAC) layer of WiMAX and exploit its flexible features to dynamically construct the MAC packet data units (MPDU). The sizes of the MPDUs are constantly modified based on the channel state information. The desired payload is obtained either by aggregation or fragmentation of the upper layer data units. The robustness of MPDUs is also made tunable by means of cyclic redundancy code bits. We consider both the scenarios- with and without feedback. We adhere to the 802.16 specifications and propose adapting the MPDU length for streaming media for better performance. Three metrics are defined- restore probability, goodput and dropping probability. Simulation experimen...