ring the service flow set-up procedure. When QoS requirements/traffic characteristics for UL traffic change, the BS may change the service flow QoS parameters, such as grant/polling interval or grant size based on predefined rules. In addition, the MS may request the BS to change the service flow QoS parameter set through signaling. The BS then allocates the radio resource according to the new service flow parameter set. To satisfy the latency requirements for network entry, handover, and state transitions, IEEE 802.16m supports fast and reliable transmission of MAC control messages. To provide reliable transmission of MAC control messages, all MAC control messages can be fragmented. The HARQ error control mechanism is applied to all unicast MAC control messages. Message timers for re- transmission are defined for all the unicast MAC control messages. The message timers may be different for various MAC control messages. If HARQ is applied during the transmission of a MAC control message, and if the HARQ process is terminated with an unsuccessful outcome before the expiration of the message timer, the MAC message management entity in the transmitter may initiate re-transmission of the entire message or the message fragment of the failed HARQ burst. When the transmitter polls a message acknowledgement, the receiver responds with a MAC layer acknowl- edgement. For fragmented messages, all fragments of the message must be received before the MAC layer acknowledgment is sent. In a point-to-multi-point topology, the network operates with a centralized scheduling service located in the BS. The BS antenna system is sectorized and the BS simultaneously serves a number of independent sectors. The BS scheduler is responsible for determining the physical transmission parameters for a particular connection based on the CQI reports from the MS (channel quality), QoS requirements, and parameters of the service flow, as well as MS bandwidth requests and fairness criteria. The QoS parameters associated with service flow and the c