 certain attributes for the associated service flow. Traffic Priority is a parameter whose value specifies the priority of associated service flow. This parameter is present for a DL or UL service flow, which are associated with any Uplink Grant Scheduling Types except UGS. Unsolicited Grant Interval parameter defines the nominal interval between successive data grant opportunities for a DL service flow, which are associated with Uplink Grant Scheduling Type = UGS or ertPS. If this parameter is set to zero, then there is no explicitly mandated unsolicited grant interval. The maximum unsolicited grant interval field specifies only a bound, not a guarantee that the rate is available. Unsolicited Polling Interval parameter defines the maximum nominal interval between successive polling grant opportunities for an UL service flow, which are associated with Uplink Grant Scheduling Type==trPP If this parameter is set to zero, then there is no explicitly mandated unsolicited grant interval. The maximum unsolicited polling interval field specifies only a bound, not a guarantee that the rate is available. The QoS classes specified in the IEEE 802.16-2009 standard are as follows [1,6,7]: Unsolicited Grant Service (UGS) is designed to support real-time uplink service flows that transport periodic fixed-size data packets such as VoIP without silence suppression. This service class provides fixed-size grants on a real-time periodic basis, which eliminates the overhead and latency due to MS bandwidth requests and ensures timely availability of the grants to meet the real-time characteristics of the service flow. The BS schedules the MS at periodic intervals based on the Minimum Reserved Traffic Rate of the service flow. The size of these grants must be sufficient to hold the fixed-length payload associated with the service flow. In order to ensure proper operation, the Request/Transmission Policy setting will prohibit the MS from using any contention request opportunities for this connection. The mandatory QoS parameters are Mi