Channel descriptor is a set of information parameters that describe the characteristics associated with a communication channel. The use of a channel descriptor can permit more accurate and successful reception and decoding of information that is sent on a communication channel.
The WiMAX system periodically sends (broadcasts) channel descriptors on the downlink channel to allow the subscriber stations to understand how to decode and transmit messages. Channel descriptors provide information about the uplink and downlink channels.
The downlink channel descriptor contains a downlink frame prefix that provides the information to the receiver about the frame structure of the downlink channel and a downlink map (DL-MAP) that defines what information will be transmitted. The DL-MAP contains a downlink interval usage code (DIUC) that defines when information will be transmitted on the downlink and what formats it is supposed to use (burst profile).
The uplink channel descriptors contain an uplink map (UL-MAP) message that defines when a subscriber station is allowed to transmit on the uplink and what formats it is supposed to use (burst profile). The UL-MAP contains an uplink interval usage code (UIUC) that defines when a subscriber station is allowed to transmit on the uplink and what formats it is supposed to use (burst profile).
Figure 1 demonstrates how the WiMAX system uses channel descriptors to define the allocated times and burst types that are used on WiMAX radio channels.
