Scanning and Synchronization to the Downlink in Initial Scanning

Subscriber Station (SS) are designed to scan their frequency lists for active downlink channel right away upon installation or following any period of signal loss. In case of signal loss, the SS will store operational parameters of the last signal and will attempt to restore the connection.

After obtaining a channel with a valid downlink signal, the SS will try to synchronize the PHY by listening for DL-MAP management messages. The SS will continue to listen for DL-MAP management messages and in the case of missing DL-MAP messages the SS will repeat the scanning and synchronization process.

WiMAX Network Entry and Initialization, part 1.

Once a SS senses a BS, for a network entry, it will first scans for downlink channel (DL) and trying synchronizes itself with the BS. After that, SS shall obtain transmit parameters, which are integrated in the Uplink Channel Descriptor (UCD), Uplink (UL)-MAP, and Downlink (DL)-MAP. The final step would be to complete initial ranging.

The BS is required to discover different received ranging codes, approximate the timing offset and the power for every user that bears and initial ranging code. The BS then broadcast the detected ranging codes with some change instruction for the proper timing and power level. Other than that, the status notifications of either ranging successful or retransmission are also broadcasted.