Software Guide

Advanced Configuration

Tsunami

800 & 8000 Series - Software Management Guide 113

: Roaming feature is applicable only to the point-to-multipoint devices but not applicable in legacy mode.

5.4.5.1 Definition(s)

Roaming Preferred Channels: A list of channels maintained by a BSU where its neighbour BSUs are operating.

Roaming Channel List (RCL): A list of channels that are learnt from the associated BSU (known as Roaming Preferred

Channels), and are not blacklisted locally on the SU. An SU uses this channel list to scan BSUs while roaming.

Usable Channel List (UCL): A list of channels that are available to an SU for the configured frequency domain and

are not blacklisted.

: Manual Blacklisting can be used to reduce the number of channels in the UCL and there by reducing the scanning and

roaming time.

5.4.5.2 Roaming Types

5.4.5.2.1 Slow Roaming

When the calculated Rx SNR, for the current link, goes lower than or equal to the configured Slow Roam Rx SNR Threshold,

then SU starts Slow Roaming.

During Slow Roaming, the SU scans channels from the RCL, one at a time. After scanning a channel, it returns back to the

channel where the current BSU operates, resumes data transfer and then jumps to another channel in the RCL, and so forth

until it scans all the channels. Once the scanning completes, the SU calculates the Rx SNR for each BSU and finds the BSU

with the highest Rx SNR value. If the BSU is better than the current BSU, then the SU roams to that BSU.

5.4.5.2.2 Fast Roaming

When the calculated Rx SNR, for the current link, goes lower than or equal to the configured Fast Roam Rx SNR Threshold,

then SU starts Fast Roaming.

During Fast Roaming, the SU starts scanning all the channels in the RCL until it finds a BSU with better Rx SNR than the

current BSU. Once it finds such BSU, the SU roams to that BSU and does not scan any more channels.

If the SU does not find a BSU with better Rx SNR, in any of the channels in the RCL, it resumes operation with the current

BSU.

If the quality of the link with the current BSU is still such that Fast Roaming procedure has to be started again, SU starts

scanning channels from the UCL, instead of the RCL, until it find a BSU with better Rx SNR. Once the whole list is scanned,

and no better BSU is found, SU resumes operation with the current BSU. SU repeats this procedure until either link quality

improves, or a BSU with better Rx SNR is found.

5.4.5.2.3 Emergency Roaming

An SU starts Emergency Roaming when the wireless link with the current associated BSU is lost for at least 1000 milliseconds.

During Emergency Roaming, the SU scans all the channels in the RCL until it finds any BSU. If the whole RCL is scanned and

no BSU is found, then SU starts scanning the channels from the beginning of the UCL, instead of the RCL. The SU keeps

scanning the channels from the UCL until any BSU is found. When a BSU is found, SU roams to that BSU.

: There is a possibility that the new BSU may not be better than the previous BSU.