RSSI threshold settings in Capacity Max.

There are three RSSI threshold settings in a Capacity Max radio which will determine how it performs when registering and while roaming between sites. This is how each of these settings work.

Acceptable RSSI Threshold

The Acceptable RSSI Threshold is used by the radio when hunting or when in an idle state and assists in determining whether the signal strength of the current or prospective control channel, is sufficient to establish and maintain communication. If the radio is hunting and finds more than one control channel that is above the RSSI Acceptable Threshold, it will attempt to register on the strongest control channel found.

As part of normal operation, a Capacity Max site will provide some information about the adjacent sites: specifically, the current control channels and site numbers.

While no calls are being passed on the control channel, radios will periodically check the signal strength of these adjacent control channels. This is done whenever needed during the 2nd slot transmission (i.e. control channel is on slot 1 and radio checks one adjacent control channel while slot 2 is being sent out). There is no sample period and the radio will continuously do this while idle and while the RSSI is above Acceptable RSSI Threshold but below Roaming RSSI Threshold.

Roaming RSSI Threshold

The Roaming RSSI Threshold assists the radio in sorting candidate control channels into two categories. Specifically, it divides the list of acceptable signals into no-roaming (shaded yellow in the above diagram) and roaming-in-acceptable (shaded green in the above diagram) areas. It also determines the strong signal area within the acceptable signal coverage. If the current control channel RSSI is above this threshold, the radio will not sample other control channels and pressing Manual Site Roam will not necessarily make the radio move to another site.

Increasing the Roaming RSSI Threshold decreases the distance from the site (i.e. signal strength) where the radio potentially starts roaming. Decreasing the Roaming RSSI Threshold increases the distance from the site where the radio potentially starts roaming (see below diagram).

Handover RSSI Threshold

Capacity Max supports an in-call handover procedure that allows radios, that are receiving a call (i.e. during hangtime), to seamlessly switch from a traffic channel on one site to a traffic channel on an adjacent site, without any holes in the received audio.

The Handover RSSI Threshold determines one of the conditions that must be met before the radio will initiate a handover: the signal of the current traffic (payload) channel must be lower than the Handover RSSI Threshold value, and at least one adjacent traffic channel must have a signal strength more than 6dB greater than the current traffic channel.

When in the green area, the Acceptable RSSI condition applies – meaning that the radio will stay on the currently roamed (home) control channel and, at the same time, will look at adjacent sites.