I have inherited a high density network comprising of older Cisco access points and the wireless clients are failing to roam. After a site survey I have found that the network is too "hot" with a large number of access points visible in almost all locations. The TPC control threshold is set to the default -70 dBm and this is what I believe is part of the issue.
According to the "Radio Resource Management under Unified Wireless Networks" document TPC evaluates the transmit power using the following equation:
Tx_Max for given AP + (Tx power control thresh – RSSI of 3rd highest neighbor above the threshold)
If the transmit power needs to be turned down a TPC hysteresis of at least 6dBm must be met.
If the transmit power needs to be turned up a TPC hysteresis of at least 3 dBm must be met.
It also has the following example:
Tx_Max = 20
Current transmit power = 20 dBm
TPC threshold = -65 dBm
RSSI of the third neighbour = -55 dBm
The TPC equation equates to 20 + (-65 - (-55)) = 10
The transmit power is reduced to 17 dBm as the TPC equation equated to 6 dBm or higher. So far so good.
According to the WLC Configuration Guides:
In applications with a dense population of access points, it may be useful to decrease the threshold to –80 or –75 dBm to reduce the number of BSSIDs (access points) and beacons seen by the wireless clients. Some wireless clients might have difficulty processing a large number of BSSIDs or a high beacon rate and might exhibit problematic behavior with the default threshold.
So if we take the same example and use a TPC threshold of -80 dBm we get:
Tx_Max = 20
Current transmit power = 20 dBm
TPC threshold = -80 dBm
RSSI of the third neighbour = -55 dBm
The TPC equation equates to 20 + (-80 - (-55)) = -5 so does this mean that the current transmit power is left at 20 dBm? If so, how does this reduce the number of BSSIDs and beacons seen by the wireless clients?
