By default this value is 100% - this means that the RF must be at 100% utilisation in order to initiate a channel change, in wireless this value is impossible to reach in the real world.
The measurement of utilisation itself is a percentage, this value is a quantity that expresses how much airtime on the current channel is occupied by 802.11 traffic originating and destined to OTHER APs or UNSUCCESSFUL communications. In other words how much air time is consumed by other APs and their clients, and by transmission collisions.
For example, AP1 has 5 clients, AP2 has none and the 2 AP’s are reasonably close by each other and on the same channel, AP1 will see some congestion, more than with 1 client, but AP2 will see much higher congestion.
The main point of utilisation is that it is a congestion measurement not necessarily related to the number of clients on an AP, but more about how much ‘clear channel airtime’ there is that has not been used by any of that APs clients.
Initially enable DCS in monitor mode and insert a value you feel appropriate for your environment, this will report what the AP sees but will not take any action. Keep in mind this might not turn out to be the same value for all AP’s in your estate; then note the log entries in the controller gui, you can also use the following OID for SNMP polling:
22.214.171.124.4.1.43126.96.36.199.188.8.131.52 Average DCS Channel Utilisation by Adjacent APs [%].