T3212 = 4 hours (default)
every 4 hours, a mobile will send a location update message to its BSS, using a SDCCH subchannel for 3 seconds 🙂
increase T3212 : instead of every 4 hours, maybe do every 6 hours.
It reduces the amount of location updates in your network, reducing the SDCCH load (and TCU load as well)
drawback : there is a timer in the NSS that can expire. If the NSS receives a LU before the expiry, then the timer is restarted. Otherwise, the mobile becomes “IMSI DETACH”-ed. So ensure that your NSS timer is well defined.
There must be another drawback, but I can’t remember…
Decrease T3212 : instead of 4 hours, do 2 hours. That will double the amount of periodic LU in your network, overloading TCUs and SDCCHs.