Regarding beacons (pilot signal) in GSM (how often?)

[ntcnjdbxz]

Hi guys,
i'm doing my Master thesis in GSM and the only one question is still opened - how often Base Station broadcasts pilot signals (beacons). I've tried to find in Internet and books but I failed. The reason - i measure DL RSSI from Mobile Stations. The measurements come from MS every 480 ms and this measurements are average for this period (480 ms). But i need to know how many measurements from pilot signal does MS to average them later. Maybe I'm wrong and during the call MS measures DL RSSI in another way?
Thanks in advance

[firstmaxim]

Hi,
GSM uses the broadcast channel, transmitted over timeslot#0 on carrier #0. However, the BCCH measurement is done over the entire carrier.
In 3G UMTS, we have CPICH broadcast coninuously, and is used for measuring the CPICH power (used for cell selection, reselection, handover, etc)
In 4G LTE, we have Reference signals being broadcast only on certain subcarriers, and that too not in a continuous manner. In this case the UE averages the signal strength.