Hi Bodoruddoza, sometimes it is not so easy. The limit for LAC area is number of paging (not the number of TRX). In the Combined BCCH/SDCCH (one TRX per cel – rural area) is theoretical limit 180,000 (no reservation for Acces grant).
with ACCG=1 is this limit 120,000. For NonComb BCCH and SDCCH/8 is this limit litle bit more than 500,000 (with ACCG=0). In reality is better to be up to 1/3 of the limit. If you set wrong LAC border MS could ping-pong between two different area. It is better to set LAC border in rural area, than to the midle of the city. In some cases you could avoid ping-pong, if you set bigger Cell Reselection Hysteresys (8dB). There could be also limit for BSC – number of paging (LAC) for one BSC.