Ayat,
– what about paging discard on LAPD link? (is your paging load per LAC>80%? if yes you may need to split concerned LACs or add a secondary broadcast channel on heavy cells)
– what is the value of your immediate assignement success rate per LAC as it also happen to reduce PSR? (congestion on signalling channel,…)
– check on the BCCH frequency plan and make sure interferences are minimised.