Hi Danish,
I am very convinced with Pix idea. but you can take into consideration that there is a logical parameter to make the MS execute location update if the MS was in IDLE state for 3 or 4 hours (configurable by the this parameter); Example: subscribers sleep at 12:00 midnight after 4 hours the subscribers MS will start generating these Location Updates, which implies in the SDCCH. But truly, that wasn’t a reason for SDCCH Blobking in my network… this return us back to Pix idea, wich is more convincible for your case. you must redimension SDCCH for cells that are on LAC borders.