Hi Kumar,
Nice book avail. on Ericsson’s website. Look in to the following link,
http://www.ericsson.com/support/telecom/index.shtml
in this, if u see, PLMN – section, u can find switch and switch control. It gives a fair idea on switch dimensioning. Printed copy is also available.
This book also might help you,
GSM Switching, Services, and Protocols — Joerg Eberspaecher.
regds.