Windows Phone Thoughts: A Look At The Inner Workings Of The Cellular Network

"Have you ever wondered why your mobile phone can alert you to new voicemail without having ever rung? Or why a text message can get through when a call can't? Maybe you've traveled across continents and been amazed at how calls still manage to follow you? Or perhaps you've noticed that sometimes your battery only seems to last a fraction of its normal life? And why can the iPhone 3G figure out your location in 3 seconds when it takes takes your car GPS 3 minutes?"

This is a pretty interesting article on layman's terms on how the cellular phone system in general works and why odd things seem to happen from time to time. After reading this, you'll know how your IMSI on your SIM is transmitted to the VLR and is then shared with the HLR at the MSC. Piece of cake.