ons are usually densely deployed, the use of the typical cell search and cell selection methods, which are utilized in initial network entry/re-entry or handover in macro base stations, would be cumbersome and would result in extreme overhead in system operation, MS complexity, and power consumption. Furthermore, private femto base stations may be overloaded with signaling with unauthorized mobile stations trying to select them as target base stations for handover or system entry/re-entry. As mentioned earlier, the femto base stations may belong to closed subscriber groups (CSG) or open subscriber groups (OSG). In CSG, the access and services are restricted to authorized mobile stations. The credentials or electronic certificates may be provided to the mobile station by the cellular system operator at the time of subscription. The serving macro BS may have the knowledge (through MS context generated following session set-up) of the CSGs where the MS may have access. The OSGs, on the other hand, are publicly accessible and no specific authorization is required. "The Global Positioning System (GPS) is a global navigation satellite system developed by the United States Department of Defense and managed by the United States Air Force. It is the only fully functional satellite navigation system in the world. It can be used freely by anyone, unless the system is technically restricted. These restrictions can be applied to specific regions by the US Department of Defense. The GPS can be used almost anywhere near the earth, and is often used by civilians for navigation purposes. An unobstructed line of sight to four satellites is required for non-degraded perfor- mance. The GPS location determination accuracy is about 15 meters (50 ft). The GPS uses a constellation of between 24 and 32 medium Earth orbit satellites that transmit precise radio signals, which allow GPS receivers to determine their current location, the time, and their velocity [13]. The Precision Time Protocol is a time-transfer protocol defined in the IEE