PCS network signaling using SS7

(PCS) facilitates the exchange of information (voice, data, video, image, etc.) for mobile users independent of time, location, and access arrangement. To support PCS, mobile communications protocols such as E I W I A Interim Standard 41 (IS-41) 112-161 or Global System for Mobile Communications (GSM) [20] have been defined for PCS Network (PCN) inter-system operations. To support interconnection between a PCN and the Public Switched Telephone Network (PSTN), it is essential that the mobile communicationsprotocol interactswith the PSTN signaling system for mobility management and call control. This article describes the interactions between a PCN and the PSTN in four aspects: Interconnection Interfaces-What are the network interfaces between a PCN and the PSTN? Message Routing-How is the information exchanged among the PCNPSTN network elements? Mobility Management-How d0es.a PCN recognize the locations of the mobile users? Call Control-How are the calls set up between the mobile users and the wireline users? Mobility management merits further discussion. In a PCN the current location of a mobile user is usually maintained by a two-level hierarchical strategy with two types of databases. The Home Location Register (HLR) is the location register to which a mobile user identity is assigned for record purposes such as mobile user information (e.g., directory number, profile information, current location,validation period). The Visitor Location Register (VLR) is the location register other than the HLR used to retrieve information for handling of calls to or from a visiting mobile user [14]. When a mobile moves from the home PCN to a visited PCN, its location is registered at the VLR of the visited PCN. The VLR then informs the mobile's HLR of its current location. The details of the registration processwill be discussed in asubsequent section. When a call is delivered to a mobile, the HLR is first queried to find its location (i.e., the VLR corresponding to its current location). The details of location tracking can be found in 1121, and the call setuphelease process is discussed in the section on PCN/PSTN call control using ISUP. Since it is likely that two PCNs are connected through the PSTN, it is important to understand how the PSTN is involved in PCS mobility management. To address these four aspects, we consider IS-41 as the mobile communications protocol and Signaling System No. 7 (SS7) [2-51 as the PSTN signaling protocol. The IS-41 protocol considered in this article is based on EIA,TIA IS-41 Revision …