Mobile Switching Center The central component of the Network Subsystem is the Mobile services Switching Center (MSC), which is shown in Figure 1-15. It acts like a nor- mal Class 5 Central Office (CO) in the PSTN or ISDN, and in addition pro- vides all the functionality needed to handle a mobile subscriber, such as registration, authentication, location updating, handovers, and call routing to a roaming subscriber. The primary functions of the MSC include Paging Coordination of call setup for all MSs in its operating area Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Introduction to GSM Introduction to GSM Figure 1-14 The TRAU. 13 Kbps 16 Kbps 64Kbps 2.048 Mbps 64 Kbps (G)MSC (30 Channel subslots @ 16 Kbps @ 64 Kbps) In between BSC and MSC Converts GSM coding into PSTN data 13 Kbps 64 Kbps 64 Kbps 13 Kbps Figure 1-15 The MSC. (GSM) MSC E1 or Better PSPDN Dynamic allocation of resources Location registration Interworking functions Handover management Billing Reallocation of frequencies to BTSs Encryption Echo cancellation Signaling exchange Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Introduction to GSM Chapter 1 Synchronizing the BSS Gateway to SMS As a CO function, it uses the digital trunks in the form of E1 (or larger) to the other network interfaces such as Packet-Switched Public Data Network (PSPDN) Public Land Mobile Network (PLMN) These services are provided in conjunction with several functional enti- ties, which together form the Network Subsystem. The MSC provides the connection to the public-fixed network (PSTN or ISDN), and signaling between functional entities uses Signaling System Number 7 (SS7), used in ISDN and widely used in current public network