r to effectively build a packet-based mobile cellular network, some new network elements, interfaces, and protocols that handle packet traffic are required. Databases (VLR and HLR) All the databases involved in the network will require software upgrades to handle the new call models and functions introduced by GPRS. The Home Location Register (HLR) and Visitor Location Register (VLR) will especially require upgrades to functionally service GPRS because both GSM and GPRS networks must track and monitor the mobile stations. The common- ality of the database creates a smoother transition using the central data- bases to manage and internetwork the two environments. However, the networks have some elements that may not be initially deployed, creating the need to establish a register (database) at the new GPRS serving nodes, such as the SGSN and GGSN. Functionally, the SGSN will act as a VLR. Figure 3-3 provides an overall reference model for the GPRS in a GSM architecture with all associated implementations. Additionally, enhancements will be made to the Equipment Identity Reg. ister (EIR) and the Authentication Center (AuC) databases to control the security and authentication of the mobile station subscriptions. Figure 3-3 = Signaling Interface SMS-GMSC SMS-C The network = Signaling and Data SMS-IWMSC reference model Transfer Interface for GSM. MSC/VLR Other PLMN 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. System Architecture Chapter 3 As mentioned, the European Telecommunications Standards Institute (ETSI) achieved a coup when the American National Standards Institute (ANSI) in North America also accepted the GPRS model. In the North American model, the past use of the Telecommunications Industry Associa- tion / Electronics Industry Association (TIA/EIA) standards was the only way that was supported for wireless cellular networks. However,