e or more Packet Data Protocols (PDPs) can be negotiated with the SGSN. Three mobility man- agement (MM) states are related to a GPRS subscriber and each state describes the level of functionality and information allocated. In idle state, the mobile station is not yet attached to the GPRS mobility management and a GPRS attach procedure must be performed. The condi- tions of the idle state are shown in Figure 5-1 when looking at the radio resource (RR) management. In ready state, the mobile station is attached to GPRS mobility manage- ment (GMM) and is known in the accuracy of the cell. Each cell in a GSM network has its own Cell Global Identity (CGI), which enables the network to identify the mobile station by the cell. Each cell is associated with a loca- tion area (LA) in GSM, but in GPRS, the association is with the routing area (RA). The mobile station may receive and send data for all relevant service types. If the ready timer (for the mobile station or SGSN) expires, the mobile station will move to the standby state. Figure 5-2 shows the condi- tions for moving to and from the ready mode. In the standby state, the subscriber is attached to the GPRS mobility management and is known in the accuracy of the routing area. The mobile 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. Main GPRS Procedures Main GPRS Procedures STANDBY Figure 5-1 Timer expires or mobile The parameters for cancels the idle state of location. the mobile. Transfer of LLC PDU Establishment of TBF. Selects a new cell to switch into. Transfer Radio Resource State Machine Figure 5-2 The MS in the ready mode. GPRS detach or cancel location. STANDBY Timer expires or mobile cancels location. Ready Ready timer expires PDU transmission/ or forced to STANDBY by abnormal RLC reception. condition. Standby Mobility Management State Model of mobile station and SGSN station perform