 Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Main GPRS Procedures Main GPRS Procedures The mobile station may also activate or deactivate PDP contexts (data addresses) with the network. A mobile station may have many active PDP contexts simultaneously. The mobile station listens to the GPRS Packet Common Control Channel (PCCCH) and may also use discontinuous reception (DRX). Discontinuous reception means that the mobile station will only use resources when data is present to receive (in the form of packets). Other times, the always-on condition is not using any radio resource. The mobility management remains in the ready mode until the ready timer expires and the mobile station then moves to the standby mode. Fig- ure 5-4 shows the process of conducting the GPRS attach as the mobile sta- tion initiates the request. GPRS Attach Scenario Using the previous statements, we can then see the procedure that the mobile station uses to attach to the GPRS network. The mobile station wants to initiate a packet data session, (for example, access the Internet or check e-mail) from a wireless network (vis-a-vis GPRS). To do this, the Figure 5-4 GPRS attach procedure to move to the ready mode. IMSI or (P_TMSI+old RAI) Attach type Multislot capability Requested READY timer value DRX parameters GPRS attach request Update Location Security Functions Insert Subscriber Data Insert Subscriber Data Ack GPRS Attach Accept Update Location Ack P_TMSI MS=READY Negotiated ready timer value Periodic RA timer 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 Chapter 5 mobile station must first attach itself to the wireless network-the SGSN to be more specific. Four steps are involved in the attach process, as shown in Figure 5-5: 1. The mobile station sends an attach request with its identity (P_TMSI