Objectives

When you complete the reading in this chapter, you will be able to

• Describe the main components of the main functions of mobility management.

• Describe the mobile-initiated attach and detach procedures.

• Understand when the network performs an attach or detach procedure.

• Discuss the role of the SGSN in the procedures.

• Understand the three states of the mobile in GPRS.

Mobility Management (MM)

Before a mobile station (MS) can send data to a corresponding host, it must attach to a Serving GPRS Support Node (SGSN). An attachment procedure (GPRS attach) between the mobile station and the network is conducted and a Temporary Logical Link Identifier (TLLI) is assigned to the mobile station. Actually, the mobile uses the TLLI after the network assigns a Packet Temporary Mobile Subscriber Identity (P_TMSI). The mobile chooses the TLLI after being assigned the P_TMSI.

After attaching, one or more routing contexts for one or more Packet Data Protocols (PDPs) can be negotiated with the SGSN. Three mobility management (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 conditions of the idle state are shown in Figure 5-1 when looking at the radio resource (RR) management.

Figure 5-1: The parameters for the idle state of the mobile.

In ready state,...