Mobility Management States IDLE (GPRS) State In the GPRS IDLE state, the subscriber is not attached to the GPRS mobility management. The MS and SGSN context hold no valid location or routing information for the subscriber. The subscriber related mobility management procedures are not performed. Parameter Planning STANDBY State In the STANDBY state, the subscriber is attached to the GPRS mobility management. The MS and SGSN have established MM contexts for the subscriber's IMSI. Pages for data or signalling information transfers may be received. It is also possible to receive pages for the CS services via the SGSN. The MS performs GPRS RA and GPRS cell selection and re-selection locally. The MS executes mobility management procedures to inform the SGSN when it has entered a new RA. The MS does not inform the SGSN of a change of cell in the same RA. Therefore, the location information in the SGSN MM context contains only the GPRS RA identity for MSs in the STANDBY state. The MS may initiate activation or deactivation of PDP contexts while in the STANDBY state. A PDP context will be activated before data can be transmitted or received for this PDP context. The SGSN may have to send data or signalling information to an MS in the STANDBY state. The SGSN then sends a Paging Request in the routing area where the MS is located. The MM state in the MS is changed to READY when the MS responds to the page and in the SGSN when the page response is received. Also, the MM state in the MS is changed to READY when data or signalling information is sent from the MS and, accordingly, the MM state in the SGSN is changed to READY when data or signalling information is received from the MS. READY State In the READY state, the SGSN MM context corresponds to the STANDBY MM context extended by location information for the subscriber on a cell level. The MS performs mobility management procedures to provide the network with the actual selected cell. GPRS cell selection and re-selection is done locally by the MS. The MS may send and recei