In GPRS IDLE state, the subscriber is not attached to GPRS mobility management. The MS and SGSN contexts hold no valid location or routeing information for the subscriber. The subscriber-related mobility management procedures are not performed.
The MS performs PLMN selection and cell selection and re-selection.
Data transmission to and from the mobile subscriber as well as the paging of the subscriber is not possible. The GPRS MS is seen as not reachable in this case.
In order to establish MM contexts in the MS and the SGSN, the MS shall perform the GPRS Attach procedure.
In STANDBY state, the subscriber is attached to GPRS mobility management. The MS and SGSN have established MM contexts as described in clause "Information Storage".
Pages for data or signalling information transfers may be received. It is also possible to receive pages for the CS services via the SGSN. Data reception and transmission are not possible in this state.
The MS performs GPRS Routeing Area (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 on a change of cell in the same RA. Therefore, the location information in the SGSN MM context contains only the GPRS RAI for MSs in STANDBY state.
The MS may initiate activation or deactivation of PDP contexts while in STANDBY state. A PDP context shall 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 STANDBY state. The SGSN then sends a Paging Request in the routeing area where the MS is located if PPF is set. If PPF is cleared, then paging is not done. 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.
The MS or the network may initiate the GPRS Detach procedure to move to the IDLE state. In IDLE state the MM and PDP contexts may then be deleted.
After expiry of the Active Timer, if running for the MS, the SGSN should clear the PPF flag in the SGSN. After expiry of the mobile reachable timer the SGSN should clear the PPF flag in the SGSN and start an Implicit Detach timer, with a relatively large value and if ISR is activated, at least slightly larger than the UE's GERAN/UTRAN Deactivate ISR timer. After the Implicit Detach timer expires, the S4-SGSN can perform an implicit detach in order to return the MM contexts in the SGSN to IDLE state.