Attach-Detach allowed (ATT)

Value range: Yes,  No

Content：It is “Attach-Detach allowed” (ATT) in Huawei data management system. It is used to inform MS whether IMSI attach-detach is allowed in this cell. If it is set to “Yes”,  the network will not process the connection to the subscriber called when MS is power-off. Thus network processing time and resource are saved. Otherwise the network will process the connection even though the MS has been powered off.

Recommendation：Yes

 

Detach process (IMSI) refers to the process that MS informs the network that it is shifting from working state to non-working state (usually a power-off process), or the SIM card is being taken out from MS, upon receiving the notice from MS, the network will indicate that the IMSI subscriber is in non-working state. Therefore, if the MS is called, the call connection will be rejected.

IMSI attach process is opposite to detach process. It is the process that MS informs the network that it has entered the service area (usually a power-on process) or SIM card has been inserted into MS. After entering service state again, MS will test whether the current location area (LAI) is the same with the latest LAI recorded in MS. If yes, MS will start IMSI attach process. Otherwise MS will start location update process (replacing IMSI attach process), upon receiving the location update or IMSI attach process, the network will indicate that this IMSI subscriber is in working state.

Note that ATT configuration of different cells in the same LAI must be the same. It is because IMSI detach process will be started when MS is power-off in the cell with ATT as 1. The network will record that this subscriber is in non-working state and reject all the called connection requests of this subscriber. When MS is power-on again, if it is in the same LAI when it was power-off (thus the LAI update process will not be started) but in different cells, and ATT of this cell is set as 0, MS will not start IMSI attach process. In this case, this subscriber will not be called normally until MS starts the location update process.