7.1 State Description for the GMLC

03.713GPPFunctional descriptionLocation Services (LCS)Release 1999Stage 2TS

7.1.1 GMLC States

7.1.1.1 NULL State

In the NULL state, a particular location request from some LCS client either has not been received yet or has already been completed. After a location request is received from a LCS client, the GMLC remains in the NULL state while the identity of the client and nature of its location request are verified. . While the NULL state exists conceptually, it need not be represented explicitly in the GMLC.

7.1.1.2 INTERROGATION State

In this state, the GMLC has sent an interrogation to the home HLR of the MS to be located and is awaiting a response giving the VMSC address and IMSI for this MS.

7.1.1.3 LOCATION State

In this state, the GMLC has sent a location request to the VMSC serving the MS to be located and is awaiting a response containing a location estimate.

7.1.2 State Functionality

7.1.2.1 State Transitions

Figure 21: State Transitions in the GMLC

Moving from NULL to INTERROGATION state:

If the GMLC does not know the VMSC address or MS IMSI when it receives a location service request from some LCS client, it moves from the NULL state to the INTERROGATION state and sends a request to the MS’s home HLR for the VMSC address and IMSI.

Moving from NULL to LOCATION state:

If the GMLC already knows both the VMSC address and MS IMSI when it receives a location service request from some LCS client (e.g. from information retained for an earlier location request for the same MS), it moves from the NULL state to the LOCATION state and sends a location request to the VMSC.

Moving from INTERROGATION to LOCATION state:

After the GMLC, in the INTERROGATION state, receives the VMSC address and IMSI from the home HLR, it enters the LOCATION state and sends a location request to the VMSC of the MS being located.

Moving from LOCATION to NULL state:

After the GMLC receives a location estimate response from the VMSC, it forwards the location estimate to the requesting LCS client and reenters the NULL state.

7.1.2.2 INTERROGATION Timer Function

The GMLC runs a timer while in the INTERROGATION state to limit the amount of time waiting for an interrogation response from the HLR. If the timer expires before an interrogation response is received, the GMLC indicates a location failure to the LCS client and reenters the NULL state.

7.1.2.3 LOCATION Timer Function

The GMLC runs a timer while in the LOCATION state to limit the amount of time waiting for a location estimate response from the VMSC. If the timer expires before a response is received, the GMLC indicates a location failure to the LCS client and reenters the NULL state.