GPRS各接口信令分析

MSBSSPAPUSMMUEIR 1. GMM.Identity Request 1. GMM.Identity Response 2. DX200.Check IMEI 2. MAP. IMEI Check 2. MAP.IMEI Check Ack 2. DX200.IMEI Check

Figure 6. Identity check procedure

1.The PAPU sends GMM.Identity Request (Identity Type=IMEI) to the MS.

The MS responds with GMM.Identity Response (IMEI). 2.If the PAPU decides to check the IMEI against the EIR, it sends

DX200.Check IMEI (IMEI) to SMMU. SMMU sends MAP.Check IMEI (IMEI) to EIR and the EIR responds with MAP.Check IMEI (Equipment status) to the SMMU. Finally SMMU sends and internal DX200.Check IMEI Ack (Equipment status) to PAPU. Equipment status can be one of the following values: \

(七) Location management procedures

The PLMN shall provide information for the MS to be able to: - detect when it has entered a new cell or a new RA; and - determine when to perform periodic RA updates.

The MS detects that a new cell has been entered by comparing the cell's identity with the cell identity stored in the MS's MM context. The MS detects that a new RA has been entered by periodically comparing the RAI stored in its MM context with that received from the new cell. The MS shall consider hysteresis in signal strength measurements.

When the MS camps on a new cell, possibly in a new RA, this indicates one of three possible scenarios:

- a cell update is required;

- a routeing area update is required; or

- a combined routeing area and location area update is required.

In all three scenarios the MS stores the cell identity in its MM context.

If the MS enters a new PLMN, the MS shall either perform a routeing area update, or enter IDLE state.

In network mode of operation II and III, whenever an MS determines that it shall perform both an LA update and an RA

update, the MS shall perform the LA update first.

Routeing Area Update Request messages shall be sent unciphered, since in the inter SGSN routeing area update case the

new SGSN shall be able to process the request.

1.Cell update procedure

A cell update takes place when the MS enters a new cell inside the current RA and the MS is in Ready State. If the RA has changed, a routing area update is executed instead of a cell update. The MS performs the cell update procedure by sending an uplink LLC frame of any type containing the MS's identity to the PAPU. In the direction towards the PAPU, the BSS shall add the Cell Global Identity including RAC and LAC to all BSSGP frames. A cell update is any correctly received and valid LLC frame carried inside a BSSGP frame containing a new identifier of the cell.

The PAPU records this MS's change of cell, and further traffic directed towards MS is conveyed over the new cell. 2.Routing area update procedure

When GPRS attached, MS detects that it has entered a new RA, and starts the Routing area update procedure. MS may also perform Periodic Routing Area Update procedure if MS's Periodic Routing Area Update timer (SGSN parameter: PRAU) has expired. If the current RA is under the same SGSN of the old RA then an intra SGSN Routing Area Updated will be performed. If the new RA belongs to different SGSN an Inter-SGSN routing area update procedure will be performed. A Periodic Routing Area Update is always an intra-SGSN RA update.

In Nokia SGSN different procedure are performed if the RA updated involved same PAPU or two different PAPU. They are described in this section.

Intra-PAPU RA update

The intra-PAPU RA update procedure is described in Figure 7.

MSBSS1. GMM.RA Update Request2. Authentication3. IMEI check4. GMM.RA Update Accept4. GMM.RA Update CompletePAPU

Figure 7. Intra-PAPU Routing Area Update Procedure 1.The MS sends the a GMM. Routing Area Update Request (Update Type, old RAI, old P-TMSI Signature) to the PAPU serving the current RA where MS is camped. Update Type indicates RA update or periodic RA update. The BSS adds the Cell Global Identity including the RAC and LAC of the cell where the message was received before passing the message to the PAPU. If the MS has a valid P-TMSI, then old RAI associated with P-TMSI is be included. At RR level the MS shall derive a foreign TLLI from P-TMSI and use it for sending the Routing area update request. If it has also stored old P-TMSI Signature, then the MS shall include the old P-TMSI Signature in the message for identification checking purposes.

2.If MS was previously located in a RA handled by the same PAPU, the PAPU already has the MM context and PDP contexts of the MS. This means that PAPU knows the relation between TLLI and IMSI. Depending on PLMN parameter %update\performs Authentication procedure toward MS (see section (五): \Authentication\ 3.Depending on PLMN Parameter \check repetition rate for periodic RA update\equipment checking functions. \Identity check procedure\section (六).

4.PAPU send GMM.Routing Area Update Accept (P-TMSI, P-TMSI Signature, Periodic RA update timer, Force to Standby) to MS. Force to Standby (SGSN parameter: FTS) may indicate \standby not indicated\timer in order to prevent the MS to perform cell updates. P-TMSI is included if the SGSN allocates a new P-TMSI. If P-TMSI was changed, the MS acknowledges the received P-TMSI with GMM.Routing Area Update Complete (P-TMSI).

Inter-PAPU RA update

The inter-PAPU RA update procedure is described in Figure 8.

MSnew PAPUold PAPUGGSNHLR1. GMM. RA Update Request2. GTP. SGSN Context Request 2. GTP.SGSN Context Response3. Authentication4. IMEI check 5. GTP. SGSN Context Ack6. Forward Packets 7. GTP.Update PDP context Request 7. GTP.Update PDP context Response8. Update location to HLR 9. GMM. RA Update Accept 9. GMM. RA Update Complete Figure 8. Inter-PAPU Routing Area Update Procedure

1.The MS sends a GMM. Routing Area Update Request (Update Type, old RAI, old P-TMSI Signature) to the PAPU serving the current RA where MS is camped. Update Type shall indicate RA update (Update Type= Combined RA/LA Routing Update will be described in module SGSN and MSC/VLR Interaction). The BSS shall add the Cell Global Identity

including the RAC and LAC of the cell where the message was received before passing the message to the PAPU. If the MS has a valid P-TMSI, then old RAI associated with P-TMSI is included. At RR level the MS derives a foreign TLLI from P-TMSI and uses it to send the Routing area update request. If it has also stored old P-TMSI Signature, then the MS shall include the old P-TMSI Signature in the message for identification checking purposes.

Note

P-TMSI Signature is a random number optionally allocated and sent by the