7.3.3 Interworking between the RNSAP User Adaptation Layer (RNA) and the Signalling Connection Control Part (SCCP)
25.4673GPPRelease 17Stage 2TSUTRAN architecture for 3G Home Node B (HNB)
7.3.3.1 General
This section describes usage of RNA and SCCP for connectivity between a HNB and a macro RNC via HNB-GW.
RNL signalling between an RNC and a HNB-GW utilises services provided by the SCCP (ITU-T Rec. Q.711 [32] / ITU-T Rec. Q.712 [33]/ ITU-T Rec. Q.713 [34]/ ITU-T Rec. Q.714 [35]) as defined for Iur interface signalling transport between two RNCs (see 3GPP TS 25.420 [31]), since the HNB-GW is seen as an RNC from RNCs being connected via the Iur interface to it.
The Interworking functions at the HNB-GW deal with:
– extracting or inserting respective RNL related addressing information on the Iurh connection or on the Iur connection of the RNC-HNB signalling connectivity,
– on Iurh, RNL related addressing information carried on RNA within the Receivers HNB RNL Identity IE and the Senders HNB RNL Identity IE,
– on Iur, RNL related addressing information is carried within RNSAP;
– for connection oriented signalling, performing appropriate mapping between RNA level and SCCP level;
– respective routing of RNSAP messages based on available address information.
In general, (i) Iur connectivity between the HNB-GW and the RNC is established by configuration, while (ii) the Iurh connectivity between the HNB and the HNB-GW is performed via the Iurh setup procedure.
The following subclauses describe the interworking between RNA and SCCP at the HNB-GW.
7.3.3.2 Establishment of signalling connection over Iurh and Iur connections between HNB and RNC via HNB-GW
7.3.3.2.1 HNB initiated
Figure 7.3.3.2.1-1: Establishment of signalling connection over Iurh and Iur connections between HNB and RNC via HNB-GW – HNB Initiated.
1. If the Source HNB is configured for Iurh-connectivity via the HNB-GW, and wants to send an RNSAP message to the Target RNC for which signalling connection over Iurh and Iur connections has to be established, it issues an RNA:CONNECT message containing the Iurh Context Id, the RNSAP PDU1, the Source HNB RNL Identity and the Target RNC RNL Identity.
2. The HNB-GW identifies the signalling interface to which the RNA message shall be routed by the Target RNC’s RNL Identity as received from the Source HNB and maintains a mapping between the RNA-based signalling connection and the SCCP-based signalling connection for the HNB-RNC end-to-end.
3. The HNB-GW sends RNSAP PDU1 to the Target RNC and the Target RNC sends back RNSAP PDU2 (see TS 25.420 [31] subclause 4.5.1.3).
4. The HNB-GW routes the RNSAP PDU2 towards the Source HNB.
5. The HNB-GW sends an RNA:Direct Transfer message, including RNSAP PDU2 received from the Target RNC.
7.3.3.2.2 HNB initiated – Refusal from RNC
Figure 7.3.3.2.2-1: Establishment of signalling connection over Iurh and Iur connections between HNB and RNC via HNB-GW – HNB Initiated with refusal from RNC.
1. If the Source HNB is configured for Iurh-connectivity via the HNB-GW, and wants to send an RNSAP message to the Target RNC, it issues an RNA:CONNECT message containing the Iurh Context Id, the RNSAP PDU1, the Source HNB RNL Identity and the Target RNC RNL Identity.
2. The HNB-GW identifies the signalling interface to which the RNA message shall be routed by the Target RNC’s RNL Identity as received from the Source HNB and maintains a mapping between the RNA-based signalling connection and the SCCP-based signalling connection for the HNB-RNC end-to-end communication.
3. The HNB-GW sends RNSAP PDU1 to the Target RNC as received from the HNB via SCCP:Connection Request and the Target RNC refuses the connection request (see TS 25.420 [31] subclause 4.5.1.3).
4. The HNB-GW maps the SCCP:CREF message into an RNA:DISCONNECT.
5. The HNB-GW sends an RNA:DISCONNECT message, including the optional RNSAP PDU2 if received from the Target RNC.
7.3.3.2.3 RNC initiated
Figure 7.3.3.2.3-1: Establishment of signalling connection over Iurh and Iur connections between HNB and RNC via HNB-GW – RNC Initiated.
1. The HNB-GW is seen by Source RNC as a (configured) neighbour RNC. Any signalling towards a target cell with a respective RNC-Id-prefix is sent to the HNB-GW. In this case the RNC triggers the SCCP connection establishment as described in TS 25.420 [31] subclause 4.5.1.3.
2. The HNB-GW has to be able (i) to extract the Target HNB RNL Id from the (Global) Cell-Id indicated in the initiating RNSAP PDU and (ii) to maintain a mapping between the SCCP-based signalling connection and the RNA-based signalling connection for the HNB-RNC end-to-end communication.
3. The HNB-GW sends an RNA:CONNECT message towards the appropriate HNB including the Iurh Context Id generated at Step 2, RNSAP PDU1 received from the RNC and the Global Ids of RNC and HNB.
4-7. At the reception of the RNA:CONNECT message, the Target HNB processes RNSAP PDU1, generates the response RNSAP PDU2. The HNB replies then with an RNA:Direct Transfer message including the new RNSAP PDU2 and the RNC and HNB Ids. The HNB-GW will forward such pieces of information to the RNC (TS 25.420 [31] subclause 4.5.1.3).
7.3.3.3 Transport of RNSAP signalling messages via signalling connection established over Iurh and Iur connections
7.3.3.3.1 HNB initiated
Figure 7.3.3.3.1-1: Transport of RNSAP messages via signalling connection over Iurh and Iur connections – HNB initiated.
If the Sending HNB wants to send an RNSAP message to the Receiving RNC for which a connection oriented data transfer service is already established, it issues an RNA:DIRECT TRANSFER message towards the HNB-GW which contains the Iurh Context Id, the RNSAP PDU and the Receivers HNB RNL Identity.
The HNB-GW will forward the RNSAP PDU to the Receiving RNC within an SCCP message.
7.3.3.3.2 RNC initiated
Figure 7.3.3.3.1-1: Transport of RNSAP messages via signalling connection over Iurh and Iur connections – RNC initiated.
If the Sending RNC wants to send an RNSAP message to the Receiving RNC for which a connection oriented data transfer service is already established, it will send to the HNB-GW the RNSAP PDU within an SCCP message.
The HNB-GW will then generate an RNA:DIRECT TRANSFER message and will route the RNSAP PDU to the correct HNB.
7.3.3.4 Release of signalling connection over Iurh and Iur Connections
7.3.3.4.1 HNB initiated
Figure 7.3.3.4.1-1: Release of established signalling connection over Iurh and Iur connections – HNB initiated.
If an HNB wants to release a signalling connection previously established over Iurh and Iur connections previously established towards an RNC, it sends an RNA:DISCONNECT message, which includes the Iurh Context Id and the Receivers HNB RNL Identity (i.e., the Global RNC Id) and may include an RNSAP PDU. The HNB-GW maps the RNA:DISCONNECT message to an SCCP:Released message and triggers the SCCP connection release procedure defined in TS 25.420 [31] subclause 4.5.1.4.
7.3.3.4.2 RNC initiated
Figure 7.3.3.4.2-1: Release of established signalling connection over Iurh and Iur connections – RNC initiated.
If an RNC wants to release a signalling connection previously established over Iurh and Iur signalling connections previously established towards an HNB, it behaves as described in TS 25.420 [31] subclause 4.5.1.4.
The HNB-GW maps the SCCP:RLSD to an RNA:DISCONNECT message and forwards it to the HNB. This last message includes the proper Iurh Context Id. the Receivers HNB RNL Identity (i.e., the HNB Global Id) and an RNSAP PDU, if previously received from the RNC.
7.3.3.5 Transport of RNSAP signalling messages via the connectionless data transfer service
7.3.3.5.1 HNB initiated
Figure 7.3.3.5.1-1: Connectionless data transfer over Iurh and Iur connections – HNB initiated.
If the Sending HNB wants to send in a connectionless manner an RNSAP PDU to the HNB-GW for the Receiving RNC, it issues an RNA:CONNECTIONLESS TRANSFER message containing the RNSAP PDU, the Senders and the Receivers HNB RNL Identities.
The HNB-GW then generates and routes the RNSAP PDU within an SCCP message towards the Receiving RNC.
7.3.3.5.2 RNC initiated
Figure 7.3.3.5.2-1: Connectionless data transfer over Iurh and Iur connections – RNC initiated.
If the Sending RNC sends an RNSAP PDU to the HNB-GW for the Receiving HNB, the HNB-GW has to be able to extract the receiving HNB’s RNL address from received RNSAP PDU. Then the HNB-GW issues an RNA:CONNECTIONLESS TRANSFER message containing the RNSAP PDU, the Senders and the Receivers HNB RNL Identities to the receiving HNB. The Receiving HNB is able to identify the sending RNC by the Senders HNB RNL Identity.