| 摘要 |
In 3GPP UMTS Systems, the underlying transport provided for the radio specific protocols is ATM. Accordingly, at the various UTRAN interfaces ATM AAL2 connections shall be established between signalling endpoints (REP, TEP) associated to respective network elements (NE1, NE2). In order to setup a connection, for example at the lur interface, the originating AAL2 endpoint S-RNC sends to the destination AAL2 endpoint D-RNC the ALCAP ERQ (Establish Request) message requesting to use a resource constituted by a channel identified by VPI, VCI and CID. If the originating AAL2 endpoint receives from the destination AAL2 endpoint the ALCAP RLC (Release Confirm) message instead of the ECF (Establish Confirm) message it considers the requested resource as unavailable (Hanging resource) and sends to the destination AAL2 endpoint a RES (Reset) message in order to force the destination AAL2 endpoint to release the relevant resource. Once the resource is released (put in idle state) the destination AAL2 endpoint sends to the originating AAL2 endpoint a RSC (Reset Confirm) confirmation message. Upon the reception of the RSC message the latter endpoint may repeats the sending of the ERQ (Establish Request) message requesting to use the released resource. The destination AAL2 endpoint allocates the resource to the lur link, whether not yet allocated, and sends back to the originating AAL2 endpoint the ECF (Establish Confirm) message. At this point the originating AAL2 endpoint considers the connection successfully established and the signalling procedure is completed (fig.5). <IMAGE> |
