3 Radio Link Layer Management Procedures

08.583GPPBase Station Controler - Base Transceiver Station (BCS-BTS) Interface Layer 3 SpecificationRelease 1999TS

This clause describes procedures related to the management of a link layer connection on the radio path.

3.1 Link establishment indication

This procedure is used by BTS to indicate to BSC that a layer 2 link on the radio path has been established in multi-frame mode at the initiative of an MS. BSC can use this indication to set up an SCCP connection to MSC.

Upon reception of a SABM frame on a link on an active channel, the BTS sends an ESTablish INDication message to BSC. The message contains the contents of the information field of the SABM frame if present.

The procedure is used in all establishment cases, for all channels and all SAPIs.

3.2 Link establishment request

This procedure is used by BSC to request the establishment of a link layer connection in multi-frame mode on the radio path.

The procedure is started by BSC sending an ESTablish REQuest message to BTS. BTS then establishes the link by sending an SABM frame. Upon reception of the acknowledgement (UA-frame) from MS, BTS sends an ESTablish CONFirm message to BSC.

In case of a failure, BTS sends a RELease INDication and an ERRor INDication message to BSC (cf. 3GPP TS 04.06).

3.3 Link release indication

This procedure is used by BTS to indicate to BSC that a link layer connection on the radio path has been released at the initiative of an MS.

When receiving a DISC frame on a link layer connection in multi-frame mode, BTS sends a RELease INDication message to BSC. (If the link layer is in idle mode, BTS will send a DM frame to MS but does not notify BSC.)

Collision cases are treated as specified in 3GPP TS 04.06.

3.4 Link release request

This procedure is used by BSC to request the release of a link layer connection on the radio path.

The procedure is started by BSC sending a RELease REQuest message to BTS. BTS then sends a DISC frame to MS. When it has received the acknowledgement (UA or DM frame), BTS sends a RELease CONFirm message to BSC.

Collision cases are treated as specified in 3GPP TS 04.06.

If BTS has repeated the DISC frame N200 times, BTS sends a RELease INDication and an ERRor INDication message to BSC (cf. 3GPP TS 04.06).

3.5 Transmission of a transparent L3-Message in acknowledged mode

This procedure is used by BSC to request the sending of a L3 message to MS in acknowledged mode.

BSC sends a DATA REQuest message to BTS. The message contains the complete L3 message to be sent in acknowledged mode.

3.6 Reception of a transparent L3-Message in acknowledged mode

This procedure is used by BTS to indicate the reception of a L3 message in acknowledged mode.

BTS sends a DATA INDication message to BSC. The message contains the received L3 message.

3.7 Transmission of a transparent L3-Message in unacknowledged mode

This procedure is used by BSC to request the sending of a L3 message to MS in unacknowledged mode.

BSC sends a UNIT DATA REQuest message to BTS. The message contains the L3 message to be sent to MS in unacknowledged mode.

3.8 Reception of a transparent L3-Message in unacknowledged mode

This procedure is used by BTS to indicate the reception of a L3 message in unacknowledged mode.

BTS sends a UNIT DATA INDication message to BSC. The message contains the received L3 message.

3.9 Link error indication

This procedure is used by BTS to indicate an abnormal case such as the following.

– a protocol error as specified in 3GPP TS 04.06, subclauses 5.6.4, 5.7.3 and annex G;

– a link layer failure, i.e. the repetition of an I-frame N200 times without an acknowledgement;

– the repetition of an SABM or DISC frame N200 times without an acknowledgement;

– the reception of an SABM frame in multi-frame established state.

When such an event has occurred, BTS notifies BSC by sending an ERROR INDication message containing the relevant cause information.