5 Services expected from signalling transport

37.4663GPPIuant interface: Application partRelease 17TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

RETAP and TMAAP requires an assured in-sequence delivery service from the signalling transport and notification if the assured in-sequence delivery service is no longer available.

5.1 Elementary procedure format

Layer 2 provides a full-duplex link for the transmission of RETAP and TMAAP messages.

There are two types of RETAP and TMAAP elementary procedures:

Class 1: Initiating messages are sent either from the primary to a secondary device, or from a secondary to the primary device, in order to initiate some action within the receiving device. The other device sends a response message completing the procedure.

Class 2: Initiating messages are sent either from the primary to a secondary device, or from a secondary to the primary device. No response message is expected.

All RETAP and TMAAP messages use the same basic format:

Table 5.1.1: Basic format for all RETAP and TMAAP messages

Elementary procedure	Number of data octets	Data
1 octet	2 octets	MaxDataReceiveLength or MaxDataTransmitLength.

NOTE: Response messages have the same basic format as initiating messages. The elementary procedure code shall be the same in the response message as in the associated initiating message.

5.1.1 Initiating message

The data part of an initiating message may contain parameters as specified in clause 6 of this TS.

5.1.2 Response message

Elementary procedures shall, unless otherwise specified, provide a response message within 1 second. The response time is measured from the time the message frame was received by the transport layer to the time the response message is ready for transfer by the transport layer.

If the class1 elementary procedure requested by the initiating message was successfully executed, the response message data part from a single-antenna device shall contain return code <OK>. Additional information may follow in the data part. The response message data part from a multi-antenna device starts with the antenna number followed by return code <OK> and optional additional information.

If the elementary procedure requested by the initiating message was not successfully executed, the response message data part from a single-antenna device shall contain return code <FAIL>.

The following octet shall contain a second return code which describes why the execution of the requested procedure failed. The response message data part from a multi-antenna device starts with the antenna number followed by return code <FAIL> and a second return code which describes why the execution of the requested procedure failed.

In some situations an initiating message can cause a change of operating conditions, for instance a SetTilt procedure might cause a RET device to discover that an adjuster is jammed or that a previously jammed adjuster works normally again. In these cases an alarm procedure reporting the change of operating conditions shall be used in addition to the regular <OK> or <FAIL> return codes in response message.

A complete annotated table of all return codes with their corresponding hexadecimal numbers is provided in annex A of this TS.

Return codes marked with an X in the Alarm column of annex A in this TS are used to report operating conditions in alarm procedures (see subclauses 6.6.5 and 6.7.6 for details).