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Content for  TS 38.455  Word version:  16.1.0

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4  GeneralWord‑p. 11

4.1  Procedure specification principles

The principle for specifying the procedure logic is to specify the functional behaviour of the terminating NG-RAN Node exactly and completely. Any rule that specifies the behaviour of the originating NG-RAN Node shall be possible to be verified with information that is visible within the system.
The following specification principles have been applied for the procedure text in clause 8:
  • The procedure text discriminates between:
    1. Functionality which "shall" be executed
      The procedure text indicates that the receiving node "shall" perform a certain function Y under a certain condition. If the receiving node supports procedure X but cannot perform functionality Y requested in the initiating message of a Class 1 EP, the receiving node shall respond with the message used to report unsuccessful outcome for this procedure, containing an appropriate cause value.
    2. Functionality which "shall, if supported" be executed
      The procedure text indicates that the receiving node "shall, if supported," perform a certain function Y under a certain condition. If the receiving node supports procedure X, but does not support functionality Y, the receiving node shall proceed with the execution of the EP, possibly informing the requesting node about the not supported functionality.
  • Any required inclusion of an optional IE in a response message is explicitly indicated in the procedure text. If the procedure text does not explicitly indicate that an optional IE shall be included in a response message, the optional IE shall not be included. For requirements on including Criticality Diagnostics IE, see section 10.
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4.2  Forwards and backwards compatibility

The forwards and backwards compatibility of the protocol is assured by a mechanism where all current and future messages, and IEs or groups of related IEs, include ID and criticality fields that are coded in a standard format that will not be changed in the future. These parts can always be decoded regardless of the standard version.

4.3  Specification notations

For the purposes of the present document, the following notations apply:
Procedure
When referring to an elementary procedure in the specification the Procedure Name is written with the first letters in each word in upper case characters followed by the word "procedure", e.g. Handover Preparation procedure.
Message
When referring to a message in the specification the MESSAGE NAME is written with all letters in upper case characters followed by the word "message", e.g. ERROR INDICATION message.
IE
When referring to an information element (IE) in the specification the Information Element Name is written with the first letters in each word in upper case characters and all letters in Italic font followed by the abbreviation "IE", e.g. Cause IE.
Value of an IE
When referring to the value of an information element (IE) in the specification the "Value" is written as it is specified in sub clause 9.2 enclosed by quotation marks, e.g. "Value".
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5  NRPPa services

The present clause describes the services an NG -RAN Node offers to the LMF.

5.1  NRPPa procedure modulesWord‑p. 12
The procedures are divided into two modules as follows:
  1. NRPPa Location Information Transfer Procedures;
  2. NRPPa Management Procedures;
The NRPPa Location Information Transfer Procedures module contains procedures used to handle the transfer of positioning related information between NG-RAN Node and LMF.
The Management Procedures module contains procedures that are not related specifically to positioning, i.e. error handling.

5.2  Parallel transactions

Unless explicitly indicated in the procedure specification, at any instance in time one protocol peer may have more than one ongoing NRPPa procedure.

6  Services expected from lower layer

Within 5G RAN, NRPPa protocol uses the services provided by the NGAP protocol. An NRPPa message is carried inside an NGAP message.
NGAP signalling is described in TS 38.413.

7  Functions of NRPPa

The NRPPa protocol provides the following functions:
  • E-CID Location Information Transfer. This function allows the NG-RAN node to exchange location information with LMF for the purpose of E-CID positioning and NR E-CID positioning.
  • OTDOA Information Transfer. This function allows the NG-RAN node to exchange information with the LMF for the purpose of OTDOA positioning.
  • Reporting of General Error Situations. This function allows reporting of general error situations, for which function specific error messages have not been defined.
  • Assistance Information Transfer. This function allows the LMF to exchange information with the NG-RAN node for the purpose of assistance information broadcasting.
  • Positioning Information Transfer. This function allows the NG-RAN node to exchange positioning information with the LMF for the purpose of positioning.
  • Measurement Information Transfer. This function allows the LMF to exchange measurement information with the NG-RAN node for the purpose of positioning.
  • TRP Information Transfer. This function allows an LMF to obtain TRP related information from an NG-RAN node.
The mapping between the above functions and NRPPa EPs is shown in the table below.
Function Elementary Procedure(s)
E-CID Location Information Transfer
  1. E-CID Measurement Initiation
  2. E-CID Measurement Failure Indication
  3. E-CID Measurement Report
  4. E-CID Measurement Termination
OTDOA Information Transfer OTDOA Information Exchange
Assistance Information Transfer
  1. Assistance Information Control
  2. Assistance Information Feedback
Reporting of General Error Situations Error Indication
Positioning Information Transfer
  1. Positioning Information Exchange
  2. Positioning Information Update
  3. Positioning Activation
  4. Positioning Deactivation
TRP Information Transfer TRP Information Exchange
Measurement Information Transfer
  1. Measurement
  2. Measurement Update
  3. Measurement Report
  4. Measurement Abort
  5. Measurement Failure Indication
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