6 Procedures

29.6743GPPInterface between the UE radio Capability Management Function (UCMF) and the Mobility Management Entity (MME)Release 17Stage 3TS

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

6.1 Introduction

The following clauses specify the procedures supported over the S17 reference points.

6.2 Node Related Procedures

6.2.1 General

The following clauses specify the node related procedures over the S17 reference points.

6.2.2 Heartbeat Procedure

6.2.2.1 General

Two messages are specified for URCMP heartbeat procedure: Heartbeat Request and Heartbeat Response. The use of these messages is further specified in clause 19B of 3GPP TS 23.007 [3] for EPC.

6.2.2.2 Heartbeat Request

The MME or UCMF may send a Heartbeat Request on a path to the peer node to find out if it is alive. Heartbeat Request messages may be sent for each peer which is known by the sender, e.g. based on the configuration.

An MME or a UCMF shall be prepared to receive a Heartbeat Request at any time and it shall reply with a Heartbeat Response message.

6.2.2.3 Heartbeat Response

The message shall be sent as a response to a received Heartbeat Request message.

6.2.3 Subscription Management Procedure

6.2.3.1 General

The URCMP Subscription Management Procedure shall be used to create or delete a subscription in the UCMF, where the subscription is to get notifications for one or more new dictionary entries creation or for the deletion of one or more PLMN Assigned UE Radio Capability IDs.

6.2.3.2 Procedures in the MME

To create or delete a subscription in the UCMF which is used to receive notifications afterwards, the MME shall initiate the Subscription Management Procedure by sending a Subscription Management Request message towards the UCMF including:

– a "Subscription Management Operation Type" IE, which is set to either "Creation" or "Deletion";

– the MME Address Information IE which is used to receive subsequent notifications from the UCMF if the operation type is set to "Creation". The MME address information includes an IP address;

– the Subscription ID which is used to address a subscription in the UCMF if the operation code is set to "Deletion";

The MME shall create only one subscription in the UCMF.

When the MME receives the Subscription Management Response message with a successful cause for a subscription creation request, the MME function shall be prepared to receive subsequent notifications at the provided MME address.

6.2.3.3 Procedures in the UCMF

When the UCMF receives a Subscription Management Request message, it shall reply with a Subscription Management Response message.

On success:

– If the operation code is set to "Creation", the UCMF shall create a new subscription together with the MME address and the timestamp of the request to create the subscription, and include the following information in the Subscription Management Response message;

– a Subscription ID;

– the current highest Dictionary Entry ID which has been allocated in the UCMF;

– If the operation code is set to "Deletion", the UCMF shall delete the subscription and include a success cause code in the Subscription Management Response message;

On failure, the UCMF shall:

– return an appropriate error cause value, e.g. MANDATORY_IE_MISSING for the creation of a subscription, or SUBSCRIPTION_NOT_FOUND for the deletion of a subscription, discard all the received information.

6.2.4 Event Notification Procedure

6.2.4.1 General

The URCMP Event Notification Procedure shall be used to send a notification for an event, e.g. the creation of one or more new dictionary entries, towards an MME which has a valid subscription in the UCMF.

6.2.4.2 Procedures in the UCMF

When one or more new dictionary entries are created in the UCMF since the time of the creation of the subscription, or when a PLMN decides to switch to operate based on manufacturer-assigned UE Radio Capability ID for a particular type of UE, the UCMF shall initiate the Event Notification Procedure by sending an Event Notification Request message towards the MME including:

– an Event Type IE, which is set to either "Creation of Dictionary Entry" or "Deletion of PLMN-assigned UE Radio Capability ID" or "NEW_VERSION_ID_OF_PLMN_ASSIGNED_IDs";

– the updated highest Dictionary Entry ID if the Event Type is set to " CREATION_OF_DICTIONARY_ENTRY ";

– a new Version ID if the Event Type is set to " NEW_VERSION_ID_OF_PLMN_ASSIGNED_IDs";

– the Manufacturer Assigned operation requested list if the Event Type is set to " DELETION_OF_PLMN_ASSIGNED_IDS " which shall include one of the following (not both):;

– one or more PLMN Assigned UE Radio Capability IDs to be deleted;

– or, one or more Type Allocation Codes in corresponding to the PLMN Assigned UE Radio Capability IDs to be deleted.

6.2.4.3 Procedures in the MME

When the MME receives an Event Notification Request message, it shall reply with an Event Notification Response message.

On success, the MME:

– may determine and then retrieve those dictionary entries which are not available yet locally using the Dictionary Entry ID if the Event Type is set to " Creation of Dictionary Entry";

– shall retrieve affected UE contexts which are using those PLMN-assigned UE Radio Capability IDs which are to be deleted and behave as specified in clause 5.11.3a of 3GPP TS 23.401 [2] if the Event Type is set to "Deletion of PLMN-assigned UE Radio Capability ID";

– may determine to retrieve a new PLMN Assigned UE Radio Capability ID, e.g. for a UE with signalling connection established to the MME;

– shall include a success cause code in the Event Notification Response message;

On failure, the MME:

– shall return an appropriate error cause value in the Event Notification Response message, e.g. MANDATORY_IE_MISSING, and discard all the received information.

6.3 Session Related Procedures

6.3.1 General

The following clauses describe the session related procedures over the S17 reference points. A URCMP session refers to a signalling transaction addressing a dictionary entry containing the mapping information between the UE Radio Capability ID(s) and UE Radio Access Capability Information.

6.3.2 Create Dictionary Entry Procedure

6.3.2.1 General

The URCMP Create Dictionary Entry procedure shall be used to create a dictionary entry in the UCMF, and obtain a PLMN assigned UE Radio Capability ID.

6.3.2.2 Procedures in the MME

When the UE Radio Capability ID, either PLMN-assigned or Manufacturer-assigned, is not received by the MME from a UE, or from the source MME during an inter MME mobility procedure or if the MME receives a rejection response from the UCMF with the cause code "NO_DICTIONARY_ENTRY_FOUND" when it uses a Manufacturer-assigned UE Radio Capability ID to retrieve the corresponding UE Radio Access Capability Information, or if the MME receives a rejection response from the UCMF with the cause code "OUT_DATED_VERSION_ID_IN_RAC_ID" when it uses a PLMN-assigned UE Radio Capability ID to retrieve the corresponding UE Radio Access Capability Information, the MME shall initiate the Create Dictionary Entry Procedure by sending a Create Dictionary Entry Request message towards the UCMF including:

– the UE Radio Access Capability Information, which is received from the eNB, encoded as specified in 3GPP TS 36.413 [8], and optionally also including information encoded as specified in 3GPP TS 38.413 [11]

– Type Allocation Code in the IMEI of the UE

When the MME receives a Create Dictionary Entry Response message with a successful cause, the MME function shall continue with the procedure which triggered the Create Dictionary Entry procedure as specified in 3GPP TS 23.401 [2].

6.3.2.3 Procedures in the UCMF

When the UCMF receives a Create Dictionary Entry Request message, it shall reply with a Create Dictionary Entry Response message.

On success, the UCMF shall check whether for the provided input a dictionary entry already exists and a PLMN Assigned UE Radio Capability ID has already been assigned. If this is not the case, the UCMF shall create a new dictionary entry with the received information and a new PLMN assigned UE Radio Capability ID. The UCMF shall include the following (already existing or newly created) information in the Create Dictionary Entry Response message;

– a dictionary entry ID;

– a PLMN assigned UE Radio Capability ID, if PLMN is configured to use a PLMN specific UE Radio Capability ID.

On failure, the UCMF shall:

– return an appropriate error cause value, e.g. MANDATORY_IE_MISSING, discard all the received information and not create any dictionary entry.

A UCMF configured to operate in Mode of Operation A (3GPPP TS 23.401, Clause 5.11.3a) shall reject the operation if the request does not contain UE Radio Access Capability Information in both the formats and UCMF is not able to find match of the received UE Radio Access Capability Information in its database.

6.3.3 Query Dictionary Entry Procedure

6.3.3.1 General

The URCMP Query Dictionary Entry procedure shall be used to retrieve UE Radio Access Capability Information from a dictionary entry in the UCMF.

6.3.3.2 Procedures in the MME

When the MME receives a UE Radio Capability ID from a UE or the source MME (during an inter MME mobility procedure), which is either PLMN-assigned or Manufacturer-assigned, while there is no corresponding UE Radio Access Capability Information stored in the MME, the MME shall initiate the Query Dictionary Entry Procedure by sending a Query Dictionary Entry Request message towards the UCMF including:

– a PLMN-assigned UE Radio Capability ID;

– or a Manufacturer-assigned UE Radio Capability ID;

– or a Dictionary Entry ID;

When the MME receives a Query Dictionary Entry Response message with a successful cause, the MME function shall continue with the procedure which triggered the Create Dictionary Entry procedure as specified in 3GPP TS 23.401 [2].

6.3.3.3 Procedures in the UCMF

When the UCMF receives a Query Dictionary Entry Request message, it shall look up the dictionary entries and reply with a Query Dictionary Entry Response message.

On success, the UCMF shall provide the information included in the dictionary entry which matches the query parameter in the Query Dictionary Entry Response message, and the following information shall be included (if available):

– the UE Radio Access Capability Information in correspondence to the querying parameter, e.g. the UE Radio Capability ID included in the request message;

– a PLMN specific UE Radio Capability ID if allocated, e.g. when the querying UE Radio Capability ID is a Manufacturer-assigned UE Radio Capability ID and if PLMN is configured to use a PLMN specific UE Radio Capability ID;

– the dictionary entry id;

– a Manufacturer-assigned UE Radio Capability ID if available;

– the Type Allocation Code.

NOTE: The UCMF will not provide the information in a dictionary entry which is already included as a query parameter in the request message.

On failure, the UCMF shall:

– return an appropriate error cause value, e.g. NO_DICTIONARY_ENTRY_FOUND, OUT_DATED_VERSION_ID_IN_RAC_ID.

6.4 Reliable Delivery of URCMP Messages

Reliable delivery of URCMP messages is accomplished by retransmission of these messages as specified in this clause.

A URCMP entity shall maintain, for each triplet of local IP address, local UDP port and remote peer’s IP address, a sending queue with Request messages to be sent to that peer. Each message shall be sent with a Sequence Number and be held until a corresponding Response is received or until the URCMP entity ceases retransmission of that message. The Sequence Number shall be unique for each outstanding Request message sourced from the same IP/UDP endpoint. A URCMP entity may have several outstanding Requests waiting for replies.

When sending a Request message, the sending URCMP entity shall start a timer T1. The sending entity shall consider that the Request message has been lost if a corresponding Response message has not been received before the T1 timer expires. If so, the sending entity shall retransmit the Request message, if the total number of retry attempts is less than N1 times. The setting of the T1 timer and N1 counter is implementation specific.

A retransmitted URCMP message shall have the same message content, including the same URCMP header, UDP ports, source and destination IP addresses as the originally transmitted message.

A Request and its Response message shall have the same Sequence Number value, i.e. the Sequence Number in the URCMP header of the Response message shall be copied from the respective Request message. A Request and its Response messages are matched based on the Sequence Number and the IP address and UDP port.

Not counting retransmissions, a Request message shall be answered with a single Response message. Duplicated Response messages shall be discarded by the receiver. A received Response message not matching an outstanding Request message waiting for a reply should be discarded.

The URCMP entity should inform the upper layer when detecting an unsuccessful transfer of a Request message to enable the controlling upper entity to take any appropriate measure.