AMF

3GPP TS 29.518 V16.2.0

Non-Access Stratum (NAS)

AMF (Access and Mobility Management Function)

Communication

讓外部服務可以透過N1 NAS messages跟UE通訊。

讓外部服務可以訂閱、取消訂閱從UE來的特殊的N1 messages。

初始化N2 messages跟AN溝通。

加密內容管理。

1. UEContextTransfer: 舊AMF將UE's SUPI and MM Context轉交給新AMF。
2. RegistrationStatusUpdate: 一般註冊過程或AMF re-allocation時，更新UE註冊狀態。
3. N1N2MessageTransfer (UE Specific)
4. N1N2TransferFailureNotification (UE Specific) : UE不回應呼叫，AMF無法用N1訊息跟UE溝通時的失敗訊息。
5. N1N2MessageSubscribe (UE Specific) : PCF訂閱N1/N2訊息通知。
6. N1N2MessageUnsubscribe (UE Specific) : PCF取消訂閱N1/N2訊息通知。
7. N1MessageNotify (UE Specific) : 訂閱AMF收到N1訊息時的通知。如AMF re-allocation或UE定位相關。
8. N2InfoNotify (UE Specific) :
9. NonUeN2MessageTransfer
10. NonUeN2InfoSubscribe
11. NonUeN2INfoUnsubscribe
12. N2InfoNotify
13. EBIAssignment
14. CreateUEContext : AMF無法服務時Handover給下一個AMF，在下一個AMF產生UE Context。
15. ReleaseUEContext
16. AMFStatusChangeSubscribe
17. AMFStatusChangeUnsubscribe
18. AMFStatusChangeNotify

Event Exposure

類似UE狀態電子報，可訂閱UE事件舉例。

最後已知UE位址、UE是否進入某特定區域、UE的Time Zone、UE註冊狀態、UE連線狀態、可及性狀態、通訊失敗狀態等等。

提供三種服務

1. Subscribe (POST新增) (PATCH修改)
   • Invoked by a NF Service Consumer, e.g. NEF(Network Exposure Function), towards the AMF, when it needs to create a subscription to monitor at least one event relevant to the AMF. NEF訂閱UE的事件通知。
2. Unsubscribe (DELETE)
   • Invoked by a NF Service Consumer, e.g. NEF, towards the AMF, to remove an existing subscription previously created by itself at the AMF. 外部服務向AMF移除目前的訂閱。
3. Notify (POST)
   • Invoked by the AMF, to send a notification, towards the notification URI, when certain event included in the subscription has taken place. 由AMF產生事件通知，如訂閱成功事件。

Location

外部服務向AMF請求定位初始化、提供位置資訊、通知位置變更。

1. Allow NFs to request the current geodetic and optionally civic location of a target UE.
2. Allow NFs to be notified of event information related to emergency sessions.
3. Allow NFs to request Network Provided Location Information (NPLI) and/or local time zone corresponding to the location of a target UE.

提供四種服務操作

1. ProvidePositioningInfo; 外部服務向5G Core要求提供使用緊急會話的UE位置。
2. EventNotify; Callback中的NotifiedPosInfo。
3. ProvideLocationInfo; 外部服務如UDM可向NPLI網路提供商位置資訊要求UE資訊。
4. CancelLocation;

MT(Mobile Terminated Service)

Send MT signalling or data to a target UE

1. 如果UE在CM-IDLE狀態則呼叫，並且在UE進到CM-CONNECTED狀態的時候回應其他NF。Paging UE if UE is in CM-IDLE(Connection Management - IDLE) state and respond other NF after the UE enters CM-CONNECTED(Connection Management - CONNECTED) state. 參考資料
   • CM-Idle : A state when Mobile does not have signalling with Core Node (AMF) e.g. RRC Idle, When UE is in CM-Idle and moving across different cells controlled by mobility based on cell reselelction.
   • CM-Connected : UE has signalling connection with AMF e.g. RRC-Connected and RRC-Inactive
2. 如果UE在CM-CONNECTED狀態，則回應給詢問的NF。Response to the requester NF if UE is in CONNECTED state.
3. 向consumer NF提供IMS語音的terminating domain選擇資訊。Providing the terminating domain selection information for IMS voice to the consumer NF.

提供兩種服務操作

1. Enable UE Reachability
   • 有Downstream需求時，使UE可連線。Shall be invoked by the NF Service Consumer (e.g. SMSFunction, SMF) to enable the reachability of the UE.
   • NF Service Consumer如SMSF或SMF應透過HTTP的PUT來跟URI的"ueReachInd"資源溝通。Shall invoke the service by using the HTTP method PUT, towards the URI of a "ueReachInd" resource.
     • 如果UE是CM-CONNECTED狀態則AMF回覆"200 OK"，包含"EnableUeReachabilityRspData" object。
     • 如果UE是CM-IDLE狀態，AMF應呼叫UE。
2. Provide Domain Selection Info
   • NF Service Consumer如UDM發起要求取得UE資訊以終結domain selection of IMS voice。Shall be invoked by the NF Service Consumer (e.g. UDM) to get the UE information for terminating domain selection of IMS voice.
   • Indication of supporting IMS voice over PS Session
   • UE跟gNB最後接觸的時戳。Time stamp of the last radio contact with the UE
   • Current Access type and RAT type
   • NF Service Consumer應透過HTTP GET來跟URI的"UeContext"資源溝通。參數設定"info-class"以取得"TADS"數值。
     • 如成功AMD回覆"200 OK"，包含"UeContextInfo"資料結構。
     • 如失敗回覆HTTP status code。