基本流程(EP):
NGAP协议由一些基本流程组成。以个基本流程是NG-RAN和AMF间的交互单元。
具有独立性和灵活性。
EP的消息构成类型:
Class1:应答类消息,有request和response过程,response会响应success或failure
Class2:通知类消息,发送notify,不用等response
Class1类response种类:
Class2类消息则认为一直是成功的。
NGAP提供UE相关和非UE相关服务:
NGAP基本流程(EP)列表
Table 8.1-1: Class 1 procedures
Elementary Procedure |
Initiating Message |
Successful Outcome |
Unsuccessful Outcome |
Response message |
Response message |
||
AMF Configuration Update |
AMF CONFIGURATION UPDATE |
AMF CONFIGURATION UPDATE ACKNOWLEDGE |
AMF CONFIGURATION UPDATE FAILURE |
RAN Configuration Update |
RAN CONFIGURATION UPDATE |
RAN CONFIGURATION UPDATE ACKNOWLEDGE |
RAN CONFIGURATION UPDATE FAILURE |
Handover Cancellation |
HANDOVER CANCEL |
HANDOVER CANCEL ACKNOWLEDGE |
|
Handover Preparation |
HANDOVER REQUIRED |
HANDOVER COMMAND |
HANDOVER PREPARATION FAILURE |
Handover Resource Allocation |
HANDOVER REQUEST |
HANDOVER REQUEST ACKNOWLEDGE |
HANDOVER FAILURE |
Initial Context Setup |
INITIAL CONTEXT SETUP REQUEST |
INITIAL CONTEXT SETUP RESPONSE |
INITIAL CONTEXT SETUP FAILURE |
NG Reset |
NG RESET |
NG RESET ACKNOWLEDGE |
|
NG Setup |
NG SETUP REQUEST |
NG SETUP RESPONSE |
NG SETUP FAILURE |
Path Switch Request |
PATH SWITCH REQUEST |
PATH SWITCH REQUEST ACKNOWLEDGE |
PATH SWITCH REQUEST FAILURE |
PDU Session Resource Modify |
PDU SESSION RESOURCE MODIFY REQUEST |
PDU SESSION RESOURCE MODIFY RESPONSE |
|
PDU Session Resource Modify Indication |
PDU SESSION RESOURCE MODIFY INDICATION |
PDU SESSION RESOURCE MODIFY CONFIRM |
|
PDU Session Resource Release |
PDU SESSION RESOURCE RELEASE COMMAND |
PDU SESSION RESOURCE RELEASE RESPONSE |
|
PDU Session Resource Setup |
PDU SESSION RESOURCE SETUP REQUEST |
PDU SESSION RESOURCE SETUP RESPONSE |
|
UE Context Modification |
UE CONTEXT MODIFICATION REQUEST |
UE CONTEXT MODIFICATION RESPONSE |
UE CONTEXT MODIFICATION FAILURE |
UE Context Release |
UE CONTEXT RELEASE COMMAND |
UE CONTEXT RELEASE COMPLETE |
|
Write-Replace Warning |
WRITE-REPLACE WARNING REQUEST |
WRITE-REPLACE WARNING RESPONSE |
|
PWS Cancel |
PWS CANCEL REQUEST |
PWS CANCEL RESPONSE |
|
UE Radio Capability Check |
UE RADIO CAPABILITY CHECK REQUEST |
UE RADIO CAPABILITY CHECK RESPONSE |
|
Table 8.1-2: Class 2 procedures
Elementary Procedure |
Message |
Downlink RAN Configuration Transfer |
DOWNLINK RAN CONFIGURATION TRANSFER |
Downlink RAN Status Transfer |
DOWNLINK RAN STATUS TRANSFER |
Downlink NAS Transport |
DOWNLINK NAS TRANSPORT |
Error Indication |
ERROR INDICATION |
Uplink RAN Configuration Transfer |
UPLINK RAN CONFIGURATION TRANSFER |
Uplink RAN Status Transfer |
UPLINK RAN STATUS TRANSFER |
Handover Notification |
HANDOVER NOTIFY |
Initial UE Message |
INITIAL UE MESSAGE |
NAS Non Delivery Indication |
NAS NON DELIVERY INDICATION |
Paging |
PAGING |
PDU Session Resource Notify |
PDU SESSION RESOURCE NOTIFY |
Reroute NAS Request |
REROUTE NAS REQUEST |
UE Context Release Request |
UE CONTEXT RELEASE REQUEST |
Uplink NAS Transport |
UPLINK NAS TRANSPORT |
AMF Status Indication |
AMF STATUS INDICATION |
PWS Restart Indication |
PWS RESTART INDICATION |
PWS Failure Indication |
PWS FAILURE INDICATION |
Downlink UE Associated NRPPa Transport |
DOWNLINK UE ASSOCIATED NRPPA TRANSPORT |
Uplink UE Associated NRPPa Transport |
UPLINK UE ASSOCIATED NRPPA TRANSPORT |
Downlink Non UE Associated NRPPa Transport |
DOWNLINK NON UE ASSOCIATED NRPPA TRANSPORT |
Uplink Non UE Associated NRPPa Transport |
UPLINK NON UE ASSOCIATED NRPPA TRANSPORT |
Trace Start |
TRACE START |
Trace Failure Indication |
TRACE FAILURE INDICATION |
Deactivate Trace |
DEACTIVATE TRACE |
Cell Traffic Trace |
CELL TRAFFIC TRACE |
Location Reporting Control |
LOCATION REPORTING CONTROL |
Location Reporting Failure Indication |
LOCATION REPORTING FAILURE INDICATION |
Location Report |
LOCATION REPORT |
UE TNLA Binding Release |
UE TNLA BINDING RELEASE REQUEST |
UE Capability Info Indication |
UE CAPABILITY INFO INDICATION |
PDU会话管理过程
包括PDU会话资源建立、释放、修改、通知以及PDU会话资源修改指示。
1、PDU会话建立过程,主要是为一个或多个PDU会话资源和相应的QoS流分配Uu和NG-U的资源,并给特定的UE建立相应的DRB。
该过程有AMF发起,NG-RAN收到请求消息,NG-RAN判断是否有AMF请求的配置资源,如果有,则执行执行被请求的NG-RAN配置并为PDU会话列表中在NG和Uu间分配资源。
2、PDU会话资源释放,目的是释放已经为特定UE建立的PDU会话资源。
该过程有AMF发起,NG-RAN在释放NG和Uu间释放通信资源。
3、PDU会话资源修改,目的是为特定的UE修改已建立好的PDU会话,并为已建立好的PDU会话发起QoS的建立、修改和释放。
该过程由AMF发起,NG-RAN判断是否有修改请求的配置资源,如果有,则NG-RAN节点将为请求的PDU会话执行修改配置。
4、PDU会话资源通知,目的是通知已经为给定UE建立的QoS流或PDU会话被释放或不再被执行,或由发出通知的NG-RAN节点再次执行。
该过程由NG-RAN节点发起。
5、PDU会话资源修改指示,目的是为NG-RAN节点请求修改已建好的PDU会话。
NG-RAN节点发起该过程,AMF将透传PDU会话资源修改指示给每个PDU资源相关的SMF。
UE上下文管理过程
1、初始上下文建立,目的是在NG-RAN节点建立需要的所有的UE上下文,包括PDU会话上下文,安全Key,移动性约束列表,UE无线能力和UE的安全能力等。如果有一个UE相关的NG连接链路存在(即NG口与AMF已建立连接)或者AMF已收到在INITIAL UE MESSAGE 中包含RAN UE NGAP ID(也表明NG口实例已建好),AMF将发起该过程。
如果NG-RAN节点不存在NG UE上下文,初始上下文建立过程将失败。
2、UE上下文释放请求(由NG-RAN节点发起),目的:由于NG-RAN节点的原因,NG-RAN向AMF发起请求释放与UE相关的逻辑NG连接。
3、UE上下文释放(由AMF发起),目的:由于一些原因,释放与UE相关的AMF与NG-RAN节点间的逻辑连接。
4、UE上下文修改,目的:修改已建立的部分UE上下文。
如果UE上下文更新不能成功执行,NG-RAN节点将回复失败。
UE移动性管理过程
1、切换准备,目的由5GC请求AMF方准备资源。一个UE只有一个在切换准备的过程。
如果5GC或目标侧不能够接受任何的PDU会话资源或在切换准备阶段有任何的失败发生,AMF将回复失败。
5、切换资源分配,目的:在目标NG-RAN节点上保留资源,以便对UE进行切换。
如果目标NG-RAN侧不接受至少一个PDU会话资源,或在切换准备期间发生故障,目标NG-RAN侧将回复失败。
6、切换通知,目的:向AMF表明UE已到达目标小区,基于NG的切换已成功完成。
7、路径切换请求,目的:请求将一个下行GTP隧道切换到新的GTP隧道。
如果5GC不能将所有PDU会话资源的下行GTP隧道端点切换到新的GTP隧道端点,AMF将回复失败。
7、切换取消,目的:使源NG-RAN侧能够取消正在进行的切换准备或已经准备好的切换。
8、上行RAN状态传输,目的:基于NG的切换启用无损切换。
9、下行RAN状态传输,目的:基于NG的切换启用无损切换。
10、寻呼,目的:AMF在具体的NG-RAN侧寻呼一个UE。