【5G核心网】 PCF之Access and Mobility Policy1. 服务架构2. 服务操作3. Npcf_AMPolicyControl API4. Data Model 数据模型

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概述

本文分析 PCF 中的 Access and Mobility Policy Control Service 接入与移动性策略控制服务

接入与移动策略控制服务由策略控制功能（PCF）提供

该服务向 AMF 提供与 AMF 接入控制和移动性管理相关的策略，并提供以下功能：

- 在 UE 注册期间基于从 AMF 请求的策略创建

- 通知 AMF 已订阅的更新策略

- UE 策略上下文的删除

1. 服务架构

接入与移动策略控制服务（Npcf_AMPolicyControl）是策略控制功能（PCF）的基于 Npcf 服务的接口的一部分。

Npcf_AMPolicyControl 服务的使用者是访问和移动性管理功能（AMF）。

AMF 通过 N15 参考点访问 PCF 上的接入和移动策略控制服务。在漫游方案中，N15 参考点位于受访网络中的 V-PCF 和 AMF之间。

**Figure 4.1.2-1: Reference Architecture for the Npcf_AMPolicyControl Service; SBI representation**

**Figure 4.1.2-2** : **Non-roaming Reference Architecture for the Npcf_AMPolicyControl Service; reference point representation**

**Figure 4.1.3-2** : **Roaming reference Architecture for the Npcf_AMPolicyControl Service; reference point representation**

1.1 PCF 策略控制功能

- 支持统一的策略框架来保证网络的行为

- 向实施这些策略的 AMF 提供与接入和移动管理相关的策略

在漫游情况下，访问策略控制功能（V-PCF）向访问网络提供本小节中描述的功能。

向 AMF 提供服务：

- Registration management;

- Connection management;

- Reachability management; and

- Mobility Management.

2. 服务操作

**Table** **4.2.1** **-1: Operations of the Npcf_AMPolicyControl Service**

2.1 Npcf_AMPolicyControl_Create

AM 策略关联的创建仅适用于正常注册的 UE，即不适用于紧急注册的 UE。

{apiRoot}/npcf-am-policy-control/v1/policies

Figure 4.2.2.1-1: Creation of a policy association

当 UE 注册并建立 UE 上下文时，AMF 可以在更新位置过程中从 UDM 获取服务区域限制，RFSP 索引和 GPSI，并应基于本地策略决定是否向 PCF 请求策略。

为了从 PCF 请求策略，NF 服务使用者（例如AMF）必须发送 HTTP POST 请求，其中资源 URI 为

“ {apiRoot} / npcf-am-policy-control / v1 / policies”，请求为 PolicyAssociationRequest 数据结构，其包括：

- Notification URI encoded as "notificationUri" attribute; and

- SUPI encoded as "supi" attribute,

当可用时包括参数：

- GPSI encoded as "gpsi" attribute;

- Access type encoded as "accessType" attribute;

- Permanent Equipment Identifier (PEI) encoded as "pei" attribute;

- User Location Information encoded as "userLoc" attribute;

- UE Time Zone encoded as "timeZone" attribute;

- Serving PLMN Identifier encoded as "servingPlmn" attribute;

- RAT type encoded as "ratType" attribute;

- Service Area Restriction s (see subclause 4.2.2.3.1) derived from the Service Area Restrictions obtained from the UDM by mapping any service areas denoted by geographical information into Tracking Area Identities (TAIs) and encoded as "servAreaRes" attribute;

- RFSP index (see subclause 4.2.2.3.2) as obtained from the UDM encoded as "rfsp" attribute;

- A list of Internal Group Identifiers encoded as "groupIds" attribute;

- if the NF service consumer is an AMF, the GUAMI encoded as "guami" attribute;

- if the NF service consumer is an AMF, the name of a service produced by the AMF that expects to receive information within Npcf_AMPolicyControl_UpdateNotify service operation encoded as "serviceName" attribute;

- Alternate or backup IPv4 Address(es) where to send Notifications encoded as "altNotifIpv4Addrs" attribute;

- Alternate or backup IPv6 Address(es) where to send Notifications encoded as "altNotifIpv6Addrs" attribute; and

- trace control and configuration parameters information encoded as "traceReq" attribute.

{"notificationUri":"http://127.0.0.1:8080/namf-xxxx/v1/am-policy/","supi":"imsi-4069300007908","gpsi":"msisdn-0900000000","accessType":"3GPP_ACCESS","pei":"imeisv-1110000000000000","servingPlmn":{"mnc":"93","mcc":"406"},"guami":{"plmnId":{"mcc":"406","mnc":"93"},"amfId":"xxxx"},"suppFeat":""}

PCF 接收 HTTP POST 请求如下处理：

- 将分配一个策略关联 ID

- 应确定适用的策略（考虑并可选地修改可能收到的服务区限制和/或 RFSP 索引）

- 对于成功的应在“位置”头字段中发送 HTTP “ 201 Created” 响应以及所创建资源的 URI

2.2 Npcf_AMPolicyControl_Update

当 NF 服务使用者修改现有的 AM 策略关联时（包括 AMF 重新定位且新的 AMF 选择保持与旧 PCF 的策略关联并更新 Notification URI 的情况）

2.3 Npcf_AMPolicyControl_UpdateNotify

2.4 Npcf_AMPolicyControl_Delete

3. Npcf_AMPolicyControl API

{apiRoot}/{apiName}/{apiVersion}/{apiSpecificResourceUriPart}

- The {apiRoot} shall be set as described in 3GPP TS 29.501 [6].

- The {apiName} shall be "npcf-am-policy-control".

- The {apiVersion} shall be "v1".

- The {apiSpecificResourceUriPart} shall be set as described in subclause 5.3.