XR Delivery in 5G SystemTS 26.928

General Delivery Categories

The following delivery categories for XR experiences are defined:

下载：无需连接即可下载和离线使用 XR 体验。 所有媒体和体验相关的流量都是下行的。

Download: An XR experience is downloaded and consumed offline without requiring a connection. All media and experience related traffic is downlink.

（被动）流式传输：从网络服务器实时消费体验。 用户不与 XR 体验交互，或者如果与 XR 体验交互，则交互不会触发任何上行链路流量。 所有与媒体相关的流量都是下行链路。

(Passive) Streaming: The experience is consumed in real-time from a network server. The user does not interact with the XR experience, or if interacting with the XR experience, the interaction is not triggering any uplink traffic. All media related traffic is downlink.

交互式（流式传输）：从网络服务器实时消费体验。 用户（或设备自动）与 XR 体验交互，交互会改变交付的内容。 流量主要是下行链路，但某些流量是上行链路，例如 XR 查看器姿势信息。 存在不同风格的交互，例如视口适应、游戏事件等。交互延迟要求可能不同，从沉浸式延迟要求到更静态的选择交互。

Interactive (Streaming): The experience is consumed in real-time from a network server. The user (or the device automatically) interacts with the XR experience and the interaction changes the delivered content. The traffic is predominantly downlink, but certain traffic is uplink, e.g. XR Viewer Pose information. Different flavours of interaction exist, for example viewport adaptation, gaming events, etc. Interaction delay requirements may be different, ranging from immersive latency requirements to more static selection interactions.

会话式：体验由两个或多个具有会话延迟要求的参与者实时生成、共享和消费。

Conversational: The experience is generated, shared and consumed in real-time from two or more participants with conversational latency requirements.

拆分计算/渲染：网络功能运行 XR 引擎以支持沉浸式场景的处理和预渲染，并且交付被拆分为多个连接，例如 拆分渲染、边缘计算等。延迟和交互要求再次取决于用例和架构实现。

Split Compute/Rendering: Network functions run an XR engine to support processing and pre-rendering of immersive scenes and the delivery is split into more than one connection, e.g. Split rendering, Edge Computing, etc. The latency and interaction requirements again depend on the use case and the architecture implementation.

5G System and Radio Functionalities for XR

XR 应用在 5G 系统中的集成是按照 3GPP TS 26.501 中定义的 5G 媒体流模型进行的。 假设 5G-XR 应用程序提供商是 XR 应用程序提供商，将 5G 系统功能用于其服务。 为此，它在 UE 上提供 5G-XR 感知应用程序，以使用 5G-XR 客户端和使用网络接口和 API 的网络功能，可能在 5G-XR 相关规范中定义。

The integration of XR applications within the 5G System is approached following the model of 5G Media Streaming as defined in 3GPP TS 26.501. Assume a 5G-XR Application Provider being an XR Application provider that makes use of 5G System functionalities for its services. For this purpose, it provides a 5G-XR Aware Application on the UE to make use of a 5G-XR client and network functions using network interfaces and APIs, potentially defined in 5G-XR related specifications.

图 4.3.2-1 中的架构表示 3GPP TS 23.501 中定义的 5G 系统 (5GS) 中潜在的 5G-XR 功能。 定义了三个主要功能： 5G-XR AF：类似于 3GPP TS 23.501 第 6.2.10 条中定义的应用功能，专用于 5G-XR 服务。 5G-XR AS：专用于 5G-XR 服务的应用服务器。 5G-XR 客户端：专用于 5G-XR 服务的 UE 内部功能。

The architecture in Figure 4.3.2-1 represents potential 5G-XR functions within the 5G System (5GS) as defined in 3GPP TS 23.501. Three main functions are defined: 5G-XR AF: An Application Function similar as defined in 3GPP TS 23.501, clause 6.2.10, dedicated to 5G-XR Services. 5G-XR AS: An Application Server dedicated to 5G-XR Services. 5G-XR Client: A UE internal function dedicated to 5G-XR Services.

在本技术报告的上下文中，5G-XR AF 和 5G-XR AS 最初被视为数据网络 (DN) 功能，并通过 3GPP TS 23.501 中定义的 N6、N3 和 Uu 与 UE 通信。 通过侧链 PC5 的通信可以替代基于 Uu 的通信。 如图所示，受信任 DN 中的功能受到运营商网络的信任。 因此，可信 DN 中的 AF 可以直接与所有 5G Core 功能通信。 外部 DN 中的功能只能使用 N33 通过 NEF 与 5G 核心功能进行通信。

In the context of this Technical Report, 5G-XR AF and 5G-XR AS are initially considered Data Network (DN) functions and communicate with the UE via N6, N3 and Uu as defined in 3GPP TS 23.501. Communication through sidelink PC5 may be an alternative to Uu based communication. Functions in trusted DNs are trusted by the operator’s network as illustrated. Therefore, AFs in trusted DNs may directly communicate with all 5G Core functions. Functions in external DNs may only communicate with 5G Core functions via the NEF using N33.

注：黄色实心框表示的功能在 5GXR 的第 3 阶段规范的潜在范围内。 灰色框表示的功能在 5G 系统规范中定义。 蓝色框指示的功能已分配给应用程序。 以上述架构为起点。 XR 相关功能专门分配给 DN 或 UE。 然而，可以为 3GPP 系统确定可以从 XR 应用程序中受益的架构扩展。 示例包括使用网络切片、边缘计算或使用 5G 服务质量。

Note: The functions indicated by the yellow filled boxes are in potential scope of stage 3 specifications for 5GXR. The functions indicated by the grey boxes are defined in 5G System specifications. The functions indicated by the blue boxes are assigned to the applications. The above architecture is used as a starting point. With XR related functions exclusively assigned to either DN or UE. However, architectural extensions may be identified for the 3GPP system that may benefit from XR applications. Examples include the use of network slicing, edge computing or usage of 5G quality of service.

5G 中集成的基本 XR 架构如图 4.3.2-2 所示。 可以考虑定义以下功能： UE 上的 5G-XR 客户端：5G-XR 会话数据的接收者，可通过 5G-XR 感知应用程序通过明确定义的接口/API 访问。 5G-XR 包含两个子功能： XR 会话处理程序：UE 与 5G-XR AF 通信以建立、控制和支持 XR 会话的传递的功能。 XR 会话处理程序公开了可供 5G-XR 感知应用程序使用的 API。 XR 引擎：UE 与 5G-XR 应用服务器通信以访问 XR 相关数据的功能，包括传感器和跟踪等 XR 相关功能，处理此数据并与 XR 会话处理程序进行通信以进行 XR 会话 控制。

A basic XR architecture integrated in 5G is shown in Figure 4.3.2-2. The following functions may be considered to be defined: 5G-XR Client on UE: Receiver of 5G-XR session data that may be accessed through well-defined interfaces/APIs by the 5G-XR Aware Application. The 5G-XR contains two sub-functions: XR Session Handler: A function of the UE that communicates with the 5G-XR AF in order to establish, control and support the delivery of an XR session. The XR Session Handler exposes APIs that can be used by the 5G-XR Aware Application. XR Engine: A function of the UE that communicates with the 5G-XR Application Server in order to get access to XR related data, includes XR relevant functionalities such as sensors and tracking, processes this data and communicates with the XR Session Handler for XR session control.

5G-XR 感知应用程序：5G-XR 客户端通常由外部 XR 感知应用程序控制，例如一个应用程序，它实现了外部应用程序服务提供者特定的逻辑并能够建立一个 XR 会话。 5G-XR 感知应用程序通过接口和 API 使用 5G-XR 客户端和网络功能。 5G-XR AS：承载 5G-XR 媒体和媒体功能的应用服务器。 5G-XR 应用程序提供商：利用 5G-XR 客户端和网络功能为 5G-XR Aware 应用程序提供 XR 体验的外部 XR 应用程序提供商。 5G-XR AF：为 UE 上的 XR Session Handler 和/或 5G-XR Application Provider 提供各种控制功能。它可以中继或发起对不同策略或计费功能 (PCF) 处理的请求，或与其他网络功能交互。在上面的上下文中，5G 无线电也可以在 5G Uu 和 5G Sidelink/PC5 之间进行区分。 Uu 是 3GPP TS 38.300 中定义的用户设备 (UE) 和无线电接入网络 (RAN) 之间的接口。 Sidelink 是一种通信模式，UE 可以借此直接相互通信，如 3GPP TS 38.300 中定义的那样。

5G-XR Aware Application: The 5G-XR Client is typically controlled by an external XR aware application, e.g. an App, which implements the external application service provider specific logic and enables establishing an XR session. The 5G-XR Aware Application makes use of 5G-XR Client and network functions using interfaces and APIs. 5G-XR AS: An Application Server which hosts 5G-XR media and media functions. 5G-XR Application Provider: External XR application provider that makes use of 5G-XR client and network functionalities to provide an XR experience to the 5G-XR Aware applications. 5G-XR AF: provides various control functions to the XR Session Handler on the UE and/or to the 5G-XR Application Provider. It may relay or initiate a request for different Policy or Charging Function (PCF) treatment or interact with other network functions. In the context of the above, 5G radio may also be differentiated between 5G Uu and 5G Sidelink/PC5. Uu is the interface between User Equipement (UE) and Radio Access Network (RAN) as defined in 3GPP TS 38.300. Sidelink is a mode of communication whereby UEs can communicate with each other directly as defined in 3GPP TS 38.300.

Quality-of-Service in 5G

5G QoS 模型基于 QoS 流。 5G QoS 模型同时支持：需要保证流比特率的 QoS 流（GBR QoS 流）和不需要保证流比特率的 QoS 流（非 GBR QoS 流）。 5G QoS 模型还支持反射式 QoS（参见 3GPP TS 23.501 的第 5.7.5 条）。 QoS 流 ID (QFI) 用于标识 5G 系统中的 QoS 流。 分配给协议数据单元 (PDU) 会话中相同 QoS 流的用户平面流量接收相同的流量转发处理（例如调度、准入阈值）。 QFI 可以是动态分配的，也可以等于 5G QoS 标识符 (5QI)。 QoS 流可能是“GBR”、“非 GBR”或“延迟容忍 GBR”，具体取决于其 QoS 配置文件，它包含如下 QoS 参数：

The 5G QoS model is based on QoS Flows. The 5G QoS model supports both: QoS Flows that require guaranteed flow bit rate (GBR QoS Flows), and QoS Flows that do not require guaranteed flow bit rate (Non-GBR QoS Flows). The 5G QoS model also supports Reflective QoS (see clause 5.7.5 of 3GPP TS 23.501). A QoS Flow ID (QFI) is used to identify a QoS Flow in the 5G System. User Plane traffic assigned to the same QoS Flow within a Protocol Data Unit (PDU) Session receives the same traffic forwarding treatment (e.g. scheduling, admission threshold). The QFI may be dynamically assigned or may be equal to the 5G QoS Identifier (5QI). A QoS Flow may either be 'GBR', 'Non-GBR' or “Delay Tolerant GBR” depending on its QoS profile and it contains QoS parameters as follows:

对于每个 QoS 流，QoS 配置文件包括 QoS 参数： 5G QoS 标识符（5QI）； 分配和保留优先级 (ARP)。 仅对于每个非 GBR QoS 流，QoS 配置文件还可以包括 QoS 参数：反射 QoS 属性 (RQA)。 仅对于每个 GBR QoS 流，QoS 配置文件还包括 QoS 参数：保证流比特率 (GFBR) - 上行链路 (UL) 和下行链路 (DL)； 和最大流量比特率 (MFBR) - UL 和 DL。 仅在 GBR QoS 流的情况下，QoS 配置文件还可以包括一个或多个 QoS 参数： 通知控制； 最大丢包率 - UL 和 DL。 3GPP TS 23.501 的表 5.7.4-1 中规定了标准化 5QI 值与 5G QoS 特性的一对一映射。

For each QoS Flow, the QoS profile includes the QoS parameters: 5G QoS Identifier (5QI); and Allocation and Retention Priority (ARP). For each Non-GBR QoS Flow only, the QoS profile can also include the QoS parameter: Reflective QoS Attribute (RQA). For each GBR QoS Flow only, the QoS profile also include the QoS parameters: Guaranteed Flow Bit Rate (GFBR) - uplink (UL) and downlink (DL); and Maximum Flow Bit Rate (MFBR) - UL and DL. In the case of a GBR QoS Flow only, the QoS profile can also include one or more of the QoS parameters: Notification control; Maximum Packet Loss Rate - UL and DL. The one-to-one mapping of standardized 5QI values to 5G QoS characteristics is specified in table 5.7.4-1 of 3GPP TS 23.501.

下载、被动流式传输和交互式流式传输最适合映射到 3GPP TS 26.501 中定义的 5G 媒体流式传输。 会话服务最适合映射到 3GPP TS 22.173 中定义的 IMS 多媒体电话服务 (MTSI)，在使用 3GPP 接入，特别是 5G 无线电技术时，侧重于 XR 媒体处理（例如信令、传输、编解码器、甲酸盐）。 预计 3GPP TS 26.114 中定义的 MTSI 客户端的媒体处理可以适当扩展，以支持 XR 应用和服务。

Download, passive streaming and interactive streaming are most suitably mapped to 5G Media Streaming as defined in 3GPP TS 26.501. Conversational services are most suitably mapped to the Multimedia Telephony Service for IMS (MTSI) as defined in 3GPP TS 22.173 with focus on XR media handling (e.g. signalling, transport, codecs, formates) when using 3GPP access, in particular 5G radio technologies. It is expected that the media handling of MTSI clients as defined in 3GPP TS 26.114 may be suitably extended in order to support XR applications and services.

Edge Computing

除了使用当今 5G 媒体流中定义的应用程序服务器外，5G-XR 应用程序可能会受益于边缘的额外处理。 在一个示例中，如图 4.3.5-1 所示，5G 网络运营商可以提供边缘平台，以支持内容提供商或云端提供的 XR 服务。

Beyond the use of Application Servers as defined in 5G Media Streaming today, the 5G-XR application may benefit from additional processing in the edge. In an example, as shown in Figure 4.3.5-1, an edge platform may be offered by the 5G network operator to support XR services served from the content provider or from the cloud.

From: http://nrexplained.com/tr/26928/xr5g