Content for  TR 26.998  Word version:  18.0.0

This clause introduces the 5G WireLess Tethered AR UE. Two sub-types are differentiated:

• Split Rendering WLAR UE. In this case the 5G phone that includes the modem also acts to support rendering of complex scenes and provides the pre-rendered data to the glass
• Relay WLAR UE: In this case, the 5G phone acts as a relay to provide IP connectivity.

Figure 4.2.2.4-1 provides a functional structure for Type 3a: 5G Split Rendering WireLess Tethered AR UE.

Main characteristics of Type 3a: 5G Split Rendering WireLess Tethered AR UE:

• 5G connectivity is provided through a tethered device which embeds the 5G modem. Wireless tethered connectivity is provided through WiFi or 5G sidelink. BLE (Bluetooth Low Energy) connectivity may be used for audio. The motion-to-render-to-photon loop runs from the glass to the phone. While the connectivity is outside of the 5G Uu domain, it is still expected that for proper performance when used for split rendering, a stable and constant delay link may be setup on the tethered connection.
• The AR Runtime is local and uses from sensors, audio inputs or video inputs, but may be assisted by functionalities on phone.
• While media processing (for 2D media) may be done on the AR glasses, energy intensive AR/MR media processing may be done on the AR/MR tethered device or split.
• Some devices might have limited support for immersive media decoding and rendering and may need to rely on 5G cloud/edge
• While such devices are likely to use significantly less processing than Type 1: 5G STAR devices by making use of the processing capabilities of the tethered device, they still support a lot of local media and AR/MR processing. Such devices are expected to provide 8-10h of battery life while keeping a significantly low weight.
• The tethered glass itself is not a regular 5G UE, but the combination of the glass and the phone results in a regular 5G UE.
• Media Access Functions are provided that support the delivery of media content components over the 5G system. Examples of the Media Access Functions are 5GMS functions, MTSI functions, web-connectivity or edge-related client functions. Detailed requirements are for study in this report.

Figure 4.2.2.4-2 provides a functional structure for Type 3b: 5G Relay WireLess Tethered AR UE.

Main characteristics of Type 3b: 5G Relay WireLess Tethered AR UE:

• 5G connectivity is provided through a tethered device which embeds the 5G modem. Wireless tethered connectivity is through WiFi or 5G sidelink. BLE (Bluetooth Low Energy) connectivity may be used for audio.
• The 5G Phone acts as a relay to forward IP packets. The 5G Phone runs a Media Session Handler including EDGE functionalities to support QoS control on the 5G System. To support proper end-to-end QoS, the media session handling needs to take into account the constraints of the tethering link to provide sufficient QoS on the 5G System link to provide adequate QoE for the end user. Details on the exact function of the relay, for example of it is on IP layer (layer 3) or on lower layer is for further study.
• Media Access functions are provided on the glass device to support the delivery of media content components over the 5G and wireless tethered link.
• The motion-to-render-to-photon loop runs from the glass to the edge and hence includes in total 4 wireless links. It is expected that for proper performance when used for split rendering, a stable and constant delay end to end link needs to be setup.
• The AR Runtime is local and uses from sensors, audio inputs or video inputs, but may be assisted by functionalities on phone.
• Media Processing is either done on the glass device or it is split with the network. In particular, relevant is that many devices have limited support for immersive media decoding and rendering and may need to rely on 5G cloud/edge.
• While such devices are likely to use significantly less processing than Type 1: 5G STAR devices by making use of the processing capabilities of the tethered device, they still support a lot of local media and AR/MR processing. Such devices are expected to provide 8-10h of battery life while keeping a significantly low weight.
• The tethered glass itself is not a regular 5G UE, but the combination of the glass and the phone results in a regular 5G UE.
• For services with low latency requirements, such as MTSI or those provided by FLUS, it may be necessary to take the status of wireless connectivity into account when configuring the services, such that the link between AR glass and 5G phone is not overly loaded. Although some work on the convergence of different acces networks is defined in [3], the coordination of the operation of Uu and wireless connectivity in such services is FFS.

A key challenge for WLAR and WTAR UEs is to properly estimate the required QoS allocations for the AR sessions. The QoS allocation must take into account the wireless/wired tethering link from the glass to the UE. This applies to all QoS parameters, namely bitrate, packet loss, delay, and jitter. The following diagram depicts a breakdown of the components contributing to the end-to-end delay as an example:

For a smooth operation of the AR session, the UE must estimate the impact of the tethering link on the overal QoS requirements. This corresponds to the Dn,1 component in the example Figure. The MSH on the UE is the best entity to perform such estimates, which it may do by:

• Running some measurement tests for latency, packet loss, and bitrate
• Exchanging information with the radio and/or AF on the QoS policy

The MSH may regularly adjust its QoS allocation based on the observation of the status of the tethering link, thus targeting a consistent end-to-end QoS experience.