Content for  TR 22.843  Word version:  19.2.0

One of the Aviation industry recommendations for UAV operation (and AAM - Advanced Air Mobility) is the ability to support robust reliability and flexible redundancy of critical communication links, including cellular, e.g., for Command and Control (C2) and other flight-critical communications. Within the context of improving 5G reliability and redundancy for UAVs, scenarios with dual subscription and multi-NW connectivity become of interest. For example, drones can be equipped with dual SIM (or dual credentials) and use one subscription for active communication with one network while the second subscription for setting up a "stand-by" connection path, to be used in case the first network becomes unsuitable or unavailable. Figure 5.9.1-1 shows, at high level, the two connectivity options, where UAV traffic is first active on the preferred network (PLMN-1), then switched to the second network (PLMN-2). Other options are not precluded, e.g., one of the two networks could be an NPN.

Which PLMN to use, and when to switch between them, would be based on specific conditions and policies configurable by the UAV owner/operator. One example is about a UAV operator ("SkyTV"), offering professional aerial video/TV services, in an environment where there is 5G coverage provided by PLMN1 (possibly shared with other PLMNs) overlapping with 5G coverage provided by PLMN2. It can be that both PLMNs are managed by the same MNO (MNO-A), or different MNOs, using different SIM/subscription credentials to access each PLMN. In order to support seamless aerial service and UAV traffic management, the whole flight path can require consistent network connection and complete network coverage. In certain areas, though, the coverage of the first PLMN cannot be guaranteed, or is not preferable (e.g. due to network congestion), while the coverage of PLMN2 is better, or preferred. In such environment, SkyTV is contracted by a national TV broadcaster for video streaming of e.g., outdoor events, races, marathons etc. To improve the reliability and QoS experience, SkyTV can equip its UAVs with dual SIM subscription (to PLMN1 and PLMN2) and configure them such that PLMN-1 is the preferred network, while PLMN-2 should be the stand-by network, together with policies and conditions for switching between them. The example is further elaborated below.

SkyTV UAV has dual SIM subscription to PLMN1 and PLMN2. It is assumed that SkyTV has negotiated with both MNOs proper data subscriptions for traffic generated by its UAVs (e.g., QoS, traffic profile/activity, charging, etc.). UAV's application is configured to use both PLMNs via both subscriptions (USIM1/USIM2), transfer user data via PLMN-1 if/when available or suitable, otherwise switch to PLMN-2. Network switch is decided and controlled by UAV or UTM, based on configured application policies in the UAV or UTM. UAV's application policy can include e.g., when/where to use connectivity via two PLMNs, which PLMN should be active/stand-by, specific C2 traffic/QoS policies, switch conditions, etc. It is assumed, in this use case, that UAV's application connects to the same USS/UTM or UAV-C during the whole flight operation (regardless of which PLMN connection is used). This scenario assumes mostly UAV-originated traffic and/or that UTM is aware of which PLMN connection is used by the UAV, so that both uplink and downlink traffic are transferred over the same active PLMN connection, and USS/UTM interacts with the active PLMN e.g., for UAS identification and traffic management. For example, when UAV application sends the data packets over one PLMN connection, the UTM can reply over the same PLMN connection.

1. An outdoor marathon event is starting, and SkyTV UAV is set to follow the peloton for all the itinerary (20 miles). SkyTV service provider has configured the UAV application with specific policy on how to route traffic over the two subscribed PLMN networks.
2. Before the kick-off, UAV's communication module using USIM1 and USIM2 is registered to both PLMNs, has established C2 connection with the UAV-C or USS/UTM, using respective subscriptions/USIM credentials, and is idle (no traffic). Based on UAV operator (SkyTV) policy, PLMN-1 is configured initially as active network (to transfer video data and C2 data) while PLMN-2 is configured as standby network.
3. At the start, UAV's application transfers real-time video data and exchange control and command data with the USS/UTM or UAV-C via PLMN1, while PLMN-2 connection remains inactive (standby connection).
4. Based on configured UAV application policies, along the itinerary, UAV video traffic and C2 data is switched over PLMN-2: UAV switches its active C2 connection with UAV-C or USS/UTM to PLMN2 while PLMN-1 becomes the standby network.
5. Later, video and C2 traffic is switched back by UAV to PLMN-1 (PLMN2 is inactive).

Steps 3 & 4 can be repeated along the route.

SkyTV video service runs smoothly for all 20 miles, with no service degradation when transitioning in and out of PLMN-1 spotty coverage areas and the UAV is under control and monitored by USS/UTM and UAV-C all the time.

There are no service requirements in TS 22.125 about UAS multi-NW/PLMN support. Other requirements (e.g., from TS 22.261 or TS 22.101) do not cover the specific target UAV scenarios and functionalities. Some examples of existing requirements are captured below:

[PR 5.9.6-001]