Content for TR 22.865 Word version: 19.2.0
5.14 Use case on service continuity for UE-to-UE communication between satellites
5.14.1 Description
5.14.2 Pre-conditions
5.14.3 Service Flows
5.14.4 Post-conditions
5.14.5 Existing features partly or fully covering the use case functionality
5.14.6 Potential New Requirements needed to support the use case
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5.14 Use case on service continuity for UE-to-UE communication between satellites p. 34
5.14.1 Description p. 34
The provision of Internet services using mega-constellations of LEO (Low Earth Orbit) satellites is a promising solution on the path to the future mobile communication systems. LEO is the Earth-centered orbit with an altitude in the range of 350km and 2000km above sea level. The LEO satellites at 600km altitude travel at a speed of about 7.8km/sec [18]. Due to the fast movement of LEO satellite, the service duration of a satellite for the coverage with 1000km diameter is less than 3 minutes. Therefore, guaranteeing robust service continuity and satisfactory user experience is the most critical issue in LEO satellite system.
In some countries, the state government operates Aviation Branches for Forest Protection Service to fight forest fires and assist in search and rescue missions [19]. The helicopters are part of the Aviation Branch and used for fire detection and firefighting, dropping water, and moving firefighters and equipment to rural and remote locations. In these locations, there may be no terrestrial network, so the helicopters and firefighters can collaborate with each other by communicating in the help of satellite. Moreover, since it takes several hours or days to complete their missions, it should be considered how to ensure the continuity of communication service using satellite access across multiple NGSO satellites.
Furthermore, the draft report of ITU-R for IMT2020-satellite requirement for mobility interruption time in satellite radio interfaces is 50ms [20].
Figure 5.14.1-1: Example of service continuity for UE-to-UE communication between satellites without going through the ground network
(⇒ copy of original 3GPP image)
(⇒ copy of original 3GPP image)
5.14.2 Pre-conditions p. 34
Satellite operator Sat-OP has deployed NGSO satellites and has an agreement with Terrestrial Operator Ter-OP to provide communication services for UEs under satellite coverage.
Firefighter A and B have signed contract with Sat-OP for communication services using satellite access. Thus, their devices can communicate with each other directly via satellite without going through the ground network.
Firefighter A and B move to the rural or remote area in which there is no terrestrial network, but the satellites operated by Sat-OP can provide communicate services.
5.14.3 Service Flows p. 34
- Firefighter A and B make a phone call or exchange some data (e.g. pictures, video streams) during their work. Then, their data traffic is routed through satellite Sat-1.
- During the communication service, if Firefighter B is located in the coverage of satellite Sat-2, Firefighter B has a connection to satellite Sat-2 and the communication between Firefighter A and B is provided by satellite Sat-1 and Sat-2 through inter satellite link.
- After some time, if satellite Sat-2 serves the area in which Firefighter A and B are located, the satellite Sat-2 takes over the data sessions for Firefighter A and B from satellite Sat-1, and then the data traffic is routed through satellite Sat-2.
5.14.4 Post-conditions p. 35
Firefighter A and B can finish the phone call or data exchange without any discontinuation of communication service with the support of multiple NGSO satellites.
5.14.5 Existing features partly or fully covering the use case functionality p. 35
Regarding TS 22.261, satellite access and satellite connectivity are supported in Rel-18, as
The 5G system shall be able to provide services using satellite access.
The 5G core network shall support collection of charging information based on the access type (e.g. 3GPP, non-3GPP, satellite access).
For a 5G system with satellite access, the following requirements apply:
- A 5G system with satellite access shall enable roaming of UE supporting both satellite access and terrestrial access between 5G satellite networks and 5G terrestrial networks.
5.14.6 Potential New Requirements needed to support the use case p. 35
[PR 5.14.6-001]
Subject to regulatory requirements and operator's policy, the 5G system with satellite access shall be able to support the establishment of a communication path between UEs via one or multiple serving satellites without going through the ground network.
[PR 5.14.6-002]
Subject to regulatory requirements and operator's policy, the 5G system with satellite access shall be able to support service continuity of a communication between UEs without going through the ground network when the UE communication path moves between serving satellites.
[PR 5.14.6-003]
Subject to regulatory requirements and operator's policy, the 5G system with satellite access shall support service continuity of a communication between UEs without going through the ground network when the communication path between UEs via one or multiple serving satellites extends across several satellites (through inter satellite links).
