The satellites have strength in their wide coverage and immunity from terrestrial disasters. The power of low earth orbit (LEO) satellites has been vividly demonstrated for communications and Earth observation in the Russo-Ukrainian War. The technical advancements are being made in both the space-grade hardware technologies and future network architecture. With anew emerging network technologies represented by virtualization and programmability such as virtual networks, edge computing, software-defined networking, and so on, satellites can provide various types of differentiated services in an efficient manner by utilizing on-board processing, computing, and caching capabilities. 

In particular, network slicing, one of the key techniques in 5G networks, can provide each network customer with a dedicated service by virtually creating an independent virtual network, called a network slice, from a physically shared common network infrastructure. Challenges in realizing network slicing in satellite networks are unique because the network is constructed over long wireless links, and each satellite node moves at very high speeds. For the given locations of ground network slice requests, access satellites should perform frequent handovers to serve the slice during the required service time. In addition, the inter-satellite link (ISL) connectivity and link distances may vary over time. 



In recent work led by Prof. Jihwan Choi in the department of Aerospace Engineering, KAIST, in collaboration with DGIST, a satellite edge computing architecture and the scheduling policy of network traffic were proposed for satellite network slicing. The results indicate that task offloading to satellite servers is more efficient for the constellation with a higher altitude with respect to on-board transmission/computation power consumption, but a lower altitude is more advantageous in terms of latency. An appropriate altitude of the satellite network should be decided with the target latency level of applications and the cost of satellite edge servers into consideration. Otherwise, the satellite edge servers may turn out to be less efficient as the number of satellite edge servers increases at low altitudes.

Slice planning in a satellite network embeds the virtual network requests (VNRs) and manages the embedded virtual networks during the required service time with handovers, if necessary, to handle the mobility of satellites. Handovers occur when the embedded satellite nodes are no longer available. Sizable ISL capacities are necessary to increase the overall network throughput because the system bottleneck is on the ISL, while sufficient access satellite capacities are useful for the system efficiency, represented by the throughput and cost ratio of the network. With access satellite handover, the end-to-end ISL routing path is jointly updated, and then the end-to-end slice is also handed over by re-embedding the expired slice. 

This work is the first attempt to propose potential satellite network slice scheduling and planning strategies with handover and ISL routing management in joint accounts, and will guide further research and hardware development with a proliferation of newly-emerging future satellite network applications. A part of this work was published in IEEE Internet of Things Journal (Volume 9, Issue 16) in 2022.