Dependency of Cell Size and Available Time to Trigger Handover on Satellite Height for 5G Non-Terrestrial Networks (NTN)

Abstract

Advancements in satellite technologies have made 5G integration in satellite networks more plausible than ever before. Especially, LEO satellite based networks are most potent for 5G integration as LEO systems offer smaller latency and low cost. This integration of LEO satellites and 5G network is known as 5G LEO non-terrestrial network (NTN). But 5G LEO NTN comes with various challenges among them, the high mobility of the LEO satellites is a key issue. It affects various mechanisms of the network. Current 5G specifications which are designed for terrestrial systems is not always suitable for LEO based 5G NTN. One of the key affected areas is handover. High mobility of the satellites require frequent and robust handover. But just fast handover leads to unnecessary frequent handovers which creates a massive problem for the whole network. A handover parameter, TimeToTrigger can be used to mitigate the issue to an extent. But available time to trigger handover for a specific scenario is not so easily determined. So, the work presented in this paper, proposes an empirical formula to calculate optimal TimeToTrigger for a given satellite altitude without the need to go through extensive simulation. Additionally, another empirical expression is derived for cell radius to simplify cell radius calculation. The equations essentially demonstrates the dependency of TimeToTrigger and cell radius on satellite height