Signalling-efficient CFRA Resource Updating for Conditional Handover in 5G-Advanced

Optimizing the mobility performance while maintaining signalling efficiency are key aspects of any handover procedure. In particular, to make this process rapid and reliable, it is important to prioritize the use of Contention Free Random Access (CFRA) during any cell change, including Conditional Handover (CHO). This paper is focused on CFRA resource updating scheme which can further increase the benefits of CHO. The investigated framework refers to our recent work and extends the previously proposed algorithm by introducing additional steps aimed at signalling overhead reduction. This excessive signalling originates from the need to update CFRA resources in CHO to maximize the number of collision-free access attempts. We provide the overview of CHO and how its performance can be enhanced. Then we depict means for deriving a handover probability matrix, which represents how likely the User Equipment (UE) will select any of the prepared candidate cells during CHO. Such matrix can be a part of Mobility Robustness Optimization (MRO) scheme. System level simulations were run to confirm the hypothesis on reduction of the signalling between the UE and the base station (BS). Most importantly, we prove that properly set probability threshold ensures low signalling amount while maintaining other key handover metrics at sufficiently high level. We conclude the paper with the future directions of our study.