Conditional Handover in 5G - Principles, Future Use Cases and FR2 Performance.

This paper elaborates on Conditional Handover (CHO) - a mobility feature designed in Release 16 of 3rd Generation Partnership Project (3GPP), aimed at improving the reliability of handover in cellular networks. CHO has turned out to be a successful feature and attracted several other areas of mobile networks, where increased reliability is also desirable (e.g. Non-Terrestrial Networks or Integrated Access Backhaul). This paper explains the principles of CHO, describes its future use in vertical areas and provides performance results showing the gains CHO may offer to 5G systems at higher frequency bands. Our simulative analysis was focused on the handover in Frequency Range 2 (FR2) and CHO recovery procedure. Results have shown that also at higher frequencies CHO can substantially reduce the mobility failures compared to baseline handover of Release 15. Moreover, it has been verified that CHO recovery can be a useful means to allow faster reconnection to the network after a failure. In certain scenarios CHO Recovery usage ratio was found to exceed 80%. The paper also outlines the future research and standardization directions in the area of CHO which appears to be a solid candidate for further development in 3GPP Release 18 and beyond.