Enhancement of Handover Management through Reconfigurable Intelligent Surfaces in a 3D Ground-Aerial-Space Network Scenario

This paper investigates the role of reconfigurable intelligent surface (RIS) for enhanced handover management in 6G networks with overlapping wireless network layers i.e., ground, aerial, and space. A high altitude platform system (HAPS) is equipped with RIS and the comparison of direct and RIS-assisted link performance is presented. To do this, the average bit error rate, the outage probability (OP), and the channel capacity of direct and HAPS-assisted links are obtained in closed form expressions. By estimating the link error probability, a novel handover mechanism exploits the use of RIS, resulting in enhanced connectivity management. Hard and soft handover modes are defined depending on the radio frequency (RF) connectivity by means of link error threshold. The decision for the handover execution is based on selecting the optimal link among multiple available ones from ground, aerial, and space layers. The performance of RIS-assisted handover mechanism has been compared to traditional hard and soft handover procedure, as well as link performance achieved with relay node. Numerical and simulation results reveal that the connectivity of a user equipment can be maintained through RIS-aided links in case of any performance degradation in the direct RF links. Particular scenarios highlight that the use of RIS for handover is preferred to traditional handover procedures, as well as relay nodes.