Handover Scheme for 5G C/U Plane Split Heterogeneous Network in High-Speed Railway

Being a promising technology for fifth-generation (5G) communication systems, a novel railway communication system based on control/user (C/U) plane split heterogeneous networks can provide a high-quality broadband wireless service for passengers in high-speed railways with higher system capacity, better transmission reliability, and less cochannel interference. However, due to its special architecture where the C-plane and the U-plane must be split and supported by a macro Evolved Node B (eNB) and a phantom eNB, respectively, it would suffer more serious handover problem, particularly in intermacrocell handover, which directly degrades its applicability and availability in high-speed railways. Moreover, no technical specification has been released about this network architecture. Therefore, this paper focuses on redesigning and analyzing technical details and handover procedures based on Long-Term Evolution (LTE) specifications to guarantee the proposed system's practicability and generality and its analytical tractability. To resolve the handover problem, this paper proposes a handover trigger decision scheme based on GM(1, n) model of the grey system theory. By this scheme, the received signal quality from the (N + 1)th measurement report can be predicted from the Nth measurement period, and the predicted values can be then utilized to make the handover trigger decision. The simulation results show that our proposed scheme is capable of triggering handover in advance effectively and of enhancing handover success probability remarkably.