Handover Scheme for 5G Communications on High Speed Trains

In recent years, High-Speed Trains (HST) have been operating in many countries at a speed of 360 km/h or more. Nowadays, more high-speed trains are being deployed rapidly worldwide. Train passengers are extensively transferring data via mobile devices. It is necessary to assure the quality of experience for the users. Due to the high speed of the HST, handover (HO) takes place too frequently. The handover failures increase with the higher moving speed. This is one of the crucial problems facing communication systems in the high-speed environment, especially for real-time services. Thus, achieving seamless mobile connectivity on HST is a major challenge. A lot of research work was done to overcome the too frequent handover problem as well as the high probability of HO failure caused by the high speed of the train. However, further work is still needed. In this paper, we propose a multi Radio-Access-Technology (multi-RAT) hybrid handover 5G scheme to overcome this problem. It utilizes vertical and horizontal handovers simultaneously in a heterogeneous multi-RAT network. We integrate the dual-link scheme using two antennas mounted at the front and rear sides of the train. The 5G tier is implemented to achieve higher data rates and larger bandwidth. This wide bandwidth is a fundamental requirement for delivering multi-Gbps backhaul connectivity to hundreds of user equipment UEs on board. The system is designed such that the network would recognize the users who frequently visit the cell, defined as "user-friendly" for this cell. In high-speed trains, the trajectory and future position of trains are easily predictable. Keeping the records and tracking the movement information of the "user-friendly" will aid in selecting predefined HO locations where the HO criterion is met omitting the time to trigger (TTT) which causes a delay and Radio link failure. The results obtained indicate that the proposed method successfully overcame the previously mentioned problems. It decreased the probability of HO failure to a negligible value. Hence, preserving seamless connectivity in the high-speed environment.