Investigating the effect of handoff algorithms on the performance of CBTC systems using physics‐based propagation models

Abstract

The performance of communication-based train control (CBTC) systems, in terms of frequency of handoffs [changing association from one access point (AP) to another] and duration of service interruptions, strongly depends on the employed handoff algorithm. In this study, the received signal strength used for the calculation of these metrics is generated by a custom vector parabolic equation (VPE) solver explicitly developed to achieve high accuracy in complex tunnel environments. The authors demonstrate that VPE is as effective and accurate as measurements in estimating the performance of CBTC systems. Additionally, they present a methodology for selecting a handoff algorithm that most enhances the performance of a CBTC system, where APs have already been deployed. The impact of handoff algorithms on system performance is investigated by considering multiple system configurations in a 5 km, curved, rectangular tunnel. A multiple-attribute decision making approach is presented to rank handoff algorithms based on their performance. To validate this proposed simulation-based framework, a CBTC system deployed in the London Underground is presented, where measurement-based ranking is compared against the one derived using VPE simulations.