MIMO-Assisted Handoff Scheme for Communication-Based Train Control Systems

Wireless local area networking technologies are widely used in communication-based train control (CBTC) systems, where handoff latency is the key factor affecting the transmission performance. A multiple-input-multiple-output (MIMO)-assisted handoff (MAHO) scheme for CBTC systems is proposed in this paper to reduce handoff latency. During the handoff procedure, the mobile station (MS) communicates with the serving access point (AP) and the candidate AP concurrently with handoff signaling transmitted by one antenna and data packets transmitted by another one so that the station can handoff from one to the other without interrupting data transmission. The interference is canceled by a zero-forcing algorithm in the uplink (UL) and by space-time block code (STBC) interference cancelation algorithms in the downlink. The handoff performance, including transmission delay of train-control-related information due to handoff, the frame error rate (FER) of the handoff signaling, the error-free period, and the required intersite distance, are analyzed and compared with traditional break-before-make schemes. The results show that the MAHO scheme can significantly reduce the handoff latency of CBTC services and that the FER of the handoff signaling is lower than traditional schemes when the data rates are no more than 13 Mb/s.