Caltrain provides a commuter rail service serving Silicon Valley along the San Francisco Peninsula, from San Francisco through the South Bay to San Jose and Gilroy. Originally a diesel-powered system, groundbreaking for an all-electric system took place in 2017, and was completed in 2024. Today Caltrain operates an electric fleet of 19 train sets comprising seven passenger cars each, with electric service between San Francisco and San Jose, and diesel trains between San Jose and Gilroy.
Caltrain EMU train set
In 2011 Xentrans was retained by Caltrain to conduct a series of workshops regarding wireless communications, and to develop commercial and technical models for delivering Wi-Fi service to passengers on diesel trains. As part of the engagement, Xentrans conducted extensive testing of cellular coverage along the Caltrain alignment with a view to use of commercial 4G mobile networks for cellular backhaul to trains. Consulting work continued along the cellular path into 2013, when it was realized that the availability of spare dark fiber along the right of way, as a result of Positive Train Control installation, presented the opportunity of building a private trackside network for train-to-ground (T2G) communications. Such a network would be entirely within Caltrain’s control for its exclusive use, whereas commercial 4G networks would be costly to use, and were already heavily contended in the area. In late 2013 Xentrans authored a detailed technical specification and financial model for a broadband wireless network utilizing poles and radios in the wayside, and wireless equipment on board trains.
Between 2014 and 2018 work continued, with investigations into the use of overhead catenary supports (OCS) for bearing T2G radios, and an RF study of potential track coverage of wireless data communications at 5.8 GHz. In mid-2019 Caltrain issued an RFP 19-J-P-114 for a consultant to provide Broadband Wireless Communications Design and Support for Railroad Operations. In October 2019 Caltrain awarded the multi-year contract to Xentrans, and work commenced on the technical specification of a private T2G network for passenger Wi-Fi and operational applications.
In October 2021 the scoped work was completed, and Caltrain issued RFP 21-J-T-057 for Broadband Communication Services using our extensive technical specifications as the basis for soliciting proposals. In December 2022 the contract was awarded to Alstom subsidiary Nomad Digital, for a solution using mmWave technology from Blu Wireless operating in the unlicensed 57-71 GHz spectrum. The system has been capable of near-gigabit speeds to train sets, and onboard passenger Wi-Fi speeds of over 300 Mbps.