Data Communication System (DCS)
The Data Communication System is the radio and backbone network that connects trains to the wayside in a CBTC system. It carries the continuous exchange of position reports and movement authorities between onboard controllers and zone controllers that moving-block operation depends on.
How it works
Trackside radio access points are installed along the line, in tunnels and at stations, connected by a fibre backbone to the zone controllers and the control center. Each train has redundant onboard radios that hand over from one access point to the next as it moves. Most deployed systems use Wi-Fi technology in the 2.4 GHz or 5.8 GHz bands; newer systems increasingly use LTE or 5G.
The DCS is engineered for availability and low latency, usually with two independent radio networks and redundant backbones. Because the safety of CBTC lies in the application protocols above it, a loss of communication causes trains to brake to a safe state rather than to proceed unsafely.
Why it matters for security
The DCS is the most exposed part of a CBTC system: it uses commodity radio technology, its access points are physically distributed along the track and its signals can be received from outside the railway's property. Interference, rogue access points or attacks on the radio encryption can degrade or halt service across a line, even if they cannot directly cause an unsafe movement.
The DCS also often shares infrastructure with CCTV, passenger Wi-Fi and maintenance systems. Keeping the CBTC traffic segregated and monitoring what actually flows between trains and zone controllers is a core control in metro cybersecurity programs.
Related solution
Securing CBTC systems without disrupting automation
How CylusOne monitors zone-controller and onboard traffic passively, without interfering with certified behavior.
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