Use of Communications Based Train Control Systems in the Presence of Radio Frequency Noise and Interference

A common concern with Communications Based Train Control (CBTC) systems is that the wireless subsystem (usually referred to as the data communications subsystem or DCS) is susceptible to radio frequency (RF) interference from the plethora of wireless devices (especially wireless local area networks or WLANs) that generally share the same 2.4 GHz spectrum as that used by the DCS. This concern is investigated in greater detail given the operational histories of two CBTC-equipped public transit lines: NYCT’s “L” or Canarsie Line in New York City and the Las Vegas monorail. Measurements of the RF environment in both locations showed a substantial level of activity in the 2.4 GHz band from WLANs and other devices but with no obvious adverse impact on the operational performance of either line. This paper presents RF measurements at 4 locations in New York City and 1 location in Las Vegas, discusses the relative severity of the RF noise and interference environment and explores why both CBTC systems are able to perform in the presence of in-band RF noise and interference without any obvious adverse impact.