Unlicensed Spectrum No Answer for Positive Train Control, Network Engineer Says
Unlicensed spectrum is no solution for positive train control, said Richard Bennett, network engineer, on the HighTech Forum blog. PTC emerged as a big issue after the May 12 deadly Amtrak derailment in Philadelphia (see 1505150047). Some public interest groups…
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argued at the time unlicensed spectrum is the answer, but it's not, at least not by itself, Bennett wrote. “One of the most important takeaways from the Amtrak derailment is the difficulty of developing new systems for old industries that use spectrum,” he said. “This is a very technical subject that is well outside the expertise of railway engineers; it’s similar in that respect to auto safety systems that are targeted to use 5.9 GHz spectrum allocated by Congress for their use. That spectrum directly conflicts with the planned expansion of Wi-Fi. These systems also stress the ability of radio engineers because they don’t know the application very well.” Bennett said LTE-unlicensed could have use in PTC. “It could very well be the case that the railroads would be best served by an LTE-U-like hybrid system that combines the licensed spectrum already in the hands of mobile operators with unlicensed spectrum capable of doing the up-close work of monitoring train speed, direction, and identity,” he said.