When train engineers talk telco

May 18th, 2012 by · Leave a Comment

This article was authored by Don Sambandaraksa, and was originally posted on telecomasia.net.

Rail operators run their own communications networks for data signalling and for voice communications.  There comes a point when the cost of maintaining these networks is such that the rail operator is tempted to forgo proprietary technologies and rely on commercial 3G and 4G networks instead.

There is also the question from the other side of the fence that since railway lines have rolled out fiber alongside their tracks for their proprietary communication networks across the country, should the train operators become infrastructure providers to telcos and lease out that fibre capacity to provide extra revenue?

This is in addition to the more obvious benefits of high speed data on trains, such as revenue and extra traffic from Wi-Fi services and security.

At the Signalling and Telecommunications Asia conference in Bangkok, I witnessed how train operators in the real world looked at the convergence that is happening, with GSM-R and with talk of using LTE to replace legacy systems. Looked, but did not touch.

The two metro lines in Bangkok depend on Tetra, a digital trunked radio 2G-era standard with very limited data speeds for day to day operations. The kind chap from the BMCL, Bangkok’s underground rail operator, said he was not even using Tetra 2 TEDS (Tetra Enhanced Data Services) yet.

The media-heavy passenger information displays in the trains instead run on a totally separate system and use 802.11n Wi-Fi on unlicenced 5-GHz to upload information such as status updates and ads to the trains. Interestingly enough, that system has been outsourced to SingTel.

During the workshop, one of the vendors was trying in vain to ask the operators (train operators in this context) why they would not consider a converged network? Would it not be more cost effective to run a single converged network for both instead of maintaining two separate networks since the standards are now in place?

The answer was a shake of the head for the most part. Operations people are concerned about safety at all costs and do not want the marketing people (which would run the passenger information displays and on-train WiFi) to get anywhere near their mission critical networks.

Integrating two separate networks on a live system was quickly dismissed as too dangerous and totally out of the question.

Upcoming train lines might use GSM-R or LTE. Perhaps. Maybe. Someday.

However, with driverless trains, the situation changes. Security suddenly means more than just basic data for telemetry and voice communications in the case of a broken down train, but now includes the need, not option, for live CCTV footage to be fed to the control room. Rather than for data to be downloaded hours after the fact as is the case in many metros today, or for no in-car CCTV at all as is the case on Bangkok’s underground, control room operators need to see what is happening in the trains at all times.

One striking factoid that emerged in Bangkok was the way the Tetra radio spectrum was allocated to the capital’s two metro rail operators. In their infinite wisdom, Thailand’s former telco regulator – the now superseded National Telecommunications Commission – gave the two rail operators the same spectrum. Not the same amount of spectrum; not the same spectrum band, but the very same spectrum on the 450-MHz band.

Now, Tetra usually runs on 380-MHz. By using 450-MHz, this means that equipment vendors are far and few between and what equipment there is comes at a much higher cost. Not that it really matters as costs can be passed on to commuters, but it was the sheer lack of regulation that made the room gasp in disbelief.

The chap from BMCL (underground) said that they had to closely coordinate their Tetra networks with the BTS (above ground) to ensure that the two did not interfere with each other.

Yes, obviously the logic of dismissing LTE because it is a consumer-grade technology and relying on mission-critical Tetra, but having to manually, ad-hoc, coordinate spectrum use must make perfect sense to some bureaucrat pushing pencils between nine to five day in, day out somewhere.

At least the new regulator is now aware of the problem and is working towards licensing out 380-MHz for rail operators to use nationwide. Of course, that does not quite help the incumbents and Thailand’s regulator has more pressing things to do, such as licence out 2.1-GHz before they sort out the mess on 380-MHz/450-MHz.

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