Feeds

Pocket Wi-Fi hotspots paralyse Chinese metro lines

Using free band to run trains oddly didn't turn out well

Secure remote control for conventional and virtual desktops

Shenzhen Metro is blaming customer Wi-Fi for disruptions to its service. The subway system for the city of Shenzhen in Guangdong province, China, depends on the unlicensed 2.4GHz band to link up its signalling systems.

Following network failures in October, and a trial blocking of 3G signals earlier this month, the Shenzhen tube operating company wrote to China's regulator asking for permission to block the signal. Caijing magazine reports that permission has now been refused, leaving Metro bosses at a loss on how to resolve the issue - which has seen two lines of the network repeatedly shut down and threatens other systems around China.

Customer Mi-Fi devices create Wi-Fi hotspots that are backhauled over China Mobile's 3G network, and they're very popular, particularly in Shenzhen - which, the South China Morning Post tells us, accounts for 80 per cent of sales. That's the legit kit, which only nudges the 100mW legal cap, but engineers trying to keep the network running reckon black-market devices are kicking out three times that amount. They add that once eight of either kind come into range then the Metro's signalling system stops.

2.4GHz is reserved, globally, for unlicensed ISM (Industrial, Scientific and Medical) use, largely because it was considered worthless as it gets absorbed by water and because the band is rife with interference from microwave ovens. However, radio is a lot cleverer these days, and Wi-Fi is squeezing every cent out of the spectrum while Bluetooth dances around it, and numerous door locks, remote controls and other consumer devices fill any gaps which remain.

Originally it was the unlicensed nature of the band which made it so popular, but these days it is also the low cost of the kit. International standardisation means a Wi-Fi router, Bluetooth headset, or just a radio chip, can be sold anywhere - providing massive economies of scale.

There's also the freedom from regulatory process. Set up a link at 5.8GHz and (in the UK) you'll have to fill in forms and register each transmitter, but do the same thing at 2.4GHz and there's zero paperwork, making deployment quicker and cheaper.

The combination of these things drove Shenzhen Metro to connect up its signalling system at 2.4GHz, only to discover that it is now polluted with customer connections.

And Shenzhen is far from alone in its plight, as the same band is used by metro systems all over China, which will similarly fail once Mi-Fi devices become popular.

Blocking the 3G signal shuts down the devices, but it's hardly a sensible solution as it aggravates commuters. However, shifting to a licensed band will be expensive - both in terms of the equipment it will require and the frequencies in which it can operate. ®

5 things you didn’t know about cloud backup

More from The Register

next story
UK fuzz want PINCODES on ALL mobile phones
Met Police calls for mandatory passwords on all new mobes
Canadian ISP Shaw falls over with 'routing' sickness
How sure are you of cloud computing now?
Don't call it throttling: Ericsson 'priority' tech gives users their own slice of spectrum
Actually it's a nifty trick - at least you'll pay for what you get
Three floats Jolla in Hong Kong: Says Sailfish is '3rd option'
Network throws hat into ring with Linux-powered handsets
Fifteen zero days found in hacker router comp romp
Four routers rooted in SOHOpelessly Broken challenge
New Sprint CEO says he will lower axe on staff – but prices come first
'Very disruptive' new rates to be revealed next week
PwC says US biz lagging in Internet of Things
Grass is greener in Asia, say the sensors
Ofcom sees RISE OF THE MACHINE-to-machine cell comms
Study spots 9% growth in IoT m2m mobile data connections
O2 vs Vodafone: Mobe firms grab for GCHQ, gov.uk security badge
No, the spooks love US best, say rival firms
Ancient pager tech SMS: It works, it's fab, but wow, get a load of that incoming SPAM
Networks' main issue: they don't know how it works, says expert
prev story

Whitepapers

Endpoint data privacy in the cloud is easier than you think
Innovations in encryption and storage resolve issues of data privacy and key requirements for companies to look for in a solution.
Implementing global e-invoicing with guaranteed legal certainty
Explaining the role local tax compliance plays in successful supply chain management and e-business and how leading global brands are addressing this.
Top 8 considerations to enable and simplify mobility
In this whitepaper learn how to successfully add mobile capabilities simply and cost effectively.
Solving today's distributed Big Data backup challenges
Enable IT efficiency and allow a firm to access and reuse corporate information for competitive advantage, ultimately changing business outcomes.
Reg Reader Research: SaaS based Email and Office Productivity Tools
Read this Reg reader report which provides advice and guidance for SMBs towards the use of SaaS based email and Office productivity tools.