Telecom Informer

    

by The Prophet

Hello, and greetings from the Central Office!

I'm a little over 800 miles off the coast of Mogadishu, Somalia.  Naturally, being Africa, it's really hot.  However, unlike Mogadishu, this is an entirely safe destination.  I'm in Seychelles, at a Mexican restaurant, watching the sun set over spectacular Lazare Bay (dotted by resorts costing upwards of $2,400 per night), and enjoying a margarita after a hard day's work.

What brought me to a place that feels like it has pretty much fallen off the map?  GPS.  Or more properly, GNSS, which is the "correct" term (at least as correct as any marketing term can be - it's really about as meaningful as 3G).  Why a new acronym?  Well, where telecommunications carriers are concerned, GPS is now an international affair.  While the first GPS system was operated by the United States (and is formally called GPS), the European Space Agency has its own system called Galileo, and the Russians have a system called GLONASS (there are also Russian and Indian systems that use geostationary satellites, so they only function in those local areas).

Whatever you want to call it, GNSS works best when you have the largest number of satellites in play.  So these days, we use all of them, because the more satellites in the mix, the more accurate the reading.  "Accurate," though.  Therein lies the rub.  You would think that with as many of these systems as exist they'd be pretty accurate, but in reality, none of them are perfectly accurate.  All sorts of things can throw a GPS reading off.  The satellites operate on atomic clocks, but as it turns out, in space these aren't always completely accurate and they experience a condition called "clock drift."

While there are measures in place to detect and correct such drift from Earth ground stations, a one nanosecond clock drift can create a meter of inaccuracy.  Additionally, the Earth's ionosphere creates attenuation, and it isn't evenly shaped.  It "breathes" like any other atmospheric system, and this leads to inaccuracy as well - up to 15 meters of inaccuracy.

That may not seem like a lot, but when it comes to driving directions, it really is a lot - especially if you are driving something that needs to be very precise, like a tractor.  In addition to clock drift and ionosphere "billows,' the Earth isn't a perfect sphere, but the math used to calculate a GPS location (more or less) assumes that it is.  All of this means that corrections are required.

When you think "GPS corrections," the first thing you probably think of is Seychelles, the second thing you think of is a Mexican restaurant, and the third thing you think of is a tractor company.  Right?  If you're wondering how they're all related, I'll explain.

As it turns out, one of the most critical applications for high-accuracy GPS is driving tractors, and Seychelles is an ideal location for measuring the ionosphere in the Indian Ocean region.  Our company has a lot of logistics experience working with telecom hardware all over the world, and somehow we ended up with the telecommunications service contract for a ground station, owned by a tractor company, that conducts these measurements.

It consists of two antennas mounted on top of a Mexican restaurant (another organization taking the same sorts of measurements built their ground station on top of a gas station down the street - you can set these up pretty much anywhere with a clear view to the horizon on all sides), some coaxial cable that hooks it up to a specialized computer system, and a really fast ADSL Internet connection.

When it's all working, the system delivers corrections to GPS (and GNSS) data that provide accuracy within an average of 10 centimeters.  However, the "really fast ADSL Internet connection" part (based on fiber to the node) isn't very common in Seychelles and the local phone company just isn't prepared to deal with it, which is how I got involved.

You see, there was a coconut.

When you rent a car here, they spend probably five minutes warning you about coconuts.  That's because some coconuts in Seychelles aren't just ordinary sized coconuts.  The coco de mer tree grows the world's biggest coconuts.  They're about as big as the midsection of a large person, but more heavy and dense.  The crazily shaped things (they look like... buttocks) weigh up to 65 pounds.  A small one weighs half that.  As it turns out, if you drop something that big and half the density of a brick onto the roof of a car, it'll collapse the roof, shattering the windshield and killing anyone inside.  The rental car guy showed me pictures.  I actually had to sign a form promising not to park a rental car under coconut trees.  So, given all of that, I really have to wonder how it was that the specialized DSLAM for this critical piece of global infrastructure was built right under a coco de mer tree.

While the situation is unusual, I have dealt with these sorts of problems before.  Catastrophic equipment failure, replacement required.  Usually, these are caused by car crashes.  The good news was that the fiber was in good shape, and no splicing was required.  I only had to replace (and reposition) the equipment.

No problem, we just needed to bring it in.  Would you believe I checked it in my luggage?  Well, I did.  Every way I looked at to ship the equipment commercially would have taken at least a week.  Sometimes just buying a ticket and flying with the gear is the fastest way to get it there, so I shepherded a whole bunch of sketchy looking stuff through Qatar en route.  Remote DSLAMs don't really require a whole lot of equipment these days, especially when only one customer is being served.

However, they are bulky because they're enclosed in a cabinet.  Fortunately, the local phone company was cooperative.  They had all of the copper and fiber capabilities and local expertise that I needed, and they had a spare cabinet; they just didn't have any of the equipment to repair the specialized remote DSLAM or the local expertise for doing so.  And by "repair" I mean "rebuild" - the cabinet was completely shattered.  It was as though a bomb had been dropped on it: the coconut scored a direct hit.  I couldn't salvage anything, especially since it had rained since the incident occurred.

In the end, it took me longer to carefully pack the components that were needed (along with spares, because you can't just run down to Graybar when you're in Seychelles if something doesn't work) and fly there (via Los Angeles and Qatar) than it took to do the job.  We stood up a new cabinet, rerouted the copper, rerouted the fiber, rerouted power, racked the gear, hooked everything up, restored the configuration, powered it on, and... it worked!  First try!  This almost never happens, but the local crew was well trained (by British Telecom) and highly professional.  They were honestly better than most U.S. crews I work with.

That's not what I'm telling the bosses at home, though.  As it turns out, Seychelles is essentially an African version of Hawai'i, but less crowded and more expensive.  It's beautiful here, the weather is warm, the beaches are spectacular, and there are perfectly legitimate martinis at what is possibly the world's most improbable Mexican restaurant.  My story, and I'm sticking to it, is that a temporary fix is in place, but I need to order parts for a permanent fix that will take at least a week to get here.  It's Africa, but I'll suffer through the sunsets and infinity pools because I always put the Customer First.

And with that, I'm going to order another margarita.  Have a wonderful summer.

Would you like to play a game?  Along with Lion and Licutis, I'll be hosting the famous TeleChallenge puzzle challenge this summer at DEFCON.

Do you believe in the Users?