Munich experiments

17.02.2012 21:57

I've spent past week just outside Munich, Germany at the Ottobrunn EADS site. Among other things at the Jožef Stefan Institute I'm also involved in the CREW project. As it's usual for such multinational projects they organize regular meetings at one of the partners and this time the turn was on European Aeronautic Defence and Space Company.

The CREW project aims to build a number of instrumented test sites across Europe that would allow experiments with advanced radio technologies, like cognitive radio and dynamic spectrum access. I'm currently working on spectrum sensing hardware for VHF and UHF TV frequency bands and even though the happenings this week didn't directly concern that, I couldn't pass on a visit to the company that makes things like Airbus aircraft and Ariane launch vehicles (in addition to some less enlightened products). Not to mention that it's always nice to put faces behind names appearing in your inbox.

Ottobrunn EADS site.

If you've been on a passenger airplane you probably know little panels above your seat that remind you to fasten your seat belt and have speakers for announcements from the crew. Behind the curtains these are currently connected to the airplane's network with cables, however airlines wish to do away with physical connections and use radio instead which would make the panels and seats below easier to rearrange. Of course, this brings problems since these panels are considered critical to passenger safety and must work even if some ignorant passenger turns on Wi-Fi on his iDevice or if a terrorist smuggles 10.000 EUR worth of signal generators on board.

This is where this group of experimenters came in. We were given a section of an Airbus 340 fuselage to work with. It happened to be furnished with first-class seating and plenty of power sockets in the floor panels, something that's sadly not part of the usual airplane equipment. After two days of setting up measuring equipment the place was so full of criss-crossed wires that it was somewhat hard to believe the objective of study was in fact wireless technology.

Aircraft meal cart full of spectrum sensing equipment.

In a nutshell, we set up two programmable 2.4 GHz transmitters at opposing corners of the cabin and then measured received power at different locations across the cabin, including one mobile one on the meal cart, with different custom (for instance the IMEC sensing engine) and commercial receivers (USRP among others). The end result, at least on our end, was a bunch of spectrograms, like the one below that was recorded with two VESNA nodes equipped with our spectrum sensing receiver.

Two spectrograms recorded at the CREW Munich experiment

If you think this is something you might show the stewardess when she next asks you to turn off your favorite gadget I must disappoint you. You will have to wait for the peer-reviewed papers that will undoubtedly be published about the experiment and even then I'm not sure you will win that argument. In that regard I am not very optimistic about the usefulness of results myself. You might do some qualitative discussions of what the cabin radio environment looks like, but I think that's about it. For anything else there are just too many unknowns even in just the physical setup of the experiment. The conclusion that cognitive radio approach will be superior for such an application was somewhat unscientifically determined before the experiment took place anyway, so you can't say that it was an unbiased effort either.

The real value of this work however was in testing all of our tools. We found several problems with VESNA nodes that need to be fixed before we deploy them in our CREW test bed, from unknown sources of clock drift to buggy software, inconvenient procedures and unfavorable reactions to lengthy USB cables. We also found sources of interference on some devices that need to be looked into and so on. Suffice to say, my wish list grew a bit over the week.

The short tour of EADS offices was quite interesting too, of course. It's a huge facility with 3.000 employees and a correspondingly large amount of amazing stuff hanging on walls and laying around workshops and hallways. Sadly the strict security didn't allow me to take pictures outside of our experiment, so I'm not able to share them here but I can say that the shapes behind frosted glass and warning signs on closed doors do well to fire up your imagination.

Posted by Tomaž | Categories: Life


USRP is a nice SDR toy once you finish ISM 433 MHz play! Your IJS group sounds interesting. I hope more than Zemanta "mehcina"?

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