CREW-TV trials

31.03.2014 21:09

The European FP7 CREW project I'm working on at Jožef Stefan Institute had a few open calls in the past two years. Anyone with an interest in one of our testbeds could apply and, if it passed a review, was given funds and support from the CREW consortium for running their experiment on our hardware.

One of the chosen experiments in the second open call was CREW-TV by Instituto de Telecomunicações from Portugal. They proposed to use our spectrum sensing network to dynamically update a database of occupied radio channels. They would then test this database by setting up an experimental video broadcasting system with dynamic spectrum access (they have an interactive demo you can click around).

The CREW-TV experiment ended this past week when experimenters from Portugal, a colleague from the Institute and myself performed an actual trial of the system in the field and took some spectrum measurements. You could see us around Logatec in a van full of laptops, instruments and a few antennas sticking out.

Van with measurement equipment and an antenna for CREW-TV trial.

Considering the amount of effort that went into this experiment from my part, the conclusions were disappointing to say the least.

The trial itself has been delayed for a month and missed an European Commission deadline because our testbed was damaged by ice. With local services still busy repairing more critical infrastructure, it was sometimes difficult to get the necessary support. Running an out-door testbed on public infrastructure has a hidden cost that shows itself in such situations. Even though people in Logatec have been most supportive of our activities, a lot of time and effort was necessary to coordinate everything across different organizations.

Discone antenna for CREW-TV trial base station.

I also learned a few hard lessons in organizing an event like this. I overestimated the amount of effort that was put into this experiment by our partners from Portugal. I should have insisted that we double check the list of required field equipment after they arrived. I should have insisted that they test their system first in the lab before attempting to set it up in the field, regardless of how confident they were. I should have insisted that we stick to reasonable working hours.

If my colleague and I would have spent two days waiting for them to debug their system at a warm desk, the trial would be a much more pleasant experience for everyone involved. Instead we were all freezing in the rain, attempted to download hundreds of megabytes of software through slow and costly mobile connections and had to mess with equipment at dangerous heights during the night.

I understand there are sometimes cultural differences and a language barrier, but at one point the hospitality must end.

Measuring DVB-T spectrum and bit error rate.

A year and a half ago our group organized a meeting for the CREW project and hosted some experiments at the then brand-new testbed. Not everything was working yet and a lot of things had to be hastily prepared in the last minute. I felt bad then because I thought we didn't show ourselves in a good light to our visitors. I guess I now find myself on a different side of a similar situation.

In the end, out of the mess of notes and spectrum measurements I have, there might be some useful data that could be used to evaluate the performance of VESNA spectrum sensors. So far some of it points at some shortcomings in detection of packet based transmissions. That would be interesting to investigate further in the lab. Other measurements are too contradictory to be of much use.

Posted by Tomaž | Categories: Life

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