Sunday, February 28, 2010

RFID reader for IETF meeting

I attend the IETF meetings whenever I can and I follow the proceedings remotely when I am not able to travel. But following an IETF session remotely is not simple: You need one application to listen to the audio stream (I use XMMS), another application to connect to the Jabber room (Pidgin) and a PDF or Powerpoint viewer to look at the slides (Evince and OpenOffice.org). On top of this complex setup, there is a lot of annoying problems: The audio stream is not very good, the audio servers crash from time to time, and people forget to speak on the microphone; very often the slides are available few minutes before the beginning of a session - it even happened that the slides are not available at all. The Jabber room is in fact used to state the name of the person talking in the microphone, because people forget very often to do this. Another usage for the Jabber room is to state the current slide on the screen.

Obviously all of this does not make for a good experience. There was multiple attempts to improve this, and I did work at a time on one of this attempts. The project was canceled after I left my job at 8x8, but I still continued to work on it on my spare time. One of the first component I designed was to capture the name of an attendee speaking at a microphone. There was some similar experiences, one during IETF 74 by Columbia University, and another during IETF 76 by the host, but my goal was a little bit different: I wanted the system to protect privacy and to be as non-intrusive as possible, so people had just to stand in from of the microphone to have their RFID tag scanned. The following picture shows how the system works:


The RFID antenna needed to be big enough so the speaker just stand naturally in front of the microphone. The RW310 has an 11" range but unfortunately only has a TTL interface which cannot be directly connected to most PC so I used a TTL to USB converter, with the whole circuit fitting inside the USB connector. The box itself was made from plexiglass - I used VariCAD to design the box and an Epilog laser cutter at Techshop to cut the plexiglass.

Finding a way to attach the RFID reader to the microphone stand was the most challenging part - I had to go through 3 prototypes until I found something that permit to change the distance between the reader and the stand and that does not unbalance the whole thing. I finally found a microphone holder that was perfect for this, with a microphone surface-mount attached on the box so the RFID reader can be easily removed at the end of the day.

Privacy is very important for the IETF meeting attendees, so there is some concerns with the introduction of RFID tags - and in my opinion, rightly so. Having an RFID tag without a way to shielding it is unwise, so I also designed a badge holder that would permit to shield the RFID tag also in a non-intrusive way, as shown in the following picture:


The idea is simple: Either you both show your name and give access to your RFID tag or you hide both. I think that this idea is key here - if you accept that people can read your name on your badge then there is no reason why you would not let an RFID reader do the same thing on your tag. The top half of the badge holder contains a metallic shield, but the tag itself is in the bottom half. When the holder is open your name is readable and your tag is not shielded; when closed both your name and your tag are invisible to the full electromagnetic spectrum.

Having the shield only on one side works because this RFID tag works at 13.56MHz (with 125 Khz tags, two layers of aluminum need to enclose the tag and this on both sides). Another reason for the 13.56Mhz tag is that it permit to store the user information directly in the tag, instead of simply retrieving a serial number and match it with a central database which, in my book, is a no-no as I want my personal data to be destroyed at the same time I destroy by badge.

Unfortunately the software is not ready at this time, but I'll try to find some time to finish it if there is enough interest in this project.
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