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X-Osc and iperf

July 24, 2013

A couple of interesting things to talk about today. First of all I paid a visit to Seb in his (incredible) office – I say office it’s very much a glorified work bench, there’s a lot of cool gear there! We had a long chat about the X-osc, and he’s given me one to use for the project as well.

One of the key things on this project is going to be getting the best performance possible out of the X-osc, as this is what will be transmitting the wifi from the glove. The x-osc uses a Microchip MRF24WG0MA to handle all its wifi operations. If you look carefully at this image of the X-Osc you’ll see that the MRF24 has a printed antenna on the PCB (it’s the squiggly bit of copper at the end of the board).

A picture of the X-osc board

The X-osc board

If the data sheet is to be believed this has some reasonably nasty pattern nulls, pointing along the board. This means that the chip will have much poorer wifi reception to and from any device that is that part of the antenna pattern. It will be interesting to see what we see when we put the board into the universities anechoic chamber and measure the radiation pattern ourselves.

Simulated radation pattern from the MRF24WG0MA data sheet - hopefully we'll get to see if it mathches the real anechoic chamber measurements  soon!

Simulated radation pattern from the MRF24WG0MA data sheet – hopefully we’ll get to see if it mathches the real anechoic chamber measurements soon!

One potential way of improving the reliability of the wifi link will be to replace this on board antenna with some form of external antenna. To this end Seb is producing a version of the X-Osc with an external antenna port so we can plug different antennas in. For this project a wearable antenna may prove to be very useful.

In other news – I also went to see Denys, who is the department’s expert at getting the Netgear R6300 to do traffic measurement. As well as giving me some of his own software to work with which I can use to effectively cause the routers to produce lots of (empty) packets in order to allow me to simulate running the system in a very busy wifi environment he also pointed me in the direction of a piece of software called iperf, which you can use to test the maximum throughput achievable of a particular network link. It’s free to download and well worth a play with, although as far as I can see where you download it from seems to rather depend on your OS…

Anyway, that’s enough for today I think – hopefully over the next couple of days I’ll get round to explaining Professor Wifi’s wireless N/G hypothesis which I’ll be testing, and also keep your eyes out for some anechoic chamber action – probably on Tuesday.

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2 Comments
  1. gsh permalink

    I don’t believe that radiation pattern!

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