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Project update – Books and Matlab

July 29, 2013

Well it’s been a few days since my last blog post, so I thought it was high time for another to explain what I’ve been up to since my last.

Sadly thus far we haven’t got the R6300s, which has limited what I’ve been able to get on with as quite a lot of the work hinges on those. Hopefully we’ll be getting them soon, but in the mean time I’ve been using the opportunity to do some swatting up on the 802.11 standard. I’m hoping to get a video out soon explaining some of the key concepts of how it works in a user friendly way (watch this space!).

Also, based on the reading I have been doing, I’ve been working on a MATLAB model to try and predict what impact the presence of traffic using the (older) 802.11g standard has on the throughput of 802.11n traffic. It seems to be generally agreed that there is a performance impact on running routers in mixed mode (i.e where 802.11g and 802.11n are both accepted by the same access point), but there are a couple of ideas floating around as to why this might be. For those reading this blog that already know about the details of wifi one suggestion is that the DIF length for the two standards is different, which then of course means that clients using the different standards do not in effect compete fairly. The alternative hypothesis is that it has something to do with the use of different frame headers – but I’m still trying to find a resource that is able to tell me what the differences are and what impact it has!

The MATLAB model is proving interesting… it is showing the expected drop in performance in 802.11n with different DIF times, but it’s a more linear graph than I was expecting when plotted against varying traffic load – I’m still tinkering with the model to see if I can get something that looks a little more believable…

Not really looking quite right at the moment - you'd normally expect a rather more exponential pattern for varying traffic load really.

Not really looking quite right at the moment – you’d normally expect a rather more exponential pattern for varying traffic load really.

If you don’t understand the guts of wifi – don’t panic! The promised explain-802.11 video will make all clear. It’s not as complicated as it sounds – promise!

Just briefly I also want to mention that I have been in touch with Priyanshi, a very clever second year electronics and communications student who is also doing a wifi based project with the department over the summer. Hopefully we’ll be able to share a lot of what we find out and help each other out! She’s also going to be writing a blog about her project, which I’ll put up as soon as I have it.

Anyway, that’s it for now. Keep your eyes peeled – hopefully there will be lots about anechoic chamber testing tomorrow!



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