Monday, 22 September 2014

Arrivals weekend

This weekend we had our annual intake of new students. As usual we spent the weekend providing support to the new newbies to enable them to get on the network, use wireless and sort out their passwords. We also spent the weekend catching up with those last minute jobs that need doing before term starts.

A wet first day


The first day was a wet one, in more ways than one. The rain was making an appearance as the first group of new students started to arrive and then we had a flood in one of our student accommodation buildings.

Wet cables

The water had made it's way into the plant room and all our kit had to be shut off in this area. Also, rather annoyingly, whoever installed the CCTV kit moved one of our IEC leads into a power strip at the bottom of the cab that they had installed (ours are halfway up to avoid such incidents) and this was submerged in water before it was all pumped away. As a lot of the ethernet cables come from the bottom of the cab, rather than the top, most of these will need to be replaced too.

As well as the student faults I had a post-installation wireless survey of the new Journalism and Economics building to carry out, that I managed early Saturday before many students had arrived. Also there were approximately 28 access points to set up in languages and another 77 to configure in Computer Science, Research and Information Studies.

I didn't get that many set up however as I was still looking at faulty wireless access points at around 5-6pm on Sunday.

One wouldn't download the image and another didn't want to boot until it had a console cable plugged in (?)

We also had to do a bodge job (yuck! - on orders from above) as a resident was asking for compensation due to a job to install properly being held up with Estates.

Couldn't connect to wireless from their room with antenna in or on the cab, no sockets or cables to use and couldn't do any drilling so a temporary fix...tape, lots and lots of tape

Needless to say it was a busy old weekend (which the tax man will appreciate).

Just want to make it through registration this week with enough time to sort out the teaching spaces and then pack all the registration kit away on Saturday for another year.

Friday, 19 September 2014

Intro To Spectrum Analysers

I've not had time to get to grips with or go through the training on how to use it but, after taking the Spectrum XT home the other day, I certainly found it useful and our team boss asked me to write a little about it.


At home my WiFi kept dropping out. It worked fine on 5GHz but unfortunately Playstations, Chromecasts and my tablet are all only capable of using the 2.4GHz frequency. I had the Wifi Anayzer app (https://play.google.com/store/apps/details?id=com.farproc.wifi.analyzer&hl=en_GB) on my phone and according to that I had a few neighbours on channel 11 and a handful on 6 (with a few in between), so channel 1 for my network seemed perfect. My signal strength seemed strong but first my tablet and then after a while my TV kept disconnecting and struggling to maintain a connection.



We recently purchased the Spectrum XT (http://www.flukenetworks.com/enterprise-network/wireless-network/airmagnet-spectrum-xt) to help with such mysteries and I borrowed it see what it could find.



I found 2 access points on channel 11 and half a dozen on 6 that the adapter could see. It also straight away solved my channel 1 problem.




As you can see in the first picture the duty cycle on channel 1 (as well as 2 and 3) is 100% and is due to a wireless security camera someone nearby has installed that is transmitting all the time. A waste of time using any of these channels then as my access point will stop beaconing and my devices attempting to associate with a duty cycle that high.

Just as I was about to put the laptop away (and move my wireless to channel 6, the least congested) my neighbour must have turned their microwave on, as you can see from the spectrogram in the second picture it caused a fair bit of noise around channel 7 and the ones around it. No wonder all my neighbours are using channel 11.The duty cycle is not high though because the microwave is not close (if it was mine it could be around 50-60%) and they do not continually transmit. If I turned mine on and tried to use the same channel it would probably halve my throughput but would/should still work.


So they mystery of the dropping out connection is solved and, in this case, the best thing is to have multiple access points on the same channel.

Roll on the time when we have 5GHz in every device!