Scott’s Weblog

Error: Timed-out thinking up post title.

I’m sure that no-one has noticed that I’ve been fairly silent on the blogging front for a while. I took a three month break from the Ph.D to do some work for Cambridge Silicon Radio. The experience working on a real-world project was great and the project itself was both interesting and challenging.

I am however looking forward to getting back into the Ph.D work. I’ve still got a week or so before the Ph.D kicks back in so at the moment I’m doing some driver work for RuralLink - specifically getting MadWiFi working better on the CPE/AP devices.

I spent a week or so before the CSR work started looking into performance improvements for MadWiFi. After spending quite a bit of time with oprofile I found a couple of areas in the driver which were causing a large number of PCI transactions to take place unnecessarily. Now, on a laptop or desktop platform this didn’t really make much difference. On an already resource-starved platform such as the Soekris 4526 however, this was resulting in some pretty significant overhead. A couple of patches to MadWiFi later (a couple merged upstream already, one that’s a bit more of a hack specific to our needs) and we’re seeing some much nicer throughput numbers. Off the top of my head, we went from being able to bridge about 9-10 Mbit/s of traffic over wireless through the wired ethernet to about ~15 Mbit/s.

The other neat hack we did was to create a transparent wireless bridge by hacking the ad-hoc demo mode to use 4-address 802.11 frames. This could already be done in other modes, but we really like ad-hoc demo due to its utter simplicity - no associations, no beacons, nothing - just passing frames.

Right now we’re working on implementing our own rate control algorithm. We seem to run into far too many problems on our networks with rate control and Perry came up with a neat idea - as is his wont - so we’re running with it. At the same time we’re looking at using it as a chance to collect large amounts of performance data to give us some deeper knowledge as to what’s going on on our networks. Hopefully lots more info on that soon.

At some point in the (very) near future I need to start thinking about the Ph.D again - I’m starting to think that I should be putting more of a measurement focus into it, but I need to nail down a few ideas first. And maybe play a bit of Guitar Hero as well

1 comment August 9th, 2007

No mesh for Minginui?

While SOWN is pretty cool, it’s looking increasingly like the Minginui network is going to have to be deployed manually, instead of as a mesh. There are just too many things getting in the way (mainly trees) to have a nice mesh setup. Looks like we’ll have one house connected to the sector antenna on the hill (must find out the name of that site) running in master mode and a few of the closer houses hanging off that as clients. Then we’ll beam over to the other side of the town with some high-gain directionals. I think a manual set up is going to be far better, given the odd layout of the town and the fact that the network is probably going to be pretty sparse. It’s also going to save a few dollars in the long run, as we can customise each node. Not all is lost though, I’ll probably use my new found knowledge of WDS (thanks to SOWN) with the mini-network I’m going to have to deploy for a PhD student later this semester.

Add comment April 8th, 2005

Meshing woes

Ugh. Roofnet is horribly horrible. I’m sure it’s great when you’re using the LiveCD, but getting it working properly on a Soekris takes far too much hair pulling. I shouldn’t have to edit Perl modules to trick things into thinking they are gateways - and then I found out that the gateway interface is hard-coded to eth0. Well, there goes that idea.
Had a very brief look at LocustWorld, but they only have CF images, which, although nice, I can’t do much with. Plus it’s geared towards their own MeshBox hardware.
SOWN is my next best bet, and it’s looking promising. Uses OSPF, which is nice and easy to understand and configure. Just need to get Pebble linux onto a Soekris, though seeing as Pebble is specifically designed for that kind of thing, it shouldn’t be a big issue.

Add comment March 30th, 2005