Which data contract?
For the past few weeks I've been trying to work out which "mobile broadband" provider to go with for my daily commute. It's a train journey from the north coast of Northern Ireland to Belfast and goes through some sparsely populated areas, so I wasn't expecting to get anything that would provide 3G all the way. However I do want a provider that can do their best to keep a session up for the journey, handing over between 2G + 3G as necessary. Coverage maps/checkers aren't too bad if you just want to check a static point, but really even then it's better to actually try the provider in the location yourself. So, armed with a bluetooth GPS (BlueNEXT BN-909GR), an Option GT 3G Quad PCMCIA card and my laptop I set about measuring signal strength along my train journey for each of the 5 providers available. I also made sure to actually try a session with them for at least one journey, because signal strength is not everything.
I wrote some Perl using Net::GPSD and Device::Gsm to query my current location, signal strength, 2G/3G status and network every 10 seconds. I did this for 3 train journeys (except for O2) and then also produced an "optimistic" file of all the data points combined for that provider.
A second piece of Perl took this data and drew the maps you see below. The graph on the right for each provider is all data points. Red means 2G, blue means 3G, green means "Limited Service" (i.e. it could see a signal, but not one it was allowed to connect to). White means that we had a GPS location and no signal at all. Click on the maps for bigger versions. You can see the route on OpenStreetMap - my graphs are a little squished horizontally, but the journey is from Castlerock (top left on the coast near Coleraine) to Belfast (bottom right).
At first glance 3 look to be the best bet. Lots of blue, a reasonably priced data plan. Except they can't hold up a session to save themselves. Not only does a 2G/3G handover almost always seem to result in a drop, but I had periods of failing to get a 2G session up at all and had some random drops while in 3G coverage as well. So strike them off.
O2 and T-Mobile don't manage any 3G outside Belfast (that's the bottom right corner btw). I found that a few periods of 3G along the journey helped a lot; it meant I could do a quick mail sync rather than the long drawn out affair it was on a 2G connection. They can both handle handover between 2G/3G and keep a session up for most of the journey, but the lack of speed counts them out.
Vodafone managed the worst reception, which is disappointing. I found them quite good when I lived in England (my datacard is from a Vodafone Pay as You Use data contract). I did find sessions being dropped during the no signal regions, so they just don't seem to be a good bet.
Which leaves Orange. I've had issues with Orange and data in the past (pre 2004 IIRC) but in testing they were able to keep a session up between Belfast and Castlerock, handling 2G/3G handover fine. Coverage was reasonably good and they manage 3G at several points along the journey (the blue points roughly correspond to Coleraine, Ballymena, Antrim and Belfast). I understand Orange have some EDGE capability, but my card doesn't do EDGE so I've no idea if that'll be an extra gain or not. I had a few issues with getting dud DNS servers but this happened with the other providers too so I was beginning to suspect the datacard of playing up. Manually setting known good servers in resolv.conf worked fine.
So, before I go and sign up to an 18 month Orange contract, what have I forgotten?