802.11n
by Jon on Nov.21, 2009, under Computer stuff
I’ve finally bought a draft-n router (dlink 615).
After debating for ages on whether to update my wireless network, I came across the router on Fleabay. Cost was all of a tenner so I thought Why not, let’s see what this ‘n’ lark is like.
If I was going to change over completely then I’d be getting dual mode access points. SWMBO’s work machine needs b/g, the WII needs b/g, so the best idea would be to dedicate 5GHz to ‘n’.
As I’m only experimenting the ‘n’ is also on 2.4GHz – nothing to do with the price, honest 
.
Recently I changed my laptop over to Ubuntu – why is another story. It’s been a big learning curve for me – I’m not really used to gui based configs. There are some bits I like and yet more that I don’t – being a gentoo type person at heart having everything gui’ised don’t really cut it. However, one of the advantages of Linux is that I can always drop back to the command line should I need to.
So, how’s the ‘n’ working. Well, I can see it and log onto the network via it.
The throughput is certainly better than when I was connected at ‘g’ but and this is a big but, I’m not convinced that I’m connecting at ‘n’. My ‘n’ router is only connected to the network via a powerline adapter so it only has about 3MB of bandwidth available to it – which it can fill at 54Mb/s without any great problem.
So what’s the big deal – take a look at this output of iwconfig:
wlan0 IEEE 802.11abgn ESSID:”dlink”
Bit Rate=1 Mb/s Tx-Power=15 dBm
That’s at odds with the gui which is reporting 48Mb/s.
iwlist wlan0 bitrate:
wlan0 unknown bit-rate information.
Current Bit Rate:1 Mb/s
hmmm – that’s a tad suspicious me thinks.
So what does iwlist think of the ‘dlink’:
ESSID:”dlink”
Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 9 Mb/s
18 Mb/s; 36 Mb/s; 54 Mb/s
Bit Rates:6 Mb/s; 12 Mb/s; 24 Mb/s; 48 Mb/s
hang on a second there. Shouldn’t there be something above 54 ?? the dlink is actually turned to ‘n’ only so why the limit ?
A quick search online and we find this problem is something to do with the way the iwlagn driver has been configured for ubuntu.
With Gentoo I never had this problem – adding bits into the kernel was really pretty straight forward, you just rebuilt the thing.
I suppose I’ll go back to running my own vanilla kernel patched with the various drivers that I’ll need. For a desktop/laptop this becomes a right pita to manage though.
There is something called backports for Ubuntu which I’m going to try out – whether anyone will have compiled in the right bit of the driver I’ve no idea.
If this actually works then the access point will move onto the GE vlan rather than the low bandwidth powerline vlan.
Then it’ll just be a case of pursuading swmbo that I need to upgrade things yet again .
Speaking of upgrades, I suppose it’s time I bought another GE switch – but decent ones are still a tad pricey.
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November 21st, 2009 on 11:21 pm
So did it work ?????
Well sort of is about the best answer I can give.
Backports certainly did something – I still never get a connection about 38Mb/s but at least that’s above 1Mb/s.
Interestingly, iwconfig can still report 0Kb/s and still get a throughput of 3MB/s which is about as good as I’ve ever seen on a G network running at 58M/s.
Now, I’ve had a lot of people telling me that 802.11n isn’t supported at all by Linux – erm, bollox. It might not be connecting at 130Mb/s like if I reboot into windows but it is definitely connecting at ’some’ level or another. I know it’s connecting to ‘n’ as that’s all the router is set to allow.
So, is it just that the driver isn’t reporting things correctly – now to find out if there’s some way of seeing connection details directly within the dlink 615.
November 21st, 2009 on 11:27 pm
So yes there is something on the router that shows connection rates:
Connect Time Mode Rate
0 days, 00:17:43 11n 117.0
So it looks like it’s a reporting issue with the driver.
If I get chance I’ll drop it onto the GigE vlan and report back on the sort of throughput I’m seeing.
I suppose I couldn’t really care what the reported speed is, what matters is the actual throughput.
November 21st, 2009 on 11:38 pm
hmmm. Just noticed that the 615 only has 100Mb FE so there’s no point dropping it into the GigE network.
How can they claim speeds upto 300Mb/s when the switch ports are only 100Mb/s, perhaps they expect you to wire in client machines and wireless servers, or is it just the ‘normal’ marketing bullshit – no prizes for a correct answer
November 24th, 2009 on 4:39 pm
hmmm. Not entirely sure this driver is overly stable.
I might try and see if I can find and Atheros based card to play with.
December 16th, 2009 on 5:24 pm
well, the stuff is just as stable on ‘n’ as on ‘g’. Surprisingly signal strength is worse – i though ‘n’ was supposed to be better ?
Throughput is better than with ‘g’ even thoughj it’s connecting at a lower bit rate – bullshit. The driver isn’t reporting something correctly, there’s no way an 18mbit connection equals a 48mbit.
Interestingly swmbo got a new laptop yesterday with a 5100agn card in it. So I might get away with getting a 5GHz box.
I need to look into dropping a cable to somewhere nearer rather than having the AP in the loft – perhaps I can hide one in the lounge