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I've come across a situation where my router/wireless card range is longer and more reliable if both are set to use the 'G' standard instead of the 'N'.

This goes against my complete understanding of wireless, and I couldn't find anything on google that started to explain why; so that I could get my house linked up on 'N', instead of falling back to 'G'.

Has anyone had this situation before? and what can I do to remedy this?

Information: (As I've said, I'm at a bit of a loss, so here is anything I think could be remotely useful; feel free to ask for more.)

Wireless Card: Beklin (N compatible, External, USB 2.0)

Wireless Router: D-Link DIR-635 (this is an N router, has run 'N' networks in other houses, and has a signal boosting/directional aerial in one of the three sockets.)

Operating System: Windows Vista (also confirmed on ubuntu/linux.)

The only other notable thing would be a cordless phone near the router, but I don't see why this would effect the 'N' signal and not the 'G'?

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I took the liberty of editing the title to be more clear - I was expecting to come in and answer "Why does my wireless work on G when it doesn't on N?" with "You don't have a wireless card that supports N networks!" until I read the question. :) –  Shinrai Jul 20 '11 at 18:05
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What frequency range does the phone operate in? What about your N? N can operate in the 2.4GHz or 5xGHz ranges. –  KCotreau Jul 20 '11 at 18:22
    
The phone is a BT Graphite 1100, and appears to be operating in the 2.4 GHz range. : And the router could work in the 40 Hz or 20 Hz and was, like the channel, automatically selecting the best option. –  thomas michael wallace Jul 20 '11 at 18:28
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2 Answers

up vote 9 down vote accepted

In general, simpler, slower modulation schemes can be received more reliably in worse conditions (less signal strength, more noise) than more complicated, faster modulation schemes.

In general, N uses faster and more complicated modulation schemes than G, and G uses faster and more complicated modulation schemes than B.

For best balance of rates and range, leave G and even B rates enabled even on your N-capable gear. But still upgrade all your Wi-Fi devices to be N-capable, so that they don't waste airtime by using G or B rates when they're close enough to the AP to use N.

Special radio modes that disable legacy G and B rates for the fastest possible N performance do so at the expense of range, and really only get a very minor performance boost out of that trade-off, and only at close ranges.

In some cases, the N-only optimizations can actually make your N gear less robust in the face of interference, especially interference from legacy G and B devices in radio range of you (e.g. your neighbor's gear). Basically you can get a small performance boost at close range if all of your gear does N-only stuff that only other N devices can see, but it means that any G or B gear in range can't see those transmissions, so they accidentally transmit at the same time and clobber your N-only transmissions. Turning off N-only optimizations can make your N transmissions more visible to legacy G and B gear, so that they stay off the channel while your N clients are transmitting.

There is one thing to be said about channels. N gear can be configured to use only legacy 20MHz-wide channels, or it can be configured to support both 20MHz-wide and 40MHz-wide channels (the 802.11n spec does not have a 40Mhz-only mode, just 20-only and 20/40). When you enable support for 40MHz-wide channels, some transmissions will effectively use two contiguous 20MHz channels. That means that if you upgraded from a G AP on channel 1 to an N AP on channel 1 in 20/40 mode, some of the N transmissions would use not just channel 1, but channel 5 as well. And since the channels overlap quite a bit in the 2.4GHz band, that means your transmissions fully or partially overlap every channel from 1 to 10. So by using 40MHz-wide channels you have to worry about how interference-free you are on a lot more frequencies than before. If you suspect this is a problem, you could reconfigure your router to only use 20MHz-wide channels. It would mean you can only get 144 megabits per second signaling rates instead of 300 megabits per second, but that might be a good trade off if you're running into interference problems on wide channels.

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that's one hell of a comprehensive answer. Thanks for taking the time to fill me in. –  thomas michael wallace Jul 20 '11 at 22:14
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You're on the right track - this is more than likely interference of some type.

The G and N signals are on different frequencies, so something (say, that cordless phone) could very well affect one and not the other. Another likely explanation is simply that there are a lot of N networks in the area and you're getting signal interference from that. (It could also be that the one type of signal penetrates the building materials at your location better than the other but this is kind of unlikely.)

You might try changing the channel your N network is on and see if that helps any to bypass interference you might be receiving. This should be very easy to do from the router interface.

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Thanks- I didn't realise G and N signals had different frequencies! –  thomas michael wallace Jul 20 '11 at 18:23
    
@thomas - I believe they're both in the 2.4-2.5GHz range (although N can run at 5GHz as well, and if you're up there that would certainly explain differences), but the channel widths are different and obviously which channel you're using has a huge effect. You'd be surprised, even if they're close, what a difference specific conflicts can make. –  Shinrai Jul 20 '11 at 18:30
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en.wikipedia.org/wiki/List_of_WLAN_channels for a list of channels. Something else to keep in mind, the higher the frequency, the shorter the distance when the power output is the same. –  dbasnett Jul 20 '11 at 18:32
    
@dbasnett makes a very good point - if the router isn't very beefy it might well be reaching the limits of its output (although since you indicate it's worked well with other machines in other locations I doubt that's it.) –  Shinrai Jul 20 '11 at 18:33
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@thomas - His is better anyway (if possibly a bit headache inducing). He's the resident network expert, after all! –  Shinrai Jul 20 '11 at 22:22
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