Take the 2-minute tour ×
Super User is a question and answer site for computer enthusiasts and power users. It's 100% free, no registration required.

I was tinkering around with my NetGear WNR2000v2 router this morning and noticed a Mode option under its Wireless Settings page.

Of the 3 - 4 Mode options available to me, the last two were:

  • Up to 145 Mbps; and
  • Up to 300 Mbps

My initial reaction was: why would anybody ever want to choose slower speeds?!?! Then I read the helper section on Mode and it mentioned that the Up to 145 Mbps option was best for small home networks (which mine is) because it is considered a Neighbor-Friendly mode.

What does this mean?!?

How does the speed of the network affect RF channels, etc. of my surrounding (neighbors') wireless networks? What are the cons/issues of increasing up to the 300 Mbps max?

share|improve this question
add comment

3 Answers

up vote 11 down vote accepted

In radio terms, this option is allowing you to select between a 20MHz and 40MHz channel width. A 40MHz wide channel allows just a little more than twice the throughput (network bandwidth) of a 20MHz channel (because you get the equivalent of two 20MHz channels plus the "gutter" between them for one signal), but it takes up two channel slots.

In the narrow 2.4GHz band (originally used for b/g with 22MHz overlapping channels), only a single 40MHz channel will fit (note that 802.11n does not allow channels to overlap). This means that all 802.11n routers set to 2.4GHz (most of them) and to 40MHz channel width (fortunately not most of them) will be sharing the exact same radio space, and thus will slow eachother down. This can have an extreme impact in environments like apartment buildings and college dorms, where 802.11n set to 40MHz in the 2.4GHz band may perform worse (in terms of network throughput) than 802.11g.

This is the key reason that the WiFi alliance and, more slowly, manufacturers promote the 5GHz band for 802.11an. It is significantly wider than the 2.4GHz band, and allows for a comfortable number of non-overlapping 40MHz channels. The 5GHz band is also used solely by 802.11an (and limited other network applications), unlike the "general home RF" 2.4GHz band that WiFi shares with older DECT, analogue audio devices, etc (which are not WiFi aware and can significantly impact performance of nearby WiFi networks).

Even in the 5GHz space, though, there are only 2, 4, or 6 (depending on which U-NII bands your devices use, which is something I'm not familiar with) 40MHz channels available, so sticking to 20MHz is decidedly more neighbor-friendly in a crowded environment.

share|improve this answer
    
Wow, great answer - thanks! Just out of curiosity, if only 1 40MHz channel can "fit" inside a 2.4GHz band, then how many 20MHz channels can it "fit"? Is this a linear relationship? Does that mean that only 2 20MHz channels could fit (bc they each take 1/2 the space)? That still seems odd, because wouldn't that mean that you could only have 2 neighbors in the same vicinity taking up the same 2.4GHz band? –  pnongrata Jan 4 '12 at 18:02
    
@zharvey: 3 20MHz channels. Or 4 if you are in a place which can use channels up to 13 (they are channels 1, 5, 9, 13 - the channels have a 5MHz spacing), but some devices cannot use channels 12 and 13, so people normally use only 3 20MHz channels and space them a bit more (channels 1, 6, 11). –  CesarB May 13 '12 at 0:03
add comment

For higher data transmission rates, your router radio broadcasts over a wider range of frequencies. This wider transmission band is more likely to interact negatively with other wireless networks in close channels.

Looking at the available wireless networks in your area, if you can view the channels those networks are broadcasting on, if there is a space of 5 or more empty channels together, telling your own router to broadcast in the middle-most channel, you're highly unlikely to cause problems with your neighbors networks.

If there is not so much room, it may be nice to use the "friendly" mode.

At the same time, who'll think that a neighbors wireless broadcast too aggressively is the cause of their new network troubles...

Personally, I'd compare real-life network speed between the two options and, if there isn't much difference in real life, I'd stick to the lower of the two.

UPDATE:

The 5 channel spread is an estimate based on realistic environments. If you're in the boonies there's no interference concerns at all. If you're in an average neighborhood, it's highly unlikely you'll find enough space in the available spectrum to avoid interference of some kind with your neighbors

share|improve this answer
add comment

Viewing Basic Wireless Settings

See link it "reduced interference with neighboring wireless networks" because it does not use "expand to the secondary channel (primary channel +4 or -4) to achieve a 40 MHz frame- by-frame bandwidth."

share|improve this answer
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.