Ask the Wi-fi Guru, Episode 39

By Aaron Weiss

August 09, 2011

This month, our guru of all things wireless explains the best way to deal with overcrowded Wi-Fi networks and helps troubleshoot a DD-WRT in repeater-bridge mode issue.

Q: I am ready to buy a new Wi-Fi router. Is it possible to have the router change its channel automatically to a less busy channel? I think my Wi-Fi is slow because I live in a city with so many Wi-Fi networks around me. I have a wireless G router, and I wonder if maybe wireless N would support automatic channel changing? -- zlater

A: If you live in a crowded Wi-Fi environment like a major city, it would be a good idea to upgrade to "wireless-N" (802.11N) gear if you can. But not for the reason you describe.

The wireless router will choose a broadcast channel based either on manual setting or automatically, but it will not "channel hop" with associated clients to continuously adapt to changing conditions.

Most wireless routers default to channel 6, which is about the middle of the wireless-G spectrum. This means that channel 6 is usually the most crowded when there are other routers nearby.

In the U.S., wireless-G networks have eleven channels, numbered from -- yes, that's right --1 to 11. Each channel encompasses a range of spectrum, and therefore the beginning and end of each range overlaps with the range of adjacent channels.

Channels 1, 6 and 11 are the only three that do not have any overlap with each other; therefore, if your wireless router is on the typical channel 6, try changing it to channel 1 or 11.

If you're curious, you can use software like Kismet (or KisMAC) to scan the routers near you to see what channels they're using. Then you'd know exactly which channel would be your best candidate to separate yourself from the pack.

What I've just told you is true when you are using wireless-G; you have even more options with wireless-N equipment. Specifically, wireless-N adds support for the 5Ghz spectrum (it also supports all of the wireless-G channels).

Because wireless-N is still a newer (and more expensive) technology, the 5Ghz spectrum is far less crowded than the 2.4Ghz spectrum used by wireless-G. To take advantage of this, you need to use wireless-N gear exclusively, meaning both your router and your wireless device. If you can do this, configuring a wireless-N router to use only the 5Ghz spectrum will give you the least-crowded wireless spectrum.

Q: I share the wireless network that connects my parents' house to their workshop via a bridge, and I've had it working for about 6 months. Here is what we have set up:

  • DSL modem
  • DIR-628 wireless router with an 8dbi omni-directional indoor antenna
  • A makeshift pointer added to the router (and pointed at the shop approximately 100 yards away)
  • A WNR2000 V2 running DD-WRT in repeater-bridge mode

I am currently sitting in the window at the shop using the Wi-Fi from the host router, but I can't get it to connect through the bridge. - Sirch

A: Don't you hate it when something that actually was working suddenly stops working, and you can't figure out why? Yeah, me too. This sounds like that kind of situation, which can be especially hard to diagnose from a distance.

Reading through your setup, one point that jumps out at me is using DD-WRT in repeater-bridge mode. In my experience, repeater mode in DD-WRT can be…flaky. Sometimes it works great, sometimes it is very stubborn.

I realize that this setup had previously been working, but I would advise first exploring whether repeater mode could be the culprit here. Maybe it has become stubborn.

One way you can test this is by changing DD-WRT from repeater mode to simple client bridge mode. In client mode, the router will become a wired bridge. Meaning, it will only connect to devices connected by Ethernet; it won't simultaneously re-broadcast the wireless signal from the primary router.

Client mode seems to be more reliable. If this test works, then you will know that repeater mode has been misbehaving or just plain not working correctly. Of course, client mode is not a permanent solution since you really want to repeat the wireless signal.

A more reliable way to create a repeater bridge is to add a second wireless router. Leave the DD-WRT router in simple client mode, and plug a second wireless router into one of the DD-WRT router's LAN ports. Configure the new router to behave as a simple AP (access point), by disabling the firewall and DHCP server. I often find this  to be the more reliable solution for permanent installations.

Aaron Weiss is a freelance writer, author, and Wi-Fi enthusiast based in upstate New York. To submit your questions to the Wi-Fi Guru, simply click on his byline (above) and put "Wi-Fi Guru" in the subject line.



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