mac geekery

Interference. It’s the biggest problem these days with wireless ethernet and it will kill the speed of your connection. A 54Mb connection is capable of 6.9MB/s at 100% performance. You won’t see 100% performance. You’ll be lucky to see 90% (6.2MB/s). But after cleaning up much of the interference with my base stations, I did see 56% of maximum two rooms over.

The first thing you need to do is see if anyone is interfering with your signal. Now I could sit here and discuss signal/noise ratios and power settings, or I can give you a pretty chart. I’m guessing you want the pretty chart.

As you can see, channel six is overrun with base stations on their default channel. I had Callisto up on channel 10 for a while, but that austin3 network showed up one day and absolutely killed my network’s performance. For a while, I blamed it on my MacBook Pro as I’d previously had an iBook G4, the superstar of reception. But then I tested the new iStumbler and saw that there were a few networks up there and absolutely no one at the low end. So, I changed the settings on my base station to be at channel 3. The results were astounding. I went from this:

To this:

Really.

The Easy and Proper Way

If you leave iStumbler open, all of your bandwidth tests will return bad results. Close the program (the widget depends on the program and is harmless) and then test your speed.

So, seeing that that wide swath of space at the lower end of the spectrum was entirely unused, I just set my channel to three and restarted the base station. I rather liked the results.

Of course, that’s the easy way. You can always do it the hard way.

The Needlessly Hard But Really Cool Way

Go to Apple’s Airport Support page and down on the right where it says “Update Your Software” you’ll see a link to the AirPort Management Tools. Get the disk image and open it up.

When you open the disk image, you’ll see two programs. Both of which we’ll use, but for different purposes. These are the standard programs that come on the Power-Over-Ethernet version of the AirPort Extreme Base Station that’s sold to large institutions, but anyone can get them. They have one very cool feature we’re going to use: signal charts.

These are PowerPC apps and I’m on an Intel machine. I blame this for the fact that the Client Monitor doesn’t work for me. It starts up, but won’t start pinging. What it does do, when it’s working, is send variable-sized ping packets to the wireless router and then chart the latency so you have an idea of how well the network is performing. Using this, you can start at one side of the room or building and pace yourself to the other side and then pause the chart and look for lulls. Go back to that point and check for interference in iStumbler and see if you can’t work out a way to fix it. You can get a kind of substitute for this program in iStumbler, but it’s only going to give you the signal level and not any indication of performance (a problem the next program has as well).

The other application, Airport Management Utility, works fine for me in 10.4.7. It’s a good thing, too, because that’s the fun one. If you have multiple base stations then you need this little application. Now, I’m not going to go into details about the main reason this application exists, mass deployment, because I really want to concentrate on the production of pretty graphs (that, and it’s off-topic).

Pick a base station on the left and then go to the Monitor tab. You’ll get a nice graph and chart of all the connected clients to the base station and their signal levels relative to the base station’s radio. Schweet.

The yellow line is the WDS master base station with the DSL connection, and the green line is my MacBook — the chart itself is for my AirPort Express, to which I am curiously connected even with my AirPort Extreme just three feet away from me.

You’ll see two numbers in the chart below: signal and noise. You want signal as close to zero as you can get it and noise as far away. The larger the delta, the better the speed (generally). These numbers are different than their counterparts in iStumbler, which uses more sane positive-integer measures with a zero-based noise measurement.

1.21 Gigawatts?![1]

If you have a WDS/roaming setup, like I do, you’re going to run into a quandary. Imagine a circular, logarithmic radio power fallout from each base station going a hundred feet out. Imagine this for all of your base stations. Note the points at which they overlap, and see what kind of signal you get there. If it’s okay, ignore me. If it’s bad, let’s chat.

WDS requires all base stations to be on the same channel. Roaming wants base stations on different channels so they don’t interfere with one another. Doing roaming with a WDS uplink is asking for problems when you get several base stations together. What you want to do is set the transmitter power down on some of the base stations so that they serve a smaller area and don’t cause as much interference.

Now, the iStumbler widget gives you a nice view of the power/signal strength of the network in question by bleeding it outside of its channel. Leave Dashboard up with that going and walk around the area you think the networks would intersect at and watch the power of both base stations. Tweak them until the power level of one of them is low in this area and the other is high. It takes some patience if you want to get it right. For home use, I wouldn’t bother, honestly, but for a large install this is rather important (though, for a large install I’m going to ask you why you’re not using an ethernet backbone rather than WDS).

Radio Ga Ga²

It’s fun stuff, this wireless ethernet. You run through the setup assistant or admin utility and have no idea how much is still abstracted away from you until you start signal-diving and tweaking things. I’ll write some more about AirPort here soon, I feel, but I felt this was the most important part of it all.

Footnotes

¹ Name that movie. Bonus points for owning the shirt.

² That pun was tied with “Spirit of Radio” to be entirely honest.

Optimizing AirPort Connectivity

Select ratingCancel ratingPoorOkayGoodGreatAwesome

Average: 5 (8 votes)