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Improving AirPort's range

Wi-Fi networks can reach only so far. The range of wireless equipment—such as the radios and antennas that are built into consumer equipment like the AirPort Extreme Base Station—can vary from network to network, even minute to minute. But when one node of a Wi-Fi network is too far from another, communications between the two break down, and your network doesn’t work.

While Wi-Fi signals are supposed to reach 150 feet in any direction from a gateway, that optimistic number is rarely reached indoors. One common cause is absorption. Building materials between two points can soak up so much of the signal that one device can’t detect another. (Brick is particularly bad for Wi-Fi because brick retains water, which readily absorbs Wi-Fi signals.) As a result, a gateway that delivers a perfect high-speed connection to a laptop from 500 feet away when it has a direct line of sight might be invisible to a laptop that’s 50 feet away when there’s a brick wall between them.

Diagnosis

There are two main indicators that your AirPort network is having range problems. First, Wi-Fi networks you know are there don’t show up in the AirPort menu. Second, when you do connect to a network, the AirPort icon in the system menu bar shows just one or two signal-strength bars and frequently slips to no bars (a grayed-out icon).

You can also check signal strength with iStumbler (donation requested), a utility that shows you a list of all in-range Wi-Fi networks and Bluetooth devices. Among other details, iStumbler shows you percentage values for the signal and noise of those nearby networks. If iStumbler shows a high noise value, then interference could be the reason you’re having network problems. But if the noise value and the signal value are both low, then range is the problem.

Solutions

If iStumbler indicates that you’re having interference problems, you can solve them by following our advice from last month’s Mobile Mac column (see Troubleshooting AirPort Interference ). If the problem really is range, there are several easy ways to solve it.

Upgrade Your Base Station Routers that are based on the Draft N specification (an early version of the 802.11n networking standard) incorporate MIMO (multiple input, multiple output) antenna arrays. MIMO can improve range (as well as speed).

The AirPort Extreme Base Stations (   ) released in 2007 use Draft N, and Apple claims that the standard has twice the range of its predecessor. In testing early this year, Macworld found that the range was indeed quite good.

Linksys and several other companies sell Draft N routers starting at $100. Because those routers improve both transmission power and reception sensitivity, you can update just the gateway and continue using the older adapters on all your computers; the range of your network should still improve.

Add an Antenna You could also install a large, strong antenna on your base station so that it could blast out more-powerful signals.

Many Wi-Fi gateways have antennas that you can unscrew and replace with another antenna that has a higher gain (produces a stronger signal). HyperLink Technologies has been selling antennas, and providing compatibility information about which gateways and wireless cards they work with, for years. The information is a bit technical, but it’s an exhaustive resource.

Apple has always kept its antennas inside the housing of its AirPort Base Stations; just a few of the 802.11g AirPort Extreme Base Stations came with an antenna jack for adding an external one. MacWireless has antennas, tools, and instructions for adding antennas to all AirPort models. MacWireless also offers a High Power 11g Access Point ($180). This unit has a regular-size antenna but a much more powerful radio, which provides more than ten times the raw output power of most consumer gateways.

There is one downside to upgrading your antenna: while it can help your network, it can also mess up others. That’s because nearby networks may pick up your signals, and their performance will degrade as they try to cope with the barrage.

Upgrade Your Radio If you have an older Mac without 802.11n built in, you can improve its range by attaching an 802.11n adapter. QuickerTek nNano USB adapter ($65), for example, works with any Mac running Mac OS X 10.3 or later. The company also has a CardBus card ($65) and PCI Card ($100) that work with PowerPC models running Mac OS 10.3.9 or higher, and upgrade kits for Intel Macs starting at $100. Other World Computing offers three alternatives, each for $68: a USB adapter (Mac OS X 10.3 or later, any model Mac), and a PCI Card and CardBus card (for PowerPC models).

All of these adapters have one important limitation: They operate only in the crowded 2.4 GHz band. But they can still improve range by transmitting farther and listening more carefully.

Add More Base Stations Another way to extend network range is to build a network with many base stations, all with the same network name. Wi-Fi adapters look for a network name, not a specific gateway. If one base station doesn’t cover your home or office, perhaps two or five—or ten—might.

You could deploy a bunch of AirPort Base Stations, but that’d get expensive. Other 802.11g and 802.11n Wi-Fi gateways cost as little as $30 to $100 each.

In a standard network of multiple base stations, you configure one base station as the gateway, plugged into a broadband router. You connect additional base stations through Ethernet, or wirelessly through WDS (Wireless Distribution System), which is built into the AirPort Extreme Base Station and other gateways.

To make the multiple-base-stations setup work, you need to configure the main base station as a gateway to your broadband connection. You then configure the other base stations to pass traffic in bridge mode; that way, they leave the responsibility for assigning IP addresses to the primary base station. To set this up with the AirPort Extreme, go to AirPort Utility’s Internet pane, select the Internet Connection tab, and select Off (Bridge) from the Connection Sharing menu. Plug the WAN (wide area network) port from these subsidiary base stations into a LAN (local area network) port on the primary base station, or into an Ethernet switch that’s plugged into the LAN port. For other base stations, you’ll have to check the manual.

As an alternative, you could use home power-line networking to connect base stations (again, see Troubleshooting AirPort Interference for more information). Many power-line vendors offer combos consisting of a wireless access point with a built-in power-line adapter; that way, you can extend your network without using WDS or Ethernet.

[ Glenn Fleishman is the author of Take Control of Your 802.11n AirPort Extreme Network ( TidBits Publishing, 2007). ]

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