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Q: I'm thinking of buying a new wireless router, and can't decide between a cheap 802.11N router and the more expensive dual-band versions. Are they worth the extra cost?

Like most other commodity devices, wireless routers have seen their prices pushed inexorably downward, with the exception being when new technology—the G and N protocols—has come onto the market. It's been a while since the N standard was introduced, so you might predict that even top-of-the-line routers would be sitting in the $50 range. They're not. Instead, prices from most manufacturers still top out at well over $100. How can they get away with that? The secret to the new high end is (primarily) the use of what's called dual-band technology, along with a sprinkling of other features that are nice, but not essential. We'll take a look at what dual band brings to the table, and whether paying more for the additional features is likely to be worth your while.

When it comes to WiFi, there are a total of four protocols and two frequencies. The initial flavor of WiFi, 802.11b, occupied the 2.4GHz area of the spectrum, which was also used by the enhanced, higher throughput G version. This tends to give it decent range, penetration, and omnidirectionality (a single antenna provides good signal in three dimensions), but the spectrum around 2.4GHz is a bit more prone to interference from other devices. As time has gone on, it has also gotten very, very crowded. If you live in a dense urban environment, it's possible to end up with so many WiFi devices trying to find space in this area of the spectrum that your router may end up dropping connections.

The alternative frequencies, at 5GHz, are much less prone to interference and are (currently, at least), a lot less crowded. There is some trade off here, as antenna designs make a big difference in terms of how the 5GHz signal propagates away from the router. Nevertheless, my personal experience has been that signals on the 5GHz frequency are quite a bit more stable, which is a very good thing if you do backups or large downloads wirelessly.

Initially, 5GHz was used only by the least popular version of WiFi, 802.11a. The latest version, N, is able to use either frequency range (although a single device can't use both at the same time—more on that later). N hardware is backwards compatible with A when it's using 5GHz, and B and G when at 2.4Ghz so, depending on what frequency you use, an N router may or may not support other devices you have. To confuse matters slightly further, there are some 802.11n devices, primarily low-power hardware like cellphones, that can't take advantage of the 5Ghz band.

Where does that all leave us? An N device operating on 5GHz is probably your best bet for a reliable, high-throughput connection, but it will most likely mean that some of your devices won't be able to get on the network.

If the environment your router is in allows you to maintain a good signal at 2.4GHz, you're set. Chances are very small that you have an 802.11a device, and setting up an N router on that frequency lets everything else hop on. If you can't maintain a stable signal or get decent throughput at that frequency band, however, things get seriously complex. You can set up your router on the 5GHz band, but that excludes all B and G devices—and even some N hardware. Servicing these devices requires you to set up a separate router operating at 2.4GHz.

Make that required. This is precisely the hassle that dual-band WiFi hardware is designed to solve. These routers have extra antennas that allow them to broadcast at both frequencies simultaneously. So a single access point can serve all classes of devices, with modern, high-throughput hardware sitting on the 5GHz channel and older equipment making do with 2.4GHz. This does require two different networks, but they're both coming from a single piece of hardware. A number of companies even offer routers that offer a third network for guest access, in which devices can get on without a password, but are only allowed to access the outside world—not any devices within the network.

One word of caution here: many manufacturers are simply adding up the total bandwidth possible on both parts of the spectrum, and claiming that's their router's maximum throughput. No single device that connects to it is actually able to use all of that bandwidth, though, so view these claims skeptically.

Although dual-band routers are coming down in price, most manufacturers are adding features in order to induce users to pay more. One of the simplest is ethernet ports, typically Gigabit, which provides a nice boost in bandwidth if you end up transferring large files or performing heavy backups on your local network. Apple, Belkin, Buffalo, D-Link, Linksys, Netgear, and TRENDnet all offer versions with gigabit ports, typically four for use for local devices. You can get cheaper hardware without them, but Ethernet is nice to have around if you end up with a file server or networked printer.

Another handy feature that many routers now have is a USB port or two, typically used for hosting a printer or portable storage device on the local network. Apple, Buffalo, D-Link, Linksys, and Netgear each offer a single USB port; Belkin offers two. Not all routers support all drive formats—Apple is probably the only one to support HFS+, for example—so it's worth diving into the tech specs to make sure you can share any existing drives you have. The same thing is true with printers, as not every USB printer will play nicely with a given router.

Do these added features make it worth paying the price for a top-end model? That's something that only you can decide given your needs and the sort of hardware you already have around. Getting a dual-band system, however, is an easier decision to make: if you've found that you need to use the 5GHz spectrum to get decent network performance in your home but still have some 802.11b or g devices around, the dual band router may make a lot of sense.