By Daniel Eran Dilger

Published: 09:00 AM EST

Apple's revised AirPort Extreme, introduced at Macworld Expo in January, offers several new features and significant improvements in wireless networking speed and reliability. Whether it is worth the upgrade price to move on up to the new 802.11n wireless technology depends upon the specific needs of potential buyers. Read all about it in our 4-page in-depth review.

The most obvious advantage of the new AirPort Extreme over Apple's previous models is support for the new 802.11n wireless networking standard. Apple says the new standard offers five times the data transfer speed and more than twice the range of devices using the former standard.

The last time a new AirPort wireless standard appeared was 802.11g, back in 2003. Apple assigned it the marketing name "AirPort Extreme" to distinguish the faster new second generation wireless networking standard from the earlier 802.11b technology that the company had been simply calling "AirPort" since its introduction in 1999.

New In N

This time around, there is no new Apple marketing name for the unwieldy mouthful of characters representing the IEEE's third generation 802.11n technical specification, but it is commonly referred to as wireless-n. One of the key technologies associated with the new wireless-n standard is its new MIMO antenna technology.

Rather than using a single radio antenna to send and receive wireless data, wireless-n devices all use a series of antennas, referred to as "Multiple-Input, Multiple-Output." MIMO technology allows wireless-n devices to more efficiently spread data over multiple radio frequencies and maintain multiple, simultaneous data streams.

The result is faster data transmission and greater signal reliability over longer distances, without a significant increase in the amount of power or bandwidth required. Wireless-n can operate on the same frequencies as existing 802.11b/g networks, and is backwardly compatible with earlier wireless devices.

How Much Faster?

Apple promises a five fold increase in speed using wireless-n, and AirPort Extreme delivers. That's in part because the wireless-n standard is a big jump in technology, but also because the former 802.11g standard was somewhat problematic. Users will likely appreciate the more reliable signal that wireless-n MIMO devices provide, and find the better coverage at least as useful as the new boost in speed.

The degree of benefit realized by the new wireless-n AirPort Extreme base station depends a lot upon how it will be used. To take advantage of its faster speeds, users will of course also need wireless-n support in all of their other devices.

Nearly all of the Core 2 Duo Intel-based Macs offer built-in support for wireless-n, apart from the entry level 17" 1.83GHz iMac. Earlier Intel Macs based on the original Core Duo or Solo, and all of the earlier PowerPC Macs lack built-in support for wireless-n.

Apple offers no wireless-n upgrade path for earlier Macs designed for the first two generations of wireless technology, in part because earlier systems' AirPort slots can't accommodate the full speed of wireless-n, and their existing built-in antennas wouldn't deliver the main MIMO advantage offered by the new standard.

Some third parties offer upgrades for certain Mac models, including QuickerTek's $149-$179 wireless-n upgrades for the Intel-based Mac mini, iMac, and Mac Book laptops. Other vendors offer external USB adapters, such as D-Link's $149 wireless-n interface, which is commonly available online for around $99.

Mixing AirPort Traffic

Of course, existing wireless clients will still work with the new AirPort Express, but won't be able to benefit from its faster speed. Using earlier 802.11b/g devices with it will actually slow down throughput for any wireless-n devices whenever those older devices are actively transmitting data.

That suggests two bits of buyer recommendations: the first is for users to consider waiting to upgrade until they have enough wireless-n devices to make use of the new speed; the second is to consider using a new wireless-n base station in tandem with an earlier existing AirPort base station for optimal speed in circumstances where there are several wireless clients with different speed capacities.

While the new AirPort Extreme can act as a drop in replacement upgrade for earlier models, it can also be configured as a parallel upgrade, set up to only talk to new devices supporting wireless-n. It can even be set up to use an entirely different frequency band, preventing any overlap or contention between existing network traffic and the new wireless-n only devices.

A Question of Need

Of course, another factor to take into consideration before building a complex system optimized to wirelessly shoot around bits at the most optimal speeds is whether wireless-n will offer any real world difference.

For users who are simply using AirPort to share an Internet connection, upgrading to wireless-n won't really make a speed difference at all; the existing AirPort Extreme 802.11g is already far faster than DSL or Cable Internet. Typical Internet access is commonly the weakest link, with speeds in the range of 1.5 - 3 Mbps, compared to the theoretical maximum of 802.11g at 54 Mbps (actual throughput is typically closer to around 20 Mbps). Upgrading the wireless network isn't going to make Internet access any faster, although it likely will help with the coverage area.

The upgrade to wireless-n is most useful to users who are sharing files between their computers. This includes both direct file sharing and remote sharing of the contents of an iTunes or iPhoto library between networked computers. While these are all possible using earlier wireless standards, the much faster speed of the new wireless-n makes for a considerable improvement in the overall experience.

Wireless USB Disk Sharing

Along those lines, the new AirPort Extreme includes a new feature to exploit its faster speed: a USB hard drive can be plugged in to set up a simple disk share that any connected Mac or PC can access. With a USB hub, multiple disks, along with multiple USB printers, can be shared among all of the networked users, whether they are wirelessly connected or plugged into the base station directly via an Ethernet cable.

This offers the potential for AirPort Extreme to serve as a simple file server for home and small office users. It also provides a convenient way for users to copy files from multiple computers to a central disk for backup purposes, and makes it easy for users to share files between Macs and PCs without setting up and managing file shares on each machine.

Some competing wireless routers also offer similar shared disk features, but few support the Mac's native Apple File Protocol file sharing; most only provide Windows' SMB file sharing. While Macs can interact with these systems, they do not provide full support for some expected Mac features such as file icons and resource forks; Apple's AirPort Extreme is both Mac and Windows savvy.

On page two: Networking with Apple TV, Apple's Web Free Interface, No Paperclip Required, Introducing the Summary Tab