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802.11b 802.11b was the first standard to take off and become ubiquitous in wireless networking. The 802.11b standard supports data throughput of up to 11 Mbps (with actual throughput averaging 4 to 6 Mbps)—on par with older, wired 10BaseT networks—and a maximum range of 300 feet under ideal conditions. In a typical office environment, its maximum range is lower. The main downside to using 802.11b is, in fact, that it uses a very popular frequency. The 2.4-GHz ISM band is already crowded with baby monitors, garage door openers, microwaves, and wireless phones, so you’re likely to run into interference from other wireless devices.

802.11g 802.11g came out in 2003, taking the best of 802.11a and b and rolling them into a single standard. 802.11g offers data transfer speeds equivalent to 802.11a, up to 54 Mbps, with the wider 300-foot range of 802.11b. More important, 802.11g runs in the 2.4-GHz ISM band so it is backward compatible with 802.11b, meaning that the same 802.11g WAP can service both 802.11b and 802.11g wireless nodes. 802.11g is incredibly popular and is only just now starting to lose out to the newest version of 802.11, 802.11n.

802.11n The 802.11n standard brings several improvements to Wi-Fi networking, including faster speeds and new antenna technology implementations.

The 802.11n specification requires all but hand-held devices to use multiple antennae to implement a feature called multiple in/multiple out (MIMO), which enables the devices to make multiple simultaneous connections. With up to four antennae, 802.11n devices can achieve amazing speeds. (The official standard supports throughput of up to 600 Mbps, although practical implementation drops that down substantially.)

Many 802.11n WAPs employ transmit beamforming, a multiple-antenna technology that helps get rid of dead spots—or at least make them not so bad. The antennae adjust the signal once the WAP discovers a client to optimize the radio signal.

Like 802.11g, 802.11n WAPs can run in the 2.4-GHz ISM band, supporting earlier, slower 802.11b/g devices. However, 802.11n also has a more powerful, so-called dual-band. To use dual-band 802.11n, you need a more advanced (and more expensive) WAP that runs at both 5 GHz and 2.4 GHz simultaneously; some support 802.11a devices as well as 802.11b/g devices. Nice!

Table 24-1 compares the important differences among the versions of 802.11.

Table 24-1 Comparison of 802.11 Standards

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EXAM TIP Know the differences among 802.11a, 802.11b, 802.11g, and 802.11n.

Other Wireless Standards

Infrared Wireless Networking

Wireless networking using infrared technology is largely overlooked these days, probably because of the explosion of interest in the newer and faster wireless standards. But it is still a viable method to transfer files on some older devices.

Communication through infrared devices is enabled via the Infrared Data Association (IrDA) protocol. The IrDA protocol stack is a widely supported industry standard and has been included in all versions of Windows since Windows 95.

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NOTE Apple computers also support IrDA, as do Linux PCs.

In speed and range, infrared isn’t very impressive. Infrared devices are capable of transferring data up to 4 Mbps—not too shabby, but hardly stellar. The maximum distance between infrared devices is 1 meter. Infrared links are direct line-of-sight and are susceptible to interference. Anything that breaks the beam of light can disrupt an infrared link: a badly placed can of Mountain Dew, a coworker passing between desks, or even bright sunlight hitting the infrared transceiver can cause interference.

Infrared is designed to make a point-to-point connection between two devices only in ad hoc mode. No infrastructure mode is available. You can, however, use an infrared access point device to enable Ethernet network communication using IrDA. Infrared devices operate at half-duplex, meaning that while one is talking, the other is listening