802.11g set to shake up WLAN market

The IEEE this week is expected to put its stamp of approval on the proposed 802.11g standard, which boosts data rates on 2.4-GHz wireless LANs from 11M to 54M bit/sec.

The IEEE this week is expected to put its stamp of approval on the proposed 802.11g standard, which boosts data rates on 2.4-GHz wireless LANs from 11M to 54M bit/sec.

For at least some enterprise network executives, the move can’t come soon enough.

“We’re looking at replacing our cable TV system, but now I can put this on a [WLAN],” says Brad Noblet, director of technical services at Dartmouth College in Hanover, N.H., where about 560 802.11b access points are deployed.

Putting a TV on every student’s laptop wasn’t an option with 802.11b access points, Noblet says. That’s because a single video stream swallows up about 2M bit/sec, about one-third of the actual throughput of an 802.11b WLAN. An 802.11g WLAN, meanwhile, boasts up to about four times the throughput of an 802.11b network.

Both 802.11b and 802.11g use the 2.4-GHz radio band. But 802.11g uses a much more efficient frequency modulation technique, called Orthogonal Frequency-Division Multiplexing. This technique is used by 802.11a, which runs in the 5-GHz band. As a result, 802.11g and 802.11a products can achieve the same 54M bit/sec data rate. Even though actual throughput is still less than half of that rate, tests show 802.11g products delivering consistently higher throughput than 802.11b or 802.11a, and doing so over much longer distances than 802.11a.

The next key step will be a new round of interoperability testing and certification by the Wi-Fi Alliance (WFA), a trade group of wireless vendors promoting 802.11 use. Publicly, the WFA has said it will launch testing very soon after the standard is accepted. One WFA member said last week that the 802.11g testing methodology has been quickly put together.

Industry participants say the big jump in throughput, plus the economics of 802.11g, might be too attractive for customers to pass up.

“There’s no reason not to [upgrade to 802.11g],” says Jeff Abramowitz, senior director for WLAN marketing at Broadcom, a chip developer. “You get better performance in speed and range, and the cost difference [with 802.11b] is almost non-existent.”

More than a half-dozen vendors have brought out 802.11g gear, most of it aimed at the residential market, on the assumption that the technical details of the IEEE proposal now require only rubber stamping by the IEEE Standards Board on June 12.

Proxim is one of the first enterprise network product vendors to integrate 802.11g into its existing product line, including client cards, and start shipments. It now offers several models of its Orinoco AP-2000, which is designed to give corporate users flexibility in deploying any combination of 802.11b, 802.11g and 802.11a access points. The company says pricing was deliberately planned to give current 802.11b users an incentive to shift to 802.11g.

Proxim estimates that an AP-2000 with one 802.11b radio has a street price of $675. For $20 more, you can get an AP-2000 with one 802.11g radio.

For about $800, users can get Proxim’s two-radio model: one slot with an 802.11b card, one slot with an 802.11g card. For about $900, a two-radio model that supports 802.11g and 802.11a is available.

That combination is one that many companies are expected to embrace. “We see a dual-band [802.11g and 802.11a] world for some time to come,” says William Rossi, vice president of Cisco’s wireless networking business. “802.11g and 802.11a will co-exist in any enterprise that needs both high data rates and [breadth of] coverage.”

Cisco has worked with chip maker Intersil on 802.11g chipsets and later this year plans to bring out an 802.11g upgrade for its Aironet 1100 access point. Eventually, Cisco says its Aironet 1200 dual-radio product will include one 802.11g and one 802.11a radio.

Another reason that many vendors and analysts expect 802.11g to grow quickly in corporate networks is that the standard includes a mechanism that lets an 802.11g access point work with existing 802.11b clients. According to Broadcom’s Abramowitz, clients that have only 802.11g can expect optimal throughput of around 24M bit/sec or slightly less.

Not perfect

But 802.11g has limitations.

The chief one is that, like 802.11b, it has only three non-overlapping channels. By contrast, 802.11a has 11.

Think of a channel as a doorway to the access point. Each access point uses one doorway, the channel assignment, to send and receive radio waves with clients. With 802.11g, you can have at most three access points close together with optimal throughput. When a fourth is added nearby, you start to get interference because the new device has to use one of the already assigned channels.

But with 802.11a, you can put 11 access points in an area, creating a much denser WLAN cell: More throughput is available, more users can connect, and interference is minimal.

Another potential problem is that the 2.4-GHz frequency is increasingly crowded. Besides being used by existing 802.11b devices, it’s also used by the growing number of low-bandwidth, short-range Bluetooth radios. Baby monitors, cordless phones and microwave ovens use the same spectrum.