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802.11g set to shake up WLAN market

802.11g set to shake up WLAN market

The IEEE has put its stamp of approval on the proposed 802.11g standard, which boosts data rates on 2.4GHz wireless LANs from 11 to 54Mbps.

Both 802.11b and 802.11g use the 2.4GHz 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 5GHz band. As a result, 802.11g and 802.11a products can achieve the same 54Mbps data rate.

Even though actual throughput is still less than half 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 the use of 802.11.

Publicly, the WFA has said it will launch testing very soon after the standard is accepted. One WFA member said recently 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.

More than half a dozen vendors have brought out 802.11g gear, most of it aimed at the residential market.

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 $US675. For $US20 more, you can get an AP-2000 with an 802.11g radio.

For about $US800, users can get Proxim’s two-radio model: one slot with an 802.11b card, one slot with an 802.11g card.

For about $US900, 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,” vice-president of Cisco’s wireless networking business, William Rossi, said.

“802.11g and 802.11a will co-exist in any enterprise that needs both high data rates and (breadth of) coverage.”

Doorway to access point

Cisco has worked with chipmaker 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.

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 2.4GHz 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.


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