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Beamforming, RF management key to 802.11n wireless LAN success

Ruckus Wireless introduced beamforming to 802.11n wireless LAN, taking aim at the RF management techniques of Cisco and other rivals.

Although the vast majority of wireless LAN deployments today are based on older 802.11a/g technology, 802.11n adoption is poised to explode. As this newer technology spreads into the market, enterprises will expect it to deliver the high bandwidth connectivity promised by the IEEE standard.

The brute force multiple-input and multiple-output (MIMO) antenna system of 802.11n gives wireless LAN technology more bandwidth and transmission power, but vendors realize that raw power at the access point isn't enough. More and more, vendors will be looking to differentiate themselves through Radio Frequency (RF) management methods such as beamforming.

According to ABI Research, 802.11 a/g technology accounts for about 84% of today's wireless LAN market. By 2012, the market will have flipped. Shipments of 802.11n technology will account for 60% of the market.

Buyers of 802.11n technology will expect these access points to deliver at least 54 Mbps. Unfortunately, some might be disappointed by slower speeds brought on by clients that are too far from access points to get a fast transfer rate. Legacy 802.11a/g clients will crawl across wireless networks, slowing down the faster 802.11n clients. Even simple things, like rearranging cubicles in an office, can slow down the wireless network.

Radio Frequency management the next WLAN battleground

To solve this problem, wireless LAN vendors are turning to RF management. Paul DeBeasi, senior analyst with Burton Group, recently blogged that RF management is the "new battlefront" in the wireless LAN market.

DeBeasi describes RF management as any technology used to control the wireless LAN's physical layer. Vendors approach this discipline in a variety of ways, and it will become difficult for enterprises to sort through which approach is best for their own requirements.

Aruba Networks, for instance, has introduced the concept of Adaptive Radio Management (PDF). Among other things, this technology analyzes the protocols that Wi-Fi clients are using in order to enforce "airtime fairness." Clients that use 802.11n are given RF priority, allowing them to get on and off the network more quickly. It can also automatically adjust power and channel assignments of access points as RF conditions change to make sure that 802.11n channels function properly.

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Aerohive Networks recently introduced its own form of RF management to its 802.11n access points. Dynamic Airtime Scheduling examines the packets it receives from access points to determine how RF conditions are affecting the quality of a connection. The access points automatically adjust by giving airtime priority to clients with better connections. This allows them to get on and off the network quickly without being slowed down by clients who have weaker connections.

Directing radio signals with beamforming

Ruckus Wireless, a relative newcomer to the enterprise wireless LAN market, introduced its patented beamforming technology to 802.11n access points this week.

Beamforming is a type of RF management in which an access point uses multiple antennas to send out the same signal. By sending out multiple signals and analyzing the feedback it gets from clients, the wireless LAN infrastructure can adjust the signals it sends out and determine the best path the signal should take in order to reach a client device. In a sense, beamforming shapes the RF beam as it traverses the physical space of the enterprise.

Ruckus has offered this technology for some time in its 802.11a/g technology. Cisco Systems introduced its own version of the technology with its new Aironet 1140 Series access point a few months ago. But Cisco's beamforming technology, "M-Drive," uses beamforming to optimize performance only for 802.11a/g clients, according to Craig Mathias, principal of Farpoint Group.

Mathias said that beamforming for 802.11n technology is extremely difficult to do. It requires multiple antennas on an access point that already has more antennas than legacy 802.11a/g access points have. To deliver beamforming on its new ZoneFlex 7962 access points, Ruckus had to build an array with 19 antenna elements.

"I think [Ruckus's new access point] is amazing, especially at the price they charge for it [$999]," Mathias said. "MIMO gives you significantly higher performance and associated other benefits, and beamforming gives you the ability to move energy in a particular direction, which will actually improve performance. These are two very powerful techniques that are being used together."

Ruckus claims that Cisco's approach to beamforming is inferior because it relies on chip-based techniques. Ruckus achieves beamforming by building it directly into the antenna elements.

"I think for most enterprises the subtlety of difference between [Cisco's and Ruckus's approaches] will be difficult to perceive," DeBeasi said. "But at a high level, [Ruckus] has a strong reputation in beamforming."

RF management: "Everyone is doing something"

DeBeasi said the larger issue right now isn't who does beamforming best but who offers the best RF management technology. He said vendors are taking a variety of different approaches to this. Enterprises will want to know how a vendor's technology performs altogether in order to meet their requirements, he said. They won't be as interested in hearing about why one approach is better than another.

"Everyone's doing something," DeBeasi said. "It could be managing transmit power, it could be forming the beam, and it could be load balancing. There are all these different ways of making this shared resource, Radio Frequency, perform the way you want it to perform."

Mathias said he thinks beamforming will become a staple of 802.11n infrastructure in the next few years. He said manufacturers of wireless LAN chips, such as Atheros, will eventually begin offering beamforming capabilities within 802.11n chips.

"Nobody is having specific conversations [with me] about it, but since most vendors have limited capabilities in terms of radio-frequency engineering, they're going to rely more and more on the chip vendor to provide that for them," Mathias said. "As soon as the chip guys come out with beamforming, I think you'll see it begin to proliferate, and of course the price will come down. But Ruckus is doing dual-radio 802.11n beamforming access points for under $1,000 right now, which is pretty amazing. That technology 10 years ago would have been impossible."

Let us know what you think about the story; email: Shamus McGillicuddy, News Editor

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