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Ruckus And On-Antenna Phased Arrays

Beamforming: The Best WiFi You’ve Never Seen
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Fortunately, an omnidirectional antenna is not the only way to obtain 360 degrees of wireless coverage. If you had enough directional antennas with overlapping cones of coverage, you could effectively cover 360 degrees. But the beauty of this sort of setup is that you don’t have to run all of those antennas all of the time. Once you get a fix on the direction of the client, you simply have to determine which set of antennas (two or more) will create an optimal beam to the desired point.

Keep in mind that this isn’t always a straight line. The client could be around a corner, and the better signal might be had by bouncing the stream off of a couple of walls rather than trying to punch straight through the obstructions. Or conditions may change. Doors can open and close. People move around. Someone might turn on a microwave oven and spew interference all over the spectrum. All of these things can alter signal paths and hamper traffic.

Traditionally, the only way an access point had to deal with dropped packets or CRC errors (corruption) was to drop transmit speeds. The PHY rate might ratchet down from 54 Mbps to 48, then 36, and so on until the client started acknowledging packet receipts. The slower the speed, though, the longer the radio stays on for a given data burst, and the longer the radio is on, the more susceptible it is to interference. So when conditions turn bad, you can get into this negative feedback loop that just slaughters performance. An intelligent antenna system will both dynamically change the beam orientation to a more optimal direction as well as forestall reducing the PHY rate until absolutely necessary.

Communication between the AP and client helps with these improvements, but it’s not strictly essential. The bulk of optimization gets done by the access point. In the tests that follow, we did not use a Ruckus client adapter for two reasons. First, Ruckus told us that 75% of the performance improvement seen above standard 802.11n comes from the access point, so adding in a proprietary client would only yield a small benefit. Second, relatively few real-life scenarios can dictate the client. It’s not like you can say, “Feel free to use my wireless LAN, but just make sure you use an XYZ adapter.”

Ruckus uses “on-antenna” beamforming, a technology developed and patented by Ruckus under the brand name “BeamFlex.” Essentially, BeamFlex uses an array of antennas and analyzes every packet to assess signal performance. Depending on the configuration, a BeamFlex access point can configure into any of thousands of possible antenna signal combinations. The access point monitors connections in real-time and modifies beams on the fly to fit dynamic conditions. Keeping with the MRC legacy, antennas that need signal boosting get boosted while those that don’t are attenuated. This results in up to a 10 dB signal gain along the target beam as well as a -17 dB interference rejection in the direction of backlobes.

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Top Comments
  • 10 Hide
    antiacid , August 17, 2009 1:13 PM
    awesome article! Thanks for exposing us to this great technology :) 
Other Comments
  • 2 Hide
    chinesemafia69 , August 17, 2009 8:16 AM
    wow....this owns

  • -6 Hide
    bucifer , August 17, 2009 8:42 AM
    This article started up pretty good with lots of technical data and the beamforming technology in theory but after that the goodness stopped.

    1.You cannot compare two products by testing them with a in-house developed software. It's like testing ATI vs nVIDIA with nvidia made benchmark.
    2.If you do something get it done, don't just go with half measures. I don't care if you didn't have time. You should have planned this from the beginning. The tests are incomplete, and the article is filled with crap of Rukus and Cisco.
  • -5 Hide
    Mr_Man , August 17, 2009 12:44 PM
    In defense of your wife, you didn't HAVE to use that particular channel to view all the "detail".
  • 2 Hide
    Anonymous , August 17, 2009 12:58 PM
    @Mr_Man: With a name like yours, I'd think that you'd sympathize with Chris a bit more :p  Unless (Mr_Man == I likes men) :D 
  • 10 Hide
    antiacid , August 17, 2009 1:13 PM
    awesome article! Thanks for exposing us to this great technology :) 
  • -4 Hide
    Pei-chen , August 17, 2009 1:17 PM
    Both Tyra and Heidi have personal issues and would be pretty difficult friend/mate.

    The network idea sounds better. I couldn’t get my 10 feet g network to transmit a tenth as much as my wired network without it dropping.
  • 3 Hide
    zak_mckraken , August 17, 2009 2:23 PM
    There's one question that I think was not covered by the article. Can a beamformaing AP can sustain the above numbers on two different clients? Let's say we take the UDP test at 5 GHz. The result shows 7.3 Mb/s. If we had two clients at opposite sides of the AP doing the same test, would we have 7.3 Mb/s for each test or would the bandwidth be sliced in 2?

    The numbers so far are astonishing, but are they realistic in a multi-client environnement? That's something I'd like to know!
  • -1 Hide
    jerther , August 17, 2009 2:28 PM
    There is so much invisible to understand in wireless technology!
  • -6 Hide
    ebattleon , August 17, 2009 3:01 PM
    You can of course get the same effect by having better antenna on both ends of the network. This would increase gain which would improve signal to noise ratio, which would improve data flow speeds. You would also get the same effect by boost in the power but that could get you in trouble with the law.

  • 1 Hide
    Anonymous , August 17, 2009 3:04 PM
    I'm not an expert on beamforming, but I'm surprised that it is useful at these frequencies. After all, the wavelength at 2.4 GHz is ~12 cm (~5 inches). That means that the pockets of constructive interference (the beam) are very small. Moving the receiver a few inches should make a big difference.

    Are you sure the differences you are seeing aren't simply due to higher power output? Couldn't the same improvements be obtained with a directional antenna like a Yagi?
  • 1 Hide
    Rancifer7 , August 17, 2009 4:00 PM
    So far quite an interesting technology. Its nice to know that at someone in the wireless world is striving to make something innovative!

    When all the major players sell items that look almost the same, act similarly, and perform almost the same, there is something wrong with the industry.
  • 1 Hide
    chaohsiangchen , August 17, 2009 4:13 PM
    Beam forming technology have been for a long time, but they are mostly used in military equipments. Phased Array radars, Synthetic Aperture Radar, Inverse Synthetic Aperture Radar, Plane Array Antenna and antenna for data link. Most consumer products still use Yagi or disk antenna. Cost is a major issue in the application. Military don't care that much about the cost.
  • 0 Hide
    scotty123 , August 17, 2009 4:23 PM
    sounds nice - but i won't get excited until it's available at Best Buy!

    One niggling concern, I felt reasonably safe with the unfocused cloud of RF surrounding me wherever I go, but I am not so sure about the tightly focused beam that the Ruckus provides. What happens to the poor joe who sits directly in the path of such a beam for 8 hours a day?
  • 1 Hide
    williamvw , August 17, 2009 4:39 PM
    Mr_ManIn defense of your wife, you didn't HAVE to use that particular channel to view all the "detail".

    LOL! True enough. It honestly was a reference file I had on hand for such testing situations. Angelini obviously showed a bit more wisdom in his choice of in-house test content.
  • -1 Hide
    williamvw , August 17, 2009 4:44 PM
    scotty123sounds nice - but i won't get excited until it's available at Best Buy! One niggling concern, I felt reasonably safe with the unfocused cloud of RF surrounding me wherever I go, but I am not so sure about the tightly focused beam that the Ruckus provides. What happens to the poor joe who sits directly in the path of such a beam for 8 hours a day?

    My absolutely unqualified opinion is "probably nothing." While the conditions are somewhat different, you might want to read a Tech Myths column segment I did over on Tom's Guide that touches on this issue. http://www.tomsguide.com/us/decibels-noise-canceling,review-1338-10.html
  • 2 Hide
    williamvw , August 17, 2009 5:17 PM
    zak_mckrakenThere's one question that I think was not covered by the article. Can a beamformaing AP can sustain the above numbers on two different clients? Let's say we take the UDP test at 5 GHz. The result shows 7.3 Mb/s. If we had two clients at opposite sides of the AP doing the same test, would we have 7.3 Mb/s for each test or would the bandwidth be sliced in 2?The numbers so far are astonishing, but are they realistic in a multi-client environnement? That's something I'd like to know!

    Excellent question, and one I hope to dive into in a later article. For now, I can only give you the anecdote on my opening page, running the same HD stream to two clients. Ruckus states that BeamFlex can sustain a 50 Mbps minimum per access point. Do the math on your client streams accordingly, I suppose.
  • -1 Hide
    bounty , August 17, 2009 5:24 PM
    williamvwLOL! True enough. It honestly was a reference file I had on hand for such testing situations. Angelini obviously showed a bit more wisdom in his choice of in-house test content.


    Honestly honey, it's just a reference file, I swear it's not porn. I challenge you to find HD streaming content from the internet that highlights the subtle nuance of flesh tones.
  • 2 Hide
    williamvw , August 17, 2009 5:28 PM
    bountyHonestly honey, it's just a reference file, I swear it's not porn. I challenge you to find HD streaming content from the internet that highlights the subtle nuance of flesh tones.

    Hey, the VS catalog mails to her, not me. I was merely trying to be a good husband and participate in her interests. ;-) ANYWAY. Back to beamforming, shall we?
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