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High-Gain Patch Antennas Boost Wi-Fi Capacity In Crowded Lecture Halls 104

Posted by Soulskill
from the it-all-comes-down-to-focus dept.
An anonymous reader writes "To boost its Wi-Fi capacity in packed lecture halls, Georgia Institute of Technology gave up trying to cram in more access points with conventional omni-directional antennas, and juggle power settings and channel plans. Instead, it turned to new high-gain directional antennas. They look almost exactly like the bottom half of a small pizza box, and focus the Wi-Fi signal from the ceiling-mounted access point in a precise cone-shaped pattern, covering part of the lecture hall floor. Instead of the flaky, laggy connections, about which professors had been complaining, users now consistently get up to 144Mbps (if they have 802.11n client radios). 'Overall, the system performed much better' with the new antennas, says William Lawrence, IT project manager principal with the university's academic and research technologies group. 'And there was a much more even distribution of clients across the room's access points.'"
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High-Gain Patch Antennas Boost Wi-Fi Capacity In Crowded Lecture Halls

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  • by John.Banister (1291556) * on Wednesday November 06, 2013 @01:11AM (#45342689) Homepage
    why cram all the bodies into the hall?
  • News? (Score:5, Insightful)

    by Andhesaidtome (2738249) on Wednesday November 06, 2013 @01:31AM (#45342763)
    It is hardly newsworthy that a group of IT network techs 'fixed' their coverage and performance problems using directional antenna technology. Radio techs have been doing exactly that since they learnt about propagation. A newsworthy story would be that they have (finally) started incorporating at least basic RF theory in all IT networking related courses and subjects.
    • This is a parroting of a marketing-derived press release. Move along. I think I'm going to move along. Thanks for the memories, Slashdot.

    • Re:News? (Score:5, Funny)

      by Gravis Zero (934156) on Wednesday November 06, 2013 @03:43AM (#45343067)

      It is hardly newsworthy that a group of IT network techs 'fixed' their coverage and performance problems using directional antenna technology.
      Radio techs have been doing exactly that since they learnt about propagation.

      so... does this mean you aren't interested in the story about how they replaced the batteries in the remote?

      • >> so... does this mean you aren't interested in the story about how they replaced the batteries in the remote?

        Maybe the batteries are dead? DNRTFA.

    • What wifi really needs is per packet rate & power control [tu-berlin.de], and for clients to select access points based on the reported QBSS channel utilisation [ipexpert.com] instead of just using rssi measurements.
    • The concepts of antenna radiation patterns and propogation has been fairly well understood for quite some time now.
    • Re:News? (Score:4, Insightful)

      by bananaquackmoo (1204116) on Wednesday November 06, 2013 @10:20AM (#45344745)
      I take it you've never actually been to a crowded lecture hall or conference room? There are thousands of these things with administrators that have no clue about this idea. It IS news to many people who are responsible for this exact sort of thing. It may not be news to you, but there have been many times where I was in a crowded area where I would kill for wifi, but it wouldn't work due to crowding.
      • I have, lamenting each time that our education system is releasing Network Admins into the wild with no RF knowledge. The story should have been...

        We have now realise the error of our ways and are introducing compulsory RF Theory subjects to all our Networking courses.

        Of course as others have said this is more marketing 'case study' by the antenna vendor than story. Notice TFA mentions that they did test antennas from other vendors, but give no indication of the relative performance. My bet is that most

  • Radiated power? (Score:5, Informative)

    by jhol13 (1087781) on Wednesday November 06, 2013 @02:04AM (#45342819)

    In Europe we limit the maximum radiated power (EIRP). This means you'd have to drop TX power and the directional antenna helps on RX only. Still might be worthwhile.
    Although there is ample proof that WiFi don't have health issues, I still want to limit the EIRP. But to what level, I do not know. I think directional antennas currently have too strict a limit - you are not supposed to be standing next to a directional antenna anyway. OTOH people hardly understand what a 20dB antenna does (in TX).

    • by Z00L00K (682162)

      Even with lower power a directional antenna will lower the interference from other cells so it is definitely worth it.

      • by jhol13 (1087781)

        Good point, I didn't think of interference at all, never have had to deal with it myself.

    • And what do you have, photon police that go around the EU hunting for people pumping more dB than is allowed?

    • The directional antenna on AP A only helps AP A on receive, not transmit.

      However, there's substantial benefits in both receive and transmit when you change all the antennas from omnis to patches: The directional antennas on APs B, C, D and E prevent their transmissions from interfering with AP A's transmissions to AP A's clients, and likewise the directional antenna on A helps B, C, D, and E.

    • Actually the directional antenna helps with both RX and TX directionality and power equally; and there's almost certainly an attenuator that offsets the aerial's gain.

      It doesn't help with the power coming from the laptop/tablet, but that's pretty small; some laptops will have gain control on their transmitters as well.

    • This is similar in the US, but it varies slightly based on frequencies, locations, and environment.

  • by Anonymous Coward

    Plugging in that antenna invalidated the FCC certification of the AP

    Georgia Tech are breaking the law!

  • I think its funny how the summary says this like its some new fantastic technology. Directional gain antennae have been around almost since radio itself. There's nothing new about this, and if I had to guess, the ham radio club at Georgia Tech has been telling them to use directional antennae for a while now. Somebody with the authority to enact it managed to convince themselves that they though of it, did it, and now we're supposed to be impressed.

    • Well, they're "new" in the sense that they just purchased them, and knowing how much red tape there can be at universities, I'd say that is something to be impressed at.
    • by CaptQuark (2706165) on Wednesday November 06, 2013 @02:55AM (#45342969)
      Directional antennas are not new. But configuring an array of directional antennas to precisely cover the seats in the lecture hall to minimize the number of users on any single access point is a new and novel way to deploy wireless access.

      Deploying the same number of omnidirectional antennas in the same space would lead to massive overlap, interference, and clients unnecessarily switching between APs when they perceived a stronger signal from a different AP.

      I haven't heard of a high density environment purposely set up this way therefor I think it is indeed newsworthy.

      ~~
      • by thegarbz (1787294)

        You're just saying that with your IT hat on. The reality is whenever you start doing some tricky stuff just hand over to the RF guys and they can do precisely this kind of coverage work with their eyes closed. It's quite basic to build a system like this, IFF you know what you're doing.

      • by aXis100 (690904)

        It's neither new nor novel, it's just that most low end IT installers havent thought about it before.

        It's exactly the same way they deploy mobile cell towers - multiple directional antennas each covering a fixed arc.

  • Are you serious? (Score:5, Insightful)

    by Mr. Freeman (933986) on Wednesday November 06, 2013 @02:39AM (#45342929)
    URGENT! URGENT! URGENT!
    DISTRIBUTION: ALL STATIONS
    MESSAGE READS:
    IT guys fix their spotty wireless coverage by installing the proper antennas.
    END URGENT MESSAGE

    Wow, thank God for that. Good thing that we have slashdot to tell us that a university installed some standard equipment on their campus. Be sure to run an article when MIT replaces a couple of their switches next month.
    • by Sockatume (732728)

      Yes, obscure technical information has no place on a site that claims to provide "news for nerds".

  • I was told by a ham radio operator back in the day that a radio setup is only ever as good as its antenna system (and that includes the coax and feedline) to me this simply sounds like they finally listened to the old man in the crew.

  • Xirrus have been doing this for years - see http://en.wikipedia.org/wiki/Xirrus [wikipedia.org] or http://www.xirrus.com/ [xirrus.com]

    They put 8 (or more) access points into a single unit, each with a directional antenna covering a segment of the room or venue. I looked at their product at a trade show or conference once (don't remember which) but it was way overkill for the spaces we had at the time which were separated with heavy reinforced concrete walls and floors, so needed an access point for each area.

  • by swb (14022) on Wednesday November 06, 2013 @08:11AM (#45343963)

    It's always remarkable what people do with 802.11, but a lot of it strikes me as a mediocre standard being (over)extended with gimmicks.

    Out of the box it works well enough for simple use, but more complex use cases (distance, density, broader coverage) seem to involve a lot of complexity to make up for the overall weakness of the standard (limited channel selection, radio power, etc).

    Are there any changes on the horizon to generate new standards that would fix this? Such as designs tailored to high-density environments (hundreds or thousands of clients off a single radio), greater channel selections, better distance capabilities, etc?

    I realize that not all of these may be something that works in a single product and that there are RF constraints that limit this, but at the end of the day the current 802.11 environment reminds me of DOS. Sure, with the right shims and magic you can run games (Quake, for the era) or a GUI OS on top of them, but there's something inherently hokey about it.

    • It's always remarkable what people do with 802.11, but a lot of it strikes me as a mediocre standard being (over)extended with gimmicks.

      Out of the box it works well enough for simple use, but more complex use cases (distance, density, broader coverage) seem to involve a lot of complexity

      Distance -- ye cannae change the laws of physics. You need one or more of: more power, more RF bandwidth, a higher gain antenna, or a coding system with less bits/s/Hz. Since you claimed power and bandwidth as problems below, I'll address them in a minute. You've already written off directional antennas as "gimmicks", and 802.11b already includes coding as low as 1Mb/s -- I don't think it's really worth putting even lower bitrates in the standard just so people can make >1 km links without having to spe

      • by swb (14022)

        Hey, I'm not an RF guy and fortunately the equipment these days (controllers + radios) take away a lot of the low-level complexity in a way that mostly works. But even then the 2.4ghz band blows in high-density office spaces like office towers. There's just too much competition and you can't do much about the 20 other visible radios, all blasting out at maximum power to try to overcome each other.

        That being said, it does still feel like a system designed for casual use (ie, a single AP allowing clients w

  • High gain directional antennas work better than low gain onni-directional antennas... Who knew?

    Wasting 75% of your transmitted power by sending your signal out in a 360 degree radiation pattern instead of focusing all your power on a 90 degree 'wedge' is just stupid - I have to wonder who designed their wifi deployment, commission-based access point salesmen or results-oriented networking specialists?

    • by queBurro (1499731)
      so... if we all mounted our APs in the roof space with directional antenna pointed down we'd *all* have better wifi rececption. For me, my AP would be one layer of plasterboard worse off than where it is now (but with a gain from the antenna hopefully). I could use a Wok instead of an aerial change so it's cheap too.
  • by Lumpy (12016)

    This is exactly how high capacity AP's work. it has basically 4 (or more, I have seen some with 8) ap's that are connected to high gain antennas that segment off what they see. An advantage of high gain antennas is that they squish their signal and receive "window" into tighter lobes.

    Honestly, if these people would take classes in RF design they would know this as the technology they are using has been around for decades, and the idea has been in use by companies covering large venues for at least a deca

  • When slashdot started some of the first stories here were about WiFi with directional antennas (eg. the famous pringles can long links). Long before I managed to get on the actual internet (instead of just a mere BBS) I knew people that were doing things with microwaves and directional antennas (microwave point to point link from a community radio studio to an FM transmitter). So is this story really just about somebody that actually decided to read up and get a clue about what were are doing instead of b
  • by koan (80826)

    What's the change in radiation exposure?

  • ... a dedicated controller to handle the new “high density group” of access points; and the controller automatically handled configuration tasks like setting access point power levels and selecting channels.

    Centralized management of the access points seems to be the solution, which doesn't require directional antennas to work.

  • by morgauxo (974071)

    I've been out of college for just barely over a decade but this is making me feel very old.

    • by Darinbob (1142669)

      Remember when we sent a man to the moon, and none of those scientists involved had access to wifi in their college lecture halls. People created the atom bomb without wifi, the first open heart surgery had no wifi enabled devices assisting, and we wrested fire from the gods on Mount Olympus without even a carrier pigeon. So why is it today that college students are unable to attend a lecture without needing connectivity? Sure, someone says they want internet access so that they can look up the material

  • Oh look! You've discovered http://en.wikipedia.org/wiki/Space-division_multiple_access [wikipedia.org]

  • ...then they could use directional antennas on cell base-stations and divide up each cell into slices!!
    Hey they could call them "sector antennas" and... oh never mind.

  • and in a professional manner works better than getting some intern who once set up a single ap for there parents to deploy a large scale wifi system - I am amazed i though wifi had magic unicorns that made it perfect!

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