Monday, June 4, 2012

Adaptive Antennas and Interference

There is quite a nice discussion going on over at GT Hill's blog about Adaptive Antennas.

One part of the discussion centers around interference rejection of such a system, by "controlling" the RF signal. This serves to increase signal gain for the intended client and reduce interference in most other directions (I agree on these points). My contention is that in a multi-cell architecture, as is typically found in most enterprise, education, healthcare, and [especially] high density environments, the increased signal gain also results in increased interference (or more aptly "contention") of other neighboring Wi-Fi cells in the path of the newly shaped signal. And, different than directional antennas, the path changes with every client that the Adaptive Antenna system is transmitting to. So, with an omni-directional coverage area and clients distributed throughout that area, interference will impact all other Wi-Fi cells around it. Not at the same time, but at different points in time depending on traffic patterns downlink to clients.

What I'm getting at is that Adaptive Antennas simultaneously reduce interference in some directions and increase it in others. I'm not saying that one outweighs the other, because I don't think anyone can predict that unless we know the specific deployment scenario and network design. My point is just that we need to acknowledge the presence of both effects (not just one, while ignoring the other).

Hopefully this makes sense. It does in my [admittedly jumbled] mind ;)

I would normally just post this in the comments section on GT's blog, but I would like to include a drawing to help convey what I'm talking about. (I'm a great artist BTW. Can't you tell!)

Adaptive Antenna's Simultaneously Decrease and
Increase Interference In Different Directions

GT - Hopefully this clarifies my opinion. Sorry to take the conversation away from your website.

Readers - please comment directly on GT's blog to keep the conversation thread in one location.



  1. Oh my, there goes the 'vendor independency' down the drain... accusing GT of vendor kool-aid in your comments is imho blasphemy by someone who works for the uncrowned king company in this respect.

  2. Haha! I don't see how asking someone for a well-reasoned position makes me not "independent". In fact, I think that is what being independent is all about, as long as I hold all vendors to the same standard, which I try to do as much as possible (yes, even my current employer).

    I was on the customer side for most of my career and just recently joined a Wi-Fi vendor. I still consider myself very independent and open-minded about all vendors and solutions. But I call it like I see it. And I'm personally always willing to be proven wrong when/if someone can articulate a well-reasoned position with supporting material. I call "vendor kool-aid" when people stand behind a position without providing a solid argument and expect people to just believe it to be true on faith alone. You must prove your arguments.

    I can't speak for others who may work where I do. I don't have control over their opinions or writings.

    Also, thanks for not following the recommendation to keep all comments on GT's website.