Historically, spatial diversity was used on long paths over non varying terrain, like deserts and lakes. Things that give off what is called specular reflections and weather refraction effects. Shooting from mountain to mountain over a bowl shaped valley is pretty bad for multipath.
For short distance WiFi, I would think it may be helpful with moving reflectors like people and cars. From: Cameron Crum Sent: Wednesday, August 26, 2015 9:38 AM To: [email protected] Subject: Re: [AFMUG] Spacial Diversity - helps how much? Spatial diversity is primarily used to combat multi-path. If you have clear los, your chances of bad multi-path are fairly small and you probably won't see a lot of benefit. If you have a lot of objects between you and the tower that can cause reflections, then it will help more. Simple enough? On Wed, Aug 26, 2015 at 10:19 AM, Adam Moffett <[email protected]> wrote: There are a couple of products out there selling 4x4 MIMO (Telrad is one, but there are others). In Telrad's case, two of the chains have a time offset from the other two, so you get two chains on each of two polarities. Their default antenna is a single sector antenna with 4 N-connectors on it, so there's no significant spacial diversity. In the past it's been suggested that we use two dual pol sector antennas and space them 3 feet apart to get spacial diversity. When I asked why they do the single antenna, a source at Telrad told me that spacial diversity "only helps a little". The party selling us the two panels considers it to add 6db when they run coverage projections. I suspect any gain from spacial diversity is going to depend on a lot of circumstances and I doubt it could be as simple as adding 6db. I'm wondering if anyone here has any opinions on the topic? Maybe even facts :) (I'm sort of eyeballing a certain guy in Utah who designs antennas and isn't trying to sell me anything.)
