diversity functionality in AP1000 series

Answered Question
Nov 6th, 2007

When I enable diversity (both integrated antennas enabled) the signal strength becomes quite variable and unstable. It does not occur when I enable only one of the 2 integrated antennas, the signal is much more stable. Does this have some explanation? Is this functioning normal?Will it happen the same if I employ 2 omnidirectional external antennas instead, as diversity method?

I have this problem too.
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Correct Answer by dennischolmes about 9 years 1 month ago

Having been one of the first Airespace engineers trained in the country let me explain the way Airespace designed the 1000 (Airespace 1250)series APs. Diversity on the integrated antennae was based on using the side(either or a or b) that the receiver heard the signal on to transmit the returning signal. The AP does NOT broadcast out of both sides at the same time. That is a little known fact and how Airespace created such a large propagation field. This can cause major problems in multipath environments or areas where the client moves quickly from one side of the AP to the other such as on a fork lift truck. Using the 1020 allows you to use external antennae and real diversity. Just make sure to enable diversity antennae on the external connectors by using two identical antennae placed an appropriate amount apart or a dual connector diversity based antenna. If you would like any other information about the 1000 series just let me know.

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john.preves Tue, 11/06/2007 - 03:23

What kind of antennas are on it now and are they the same distance apart as the connectors on the AP?

If you are using two patch antennas and have them spread out or something, you will no longer have diversity past a certain point. They must be 180 degrees out of phase in order to be of some use and to be honest with you that's not easy to pull of with out using the fixed Onmi directional antennas.

Since your antennas are most likely no longer 180 out from each other when the primary antenna recieves a signal it perceives to be weak the other antenna is not in a physical position to be useful. You would be better off (most likely) by disconnecting the secondary antenna and turn the Rx/Tx diversity back to primary (right or left whichever is your primary marked on the AP near the connector.)

kikonannn Tue, 11/06/2007 - 08:00

First I was using just the 2 integrated antennas that come with the AP1020, this is when I have the very unstable signal strenght. And I don't really know if this is normal or not. The difference in strength between the minimun and maximun is 14dB while data transmission is taking place.

Today I've checked the performance of using 2 omnidirectional external antennas (I think they are AIR-ANT4941) connected to the AP external conectors instead of using the internal antennas. I've connected them directly to the connectors with no cable so they are pretty close to each other (the width of the AP). The result is that the strenght varies a bit less (now only 6dB between maximun and minimun). Why do you think the perfomance with 2 external antennas seems to be better in contrast with when using the internal antennas?Is it normal to have these instabilities in the signal and why do they exist?

Thanks

Correct Answer
dennischolmes Wed, 11/07/2007 - 04:10

Having been one of the first Airespace engineers trained in the country let me explain the way Airespace designed the 1000 (Airespace 1250)series APs. Diversity on the integrated antennae was based on using the side(either or a or b) that the receiver heard the signal on to transmit the returning signal. The AP does NOT broadcast out of both sides at the same time. That is a little known fact and how Airespace created such a large propagation field. This can cause major problems in multipath environments or areas where the client moves quickly from one side of the AP to the other such as on a fork lift truck. Using the 1020 allows you to use external antennae and real diversity. Just make sure to enable diversity antennae on the external connectors by using two identical antennae placed an appropriate amount apart or a dual connector diversity based antenna. If you would like any other information about the 1000 series just let me know.

kikonannn Thu, 11/08/2007 - 07:38

Thank you very much to both of you for your answers. They were really helpful.

ericgarnel Thu, 11/08/2007 - 08:55

Ok,

Shoot me if this sounds dumb, but if the 1000 series is set to 1 side only, is the pattern then 180 degrees or 360?

dennischolmes Thu, 11/08/2007 - 09:18

The side is only set to "one side only" when you turn off diversity. With diversity turned on, the unit listens with both sides and then replies on the side it chose to use the receiving signal from. In other words it hears the signal from the client on side b better than side a. It will then send the signal out of side b's antenna for return traffic to the client. This is a problem if the client has moved from side b to side a of the AP. Now lets say that the multipath issue is causing the signal to bounce all around and the AP transmits back to the client on the wrong side. You see how this could cause client drops?

ericgarnel Thu, 11/08/2007 - 09:28

That clarifies it a lot. It is somewhat similar to Vivato's phased array approach in behavior.

Yes, we have a fun environment for wifi.

The north side of the faciilty was designed & built int 2000. The walls have 1/4" steel plate in aluminum frame decoration on the bottom half and rippled stainless steel paneling on a lot of the top half, not to mention the 2 -3' thick concrete, steel girders, conduit out the wazzoo. Having observed many conventions, we do not see much if any roaming. clients tend to squat by power outlets and remain there

dennischolmes Thu, 11/08/2007 - 09:30

I myself am personally a big fan of the 1000 series APs. I fought to keep them but alas unsuccessfully.

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