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MIMO antennas. To be or not to be.... this is the question!

Posted: Thu Mar 25, 2010 5:36 pm
by taglio
Hi there,

please help me :? i don't understand how i have to choose MIMO antennas.

In the actuality i use mikrotik, ubiquiti and compex MIMO radios, all 2x2 MIMO.

I have in my knowledge a big lack...i don't understand what kind of MIMO antenna i have to use in my real world application.

Simply imagine a very known scenario.... A tower with 3 sector antennas of 120 degrees for the base station and number of subscriber with panel [or grid if you can find in the marquet {WHEREEEE ????}] antennas.

The question of 1 million of dollar is:

The antennas would have two [or three....] "modules" [or inside antenna.. i don't know the exact name] that will work in the same polarity, or i have two use different polarity [vertical, horizontal and 45 degree....].

In my opinion i will have to use antennas with same polarity modules.... but.... per examples Mars [http://www.mars-antennas.com/] sales dpto say to me that i have to use different polarization... .and other example in the data-sheet of of AirMax5 Sectors antennas [http://ubnt.com/downloads/AirMax5GSectors.pdf] you can see that those antennas use different polarization...

What is your real world experience MK guys???

Best Regards,

RG.

Re: MIMO antennas. To be or not to be.... this is the questi

Posted: Thu Mar 25, 2010 6:15 pm
by JorgeAmaral
Try to understand this: http://en.wikipedia.org/wiki/IEEE_802.11n-2009

And the search google for: spatial diversity technology

802.11n 2x2 is based on spatial streams, so you need to have antennas with different polarization.

Right now their is a lack in dual polarization antennas. We need to wait for the market to start supplying these.

Kindly regards,

Jorge Amaral

Re: MIMO antennas. To be or not to be.... this is the questi

Posted: Thu Mar 25, 2010 6:36 pm
by taglio
Thank you for rapid reply.

Ok i can understand this for professional equipment connection [base station + CPE subscriber].

But let me speak about connection between a MIMO AP [simply image routerboard 411A + an R52N radio] and netbooks or notebooks or pda..... and so on.

No i have two MIMO chain on the radio..... The radio on those hosts have dual polarity antennas???????? I don't think so.... i don't have to use simply to omnidireccional normal antennas?

Thank you,

RG

Re: MIMO antennas. To be or not to be.... this is the questi

Posted: Thu Mar 25, 2010 7:19 pm
by InoX
mimo works also with same polarity. For example we use a dual feeder for RocketM, H polarised only and works very good. A simple router has only 2-3 antennas of the same polarisation.

Re: MIMO antennas. To be or not to be.... this is the questi

Posted: Thu Mar 25, 2010 8:39 pm
by JorgeAmaral
If it works, yes, is it the better approach? no

The principle off spatial stream is different paths.

From intel website:
MIMO makes antennas work smarter by enabling them to combine data streams arriving from different paths and at different times to effectively increase receiver signal-capturing power. Smart antennas use spatial diversity technology, which puts surplus antennas to good use. If there are more antennas than spatial streams, as in a 2x3 (two transmitting, three receiving) antenna configuration, then the third antenna can add receiver diversity and increase range.

With same polarity, there is a big change of receiving signals with the same path, and you will not benefit of spatial stream.

Kindly regards,

Jorge Amaral

Re: MIMO antennas. To be or not to be.... this is the questi

Posted: Thu Mar 25, 2010 11:50 pm
by Muqatil
[OT] Jorge, can you contact me on skype? :) [/OT]

Re: MIMO antennas. To be or not to be.... this is the questi

Posted: Fri Mar 26, 2010 11:42 am
by taglio
Ok, so it seems that is better use different pol. but we can use same polarity antennas [and we lost some benefits].

Internal laptop MIMO antennas use different pol. antennas?? Or simply use 1 chain?

Regards,

RG

Re: MIMO antennas. To be or not to be.... this is the questi

Posted: Fri Mar 26, 2010 9:38 pm
by JorgeAmaral
[OT] Jorge, can you contact me on skype? :) [/OT]
Of course ;)!!!

Re: MIMO antennas. To be or not to be.... this is the questi

Posted: Mon Mar 29, 2010 11:46 am
by taglio
PONG...