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

RouterOS Wireless Networking
1

Hi there,

please help me :confused: 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.

2

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

3

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

4

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.

5

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

6

[OT] Jorge, can you contact me on skype? :slight_smile: [/OT]

7

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

8

Of course :wink:!!!

9

PONG…