MIMO Antenna placement

[maweigel]

Hi,

What are the rules for external MIMO antennas?

Accesspoint such as AIR-AP1852E, C9115AXE have multiple RP-TNC connectors for external antennas.

1. Do i have to put antennas on all 4 connectors? Or is it o.k. to just use one or two? What to do with the remaining connectors: leave them open? 50ohm terminator?

2. Do all the antennas have to be of the same type? Or can i combine a high gain antenna for "far away" users with a "big angle" antenna for "near" users?

3. Do all the AP-antennas have to see each other (like in a group or phaseshift antenna)? Or should they not see each other (e.g. different polarisation, stacking above each other, etc.)?

4. Is it o.k. if the client device sees multiple AP antennas concurrently? Or should the AP antennas be separate in a way, so also the client does not see multiple AP antennas?

Best Regards

Matthias

[pieterh]

if your object is to use MIMO, one of the techniques it depends on is "diversity".

This means the signal from the client needs to be sent/received using multiple antennae.

But the signal processed by each antenna is slightly different which effectively results in a directional effect (incomming and outgoing). 

NB! Cisco portfolio contains antenna that internally contain multiple antennae with 4 separate cables/connectors to the AP.

  but on the 1800 series you can use either dual band or 2x2,4GHz on A-side and 2x5GHz on B-side

the antennae basically need to be

- of same sensitivity (lets say same model)
- not to widely apart

- not to close together.

- for maximum streams you need to use all antenna ports (all radios) 

(   3x3 means 3 streams using 3 antenna sending +1 receive)