MIMO with two different antennas

RouterOS Wireless Networking
1

Hi,

has anybody tried running 802.11n 2x2 MIMO with two different antennas? This configuration is interesting when you want to have a wider signal coverage which you cannot accomplish just by using single antenna type due to the limited antenna patterns.

For example, I’m using 3 dB omni antenna which has very good coverage in horizontal plane, but doesn’t really work for higher elevation angles (e.g. client on nearby hill or very tall building), Therefore I’m trying to combine omni antenna pattern and 14 dBi patch antenna pattern to get better coverage. This works, but with lower throughput than I’m getting with 2x2 patches MIMO or even 1x1 patches SISO.

In theory, what is the EIRP when two antennas with significantly different gain are used? When two identical antennas are used e.g. two 14 dBi patches, EIRP is calculated as tx power - tx line losses (1-2 dB) + antenna gain (14 dB) + 3 dB… We are adding 3 dB because output power doubles with additional antenna used for MIMO. What is the equation if we have different antennas, e.g. 3dBi omni and 14 dBi patch?

Regards
Zreno

2

I think it would still add 3dB. It is more a function of MIMO than the antenna that adds the additional gain.

I am trying something similar. Small scale AP starting in an rural area, one 15dBi and 1 10dBi. Three reasons, one being price, two being I had the 10 just sitting in a closet, three, the vertical beam width.

Playing with it on the ground has shown promise, but it has been pretty difficult to get a tower climber out here.