ePMP3k + TwinHorn Bracket

[Sergio STL]

Hi,

I have some doubts about how to install ePMP3k + TwinHorn Bracket. In the ePMP3k, we have two MU-MIMO modes implemented:

1. MU Sector based on angle diversity.
   It requires antenna array with radiating elements spaced horizontally.
   MU grouping is based on Azimuth metric.

2. MU Omni or Split-Sector.
   Based on isolated antennas connected to e3k chains 0/1 and 2/3. This is the case if we use, for example, two asymetric horns without overlapping coverage.
   MU grouping is based on Sector detection metric.

Could you confirm me if TwinHorn bracket belogs to the option 1? With TwinHorn bracket the antennas are separated vertically and not horizontally. Could you tell me if we have the same performance with this fixed vertical separation?

We need to know also have to connect both antennas to the radio when we use the TwinHorn. I can´t find any installation document.

Regards.

[Tom]

Hi Sergio,

You can use TwinHorn Bracket mounted Horns in both modes. The differences are following:

1. MU sector with angle diversity - based on the general theory of MU MIMO with array of antennas, they can be spaced horizontally as well. The resulting performance depends on how the radio operates. We have no detailed documentation to ePMP 3000 so we cannot comment on the results you should be seeing.

2. Split sector - this one is easy to understand and safer, you cannot go wrong with this mode.

If you feel like experimenting, my advice would be to test both modes for a period of time and on the solid base of the gathered data decide which mode brings you more value / better performance.

You don't need to connect both horns on a THB to a radio, you can connect them to different radios or connect just one if you don't have use for the additional capacity at the moment.

[And]

1. Where there are contradictions?
'We have no detailed documentation for ePMP 3000 so we cannot comment on the results you should be seeing "
Your Twin Horn Bracket product datasheet indicates compatibility with Cambium Networks ™ ePMP ™ 3000.

2.ePMP line developer (https://community.cambiumnetworks.com/t/epmp-3000-with-rf-elements-horn/64475/10?u=modcn)
@Dmitry Moiseev wrote: Hi, To avoid speculations I would like to make the following statements:
1. If you use a pair of horns with the official RF Elements "Twin Horn Bracket" you will not see any MU-MIMO. Although besides MU-MIMO system will work perfectly fine.

Who is speculating here?
Do you have any disagreements with Cambium?

Edited July 15, 2021 by And
a little more polite

[Tom]

Hi And, no speculations here. What Dmitry says is true - the MU-MIMO will not work with horns attached to THB.

However, you can use the radio with THB in the 4x4 MIMO no problem. 

[And]

Do you have any idea why with ePMP ™ 3000 Dual Horn MU-MIMO Antenna will be MU-MIMO, but with THB will not?

[Tom]

Yes, the ePMP 3000 MU-MIMO works if the antennas have horizontal spacing, without it, it won't work. They can be somewhat vertically spaced, but the horizontal spacing or lack there of makes it or brakes it.

It has to do with the radiation pattern of the array - if the antennas are above each other the coverage of the array looks almost identical as if you used just one antenna (except the further reach because of the array effect). Once the antennas are horizontally spaced, the coverage you see shows minima and maxima depending on the antenna spacing, that result in the possibility of 'spatial filtering' and polarization division into 2 user groups and therefore MU-MIMO.

In the near future we will release a video about this, so stay tuned to our YT channel and SM outlets..

[And]

Some WISPs with epmp3000 and two horns achieve MU-MIMO by pointing each horn to the other side (each horn only sees its own CPE group). If I'm not mistaken, it's called the split sector. You could make such a bracket, where it is possible to place 2 horns (symmetrical and asymmetrical) and where each can be adjusted to its side (both horizontally and vertically).

Edited July 20, 2021 by And
word antenna, replaced by horn

[Tom]

That is interesting, and how exactly do those WISPs identify that the radio works in MU-MIMO besides the grouping of the CPEs? Regarding the bracket suggestion, maybe in the future we'll make what you suggest, thanks for the tip..

[And]

After what you wrote, I repeat that I do not really know. From the comments, I conclude that only few know exactly how it works. Many experiment, but I want to stick to academic knowledge at first and only then experiment (eg with Fresnel / Arago / Stand waves specific).

I previously assumed that 4x4 MU-MIMO is a group (possible in a different horizontal plane) and in a group it works according to the lowest MCS (if someone in the group has only MCS2 then it will be the whole group), therefore, MU-MIMO is used only if if SU-MIMO can no longer be effective (the AP itself calculates which option will be more efficient).

The Cambium forum has WISP, which with horns placed on their side, trying to realize 4x4 and MU-MIMO - https://community.cambiumnetworks.com/t/epmp-3000-ap-and-dual-horns/67660

How is it really there - 4x4 SU-MIMO with THB, 4x4 with horns in different directions, with Cambium Dual Horn (I heard you developed) and MU-MIMO with / without band? Can you tell us now without waiting for a webinar, video, etc.?

Edited July 27, 2021 by And
Picture added & edit link

[Tom]

Seems like the link you shared is broken

As RF elements, an antenna manufacturer, we can tell with certainty how our antennas work and what they do. Since this particular MU-MIMO implementation is a feature of the radio, in-depth questions should be directed to the radio manufacturer.