Industry Forums > Wireless Service Providers > Anyone using 3x3 antennas outdoors?

Anyone using 3x3 antennas outdoors?

I came across three different sources for case studies of 4x4 MIMO LTE.

They reported only one optimum path polarity consistently supported a 75 Mbps stream and the other polarities provided clean up to pick up the load when the optimum path degrades.

They also reported where there were two each less than optimum paths, the other two paths provided clean up.

They didn't' see more than two optimum paths at any given time, and they also saw four very less optimum paths combine to proved 75 Mbps throughput.

I see some 3x3 panels out there, probably just an array of patches inside. My thought was that 3 separate 8dBi patches with more space between would be better and cheaper than those ... but it does not seem to help much over 2x2 at long range.

»Thinking out of the box ... Gigabit PTMP?
Quantenna 4x4 discussed long ago. Performance indoors was like the new 802.11ac radios but less spectrum usage. I tried outdoor 4x4 setups a few times but does not scale in distance.

»[Equipment] Tiniest triple radio setup
This old thread shows a very rare miniPCI with 3 completely independent 802.11a/b/g radios. I could even do tricks like running 5.3;5.8 and 2.4 simultaneously to reach 100mbps+30mbps TCP full duplex. That radio paralleling method actually performed well at very long range using very low TX power and narrow beam antennas. But they don't make them any more.

I also had brief access to an FPGA-based 8x2 MIMO platform and that actually scaled well in distance even with 7-9dBi rubber ducks at the AP side and rubber duck or patch antenna at CPE. But those platforms are so expensive that only cellular companies can afford them.

reply to lutful
I was told by a manufacturer that in their case the radio only used the two of the 3x3 antennas that had better links.

Appears consistent with what I was saying above with 4x4 MIMO LTE.

Correct

reply to lutful
MIMO is based on a 20dB isolation factor which is only created with a 90 degree polarity differential. That means a single antenna can only handle up to a 2x2 feed. Others claim a 45 degree offset but then you can't use either of the other polarities. The only way to make it work is to use two 2x2 antennas and they have to be separated by a certain minimum distance, depending on how far the link is. The farther the link, the more the antennas have to be separated. Although Quantenna can do 4x4, that's only for very, very short ranges relative to what a WISP needs.

reply to lutful
As i posted in the UBNT forum,
Case studies of 4x4 MIMO LTE shows only one chain carries the burden of data and other three chains for error correcting redundancy.

A reply pointed out that LTE is different.

I was going to reply to that, but the new forum editor deleted my entire post when the preview crashed with an HTML error.

I was trying to say the salient point was not because it was LTE, but rather the efficacy of a 4x4 MIMO regardless if LTE, HPSDA, WiMax, or 802.11ac is used.

With 802.11ac in 2x2 mini, its really no different. Both streams carry traffic on both channels. With dual antennas, all 4 channels will carry traffic.

In terms of separating the antennas, I remember that that 1 mile needed the antennas at least 5 feet apart.

reply to rconaway8

reply to lutful
The only other number that comes to my fading memory is 100' at 100 miles. That at least gives you a scale to work from.

reply to lutful

Based on tests so far, I am guessing that stronger side lobes and weaker polarization of panel antennas are compromising 3x3 operation. However, I have to learn a lot more MIMO theory to prove that hunch.

Based on that chart, I will suggest 3 circular polarization dish antennas with 3m separation between them and 3 cables coming from the radio as equal length as possible. Just to use both circular polarizations in the link, middle dish will be LHCP and the outer two dishes RHCP.

Now if 3x3 does not work out as expected with all that effort, it is back to 2x2 using LHCP+RHCP feed on a single dish.