Link Capacity Question

Nick8 · December 14, 2019, 4:54pm

Hi all,
I have a link running using 2x40MHz channels in auto mode. Been really solid and is starting to push over 300Mbps sustained through the prime time hours. Is there any rush to move to 2x80MHz given that data throughput rate? I just want to make sure I’m understanding the way auto mode works that it can use most link capacity in one direction as the load is very asymmetrical? I guess more of a confirmation of my numbers in relation to that.
Signal/MAC/Phy pic below:

Mimosa1

The RX MAC rate bounces between 360 and 480 while the TX is pretty steady. Any feedback much appreciated.

William5 · December 16, 2019, 11:36pm

I am guessing you mean “auto” as in the link split ratio?

If so, the MAC Tx/RX 480/432 is the maximum in any one direction throughput that can go through the link.

So yes, if what I think you said is what you mean, you are correct.

If there isn’t other 24 GHz in the area and you don’t plan on putting up more 24 GHz radio then I would go to an 80 MHz wide channel.

Nick8 · December 17, 2019, 12:10am

Thanks, was wondering if the MAC rate was a hard stop for traffic in one direction. And yes you interpreted my setup exactly right. I can go to 2x80 if needed but is there any benefit to switching the ratio first to 75/25 and staying at 2x40 instead of jumping right to max? Definitely don’t need a high upload rate. Just wondering if the MAC rate in auto mode indicates a max throughout that I can’t get around. Thanks again for the input.

William5 · December 17, 2019, 3:31pm

There is no point in going to fixed frames if you are not trying to use multiple B24s at the same location and want to avoid interference. The Auto (Flexible Frames in Ubiquiti terms) will allocate however much bandwidth is needed in either direction up to the total that is available.

Check out these pages for more info.

https://mimosa.co/white-papers/tdma

http://backhaul.help.mimosa.co/backhaul-ug-tdma-configuration

http://backhaul.help.mimosa.co/backhaul-faq-what-is-mac-throughput

Nick8 · December 18, 2019, 2:27am

Thanks @William5 great help like always. Any thoughts out there if 1x80 is any better than 2x40? I can’t seem to find much for Mimosa documentation on what value to place on the CDF levels in the local analyzer but I am seeing some purple coloured spikes I may be able to work around at 1x80 instead of 2x40. From the max TX Power Details section I don’t think it gives me a signal boost on one channel vs two like the b5’s. I don’t think it’s an issue to move to 2x80 just trying to keep options as open as possible for a potential second link in the future. I have some further questions on why I can’t seem to use the whole Canada frequency band but maybe will pose that to support.

William5 · December 18, 2019, 3:22pm

Definitely talk to Mimosa Support about the frequency range question, this isn’t the first time I have heard someone complain about it.

I just got the hardware for my first B24 link, so I can’t comment too much, but if you play with Mimosa’s link planner there is a difference in throughput that is available between 2x40 and 1x80. I would take a spin there for a bit and see what will work best for you.

Side note: 24 GHz is a pretty narrow beam and it’s somewhat difficult to self interfere. Unless you are trying to have the antennas shoot along the same path and be located very near each other I think you won’t have much self interference, especially if you go to a fixed frame mode.