Meet our new backbone

We've been running for 2.5 years now, have around 200 antenna in the field and cover around 300 square miles of very hilly, covered in trees, rural Scotland. So cold and wet too. And thats just in summer.

We have all the same growing pains that every other WISP has. The balance between cost and reliability, distance and throughput, performance, etc.

Our network Backbone is the bit that joins all the small bits together. Just like a spine. In January this year, in response to continued Ubiquiti AC firmware issues, I took delivery of the first three pairs of Mimosa B5 devices here in the UK. Within days they were up, working and have not given serious bother in 11 or so months. 

These dishes are around £1,200 a pair, and can reliably shift in excess of 800mb/s. We now have four pairs linking some of our largest transmission sites.

When Patrick at MS Distribution called and told me about the Mimosa B5 Lite - a smaller, cheaper brother but still capable of shifting 500mb or more - I immediately ordered six pairs. (Oh - can't praise MS Distribution enough. Without their support, we would have long folded. Good guys).

We took delivery of the first pair of Lites on the 28th of August. Nice little devices - physically much smaller than the Nanobeam 400 (400mm diameter) units they will ultimately replace. The pair comes in a single HUGE box, complete with mounting kits, coach bolts, jubilee clips, cable glands and a suspicious tube of 'Super Lube' (No, I have no idea either).

So far so good. This is what it looks like on the wall:

The dish to the right is a Ubiquiti PowerBeam NB400 (M5) with an RF Elements shielding kit on it. The one on the left is the Mimosa Lite, obviously. The wall is around 150 years old. Both cost around the same.

In this case, I've just re-used the Ubiquiti Mounting Arms (It was already on the wall). The Mimosa supplied ones are white. And a bit on the flimsy side, but I do test the arms by dangling myself off them, so my definition of 'flimsy' is 'I don't think it'd take the weight of an overweight man'. 

You can see from the photo that it's more akin to an NB300 in size. And since it's mostly plastic and shielding is very light. Ever tried to mount a 1m+ sized Rocketdish weighing 17kg? This comes in at less than 1kg. No problem.

What does it really look like?

Excuse the cable lashing - I hadn't actually finished tidying up before I took the picture. The important thing to understand from this that the vertical adjustment in the dish is provided by the bracket itself. 

This itself is a bit of a pain. Okay, in this case, the wall the bracket is mounted to is almost perfectly perpendicular to the desired target. But thats not always the case. If the wall was at only 45 degrees, and we used the vertical of the bracket to adjust it, the dish itself would be pulled off of a perfectly vertical axis.

So with this dish - plan ahead.

The other thing to note is that all the Mimosa dishes are 48v. The bigger ones use all 8 cores in a PoE ethernet cable, and the lights only use four cores. Don't mix up the PoE blocks. Or do as I do and use Netonix Switches everywhere - they can cope with traditional Ubiquiti 24v devices, standard 24v PoE as well as non-standard and standard 48v devices like these.

Just be careful what power you run to your remote device. Label the cables!

Lets talk about performance.

Size: You can see that these Lites are physcially small. The B5's are more akin to NB400's in size (400mm or so diameter dishes). We found that 10 miles was a good maximum usable range on the B5's, and we're guessing that 5 miles or less is a good working maximum on the Lites. (You can get connectorised B5's that bolt onto the back of Ubiquiti Rocketdishes - they go right up to 5 feet in diameter if you really want to transmit 50 miles).

Throughput: The B5's have GPS built right in. Why? It's not as if they're going to drive around and get lost, right? Well, the B5's use the GPS timing signal to predict exactly when the transmission packet will end - and give far better timing resolutions to the signals in general. This works because both ends have access to the same clock which has a resolution measured in millionths of a second. The Lites do NOT have GPS built in, so we're surviving on just the excellent radios. So give the little brothers a break. 

Performance: Here's a screenshot from one of these Mimosa Lite Links.

A few things to explain. The graph at first glance looks terrible - look at how much it's bouncing around? Wait. Look at the scale. Its holding between 299 and 301 mb/s of ACTUAL transmission performance - not the carrier. So actually its very very stable. And it's been stable for 7+ days (last time we worked on this link).

This little Mimosa Lite link is the link that just keeps on working, day in, day out. It's only really got 20db of SNR - the noise floor isn't the usual -100db we see on empty air - its in a quite busy area. And we're using (at this point in time) a whopping 0.9% of the link capacity.

I don't know about you, but £200 for this link? Bargain.

The screenshot is from the Mimosa Cloud management platform - there are similar graphs on the device, and since it's a full SNMP client, you can use other packages if you have them.  The Mimosa Cloud is being upgraded so it keeps more than 24 hours of figures - we're buying into that as soon as it appears.

Pros: 

  • Cheap. 
  • Easy to handle
  • Robust, Reliable
  • Built in shielding
  • It all comes in one box

Cons: 

  • Funky bracket assembly
  • Not yet Point to Multi-Point. Backhaul only. PTMP is coming, but like all things Mimosa, they don't release code till they're convinced it works. After all the scar tissue down my back from Ubiquiti, I'm also quite happy to wait for it to work. Soon, perhaps.

They've solved a number of issues in my network. I think they'll probably help you too. 

 

Bill Buchan