450M Efficency Rating Question

Under Tools > Link Capacity Test when you run a Link Test with Multiple VCs in the 3rd colum the AP gives an efficency rating of each of the registered SMs. This has been a really useful tool for the 450Ms (thank you) in finding trouble subscribers and increasing the capacity of the AP.

Here is my question: What does the efficency rating actually indicate?

The reason I ask this is because we have noticed a huge variation in some of the results just by running the test multiple times in the same 2 minute window with out making any changes.

Please see the below results: Same SM, Same Session, 2 minute difference, 92% efficnecy change!

That is the same SM in question has a -67 signal at 1.9 miles and no issues. I monitored the Link Status page and see no changes as well:

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Hi,

Efficiency is simply 100*(frags received/frags transmitted), rounded down to the nearest integer.

On the first test it was trying to do MUMIMO at 6x, but the link could not support it.

On the second test the AP had dropped the supported MUMIMO rate to 4x. At this rate it passed the majority (96%) of frags during the test successfully.

The Link Status page only displays the SU-MIMO rate (at the moment), so you won't have seen this change as the SM can sustain 6x in non-MUMIMO mode.

regards,

Andrew.

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Andy

First, let me say thank you


Let me ask you something stupid... with a frame rate of 2.5ms and the claim that the medusa recalculates groupings 400 times a second do these types of customers that fluctuate so dramatically cause a significant overhead when it comes to processing and packet throughput handling?


Like I said, stupid question, but I am wondering as the customer counts increase to over 100 with these types of sampling and adjustments being made it has to contribute to some type of cost that affects performance.

Hi,

Not a stuoid question, but it is something we considered from the outset. We  have a fast multicore processor and a much bigger and faster FPGA than on other 450 AP products so we can split the tasks up and make sure everything gets done in time. There are real time monitoring points in the code to make sure no task is taking longer than it should and everything is still co-ordinated. There are a couple of big test rigs in Ashburton and Rolling meadows with 238 SMs connected that we use routinely to stress test the AP under heavy load. This has allowed us to find and remove any choke points in the system.

We're still pushing it to go faster though, especially for bandwidths >20MHz.

regards,

Andy.

238 SM’s? What speeds are you offering? We can’t even offer 20Mbps to our customers and our AP is only at around 100 sm’s. The link efficiency and grouping is very solid. Modulation is also very good.

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Hi Showy199,

To be clear the 238 SMs are in a system test facility here at Cambium Networks. I'm not a WISP !

238 SMs is a system limit and a worst case scenario for getting all the required processing done in the time required. We need to form the best groups for MUMIMO beamforming and more SMs gives the algorithm more options to sort through. It's not not necessarily a recommended setup, we just have to make sure it doesn't break the system.

If you have concerns over your system performance it might be worth starting a new thread/discussiuon with a description of your setup and Multi VC link test results with and without MUMIMO enabled. Then there could be a comparison with other 450m systems out in the wild and the packages other WISPs offer. Or if you prefer a support ticket could be raised.

best regards,

Andy.

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