BH latency

Products ePMP
1

I have a BH pair of ePMP1000's on a non DFS channel, 3.5FW and stellar signal; however we have been noticing a 17ms latency between the pair.  Is this normal ?

2

What mode are you using... ePTP, TDD-PTP, TDD, flexible or fixed ratio, 5 or 2.5ms?

For lowest latency, you'll want to use ePTP mode, second lowest latency will be TDD-PTP mode with a 2.5ms flexible frame.

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3

Usisng TDD-PtP, 75/25.  Is flexible mode the prefered mode in PtP?  Is there a recomended standard configuration for BH on ePMP1000?

4

Which mode you use depends on your goals.

For lowest latency, and arguably the fastest throughput, use ePTP. The drawbacks are that you cannot use GPS sync with this mode, and you can't set an MCS ceiling to combat jitter if there's interference.

For second lowest latency, but slightly less throughput, use TDD-PTP mode using flexible frames and a 2.5ms frame time. The drawbacks are that you cannot use GPS sync, and there are only limited channel width options available with 2.5ms frames.

For third lowest latency, but slightly higher throughput then 2.5 frame mode, use TDD-PTP mode using flexible frames and 5ms frame time. The drawbacks are that you cannot use GPS sync, and you have slightly higher latency then the first two options.

If you need to do anything using GPS sync, then the above three options will not work for you. You will have to chose TDD-PTP mode, along with a frame ratio, and 2.5ms or 5ms frame windows. Again, choose 2.5ms from lower latency and about 10% less throughput, or choose 5ms for higher latency and about 10% more throughput.

Assuming that you don't need GPS sync... I'd probably try ePTP and start there and see if it meets your needs. Again, if you need GPS sync, then your options are pretty limited.

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5

Great summary of the different options, Eric!

Sherwood, Right off the bat, for BH, you should use ePTP mode. However if you want to sync, then you need to match the configuration of the AP (PMP or PTP) that you are trying to sync with.

Thanks,
Sriram

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6

For PTP in ePMP I would definitely do ePTP as well (from an operator perspective, Sri is a good guy that works at the manufacturer :)

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