Lower ePMP latency

Hi everyone,

I noticed PMP 450i have far less latency than ePMP 2000.

Will Cambium do something in the future to reduce latency between SMs and AP on ePMP?

Using 2.5ms frame size, with 36 users, I have an avg ping of 14-15ms, but 10% less throughput.

Using 5ms frame size on the same AP, I have an avg ping of 28-30ms.

Results are similar with less users.

On PMP 450i I have 3 users on 2.5ms frame size and I have an avg ping of 7ms.

I understand that's a different product line and product price, but the latency increase is noticeable on ePMP vs other non-synced systems.

Ok, you're right, is more consistent, ePMP gives you more bandwidth, and that's ok, but imagine a network where you have 40-50ms on national servers on fiber backbone, add some wireless backbone latency, it's simple to reach near 100ms values on 5ms frame size in speedtest.net test, and using 2.5ms frame size you have 10% less throughput, so it means less users on the AP.

In a fiber world, where you have far less latency, I think Cambium should work on that part a bit more, to make simpler for us to compete with fiber.

Sometimes you have users playing online gaming and are ok with your bandwidth profile as a WISP, but prefer fiber because of latency.

Hi guiseppe4, 

The 450 is custom hardware and all the scheduling happens in the FPGA vs. MAC. On ePMP, since this is a standardized chipset, the TDD schedling needs to be done at the MAC layer. In addition, ePMP is not able to break the packets into smaller fragments (like 450 can) in order to reduce latency. That said, there are other enhancements we can make to reduce latency slightly but it is not planned. 



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Please plan this, is very important to reduce latency, even slightly reduced is ok :slight_smile:
How much ms do you mean by ‚Äúslightly‚ÄĚ?

Hello Sriram!

This has to be top priority. The latency issue is the weakest point today in the ePMP in my opinion.

(and I am a fan number one of the product, having a big network ...)


Is Cambium doing something in this direction?


You should compare apples to apples. The latency on the epmp is similar to a ubnt ac fixed frame. If you want lower ms, buy the 450. Otherwise be happy you have some high quality product at low cost.

I have to disagree. If a Cambium team member says that something can be done to reduce latency, this has to be a priority. The PMP450 is an excellent product, however, it does not fit 90% of the world markets due to the price.

Myself would very much like to have my entire network with Medusa. The problem is: because of the value of the currency of my country, it comes at the price of a house. There is no ROI.



Whay is 5ms more latency a problem, as long if is consistent and there is no jitter ? 

I'm not making a criticism.

I am a distributor of the product and I have a provider with more than 2,000 CPEs installed.

I love the product and I do not change it for nothing. Working with Cambium is a peace. In my country I am the greatest point of contact and encouragement to use ePMP.

For the gamer player it makes a difference. And it's not just 5ms more. It's 10, 20ms more. If the product can be improved, why not do it?

@Zucchi wrote:

.....And it's not just 5ms more. It's 10, 20ms more. If the product can be improved, why not do it?

Just curious, at what reduction in latency would you find acceptable? I ask because Sriram stated a -slight- reduction in latency was possbile. If he could knock 10% off this would only reduce the latency by 1-2ms. Even if he could reduce it 20% that would be 2-4ms.  

For me, let's that on PMP would be 10ms good enough.

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I have no expectations. 

1-2ms or 2-4ms is always welcome.