ePMP TDD Sync vs Max Range

[terintamel]

ePMP TDD Sync Sources White-paper

Applicable versions: 5.11.0 and above Applicable platforms: All GPS equipped Cambium ePMP radios employ Time Division Duplex (TDD), dividing each frequency channel into discrete downlink and uplink slots. Without synchronization, each Access Point (AP) determines its transmit timing independently. In multi-AP environments, this results in self-interference: the transmit cycle of one AP overlaps with the receive cycle of a neighbouring AP, degrading uplink performance and preventing effective f…

I believe I asked before if max range was a parameter of propery syncing and was told that it was not, but this post says it is. Which is correct?

How does Max Distance work?

Yes, you’re right. It’s simply used to prevent SMs from connecting beyond that distance. For ePMP equipment, the Max Range defines the maximum distance at which SMs are allowed to connect to the AP. The actual distance to each SM is calculated automatically behind the scenes and used for data transmission. As you cannot put in a decimal value like 4.2 miles and only whole numbers, what is the proper distance you would put for an SM that is 4.1 miles away to allow it to connect? 4 or 5 5 Tha…

This seemed to say Max distance was only to prevent radios connecting outside the defined distance set.

ePMP 4k Frequency reuse question

I know DL/UL ratio and frame size must be the same, but when setting up frequency reuse do the following settings also have to be the same on all synced APs? Max Range Guard Interval

This one said neither max range or guard interval were used for sync.

[Eric_Ozrelic]

@terintamel

I believe I asked before if max range was a parameter of propery syncing and was told that it was not, but this post says it is. Which is correct?

If you’re sync’ing ePMP with PMP450, then yes, the distance setting does matter. Co-location mode should also be enabled when sync’ing with 450.

The Guard Interval setting has no bearing on sync.

You can find various free tools for calculating sync settings here:

https://support.cambiumnetworks.com/files/colocationtool/

[terintamel]

Just syncing 4500 or 4600 colocated APs.

[brubble1]

I’m pretty sure I’ve seen cambium white papers for ePMP sync the have said in one paragraph that the distance setting is not required to be the same for sync to work but is strongly recommended and two paragraphs later say it is “required” for sync to work properly. There have been several posts over the years of people posting “proof” it drifts if you don’t set them the same but I never really paid any attention to them because we have been doing GPS sync since the Canopy days and both Canopy and 450i absolutely required distance to be the same, and more when mixing Canopy with 450i , we have always kept distance the same across all APs of the same frequencies because I had enough problems to troubleshoot without adding “ I wonder if the distance setting not matching all the APs is causing this problem”.

[Ashraf_Nusairat]

You are right, in a ePMP ONLY network with GPS sync and frequency reuse, the distance must be set the same on ePMP APs with the same frequency. The distance plays a factor in the TDD DL & UL subframe duration and must be the same to eliminate self-interference.

[Eric_Ozrelic]

@Ashraf_Nusairat

the distance must be set the same on APs with the same frequency

Does this same rule apply for those AP’s that share adjacent channels?

When using Cambium’s sync spreadsheets, it appears as though there’s quite a bit of leeway allowed for different AP distances before sync issues are flagged. As an example, here’s 5 miles for one AP and 20 miles for another:

[Ashraf_Nusairat]

Eric, I was referring to ePMP APs only sync. When it comes to synchronization with PMP, the ePMP-PMP Co-location tool must be used to guide the exact configuration of the 2 systems.

I edited my first reply to clarify that. (Thank you)