Minimum bandwidth needed for FEC

Is there a downside to enabling Forward Error Correction other than data usage? Like, is there a minimum bandwidth, where below you are just constraining the bandwidth further by sending redundant data, and ultimately end up with poorer results?

We are using Speedfusion cloud to bond T-Mobile and Verizon on a Balance 20X, but we often are between the 10/5 and 20/10 MB/s range, and I don’t want to enable something that may have a negative affect. Thanks!

FEC has two settings Low and High.

There is an expected overhead of 13.3% and 26.7% respectively.
FEC works on the TX/upload traffic on the device it is enabled on.

So in your case above at 5MBps upload you’d have 4.34MBps or 3.67Mbps of available bandwidth for data depending on the set level of FEC.

At 10Mbps upload you’d have 8.67Mbps or 7.33Mbps available depending on FEC level.

I think the only way you will know for sure is to test it in the location in practice.

I’ve been in one location where a cellular connection provided between 5 and 45 mbps and there was lots of interference and contention on the cell tower, and FEC low helped noticeably with not only consistency but also improved the overall speed noticeably with (despite the overhead.)

Whereas in another location where I had a max of 20 and a min of 4, disabling FEC was noticeably better as it didn’t appear to help and so saving the overhead was the way to go for that location.

As a random though, maybe in the future there could be software in the device that could spot the need for FEC (delayed packets where FEC could save the need for a retransmit) and enable it, and then disable it automatically when conditions improve and it is no longer providing an advantage.