I know if I need sync then TDD PtP mode in Fixed ratio is the way to go, but if I do not need the PtP link synced which is better for performance and stability? ePTP or TDD PtP flexible and what are the key differences?
This would be a 4600C PtP link.
That kind of answers my question but not fully. On ePMP 4K what is the main difference between ePTP mode vs TDD PTP Flexible? Both you give up GPS sync, which is fine for my use case.
For ePTP mode you can configure between throughput or latency (frame size), but with TDD PtP flexible mode I can take advantage of Asymmetric Uplink Bandwidth but I assume a static frame size.
Does TDD have more robust interference and noise rejection over ePTP mode? Does it have a better rate algorithm?
ePTP gives you more tput and lower latency.
As to your other questions, I don’t know. I don’t think there’s ever been an instance where we’ve used flexible TDD for a PtP, because ePTP has always been perceived to be superior.
There must be something different as they have both TDD mode and TDD PtP mode as explicit selections on the AP side. On the SM side you only have TDD or ePTP mode.
Maybe someone from Cambium can chime in on if there are any benefits to TDD PtP mode when in Flexible framing, because if it is just the same as regular PtMP TDD mode then why have the option?
I get that TDD PtP mode is beneficial if you used fixed framing and GPS sync, but when running flexible you don’t get either of those benefits.
Also would love to know if ePTP mode or TDD PtP mode have seen any improvements with the FW releases since 5.10 or if the only wireless performance improvements have been for the TDD PtMP mode.
I have not tried TDD PtP Flexible yet, but upgrading the PtP link from 5.10.1 to 5.12.0 did yield an improvement in modulation on ePTP mode from Downlink mostly DS9 and Uplink mostly DS11 to Downlink now DS11 and Uplink now DS12.
Hello,
Based on our testing and fieldwork, we agree with you that ePTP offers higher throughput and lower latency but is vulnerable to interference.
TDD offers greater range and channel asymmetry, and is more robust against interference.
One fundamental difference is that the radio is versatile depending on the scenario. It can function as an AP (PtP or PtMP) or an SM (PtP or PtMP); that is why it offers both TDD and TDD PtP modes.
If you look at a radio designed exclusively for PtP, you will see that it offers more than just TDD PtP or AP TDD modes.
When you configure a radio as an AP TDD, you are instructing the AP to schedule its radio resources to serve multiple SMs under varying conditions, such as:
In fact, such a radio—like the PMP3000—is more robust, physically larger, and equipped with more memory and processing power, yet it is limited to the AP TDD mode.
When you configure it for TDD PtP, you are telling the AP to serve only a single SM. The system has a much better understanding of the link’s status.
It does not have to share radio resources with 20, 30, or 50 other SMs.
This allows it to optimize the frame for the throughput and latency of that single link.
The ePTP mode is even more specialized for PtP:
TDD PtP exists not merely to “perform PtP,” but to allow that PtP link to function as a synchronized member of a TDD network.
This is precisely what makes TDD PtP a much more attractive option than ePTP when you have multiple ePMP units on the same tower.
image 1
GPS Sync is not used to directly improve signal, MCS, or range. It is primarily used to COORDINATE TRANSMIT/RECEIVE TIMING between TDD radios and reduce interference between them.
image 2
a short sentence:
ePTP → PERFORMANCE for PtP
TDD PTP Flexible → PtP + TDD + DYNAMIC DL/UL
TDD PTP Fixed → PtP + TDD + GPS SYNC
TDD PMP → MULTIPLE CLIENTS + TDD
TDD PMP Flexible → MULTIPLE CLIENTS + TDD + DYNAMIC DL/UL
Grades:
