synchronizing TDM- via GPS

Hello,We considering installing two links in two different directions on a tower using PTP 650 , But do we use these links to transport T1 (TDM - voice in real time) when synchronizing via GPS we increase the latency?


Hi Arturo,

That's a good question. The TDM end-to-end latency depends (amongst other things) on the wireless TDD frame duration.

When TDD Synchronization mode is disabled, the radio selects the optimum wireless TDD burst duration and frame duration, as a compromise between low latency and high capacity.

When TDD Synchronization is enabled (with or without GPS) the wireless TDD burst duration and frame duration become separately configurable. You can optimise the TDD frame for low latency or high capacity or a compromise between the two. If you configure the link for the lowest compatible frame duration then TDM end-to-end latency is likely to be roughly the same as the case where TDD Sync is disabled.  On the other hand, if you manually configure TDD Sync with a long burst duration and a long frame duration, capacity might be increased, but the TDM end-to-end latency will certainly be extended.

You can find a very accurate estimate of the TDM end-to-end latency for different wireless configurations using LINKPlanner, and here you can experiment with different TDD Sync frame settings.


Thank you very much for your excelent contribution!!!!!

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Just to be on the safe side, I'm assuming that the GPS receiver is used for TDD Synchronization of the two PTP 650 links.

In this case, GPS is not used to synchronize the TDM circuit(s).

It's also worth pointing out that the TDM latency reported by LINKPlanner is for a TDM circuit using the Cambium NIDU. A TDM circuit created using a standard TDM multiplexer will have a significantly longer latency.