Listen Before Talk - based on SM noise as well?

Does listen before talk look at the noise levels the SMs are seeing when selecting which channel to use, or does it only use the noise level mesaured at the AP?

Hi Ted,

It will sense the energy received at the AP and if energy exceeds the detection threshold it will cause the AP to stop the transmission on the current channel.

Only the AP performs the detection.The SM cannot transmit data until it is allocated bandwidth from the AP.

I hope this clear's the confusion.


That's a shame.  I would really like see some more intelligent noise avoidance akin to what the PTP products do.

We're in a very loud environment with a lot of trees, so frequency selection is a very finicky process, and every time our competitors' equipment restarts because of a power outage or something similar, I have to redo the frequencies on nearby towers.

Hi Ted,

I am not sure why you are facing this issue, because once the AP cease transmission on the current channel it will switch to the next channel on its prioritized list of alternate channel frequencies.

A channel availability check is performed over a pre-determined time interval on any alternate channel before the AP is allowed to initiate transmission. If no alternate channels are configured, the AP will wait a pre-determined channel back-off time on the existing channel before attempting to initiate transmission. If the running average of the energy sensed during the channel back-off time is below the detection threshold, the AP is allowed to initiate transmission.

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It's not a problem with listen before talk; I was just hoping that LBT could be used as a form of DFS, but it doesn't sound like that's what it's intended for.

Listen before talk is only active for this radio due to regulatory requirements.  If this wasn't in there, the product would have only been issued a grant to operate from 3650-3675.