How do acknowledgments work in a frequency hopping system?

[e100]

Tried searching on Google without much luck, perhaps because I don't know what key words to search for.

Once a transmitter has finished sending a message does it listen for an ack on the same frequency before jumping to the next frequency in the series. Presumably it cannot wait for too long otherwise it'll miss the scheduled transition to the next frequency.
Also, what happens if the receiving party is in the middle of sending an ack when the next frequency hop is supposed to happen?
Is this solved by effectively having dead zones on either side of a hop where two parties are neither transmitting or receiving? If so does that make it less efficient in terms of bits per second?

Mike

[Benta]

I think you are mixing up modulation (frequency hopping) with signalling.
The frequency hopping occurs continuously and independently of the data being transmitted. It is quite possible, even likely, that a lot of frequency hops occur during the transmission of a message.
The acknowledgement is just another message being sent/received.

Systems I've seen are "always on" when active. One could imagine a system where TX/RX are turned off between messages, but then resyncing the hopping is needed before each message, which is time consuming and inefficient.

[e100]

OK, thanks that makes things a bit clearer.