What is the meaning of that "The transmission rate is negotiated over the air"?

[iBaBei]

When I study the ANT example, ANT Advanced Burst, in SDK document, I see this: The transmission rate, along with optional features such as frequency hopping, is negotiated over the air, offering backward compatibility with implementations that support only standard burst. What is the meaning of this?

[shibshab]

I'm not familiar with ANT, but I assume it works in a similar manner as BLE.

It most likely means that the devices will transmit packages to each other describing what features they support and not. If both devices support a feature (such as Advanced Burst), it will typically be enabled.

Since Advanced Burst was a recent addition to ANT (I assume) and some devices might not support it, it is important to do this "do you have this feature" checking, before enabling them. If the devices did not do this check, they might enable some feature which the other device in the connection does not support. This is what they mean with backward compatibility.

As an analogy, it is like two dancers which have never met dancing together. There is a well define basic move which everyone knows, so they start of by doing only this. Then they can ask each other: "Hey do you know that move when I swing my leg over your head and then drag you between my feet?" If this is the case, then they have enabled "Advanced Swing" and can start doing that from now. All this without the risk of breaking a leg attempting to perform the "Advanced Swing" with a person that does not support it.

[Petter Myhre]

Could you be more specific on where you see this?