[mrb]

"not even radio-compatible"

Bluetooth 1.0 uses GFSK at 1 Msym/s, just like BLE / Bluetooth 4.0. So it's the same r/f modulation protocol (it's the higher layers that are incompatible.) Is it the actual GFSK parameters, eg. frequency shifts, that are different?

I know that Bluetooth 2.0 and 3.0 use different r/f modulation (π/4-QPSK and 8DPSK at 1 Msym/s), but why do people say Bluetooth 4.0 is so different when it seems to be the same as Bluetooth 1.0?

[sampullman]

One difference is that BLE uses 40 channels in its adaptive frequency hopping scheme, from Wikipedia: "Instead of the Classic Bluetooth 79 1-MHz channels, Bluetooth Smart has 40 2-MHz channels"

Now that I write it out, I see that frequency hopping would count as a "higher layer," but I think it's still managed in hardware, which could be why there are many BLE-only chips. It's possible the GFSK parameters are also different, and of course the layers above the link manager are vastly different (for some reason).

https://en.wikipedia.org/wiki/Bluetooth_low_energy#Technical...

[Kliment]

A major difference is that while original Bluetooth used time-based channel hopping BLE uses sequence-based channel hopping. This means you don't have to keep your local clock or receiver running to know what channel to listen to, rather you listen on a given channel just before you want to speak/receive something and once something shows up there you know where you are in the sequence. BLE-only chips can basically be entirely powered off most of the time without losing connection, whereas bluetooth needs a running clock or a large receive window to stay connected.