Echo Cancellation is performed by an advanced algorithm which reads both the mic signal and the current wav signal, processes them, and provides a clean mic signal, free from what it heard over the speakers. This is stack independent, and has nothing to do with bluetooth. We currently are investigating ECNR software, and plan to implement it in the future. For now though, any bluetoth solution you'll use out there over a pc, will have the echo. Unless you can manually turn on ECNR in your sound card driver, which we have seen before, when the driver is capable of using Microsoft ECNR. I have not seen any Windows bluetooth stack front ends that utilize the Microsoft ECNR, which I guess is possible bu no one has done it.