Finite-precision design and implementation of all-pass polyphase networks for echo cancellation in sub-bands

All-pass polyphase networks (APN) are particularly attractive for acoustical echo cancellation (AEC) arranged in sub-bands. They provide lower inter-band aliasing, delay and computational complexity than their FIR counterparts. Moreover, APNs achieve higher echo return loss enhancement (ERLE) performance and faster convergence than full-band processing. In the paper, the finite precision implementation of APNs is addressed. A procedure is presented for re-optimising the all-pass coefficients of the prototype low-pass filter for finite precision operation. Robust finite precision implementation of a prototype low-pass filter is discussed. The results of a set of AEC experiments are reported with full and 16-bit precision implementation.