Fast direct implementation of block adaptive FIR filtering

The authors describe a direct, fast, and efficient method of implementing time-domain block LMS (least mean squares) adaptive FIR (finite impulse response) filtering using radix-2 decomposition of the input data but no transforms. The same method can be applied to the implementation of time-domain block LMS adaptive FIR filters where the weight vector is updated in the transform domain and of frequency-domain block LMS adaptive FIR filters. The method is well suited to implementation on DSP (digital signal processing) architectures based on multiply-accumulate. Computational complexity comparisons show that the block length and number of weights can be traded for reduction in computational complexity and that the method is the most efficient for block lengths less than about 16, for a typical filter length