Fast blind equalization by using frequency domain block constant modulus algorithm

This paper presents fast algorithms for the CMA (constant modulus algorithm), which is one of the widely used blind equalization algorithms. To derive the fast algorithm of the CMA for high-speed equalization, we first introduce BCMA (block CMA) which adjusts the equalizer coefficients by block processing of the received symbols in the time domain. Based on the BCMA, we propose the FBCMA (frequency domain block CMA) which employs fast linear convolution in the DFT domain by using the overlap save method. In this paper, a non-linear error function in the frequency domain is derived using the Parseval´s relation. Also, an adaptive algorithm in the DFT domain is developed to adjust the DFT domain filter coefficients. If the block size and filter length is N, the multiplications required for the conventional CMA and proposed FBCMA are in the order of O(N²) and O(N log N), respectively. The computer simulations show that the proposed FBCMA presents comparable performance to the conventional CMA, while requiring less computations