A novel fast computation without divisions for MMSE equalizer and combiner

In this paper, we propose a novel fast and low complexity algorithm of computation for minimum-mean-square-error (MMSE) equalizer or combiner without divisions. Multiplicative effect of fading channel should be compensated by divisions at the receiver. Therefore, equalizer or combiner at the receiver is derived by inverting the channel impulse responses. Here, the number of divisions equals to the number of subcarriers. For the next generation with high bit rate applications, these divisions are necessary to be computed in a very short time and may impact to the increasing of hardware complexities. The main contribution of this paper is a proposed fast algorithm by replacing the large number of divisions with multiplications and subtraction due to its lower complexity. We improve the performance of Newton-Raphson Method by a range extension so that the Newton-Raphson Method is applicable for MMSE computation with small number of iterations. Our results in Carrier Interferometry Orthogonal Division Multiplexing (CI/OFDM) confirm that with only two iterations, performance of the proposed algorithm can achieve the similar performance as the normal computation with divisions.