An Equalization Initialization Procedure for MDM Systems Based on Orthogonal Matching Pursuit

In this letter, a new initialization procedure is proposed for channel equalization in the mode division multiplexing (MDM) systems. The initialization procedure is based on the orthogonal matching pursuit (OMP) algorithm. With the proposed method, it is possible to use a short training sequence (TS) to estimate the initial tap values for the constant modulus algorithm (CMA), and the CMA provides further channel equalizer optimization afterward. It is found that with the aid of the OMP algorithm, the length of the TS can be as short as 256 symbols for an MDM system with 35-ns delay spread, which is only 1/16 of the TS length required by the least square algorithm. The OMP based semi-blind algorithm has shorter TS length and a lower computational cost in comparison to the full TS-based channel equalization approaches and a better convergence performance in comparison to the full blind channel equalization algorithms.