수중통신에서의 SOS 블라인드 등화기의 DD 기법 개발

Abstract

The paper deals with a direct decision method to improve the performance of a SOS(second order statistics) blind equalizer for underwater acoustic transceivers. In underwater acoustic communication field, the received signals at an acoustic transceiver are seriously distorted by many reflected acoustic rays from surface and bottom of water. To efficiently recover the desired signals from the distorted signals, equalizers can be applied to acoustic transceivers. There are two types of equalizers, with or without some training signals. One hand, the equalizer with training signals which is applied to the most of the underwater acoustic transceivers can reduce the transmission throughput because of additional signals with limited bandwidth. On the other hand, the equalizer without training signals which is called as a blind equalizer enables to transmit more information at the same bandwidth than the former equalizer. Blind equalizers are also categorized by two types. one is a HOS(higher order statistics) type, and another is a SOS type. the HOS blind equalizers had extremely complex structures, and suffered from heavy calculation load, because of higher order statistics in the equalizing algorithms. Whereas, SOS blind equalizers are far more simple than the former ones, by not using higher order statistics, but only using second order statistics. In this paper, I introduce a simple decision method to improve the performance of a SOS blind equalizer. Simulations and anechoic water tank experiments provide a demonstration about the performance improvement of SOS blind equalizer appling the proposed decision method.