A Recursive Gaussian Newton Based Variable Parameter Adaptive Receiver for Single-Carrier Underwater Acoustic Communications

A direct adaptive equalizer (DAE) combined with a digital phase-locked loop (PLL) is a widely used receiver scheme for single-carrier underwater acoustic (UWA) communications. Ever since its birth, numerous ameliorated DAE+PLL schemes have been proposed, including sparsity-aware schemes and variable parameter (VP) schemes. The sparsity-aware designs have been extensively investigated. In contrast, the VP-DAE+PLL schemes received very little attention. Under harsh channel conditions, e.g., communication channels among moving unmanned underwater vehicles (UUVs), it is necessary to employ dynamic parameters so as to achieve robust performance. In this paper, we propose a new VP-DAE+PLL scheme in which the VP is achieved via a recursive Gaussian-Newton (RGN) algorithm instead of conventional stochastic gradient descent (SGD) method. At-sea experimental results are provided to verify the advantages of the proposed RGN-VP-DAE+PLL scheme. It showed the proposed scheme achieves better performance than existing SGD-based VP-DAE+PLL schemes with a slight complexity overhead. Moreover, it is less sensitive to initial parameter setting.