DSP based real-time single carrier underwater acoustic communications using frequency domain turbo equalization

In this paper, a DSP based real-time single carrier underwater acoustic communication system is developed. The designed receiver system operates in frequency domain for low complexity equalization. The turbo principle is incorporated into channel equalization and channel estimation processes to improve the system reliability. The channel is treated as stable within each small block and iteratively estimated based on LMS method and soft information provided by channel decoder. The soft LMS channel estimation is able to achieve better performance than conventional phase compensation scheme in single carrier frequency domain system. The receiver system is implemented on a floating point DSP running at 350 MHZ. Through careful optimization, the real-time processing is achieved with sufficient margin for both single-hydrophone receiver and multi-hydrophone systems. The designed system has been tested by both tank experiment and sea trials and achieves satisfied performance.