A novel LT-Turbo equalization for long-range deep-water acoustic communication

Abstract

Long range deep-water acoustic communication (LDAC) is challenging due to low SNR and time- space-varying channel parameters. Since there exists the long feedback delay, it’s hard to construct the feedback channel in LDAC. So the feedback based error control methods and the link-layer framings are all disabled in LDAC. To solve these problems, the Ludy Transform code (LT code), which is a kind of rateless fountain code, is introduced to replace the traditional channel code of the classical LDAC system. LT code brings in the rateless property and the channel independence which are the foundation of the no-feedback link-layer framing, but the performance of this receiver scheme has a distinct gap compared with the theoretical bound. So a LT-Turbo equalization method is proposed, where the adaptive linear equalization and the decoder of LT code are jointly optimized in an iterative process. The simulation results show that the LT-Turbo equalization could get a lower bit error rate than the classical method under various kinds of channels. The results of another contrastive simulation between the LT-Turbo equalization method and the classical time domain retransmission method show that the minimum required code redundancy of LT-Turbo equalization is only 1/2 of the classical time domain retransmission method in the same low-SNR deep-water acoustic channel, which proves the excellent performance of the LT-Turbo equalization.