A low-complexity orthogonal time frequency space modulation method for underwater acoustic communication

Abstract

Compared with the orthogonal frequency division multiplexing (OFDM) modulation, the orthogonal time frequency space(OTFS) modulation has a lower peak-to-average power ratio. It can effectively resist the time selective fading caused by the Doppler effect and has significant performance advantages over doubly dispersive channels. However, the conventional OTFS linear minimum mean square error (LMMSE) method has a high complexity and is not easy to process in real time. In order to solve this problem, we propose a low-complexity equalization algorithm with infinite norm constraints based on the optimal coordinate reduction. The equalization algorithm not only obtains the optimal solution through a certain number of iterations and avoids direct matrix inversion but also equalizes infinite norm constraints to improve the symbol detection performance gains. At the same time, the OTFS delay-Doppler channel matrix we utilize is sparse and the two-norm squares of each column vector equally reduces the complexity of optimal coordinate descent. Finally, the simulation in the underwater acoustic communication scenario we designed verify the effectiveness of the proposed equalization algorithm. The simulation results show that the performance of the proposed equalization algorithm is close to that of the LMMSE method, while its low complexity is ensured.

Hamming Distance Optimized Underwater Acoustic OTFS-IM Systems

“…In [9], the author analyzes the performance of coded OTFS on high mobility channels and proves the basic trade-off between the coding gain and diversity gain of the system. Capable of providing stable communication in time-varying environments, the time-varying and strong Doppler effects of the underwater acoustic channel fit well with the characteristics of OTFS, making OTFS modulation techniques a hot research topic in underwater acoustic communications [12][13][14][15][16]. In [12], OTFS modulation technology was first applied to the field of underwater acoustic communication, and the performance of OTFS in underwater acoustic communication was verified by bit error rate (BER), spectrum effectiveness (SE), and peak to average power rate Entropy 2023, 25, 972 2 of 13 (PAPR).…”

“…At the receiving end of the system, Ref. [14] proposed an optimal coordinate descent infinite parametric constrained equilibrium algorithm for the problem of high complexity of the linear minimum mean square error (LMMSE) algorithm, which reduces the complexity of the system while ensuring the BER performance of the system. In contrast, Ref.…”