Frequency Offset Estimation for High Data Rate Acoustic MIMO-OFDM Systems

Multiple-input multiple-output (MIMO) communication techniques are considered with the goal of increasing the information throughput via spatial multiplexing over an underwater acoustic link. Our focus is on designing a frequency offset compensation algorithm for the MIMO system based on multicarrier modulation in the form of orthogonal frequency offset compensation (OFDM). The system relies on the simultaneous estimation of parallel transmit channels and multichannel receive-side data detection. The frequency offset compensation method utilizes a set of hypothesized frequency offsets and proceeds to detect the data symbols in the MIMO-OFDM system. We assess the system performance in terms of per user bit error rate (BER) and demonstrate the proposed methods using MIMO-OFDM recordings collected over a 14 km link off the coast of Kochi Prefecture, Japan, in July 2022. The low complexity and excellent performance of the proposed frequency offset compensation algorithm for MIMO-OFDM systems make it practical for future hardware implementations.