A Study of Time Domain Adaptive Decision Feedback MSK Equalization over Time-varying Underwater Acoustic Channel

Abstract

Minimum shift keying (MSK) shows better bandwidth efficiency than phase-shift keying due to its constant envelope property. The performance of block linear equalization (BLE), commonly used for MSK communication in radio communication systems, is limited in the complex time-varying underwater acoustic (UWA) channel because BLE cannot track channel changes within the data block. A time-domain adaptive decision feedback equalization (TD-ADFE) method based on Laurent’s decomposition is proposed to address issues pertaining to MSK communications over UWA communication. The method can effectively track the time-varying UWA channel through that the output of encoder updates the equalizer coefficient iteratively, which comprises matched filter, equalizer, differential decoding, and differential encoding. According to the numerical simulation results, the TD-ADFE performed better than FD-BLE over time-varying UWA channel by approximately 5.5 dB when the bit error rate (BER) was 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> . The sea trial results over 28 hours demonstrated that the BER of TD-ADFE was 36.8% lower than FD-BLE.