Joint blind frequency-domain equalization and decoding for rateless underwater acoustic communication

To increase bandwidth efficiency and adapt to the bandwidths of different underwater acoustic channels (UAC), a joint blind frequency-domain equalization (BFE) and rateless decoding approach for underwater acoustic communication is proposed. Considering the complexity and improving the equalization performance, a variable frequency-domain tap-length linear BFE (VFTL-LBFE) is firstly proposed. In contrast to the existing approaches, the VFTL-LBFE can dynamically adjust the frequency-domain tap-length according to the specific UAC. Then, to increase the bandwidth efficiency and better utilize the different bandwidths, a joint VFTL-BFE and rateless decoding (JVFTL-BFE-RD) approach is proposed. To process the feedback soft information from the rateless decoder, the LBFE is revised to decision feedback structure. In the process of obtaining feedback soft information from rateless decoding, unlike the existing approaches, the proposed approach does not need to know the noise variance. Therefore, an iterative loop is formed, through exchanging log-likelihood information between the BFE and the rateless decoder, the detection performance can be significantly improved by the iterative process, as a result, the communication efficiency can be further improved. The simulation results verify the practicability and show that the proposed method has superiorities over the existing approaches.