Blind receivers for MSK signals transmitted through shallow water

In this paper, blind receivers for minimum shift keying signals transmitted through shallow water are proposed. After having introduced the modulation scheme and its favorable properties, two different blind receiver structures are studied. The first processing step in both cases is explicit non-data-aided timing recovery, a task that has often been neglected in other work. Then, joint blind adaptive multichannel equalization and phase recovery is performed. The adaptive setting of the equalizer is attained by either the constant modulus algorithm or a decision-directed approach. Both structures have been tested with measured shallow water data gathered during the ROBLINKS 1999 sea trial. The obtained results suggest MSK as a useful modulation scheme for underwater communications and demonstrate that completely blind processing of the received signals is possible.