Proposing STBSC (space-time block spreading coding) scheme for improving underwater acoustic multipath communication

Having reviewed what we believe are the shortcomings of Refa.1, 2 and 3, we propose STBSC scheme for communicating in underwater acoustic channel (UAC) with multipath spreading and propagation delays. Sections 1 and 2 explain the STBSC scheme. The core of the scheme consists of: (1) the space-time block coding scheme splits transmission data into several groups of transmission signals; (2) each group is then spread with different orthogonal spreading codes; (3) the coherent dispreading signals are input to a decoder for maximum likelihood decoding independently; we use eqs. (4) and (10) respectively to form statistical decision variables. Section 3 performs numerical simulations of the STBSC scheme in the channel of multipath spreading and propagation delays as shown in Table 1. The simulation results, given in Fig.1, indicate preliminarily that the STBSC scheme, which uses the two-transmitter and one-receiver transducer, obtains 2 dB diversity gain and that the STBSC scheme that uses the Rake-type receiver obtains 2.5 dB additional diversity gain.