Energy-Efficient Joint Source-Channel Coding for Optical Wireless Underwater Networks

We describe a novel joint source-channel coding scheme for short-range optical wireless links in underwater sensor networks. We present a procedure that maps source symbol sequences to ON-OFF waveforms in the modulation space such that the energy consumption of modulation per source symbol is minimized. We apply this procedure to two settings: the single-dimensional and vector i.i.d. source processes. We show that the energy consumption per source symbol decreases as the length of the modulation waveform increases; however, for a fixed length modulation waveform, this decrease is not monotonic in the length of the source symbol sequence used. We present simulation results for two Gaussian processes that are correlated with each other, and quantitatively demonstrate the effects of the correlation coefficient between the two processes on the minimum energy of modulation that can be achieved per vector source symbol.