Performance Evaluation of $$\pi /4$$ π / 4 -DQPSK OFDM over Underwater Acoustic Channels

Abstract

This paper investigates the performance of orthogonal frequency division multiplexing (OFDM) with $$\pi /4$$ź/4-differential quadrature phase shift keying ($$\pi /4$$ź/4-DQPSK) modulation, over underwater acoustic (UWA) channels. The orthogonal multicarrier scheme with non-coherent detection technique results in spectrally efficient, reliable and simple receiver design. $$\pi /4$$ź/4-QPSK has less envelop fluctuation and performs better in multipath UWA channels. It is shown that with a pair of hydrophones for reception and maximum-ratio combining (MRC) technique, one can achieve considerably low bit-error-rate (BER) at practical signal-to-noise ratio (SNR) value. Further, the BER expression for such a scheme is obtained by using the probability density function and is shown to consist of a series with fast converge rate. The series solution approximation provides a reasonable match between the simulation and the analytical results with and without the MRC diversity technique.