A low-complexity fading simulator for underwater acoustic communication channels

Abstract

Shallow water is an extremely complicated place for communications, and realistic channel models can provide an effective tool for system design. This paper proposes a low-complexity simulator that generates channel impulse responses for broadband frequency-selective acoustic channels. It uses a sum-of-sinusoids (SoS) method to generate Doppler fading impulse responses for wide-sense stationary correlated scattering (WSSCS) Ricean fading channels. The line-of-sight component is obtained by G0(t,τ0)=A0exp[2π(1+ε0)ftcosα0+φ0δ(τ−τ0 ) and the scatterers by Gs(t,τ)=∑n=1NAnexp{j[2πft∑m= 1M(1+εm)cosαm,n+ψnδ(τ−τn), where the random parameters An, αm,n, ψn, and τn are, respectively, the attenuation coefficients, impinging angles, initial phases, and path delays. The Doppler scaling is (1+εm)f, where f is the carrier frequency and εm depends on the speed of sound propagation in water and the velocities of the transmitter, receiver, and wind. Nonuniform probability density functions are selected for impinging angles αm,n to account for the nonisotropic waveguide effect in shallow-water channels. The proposed simulator is a general stochastic model that does not require site-specific information. It only uses 6N+4 random variables and requires O(N) multiplications and additions, where N is on the order of several tens. This low-complexity simulator can be easily implemented by real-time digital signal processors.