PROJECT TITLE :

Measurements and Modeling of Effects of Out-of-Plane Reverberation on the Power Delay Profile for Underwater Acoustic Channels

ABSTRACT:

Long reverberation tails are usually observed in shallow-water acoustic channel impulse responses (CIRs). Examples from 3 considerably different environments along the Norwegian coast are presented. It's shown that 2-D propagation modeling fails to reproduce the long tails. Nevertheless, inclusion of the impulse response tails is critical in affiliation with model-based mostly simulators of communication performance, to avoid too optimistic estimates of bit error rates, etc. This is often demonstrated by simulation examples for one in all the environments, comparing results for truncated and complete impulse responses. High wind speeds and Doppler spread signals indicate that surface reverberation must be taken into consideration for modeling the tail energy. In bistatic situations such as the ones considered here, backscattering computations in an exceedingly single vertical two-D plane don't seem to be sufficient. A 3-D ray-based mostly model, Rev3D, is used to incorporate effects of out-of-plane scattering from the sea bottom plus the ocean surface. The scattering-strength functions include azimuthal variation, with considerably enhanced scattering close to the forward direction. Rev3D modeling supports the hypothesis that out-of-plane scattering and reverberation are main mechanisms behind the observed continuous, exponentially decaying impulse responses. Modeling incorporates offered environmental information concerning sound-speed profiles, bottom topography and type, surface wave spectra, etc. Sensible agreement of measured and modeled time series is obtained for 2 of the locations. For the remaining location, modeling correctly recovers a considerably lower decay rate of the reverberation tail compared to the opposite locations, however the modeled decay rate is somewhat too massive.