Wideband multichannel time-reversal communications in a tunnel-like structure

The development of multichannel time-reversal (T/R) processing continues to progress rapidly, especially when the need to communicate in a highly reverberant environment is critical. One such environment is a tunnel or cave, or even a pipe with many obstructions, multipath returns, severe background noise, disturbances, path disruptions (bends) as well as a long propagation path (∼120 ft.). For this environment, multichannel T/R receiver designs have been extended to include a wideband processor and modulation scheme along with designs to communicate in the highly reverberative tunnel-like environment that includes high background noise levels and disturbances. The acoustic information signals are transmitted by an 8-element host or base station array and received some distance away with a significant loss in transmitted signal levels. In this paper the results of the new wideband processor and modulation scheme coupled with the underlying T/R theory are discussed to demonstrate the overall performance for both high and low bit-level designs in the tunnel.