Through-the-earth communication: Experiment results from Billie Mine and Mississippi Chemical Mine

As part of the Lawrence Livermore National Laboratory (LLNL) effort to evaluate ''Through-the-Earth Communication'' (TEC) as an option for military communication systems, experiments were conducted involving transmission, reception, and performance monitoring of digital electromagnetic communication signals propagating through the earth. The two experiments reported on here not only demonstrated that TEC is useful for transmissions at digital rates above a few bits per second, but also provided data on performance parameters with which to evaluate TEC in various military applications. The most important aspect of these experiments is that the bit error rate (BER) is measured rather than just estimated from purely analytic developments. By measuring this important parameter, not only has more credibility been lent to the ''proof of concept'' goals of the experiment, but also a means for judging the effects of assumptions in BER theoretical models has been provided. 4 refs., 35 figs., 3 tabs.