Underground cross-border tunnels of all sizes and shapes are an increasingly important threat to our National security. Finding cross-border tunnels is a challenging task and once found, an additional challenge is secure and map the entire underground tunnel. Manned entry into these dangerous underground environments is a risky endeavor. The use of robotics offers a great improvement over human entry into these tunnels. To function effectively, tunnel robots require a wireless communications link. In our Phase I effort, we demonstrated the feasibility of a flexible and highly adaptable electromagnetic (RF) communications link for underground robotics. The link is bi-directional. We developed an adaptive parametric signal processing scheme where the relationship between data rate, communications range, power, covertness, etc. can be optimized for a given communications link because the underground electromagnetic electrical properties can greatly vary from site to site. By using a software defined radio approach this optimization can be user-adjusted or automatically optimized in the field. Frequencies of operation can range from several kHz to several MHz. Data rates will be sufficient to transmit slow scan imagery. In Phase I we showed that data rates of greater than 100 kbps could be supported at horizontal ranges of 125 meters from a tunnel that was 21.5 meters deep. This tunnel was in a copper bearing formation and represented a worst case environment for electromagnetic through-the-earth communications. In this Phase II effort, we proposed to continue developing an advanced prototype of the system, implement into an operation robot, and test the system using field demonstrations of the system at several underground tunnel test sites.
