A Comparison between Performances of QPSK and 16QAM Signals for a Underground Multiuser Scenario

We will present a security/disaster scenario for a communications system with multiple access and code division in direct sequence where a number of sources communicate concurrently over the same physical channel. Since the main difference between the underground communications and the terrestrial one is the communications medium, we have investigated the specific propagation problems in dielectric medium for 16QAM and QPSK modulated signals. We found that QPSK technique is a better choice for propagation at large distances (over 200m) while for short distance transmissions, the 16QAM has some clear advantages.