Enhancing spectral efficiency of Transform Domain Communication Systems by using a multidimensional modulation

Transform Domain Communication System (TDCS) is a Cognitive Radio technology that has been thoroughly studied by the Air Force Institute of Technology because of its resiliency against jammers or interferences while being noise-like. However TDCS' huge disadvantage is its low spectral efficiency. In this article, we propose the use of a dense multidimensional modulation to counteract this property. We develop the theoretical Bit Error Rate (BER) performance and show that the theory matches well the simulation. We point out that this modulation can compete with QPSK systems in terms of spectral efficiency while keeping TDCS' intrinsic assets.