Spectral Efficiency Optimized Secure Broadcasting using Adaptive Modulation, Coding and Transmit Power

In this article there is presented a new method for spectral efficiency optimized transmission in a broadcast network, in which besides maximizing exploitation of network's resources there will be provided physical layer security for each user's data, i.e., transmission scenario is designed in a way that data of each user just is detected at the corresponding receiver with a proper error probability and error of detection at the unintended receivers is acceptably high. A bit error rate (BER) constraint for each user and an average power constraint for the transmitter are provisioned while a weighted sum of spectral efficiencies is maximized. In the proposed method there is used discrete rate adaptation through adaptive modulation and coding based on signal to noise ratio (SNR) of the links. Accurate and approximate solutions are presented to solve the optimization problem. The approximate solution besides having little difference with the accurate solution in the performance view has acceptable complexity. Numerical evaluation signifies that considering security constraint results in a little decrease in achievable rates, but in turn it helps to keep confidentiality of the information.