Covert Channel Based on Quasi-Orthogonal Coding

The paper presents a method of creating hidden channel using signals’ superposition. According to this idea, transmitter simultaneously sends overt and covert (secret) signals, whereby the signal is carrier for one. Due need ensure low probability detection communication, should have power. This implies number problems relating its correct reception. similar non-orthogonal multiple access (NOMA) systems, where collective superposition signals with different powers dedicated users. In case, successive interference cancellation (SIC) process used in receiver separation component signals. SIC requires accurate estimation. Even small estimation error causes significant increase bit rate (BER), performance degradation, or connection loss transmission. due residual signal, i.e., remnant cover after an imperfect operation. proposes transforming (i.e., encoding) applied such way that quasi-orthogonal signal. proposed model based on appropriate sorting and, compared methods fixed constellation points, provides BER while maintaining high protection against as measured by Kolmogorov–Smirnov distance. solution was tested USRP-2920 software-defined radio platform.