Enhancing the Security Performance of OSTBC Using Pre-Equalicodization

In this study, we first quantify the secrecy performance achieved by employing precoded orthogonal space time block coding (POSTBC) in order to use it as a benchmark for comparison purposes with a new proposed security scheme. In POSTBC, space time codewords are precoded before being transmitted with an optimum pre-coding matrix based on the main channel of the legitimate parties. The obtained results demonstrate a considerable secrecy gap region in the resulting bit error rate (BER) performance due to using POSTBC. Afterwards, a new method called pre-equlicodization (precoding along with semi pre-equalization) is proposed to further enhance the secrecy performance. In pre-equlicodization scheme, the transmitted symbols are precoded by a new modified matrix called pre-equalicodizing matrix. This matrix is built by manipulating each row element in the optimal selected precoding matrix by the corresponding amplitude square inverse of the estimated channel gain over each data stream. The comparative simulation results prove that the employment of the proposed method can provide robustness against eavesdropping while assuring confidentiality and reliability between the legitimate communication parties albeit Eve is considered to have full knowledge of the used method, but not the main channel since TDD is adopted.