Jinsong Hu

Robust Synthesis Method for Secure Directional Modulation With Imperfect Direction Angle

Directional modulation (DM) is a secure transmission technology that is able to retain the original constellation of transmitted signals along the desired direction, while distort the constellation in the undesired directions at the same time. In this letter, we develop novel and robust DM synthesis methods for enhancing the transmission performance. Specifically, we first propose a low-complexity dynamic DM synthesis method. In this method, we derive a closed-form expression for the null space of conjugate transpose of the steering vector in the desired direction. Based on the expression derived, we construct a projection matrix in order to form artificial noises to those undesired directions. Then, we focus our attention on more practical scenarios, where there is uncertainty in the estimated direction angle. This uncertainty will cause estimation errors and seriously jeopardize the receiving performance in the desired direction. To mitigate the uncertainty effect, we further propose a robust DM synthesis method based on conditional minimum mean square error. The proposed method aims to minimize the distortion of the constellation points along the desired direction. Simulation results show that our proposed robust DM method is capable of substantially improving the bit error rate performance compared with the state-of-the-art methods.

Secure precise transmission with multi-relay-aided directional modulation

In the conventional directional modulation (DM) system without relay aiding, when the eavesdropper locates within the main-beam of the desired direction, it can intercept the confidential message from source Alice. In this paper, we propose a strategy to enhance physical-layer security of direction modulation in wireless transmission with the help of multi-relay cooperation. In this scenario, the confidential messages are forwarded to the desired destination receiver, and the artificial noise (AN) is enforced to the eavesdroppers with the aid of multi-relays and direction modulation such that the eavesdropper can not successfully recover the useful information from its received signals. The simulation results show that the proposed method achieves a significantly higher signal-to-interference-plus-noise ratio (SINR) peak at the destination position than at other positions outside the main-beam of the desired position and its secrecy rate performance at undesired position is so poor that the secure transmission is guaranteed.

Spatial channel pairing based coherent combining for relay networks

In this paper, spatial channel pairing (SCP) is introduced to coherent combining at the relay in relay networks. Closed-form solution to optimal coherent combining is derived. Given coherent combining, the approximate SCP solution is presented. Finally, an alternating iterative structure is developed. Simulation results and analysis show that, given the symbol error rate and data rate, the proposed alternating iterative structure achieves signal-to-noise ratio gains over existing schemes in maximum ratio combining (MRC) plus matched filter, MRC plus antenna selection, and distributed space-time block coding due to the use of SCP and iterative structure.