Abstract
Information transmission in wireless communication systems is traditionally protected by cryptographic techniques at the higher layers. Recently, a method of physical layer security has attracted much attention because it can potentially provide lower probability of interception of the signals at the eavesdroppers and hence augment the link security in addition to the conventional encryptions. In this paper, we propose a novel approach to securing transmit-beamforming systems by using uniquely designed jamming noise signal, which can significantly degrade the signal quality at the eavesdropper but not at the intended receiver. The jamming noise signal is generated from the null space of the channel matrix. An eigenvector-based implementation of this theoretical method is also provided. Unlike previous physical layer security methods, the proposed approach can provide secure communications over systems with arbitrary antenna configurations. Our proposed method offers more degrees of freedom to generate the jamming noise signal, resulting in the eavesdropper being unable to decode the information signals. Moreover, the eavesdropper cannot influence the system secrecy capacity by employing more antennas or by moving close to the transmitter. Simulation results show that the secrecy capacity increases significantly, by about 7?bits/s/Hz for a 4?x?4 antenna configuration, under typical transmit power constraints. Copyright (c) 2011 John Wiley & Sons, Ltd.