Abstract—The use of signal processing techniques to protectwireless transmissions is proposed as a way to securewireless networks at the physical layer. This approachaddresses a unique weakness of wireless networks wherebynetwork traffic traverses a public wireless medium makingtraditional boundary controls ineffective. Specifically, arandomized array transmission scheme is developed to guaranteewireless transmissions with inherent low-probabilityof-interception (LPI). In contrast to conventional spreadspectrum or data encryption techniques, this new methodexploits the redundancy of transmit antenna arrays fordeliberate signal randomization which, when combined withchannel diversity, effectively randomizes the eavesdropper’ssignals but not the authorized receiver’s signals. The LPIof this transmission scheme is analyzed via proving theindeterminacy of the eavesdropper’s blind deconvolution.Extensive simulations and some preliminary experiments areconducted to demonstrate its effectiveness. The proposedmethod is useful for securing wireless transmissions, or forsupporting upper-layer key management protocols.

Index Terms—antenna array, transmit beamforming, diversity,channel, wireless information assurance

Cite: Xiaohua Li, Juite Hwu, and E. Paul Ratazzi, "Using Antenna Array Redundancy and Channel Diversity for Secure Wireless Transmissions," Journal of Communications, vol. 2, no. 3, pp. 24-32, 2007.