Using Antenna Array Redundancy and Channel Diversity for Secure Wireless Transmissions

The use of signal processing techniques to protect wireless transmissions is proposed as a way to secure wireless networks at the physical layer. This approach addresses a unique weakness of wireless networks whereby network traffic traverses a public wireless medium making traditional boundary controls ineffective. Specifically, a randomized array transmission scheme is developed to guarantee wireless transmissions with inherent low-probabilityof-interception (LPI). In contrast to conventional spread spectrum or data encryption techniques, this new method exploits the redundancy of transmit antenna arrays for deliberate signal randomization which, when combined with channel diversity, effectively randomizes the eavesdropper’s signals but not the authorized receiver’s signals. The LPI of this transmission scheme is analyzed via proving the indeterminacy of the eavesdropper’s blind deconvolution. Extensive simulations and some preliminary experiments are conducted to demonstrate its effectiveness. The proposed method is useful for securing wireless transmissions, or for supporting upper-layer key management protocols.