ISSN : 1796-2021
Volume : 2    Issue : 3    Date : May 2007

Using Antenna Array Redundancy and Channel Diversity for Secure Wireless Transmissions
Xiaohua Li, Juite Hwu, and E. Paul Ratazzi
Page(s): 24-32
Full Text:
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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.

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