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Mathematical Problems in Engineering
Volume 2013, Article ID 686403, 7 pages
Research Article

Securing Communication via Transmission of Artificial Noise by Both Sides: Bipolar-Beamforming Optimization

1Department of Electronic Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
2Department of Electronic Engineering, Ohio State University, Columbus, OH 43210, USA

Received 30 August 2013; Accepted 8 November 2013

Academic Editor: Hao Shen

Copyright © 2013 Yongkai Zhou et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The paper considers the secure transmission in a wireless environment in which both the transmitter (Alice) and the legitimate receiver (Bob) send artificial noise (AN) to interfere with the eavesdropper (Eve). Optimal design is analyzed in detail for this AN-by-both-side model to deal with Eve’s stochastic channel condition and random spatial distribution. Bipolar-beamforming is first proposed to jointly design Alice and Bob’s transmitting signals. By optimally assigning the transmitting antenna for Bob and allocating the power ratio between Alice’s information and the AN signal, maximum secrecy capacity can be achieved. Simulation is done to illustrate the process of bipolar-beamforming optimization. Results show that the AN-by-both-side model has good secrecy performance on both average and extreme conditions as Eve approaches Alice or Bob.