The broadcast nature of the wireless medium makes the communication over this medium vulnerable to eavesdropping. In this paper, we propose a directional sensitive modulation signal transmitted by Monopulse Cassegrain antenna for physical (PHY) layer security transmission. The main idea is that the sum beam transmit communication signal, simultaneously, and two difference beams transmit artificial noise to guarantee secure transmission of the sum beam. The eavesdropper's channel is degraded by artificial noise, but the desired receiver's channel does not affect because of the spatial orthogonality between the sum beam and two difference beams. In this way, the desired receiver can demodulate the communication signal while the eavesdroppers learn almost nothing about the information from its observations. A closed-form expression of the secrecy capacity is also derived for this practical transmit scheme from the viewpoint of information theoretic. Finally, simulation results show that the proposed signal can significantly improve the performance of secure wireless communications.
2. Oliveri , G. and L. Poli, "Synthesis of monopulse sub-arrayed linear and planar array antennas with optimized sidelobes," Progress In Electromagnetics Research, Vol. 99, 109-129, 2009.
3. Aziz, A., Q. A. Naqvi, and K. Hongo, "Analysis of the fields in two dimensional cassegrain system," Progress In Electromagnetics Research, Vol. 71, 227-241, 2007.
4. Ghaffar, A., Q. A. Naqvi, K. Hongo, "Analysis of the fields in three dimensional cassegrain system," Progress In Electromagnetics Research, Vol. 72, 215-240, 2007.
5. Rocca, , P., , L. Manica, and A. Massa, "Directivity optimization in planar sub-arrayed monopulse antenna," Progress In Electromagnetics Research Letters, Vol. 4, 1-7, 2008.
6. Pal, S., S. Das, A. Basak, and P. N. Suganthan, "Synthesis of difference patterns for monopulse antennas with optimal combination of array-size and number of subarrays --- A multi-objective optimization approach," Progress In Electromagnetics Research B, Vol. 21, 257-280, 2010.
7. Debbah, M. , H. El-Gamal, H. V. Poor, and S. Shamai, "Editorial: Wireless physical layer security," Eurasip Journal on Wireless Communications and Networking, Vol. 2009, 2009.
8. Khisti, A. and G. W. Wornell, "Secure transmission with multiple antennas I: The MISOME wiretap channel," IEEE Transactions on Information Theory, Vol. 56, No. 7, 3088-3104, 2010.
9. Khisti, A. and G. W. Wornell, "Secure transmission with multiple antennas --- Part II: The MIMOME wiretap channel," IEEE Transactions on Information Theory, Vol. 56, No. 11, 5515-5532, 2010.
10. Hero, A. O. and III, "Secure space-time communication," IEEE Transactions on Information Theory, Vol. 49, No. 12, 3235-3249, 2003.
11. Hyungjin, K. and J. D. Villasenor, "Secure MIMO communications in a system with equal numbers of transmit and receive antennas," IEEE Communications Letters, Vol. 12, No. 5, 386-388, 2008.
12. Csiszar, I. and J. Korner, "Broadcast channels with confidential messages," IEEE Transactions on Information Theory, Vol. 24, No. 3, 339-348, 2003.
13. Krikidis, I., J. Thompson, and S. Mclaughlin, "Relay selection for secure cooperative networks with jamming," IEEE Transactions on Wireless Communications, Vol. 8, No. 10, 5003-5011, 2009.
14. Lun, D. , H. Zhu, A. P. Petropulu, and H. V. Poor, "Improving wireless physical layer security via cooperating relays," IEEE Transactions on Signal Processing, Vol. 58, No. 3, 1875-1888, 2010.
15. Simeone, O. and P. Popovski, "Secure communications via cooperating base stations," IEEE Communications Letters, Vol. 12, No. 3, 188-190, 2008.
16. Goel, S. and R. Negi, "Guaranteeing secrecy using artificial noise IEEE Transactions on Wireless Communications,", Vol. 7, No. 6, 2180-2189, 2008.
17. Zhu, J., J. Mo, and M. Tao, "Cooperative secret communication with artificial noise in symmetric interference channel," IEEE Communications Letters, Vol. 14, No. 10, 885-887, 2010.
18. Li, Z. and X.-G. Xia, "A distributed differentially encoded OFDM scheme for asynchronous cooperative systems with low probability of interception," IEEE Transactions on Wireless Communications, Vol. 8, No. 7, 3372-3379, 2009.
19. Ma, R., L. Dai, Z. Wang, and J. Wang, "Secure communication in TDS-OFDM system using constellation rotation and noise insertion," IEEE Transactions on Consumer Electronics, Vol. 56, No. 3, 1328-1332, 2010.
20. Dai, H. and Y. Zhang, "A real orthogonal space-time coded uwb scheme for wireless secure communications," Eurasip Journal on Wireless Communications and Networking, Vol. 2009, 2009.
21. Li, , X.-H. and J. Hwu, "Using antenna array redundancy and channel diversity for secure wireless transmissions," Journal of Communications, Vol. 2, No. 3, 24-32, 2007.
22. Song, M.-Z. and T. Hong, "Sum and difference multiple beam modulation transmitted by multimode horn antenna for inverse monopulse direction-finding," Progress In Electromagnetics Research, Vol. 82, 367-380, 2008.
23. Song, M. Z. and T. Hong, "Microwave space modulation carrying azimuth and elevation transmitted by monopulse antenna," Journal of Electromagnetic Waves and Applications, Vol. 22, No. 2-3, 277-289, 2008.
24. Daly, M. P., E. L. Daly, and J. T. Bernhard, "Demonstration of directional modulation using a phased array," IEEE Transactions on Antennas and Propagation, Vol. 58, No. 5, 1545-1550, 2010.
25. Daly, M. P. and J. T. Bernhard, "Directional modulation technique for phased arrays," IEEE Transactions on Antennas and Propagation, Vol. 57, No. 9, 2633-2640, 2009.
26. Daly, M. P. and J. T. Bernhard, "Beamsteering in pattern reconfigurable arrays using directional modulation," IEEE Transactions on Antennas and Propagation, Vol. 58, No. 7, 2259-2265, 2010.
27. Babakhani, A., D. B. Rutledge, and A. Hajimiri, "Transmitter architectures based on near-field direct antenna modulation," IEEE Journal of Solid-State Circuits, Vol. 43, No. 12, 2674-2692, 2008.
28. Aziz, A. , Q. A. Naqvi, and K. Hongo, "Analysis of the fields in two dimensional cassegrain system," Progress In Electromagnetics Research, Vol. 71, 227-241, 2007.
29. Mehmood, M. Q., M. J. Mughal, and T. Rahim, "Focal region fields of cassegrain system placed in homogeneous chiral medium," Progress In Electromagnetics Research B, Vol. 21, 329-346, 2010.
30. Yin, J., J. A. Aas, J. Yang, and P. S. Kildal, "Monopulse tracking performance of multi-port eleven antenna for use in satellite communications terminals," IET Seminar Digest, Vol. 2007, 11961, 2007.
31. Ling, C. C. and G. M. Rebeiz, "94 GHz planar monopulse tracking receiver," IEEE Transactions on Microwave Theory and Techniques, Vol. 42, No. 10, 1863-1871, 1994.