High-Altitude Platform (HAP) is a promising technique for providing wireless communications services with improved performance compared to terrestrial and satellite systems. A critical issue in this emerging system is the difficulty of providing user location information through two-dimensional direction-of-arrival (2D-DOA) estimation due to the high computational complexity and the large covered area. Therefore, in this paper, an efficient technique has been proposed to determine user location through 2D-DOA with a reduced processing time. The proposed technique estimates the 2D-DOA in two stages. In the first stage, a low-resolution 2D-DOA estimation technique will be utilized, such as Bartlett algorithm performed on a low-resolution distance grid, then a suitable threshold is applied on the normalized Bartlett 2D-DOA spectrum to define ground windows for the next high-resolution 2D-DOA stage. The second stage is carried out by a high-resolution technique such as MUSIC algorithm and will be performed on a high-resolution distance grid. Two scenarios are examined for the proposed technique to investigate the reduction in processing time compared with the conventional 2D-DOA MUSIC algorithm without windowing. Simulation results show that at 40 meters resolution, the required processing time is only 20% of the conventional MUSIC algorithm and can be further reduced to 4% at resolution of 100 meters at the same array size. In addition, the proposed technique can be applied to any other efficient low-complexity 2D-DOA algorithms.
2. Mohammed, A., S. Arnon, D. Grace, M. Mondin, and R. Muira, "Advanced communication techniques and applications for high altitude platforms," EURASIP International Journal of Communications and Networking, Vol. 2008, 934837, 2008.
3. Mohammed, A., A. Mehmood, F. N. Pavlidou, and M. Mohorcic, "The role of high-altitude platforms (HAPs) in the wireless global connectivity," Proceedings of the IEEE, Vol. 99, No. 11, 1939-1953, Nov. 2011.
4. Kim, J., D. Lee, J. Ahn, D. S. Ahn, and B. J. Ku, "Is HAPS viable for the next-generation telecommunication platforms in Koria," EURASIP International Journal of Communications and Networking, Vol. 2008, 596383, 2008, Doi: 1155/2008/596383.
5. Dessouky, M., H. Sharshar, and Y. Albagory, "Improving the cellular coverage from a high altitude platform by novel tapered beamforming technique," Journal of Electromagnetic Waves and Applications, Vol. 21, No. 13, 1721-1731, 2007.
6. Hofmann-Wellenhof, B., H. Lichtenegger, and J. Collins, Global Positioning System Theory and Practice, 2nd Edition, 1993, Print ISBN: 978-3-211-82477-1, Online ISBN: 978-3-7091-3293-7.
7. Krim, H. and M. Viberg, "Two decades of array signal processing research," IEEE Signal Processing Magazine, Vol. 13, No. 4, 67-94, Jul. 1996.
8. Harabi, F., A. Gharsallah, and S. Marcos, "Three-dimensional antennas array for the estimation of direction of arrival," IET Microwaves, Antennas & Propagation, Vol. 3, No. 5, 843-849, Aug. 2009.
9. Zhang, X., M. Zhou, H. Chen, and J. Li, "Two-dimensional DOA estimation for acoustic vectorsensor array using a successive MUSIC," Multidimensional Systems and Signal Processing, Vol. 25, No. 3, 583-600, Jul. 2014.
10. Agatonovic, M., Z. Stankovi´c, I. Milovanovi´c, N. Donˇcov, L. Sit, T. Zwick, and B. Milovanovic, "Efficient neural network approach for 2D DOA estimation based on antenna array measurements," Progress In Electromagnetics Research, Vol. 137, 741-758, 2013.
11. Diab, W. G. and H. M. Elkamchouchi, "A deterministic approach for 2D-DOA estimation based on a V-shaped array and a virtual array concept," IEEE 19th International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC 2008, 1-5, 2008.
12. Lee, J., I. Song, H. Kwona, and S. R. Lee, "Low-complexity estimation of 2D DOA for coherently distributed sources," Signal Processing, Vol. 83, No. 8, 1789-1802, Aug. 2003.
13. Schulz, D. and R. S. Thomae, "Search-based MUSIC techniques for 2D DOA estimation using EADF and real antenna arrays," WSA 2013 — 17th International ITG Workshop on Smart Antennas, 1-8, Stuttgart, Deutschland, 2013.
14. Raich, R., J. Goldberg, and H. Messer, "Bearing estimation for a distributed source via the conventional beamformer," Ninth IEEE SP Workshop on Statistical Signal and Array Processing, Proceedings, 5-8, Sep. 14-16, 1998.
15. Zhang, X., J. Li, and L. Xu, "Novel two-dimensional DOA estimation with L-shaped array," EURASIP Journal on Advances in Signal Processing, Vol. 2011, 50, Aug. 2011.