Abstract
High-altitude platform (HAP) is promising for providing efficient wireless communications services. One of the critical issues in HAP communications is the difficulty to localize users 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 is proposed to determine user location through 2D-DOA with a reduced processing time. The proposed technique estimates the 2D-DOA in two successive stages; the first will utilize a low-resolution 2D-DOA estimation technique such as Bartlett algorithm performed on a low-resolution distance, then applying a suitable threshold on the normalized Bartlett 2D-DOA spectrum to define ground windows over which the next high-resolution 2D-DOA stage will be performed such as MUSIC algorithm. Two scenarios are examined for the proposed technique to investigate the reduction in calculations time compared to the conventional 2D-DOA MUSIC algorithm without windowing. Simulation results show that at a resolution of 40 m, the required processing time is reduced to 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 is flexible and can be applied for any other efficient low-complexity 2D-DOA algorithms.