Browsing by Author "Xia,Xiang-Gen"
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Item Beamforming Based Full-Duplex for Millimeter-Wave Communication(MDPI AG, 2016-07-21) Liu,Xiao; Xiao,Zhenyu; Bai,Lin; Choi,Jinho; Xia,Pengfei; Xia,Xiang-Gen; Xiao Liu, Zhenyu Xiao, Lin Bai, Jinho Choi, Pengfei Xia, Xiang-Gen Xia; Xia, Xiang-GenIn this paper, we study beamforming based full-duplex (FD) systems in millimeter-wave (mmWave) communications. A joint transmission and reception (Tx/Rx) beamforming problem is formulated to maximize the achievable rate by mitigating self-interference (SI). Since the optimal solution is difficult to find due to the non-convexity of the objective function, suboptimal schemes are proposed in this paper. A low-complexity algorithm, which iteratively maximizes signal power while suppressing SI, is proposed and its convergence is proven. Moreover, two closed-form solutions, which do not require iterations, are also derived under minimum-mean-square-error (MMSE), zero-forcing (ZF), and maximum-ratio transmission (MRT) criteria. Performance evaluations show that the proposed iterative scheme converges fast (within only two iterations on average) and approaches an upper-bound performance, while the two closed-form solutions also achieve appealing performances, although there are noticeable differences from the upper bound depending on channel conditions. Interestingly, these three schemes show different robustness against the geometry of Tx/Rx antenna arrays and channel estimation errors.Item Road-Aided Ground Slowly Moving Target 2D Motion Estimation for Single-Channel Synthetic Aperture Radar(MDPI Ag, 2016-01-31) Wang,Zhirui; Xu,Jia; Huang,Zuzhen; Zhang,Xudong; Xia,Xiang-Gen; Long,Teng; Bao,Qian; Zhirui Wang, Jia Xu, Zuzhen Huang , Xudong Zhang, Xiang-Gen Xia, Teng Long and Qian Bao; Xia, Xiang-GenTo detect and estimate ground slowly moving targets in airborne single-channel synthetic aperture radar (SAR), a road-aided ground moving target indication (GMTI) algorithm is proposed in this paper. First, the road area is extracted from a focused SAR image based on radar vision. Second, after stationary clutter suppression in the range-Doppler domain, a moving target is detected and located in the image domain via the watershed method. The target's position on the road as well as its radial velocity can be determined according to the target's offset distance and traffic rules. Furthermore, the target's azimuth velocity is estimated based on the road slope obtained via polynomial fitting. Compared with the traditional algorithms, the proposed method can effectively cope with slowly moving targets partly submerged in a stationary clutter spectrum. In addition, the proposed method can be easily extended to a multi-channel system to further improve the performance of clutter suppression and motion estimation. Finally, the results of numerical experiments are provided to demonstrate the effectiveness of the proposed algorithm.