Angle-Threshold Random Beamforming Scheme for Multi-Antenna System

Codebook-based multiple input multiple output(MIMO) beamforming can significantly improve the system spectral efficiency with limited feedback and gets widely adopted.However,this scheme has a drawback of heavy feedback load that the sum feedback rate can be a bottleneck for the communication system,especially when the number of users is large.In this paper,a new scheme using pseudo-random beamforming vectors and angle based threshold in the feedback process is proposed.In the proposed scheme,both the base-station and the users have no need to store a codebook.In each access procedure,the base-station generates a pseudo-random beamforming vector,and each user calculates the angle between the beamforming vectors and its channel state information(CSI) vector.If the angle is less than a predefined angle-threshold,the user feeds back its channel quality indicators(CQI),otherwise it keep silence.Compared with the codebook based scheme,the proposed scheme can largely reduce the sum feedback rate with negligible throughput loss.In particular,when the system has a constraint on the total sum feedback rate in uplink channel,the proposed scheme can increase the system throughput significantly.

地图综合中曲线局部尖锐凸角的光滑方法

地图制图综合过程中,线状要素经过一系列的选取、化简等处理后,经常会生成少量尖锐的凸角。针对已有的算法在解决这个问题时大多对曲线上全部的节点进行整体光滑处理,在很多不必要光滑的地方增加了大量的冗余节点,且效率不高的问题,该文基于线性迭代法提出了一种曲线局部尖锐凸角的光滑方法。首先建立了基于角度阈值的尖锐凸角判断原则,然后据此设计了具有可控性的尖锐凸角自动识别处理方法,以探索最佳的角度阈值实现曲线光滑处理,最后以广州某市的地理国情普查水系数据为例对该文方法进行了检验。实验结果表明,当角度阈值在[150°,160°]范围内时,该文方法不仅消除了曲线局部尖锐的凸角,而且有较好的光滑效果和较高的处理效率。