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构思了一种智能超表面(Reconfigurable Intelligent Surface, RIS)辅助去蜂窝大规模多输入多输出(Cell-free Massive Multiple-Input Multiple-Output, CF mMIMO)通信系统,提出了一种低复杂度预编码和RIS反射相位交替优化(Alternating Optimization, AO)算法。对于传统正则化迫零(Regularized Zero Forcing, RZF)预编码算法复杂度过高的问题,利用共轭梯度(Conjugate Gradients, CG)法,提出一种低复杂度的RZF-CG预编码算法,将RZF预编码的逆矩阵转换为线性方程组最小化问题,推导算法的残差以更新搜索方向,迭代求解逆矩阵。以最大化系统用户的总频谱效率为目标,推导了RIS相位闭合表达式,基于统计的信道状态信息提出一种低复杂度的投影梯度上升(Projected Gradient Ascent, PGA)算法。仿真结果表明,所提的AO算法能有效地提升系统性能,算法复杂度降低了约73.2%。 相似文献
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虽然智能反射表面(IRS)单元可以通过改变相移和反射系数来增强系统性能,但是用户运动和时延等未知因素使反射波束无法准确覆盖用户。为此,提出一种面向移动用户的波束追踪与覆盖增强算法。首先,根据用户的初始位置、运动方向和速度等信息,估算IRS的目标覆盖区域;然后,对IRS单元进行分组,并设计不同分组单元的反射相移使反射波束指向目标区域的相邻位置,进而实现对用户可能位置的有效覆盖;最后,采用注水算法分配由基站(gNB)发射在IRS不同分组单元上的波束功率,实现对目标区域覆盖的增强。 相似文献
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A new analytical expression is presented for the instantaneous power Probability Density Function (PDF) of receiver signals over composite κ-μ/gamma fading channels. Moreover, the exact expression of channel capacity is derived in the form of an infinite series, while an accurate approximation expression is obtained in closed form. To reveal the implications of the model parameters on capacity, we provide an expression for the case of a high-SNR environment. The relationship of the presented results with previously reported results on generalised-K and K fading chan-nels is also discussed. Finally, numerical and simulation results are presented to prove the correctness of our derived expressions. 相似文献
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