In a massive multi-input multi-output (MIMO) cellular communication system, the conventional beam-sweeping scheme for common message broadcasting provides high beamforming gain but requires too many time slots due to the narrowness of the beams. To reduce the beam sweeping time while maintaining a sufficient beamforming gain, this paper focuses on designing broad beams with tunable beamwidths. First, by over-sampling a step-chirp analog signal, we construct a novel sequence family termed the generalized step-chirp (GSC) sequence with a simple closed-form expression, in which some parameters can be tuned to flexibly adjust the beamwidth and coarsen the phase resolution. The beamforming matrix of a uniform rectangular array (URA) of single–polarized antennas can be taken as the outer product of two GSC sequences. Second, by exploiting the full degree of freedom of URA of dual-polarized antennas, we further reduce the power variations in the passband by using a numerical algorithm. The algorithm can be drastically accelerated by exploiting the specific structure of the problem. Both schemes can be implemented using an analog phase shifter network (PSN) with finite resolution.

中文翻译：

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广播频道的宽波束设计


在大规模多输入多输出（MIMO）蜂窝通信系统中，用于公共消息广播的传统波束扫描方案提供了高波束成形增益，但由于波束较窄而需要太多时隙。为了减少波束扫描时间，同时保持足够的波束形成增益，本文重点设计具有可调谐波束宽度的宽波束。首先，通过对步进线性调频模拟信号进行过采样，我们构建了一个新颖的序列族，称为广义步进线性调频（GSC）序列，具有简单的封闭式表达式，其中可以调整一些参数以灵活调整波束宽度和粗化相位分辨率。单极化天线均匀矩形阵列（URA）的波束形成矩阵可以视为两个 GSC 序列的外积。其次，通过利用双极化天线URA的完全自由度，我们使用数值算法进一步减少了通带中的功率变化。通过利用问题的特定结构可以大大加速该算法。这两种方案都可以使用具有有限分辨率的模拟移相器网络（PSN）来实现。