Angle of Arrival (AoA) estimation with localized hybrid arrays is challenging in millimeter-wave (mmWave) communication systems. Most existing solutions quantize AoAs into limited values with relatively low accuracy. This paper presents a multi-AoA estimation scheme which is capable of estimating multiple AoAs from multiple users with low complexity. Specifically, we design a path filter via combining the received signals for each subarray. Each path filter enables a certain range of AoAs to pass through while suppressing the rest. Then we can use low-complexity cross-correlation operations to obtain continuous AoA estimates. Association of paths to users is further achieved by a follow-up pseudo-random codes based correlation operation. The scheme is first presented for a narrowband system and then extended to wideband with frequency selectivity. We also introduce new metrics and derive the lower bound of mean square error for evaluating the accuracy of AoA estimates, as conventional metrics face difficulties in the presence of multiple closely located AoAs. Extensive simulation results are provided and validate the effectiveness of the proposed multi-AoA estimation scheme.

中文翻译：

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用局部混合子阵列估计毫米波系统的多个到达角

在毫米波 (mmWave) 通信系统中，使用局部混合阵列进行到达角 (AoA) 估计具有挑战性。大多数现有解决方案以相对较低的精度将 AoA 量化为有限的值。本文提出了一种多 AoA 估计方案，该方案能够以低复杂度估计来自多个用户的多个 AoA。具体来说，我们通过组合每个子阵列的接收信号来设计路径滤波器。每个路径滤波器都允许一定范围的 AoA 通过，同时抑制其余的 AoA。然后我们可以使用低复杂度的互相关操作来获得连续的 AoA 估计。通过后续基于伪随机码的相关操作进一步实现路径与用户的关联。该方案首先针对窄带系统提出，然后扩展到具有频率选择性的宽带系统。我们还引入了新的指标并推导出均方误差的下限来评估 AoA 估计的准确性，因为传统指标在存在多个紧密定位的 AoA 时面临困难。提供了广泛的模拟结果，并验证了所提出的多 AoA 估计方案的有效性。