We consider a cellular network, where the uplink transmissions to a base station (BS) are interferenced by other devices, a condition that may occur, e.g., in cell-free networks or when using non-orthogonal multiple access (NOMA) techniques. Assuming that the BS treats this interference as additional noise, we focus on the problem of estimating the interference correlation matrix from received signal samples. We consider a BS equipped with multiple antennas and operating in the millimeter-wave (mmWave) bands and propose techniques exploiting the fact that channels comprise only a few reflections at these frequencies. This yields a specific structure of the interference correlation matrix that can be decomposed into three matrices, two rectangular depending on the angle of arrival (AoA) of the interference and the third square with smaller dimensions. We resort to gridless approaches to estimate the AoAs and then project the least square estimate of the interference correlation matrix into a subspace with a smaller dimension, thus reducing the estimation error. Moreover, we derive two simplified estimators, still based on the gridless angle estimation that turns out to be convenient when estimating the interference over a larger number of samples.

翻译：我们考虑一个蜂窝网络，其中基站（BS）的上行传输受到其他设备的干扰，这种情况可能出现在无小区网络或使用非正交多址接入（NOMA）技术时。假设基站将这些干扰视为额外噪声，我们专注于从接收信号样本中估计干扰相关矩阵的问题。我们考虑配备多天线并在毫米波（mmWave）频段工作的基站，并提出利用这些频率下信道仅包含少量反射这一特性的技术。这导致干扰相关矩阵具有特定结构，可分解为三个矩阵：两个矩形矩阵取决于干扰的到达角（AoA），第三个方阵维度较小。我们采用无网格方法来估计到达角，然后将干扰相关矩阵的最小二乘估计投影到较低维度的子空间中，从而减少估计误差。此外，我们推导了两个简化估计器，它们仍基于无网格角度估计，在估计大量样本的干扰时更为便捷。