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Massive MIMO plays an important role for future cellular networks since the large number of antenna elements is capable of increasing the spectral efficiency and the amount of usable spectrum. The 1-bit analog-to-digital converters can drastically reduce the resulting complexity and power consumption. Therefore, we investigate the Direction of Arrival (DoA) estimation using 1-bit measurements of many antenna elements in this paper. We extend Binary Iterative Hard Thresholding (BIHT), an efficient sparse recovery algorithm from the area of Compressed Sensing (CS) that takes the 1-bit quantization explicitly into account, to complex-valued signals and multiple measurement vectors such that it is applicable to 1-bit DoA estimation with multiple snapshots. The comparison of the resulting Complex-valued BIHT (CBIHT) algorithm to subspace-and CSbased methods in terms of both DoA estimation performance and computational complexity demonstrates that CBIHT is well suited for scenarios with many antenna elements and a few snapshots.

Millimeter-wave (mmWave) communications plays an important role for future cellular networks because of the vast amount of spectrum available in the underutilized mmWave frequency bands. To overcome the huge free space omnidirectional path loss in those frequency bands, the deployment of a very large number of antenna elements at the base station is crucial. The complexity, power consumption and costs resulting from the large number of antenna elements can be reduced by limiting the number of RF chains. This leads to hybrid precoding and combining, which, in contrast to the traditional fully digital precoding and combining, moves a part of the signal processing from the digital to the analog domain. This paper proposes new algorithms for the design of hybrid precoders and combiners in a multiuser scenario. The algorithms are based on the previously proposed Linear Successive Allocation method developed for the traditional fully digital version. It successively allocates data streams to users and suppresses the respective interstream interference in two stages, which perfectly matches the hybrid architecture. Furthermore, a low-complexity version is developed by exploiting the typical structure of mmWave channels. The good performance of the proposed method and its low-complexity version is demonstrated by simulation results. Index TermsMultiuser communications, mmWave communications, hybrid precoding, linear successive allocation method, structured mmWave channels.The authors are with Methods of Signal Processing,

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