In this paper we investigate the design of compressive antenna arrays for direction of arrival (DOA) estimation that aim to provide a larger aperture with a reduced hardware complexity by a linear combination of the antenna outputs to a lower number of receiver channels. We present a basic receiver architecture of such a compressive array and introduce a generic system model that includes different options for the hardware implementation. We then discuss the design of the analog combining network that performs the receiver channel reduction, and propose two design approaches. The first approach is based on the spatial correlation function which is a low-complexity scheme that in certain cases admits a closed-form solution. The second approach is based on minimizing the Cramér-Rao Bound (CRB) with the constraint to limit the probability of false detection of paths to a pre-specified level. Our numerical simulations demonstrate the superiority of the proposed optimized compressive arrays compared to the sparse arrays of the same complexity and to compressive arrays with randomly chosen combining kernels.

Abstract-This work evaluates interference mitigation mechanisms to enable the operation of self-organizing hybrid terrestrial-satellite networks with aggressive frequency reuse between terrestrial and also satellite links. The objective is to take advantage of the improved capacity and resilience to congestion of such networks while assuring and efficient use of the spectrum. In particular, single-and multi-user hybrid analog-digital beamforming (HADB) techniques are considered as well as hybrid carrier allocation. The simulation results show network spectral efficiency improvements, with respect to conventional terrestrial backhaul systems, up to 2x when applying carrier allocation, and between 3.5x to 9x applying HADB in different environments.

This paper focuses on the design of linear baseband precoding and combining techniques for millimeter wave (mmWave) multiple input multiple output (MIMO) backhaul networks. We consider a scenario known as MIMO multi-X channel with L transmitter base stations and K receiver base stations, each equipped with multiple antennas, where each transmitter base station communicates simultaneously with all receiver base stations. The extremely short wavelength of mmWave requires the use of large antenna arrays at the base stations (BS) to combat the high path loss to achieve sufficiently high link gains, enabled by directional beamforming. As signal processing with large antenna arrays lead to implementations that are associated with high power consumption and high hardware complexity, hybrid (analog/digital) precoding/combining has been proposed recently to overcome these limitations. The design of such hybrid precoders/combiners is typically performed separately for the analog and the digital domains. In this work, we propose several novel low-complexity schemes suited for the digital part of such hybrid precoders/combiners. Our solutions are based on block-diagonalization and minimum mean squared error (MMSE) techniques and assume the availability of partial knowledge of CSI at each BS in the network. Finally the simulation results demonstrate the potential gains of the proposed algorithms

This paper considers the design of precoding and decoding techniques for backhaul networks at Ka band. In this frequency band, large antenna arrays must be employed with appropriate beamforming and precoding techniques to combat the high path loss. Traditional multi-antenna systems use digital baseband beamforming and precoding that is not economical for large antenna arrays due to its cost and power consumption. Recently, hybrid analog-digital solutions were suggested for millimeter wave multiple-input-multiple-output systems. They rely on two steps. The first step consists of an analog only beamforming which aims at the exploitation of the high antenna gain offered by the large-scale antenna array. The second step mitigates the multiuser interference by means of digital precoding. In this paper, we focus on the second step of the hybrid precoding. We propose a solution for interference mitigation in multi-base station scenarios. Our solution is based on a block diagonalization technique and requires full channel state information at each base station of a backhaul network. The performance of the algorithm is compared to a partial block diagonalization which was originally proposed for the single base station downlink scenario

This paper focuses on the optimization of uniform circular antenna array (UCA) structures equipped with analog combining networks for direction finding applications. For such type of arrays, the specific choice of the combining matrix has a crucial impact on the effective radiation pattern and the sensitivity of direction-of-arrival (DOA) estimation. A design framework for constructing the combining network is proposed that improves the DOA estimation performance of the array while limiting the probability of false detection of the DOA estimator to a desired value. In detail, we first derive an analytical expression for the false detection probability of the DOA estimator. This function together with the Cramer-Rao bound are then used to find the optimal combining matrix and array aperture size for a given number of sensor elements and combiner output (baseband) channels. We provide design examples to demonstrate the effectiveness of our approach