Hybrid beamforming for single-user MIMO with partially connected RF architecture

Abstract

support only one-stream transmission and is not viable for multi-stream case [6]. To exploit the full potential of both spatial multiplexing and beamforming in a MIMO system, fully digital beamforming architecture is leveraged [7], [8]. Implementing a fully digital MIMO beamformer requires one radio frequency (RF) chain per antenna element. Due to the high number of power-hungry RF components, such as digital-to-analog converters (DACs), in conventional digital beamforming, the practical implementation of a massive MIMO system requires new approaches to be realized [2], [6]. As a solution, the combination of both digital and analog beamforming, using a limited number of RF chains, known as hybrid beamforming (HBF) has been considered.HBF splits the whole beamforming process into digital and analog parts, that enables multi-stream transmissions with a reduced complexity [6], [7]. Various HBF methods are proposed for fully and partially connected RF architectures in the literature [9]-[13], ranging from theoretical rate maximizing solutions to heuristic algorithms. In a fully connected HBF architecture, each RF chain is connected to all antennas [7], [10]. For a practical implementation of a mm-wave massive MIMO system, the fully connected structure may be too complex to be used due to very challenging and lossy RF signal division and combining processes. A more practical solution is to use partially connected RF architecture, in which each RF chain is connected only to a subset of the antenna array, called a sub-array [14], [15].Partially connected RF architecture itself can be divided into two categories, i.e., full-array-based and sub-array-based processing structures. In full-array-based processing, all data streams are conveyed to all sub-arrays. Thus, each stream is transmitted via its corresponding beam which is generated by using all sub-arrays and their antennas. This implies that full beamforming gain is potentially available. However, the directions of different beams are interdependent due to the partial connectivity. This sets restrictions to the beam generation and leads to suboptimal beam directions. In sub-array-based processing, each sub-array transmits only a single data stream. This leads to a more efficient and flexible beam design process. However, the beamforming gain is limited by the number of antennas per sub-array.Most of the HBF works in the literature use only phase shifting in the analog beamforming process [10]- [13]. However, employing analog amplitude control in addition to phase Abstract-Hybrid analog-digital beamforming has been recognized as a promising solution for a practical implementation of massive multiple-input multiple-output (MIMO) systems based on millimeter-wave technology. In this paper, three hybrid beamforming algorithms are proposed for single-user MIMO systems with partially connected radio frequency (RF) architecture, including a singular value decomposition (SVD) matching algorithm, an iterative orthogonalization algorithm, and a transmitreceive zero forcing (ZF...

A Kronecker-Based Sparse Compressive Sensing Matrix for Millimeter Wave Beam Alignment

“…We further assume that phase shifting as well as the amplitude control can be performed in the analog domain. This is a practically feasible assumption for mmWave systems as it has been shown in the literature [14] [15]. Assuming θ l ∈ [− π 2 , π 2 ] and φ l ∈ [− π 2 , π 2 ] respectively the AoD and AoA of the lth propagation path between the BS and UE, the array response vectors are given by…”

“…Since we intend to construct a deterministic sensing matrix for the sparse formulation (15), we should design deterministic BF codebooks for the BS and UE. As we showed earlier, each measurement is made based on the Kronecker product of the two vectors w .…”

Fully-/Partially-Connected Hybrid Beamforming Architectures for mmWave MU-MIMO

“…However, the signaling freedom is also drastically reduced and the corresponding optimization computational complexity is typically prohibitive for practical real-time implementations. These drawbacks motivate the exploration of an analog precoding architecture with both phase and amplitude controls [9,10]. In fact, it has been demonstrated in practice that simultaneous phase and amplitude control is fully feasible at mmWaves with good accuracy, low complexity, and low cost [11,12].…”

“…In this section, we resort to the 3D geometry based channel generator QuaDRiGa [30] to show that our numerical results are quite consistent with practical mmWave communication channels. 10 More precisely, we apply our BA and precoding schemes over ∼ 3 × 10 5 channel snapshots generated by QuaDRiGa. These channel snapshots correspond to a short segment of time evolution, where the BS is stationary and the speed of each UE along its moving direction is 1 m/s.…”

Rate Maximization for Partially Connected Hybrid Beamforming in Single-User MIMO Systems

“…The HBF process of partially connected architecture can be divided into full arrayand subarray-based processing strategies. In a full array-based processing design, all data streams are communicated to all subarrays while in a subarray-based processing strategy, each data stream is communicated to only one subarray [5]. The former approach can exploit all antennas for beamforming of each stream.…”