An Efficient Low-Complexity Method to Calculate Hybrid Beamforming Matrices for mmWave Massive MIMO Systems

Hybrid analog and digital beamforming is a promising technique for large-scale MIMO systems since it can achieve a performance close to the performance of the conventional fully-digital beamforming schemes, but with much lower hardware implementation complexity and power consumption. One of the major challenges in hybrid beamforming is to design the hybrid beamformers for broadband systems with frequency-selective channels. This is because in broadband systems, it is desirable to design the same analog beamformers for the entire band while adapting digital beamformers in each frequency tone. In this paper, we consider the hybrid beamforming design for large-scale MIMO systems with orthogonal frequency division multiplexing (OFDM) modulation. Specifically, we propose a unified heuristic design for two different hybrid beamforming structures, the fully-connected and partially-connected structures, to maximize the overall spectral efficiency of a broadband system. Numerical results show that the proposed algorithm outperforms the existing hybrid beamforming designs and further the proposed algorithm for the fully-connected structure can achieve spectral efficiency close to that of the optimal fully-digital solution with much less number of RF chains.

SummaryThe advanced wireless communication system requires abridged energy consumption, enhanced data rate, and good signal coverage. The massive MIMO technology for 5G systems has been developed to accommodate several users simultaneously with superior throughput. The claim for high data rate wireless communication services is expanding quickly as time goes. Thus, the key difficulty is that as the number of users grows, the number of phase shifters grows as well, causing the system to consume more power; as a result, the system's energy efficiency decreases. Hybrid beamforming has recently emerged as an attractive technique for millimeter‐wave (mmWave) communication systems. The analog beamformer in the RF domain and digital beamformer in the baseband are coupled through a minimal number of RF chains in hybrid beamforming architecture. Hybrid beamforming utilizes fewer RF (radio frequency) chains than the total number of antennas to have a lower energy consumption design. The hybrid beamforming for a mmWave‐based massive MIMO system through different phase shifter selection mechanisms is proposed to achieve the highest energy efficiency for mmWave communications systems. The fully connected with phase shifter selection, sub‐connected with phase shifter selection (SPSS), and fully connected and sub‐connected with phase shifter selection with halved and doubled switches are considered for this research. The simulation results show the SPSS with halved switch outperforms on energy efficiency.

With the growth of the scale of antenna arrays, the full digital beamformer, which requires one dedicated radio frequency (RF) chain per antenna element, is costly and of power consumption. The hybrid beamformer, which offloads part of the beamformer to the analog domain via phase shifters, is an alternative to the full digital beamformer for large-scale antenna arrays. The whole hybrid beamformer is equivalent to the product of a reduced digital beamformer and an analog beamformer. Whereas, the analog beamformer subjects to a constant modulus constraint, because the phase shifters can only control the phase of signals. Due to the non-convex constant modulus constraint, the global optimal hybrid beamformer is infeasible. Therefore, a novel alternating iterative hybrid beamforming algorithm is proposed in this paper. The algorithm divided the analog beamforming matrix and digital beamforming matrix into column blocks and row blocks respectively, only one column of the analog beamforming matrix and one row of the digital beamforming matrix are updated in each processing cycle. The optimal column of the analog beamforming matrix is obtained by the partial derivative of the phase angle of the entries of the analog beamforming matrix, and the corresponding row of the reduced digital beamforming matrix is computed by the least square method. All of the columns of the analog beamforming matrix and rows of the digital beamforming matrix are updated one by one, meanwhile, the residual error of the hybrid beamformer is reduced gradually. Simulation results show that the proposed approach achieves higher achievable data rate compared with the previous works.

In multiuser millimeter wave (mmWave) massive MIMO systems, hybrid beamforming (HBF) is widely applied to save power and cut down on hardware costs. Hybrid beam- forming can be divided into two stages: analog beamforming in the RF domain usually implemented with phase shifters and digital beamforming in the baseband domain. Constrained by cost, volume and production process, imperfect phase shifters have phase-shifting error and gain error. In this paper, we study the influence of phase-shifting error and gain error upon the performance of the multiuser mmWave massive MIMO systems. We derive the lower bound of the rate loss, which is tight with the large antenna arrays. Both the theoretical results and simulation results show that there is an achievable sum rate ceiling due to phase-shifting error and gain error. The analytic procedure can be applied to many HBF algorithms.

This paper designs a novel hybrid (a mixture of analog and digital) beamforming and examines the relation between the hybrid and digital beamformings for downlink multiuser massive multiple input multiple output (MIMO) systems. We assume that perfect channel state information is available only at the transmitter and we consider the total sum rate maximization problem. For this problem, the hybrid beamforming is designed indirectly by considering a weighed sum mean square error (WSMSE) minimization problem incorporating the solution of digital beamforming which is obtained from the block diagonalization technique. The resulting WSMSE problem is solved by applying the theory of compressed sensing. The relation between the hybrid and digital beamformings is studied numerically by varying different parameters, such as the number of radio frequency (RF) chains, analog to digital converters (ADCs) and multiplexed symbols. Computer simulations reveal that for the given number of RF chains and ADCs, the performance gap between digital and hybrid beamformings can be decreased by decreasing the number of multiplexed symbols. Moreover, for the given number of multiplexed symbols, increasing the number of RF chains and ADCs will increase the total sum rate of the hybrid beamforming which is expected.

Millimeter wave communications (mmWave) has been considered a key enabling technique for 5G systems since it offers orders of magnitude more spectrum than current frequency bands. Unlike conventional multiple input multiple output (MIMO) networks, beamforming in millimeter-wave systems cannot be accomplished using digital techniques since only a limited number of analog-to-digital converters and mixers can be handled due to their cost and power consumption. Recently, there has been a lot of interest in a hybrid beamforming transceiver design, which includes an analog and digital beamformer, as a less expensive alternative. However, the optimal design for these hybrid beamformers has not yet been fully established. In order to approach the complex performance of the fully digital beamformer, this work will provide efficient alternative minimization techniques for a hybrid beamforming structure, namely the manifold-based geometric fully-connected antennas. According to simulation data on bandwidth efficiency, the proposed iterative algorithm performs much better than the baseline hybrid beamforming approach, namely the MMSE-MP algorithm (about 6.8% for a particular situation). Additionally, based on the recommended techniques, comparing the simulation results of the two hybrid beamforming structures will yield vital design information.

Fully-dynamic and hardware-efficient analog architecture for terahertz wideband hybrid beamforming with multi-channel low-resolution phase shifters

Reconfigurable intelligent surface (RIS)-assisted millimeter-wave (mmWave) communication systems relying on hybrid beamforming structures are capable of achieving high spectral efficiency at a low hardware complexity and low power consumption. In this article, we propose an RIS-assisted mmWave point-to-point system relying on dynamically configured subarray connected hybrid beamforming structures. More explicitly, an energy-efficient analog beamformer relying on the twin-resolution phase shifters is proposed. Then, we conceive a successive interference cancelation (SIC)-based method for jointly designing the hybrid beamforming matrix of the base station (BS) and the passive beamforming matrix of the RIS. Specifically, the associated bandwidth-efficiency maximization problem is transformed into a series of subproblems, where the subarray of phase shifters and RIS elements is jointly optimized for maximizing each subarray’s rate. Furthermore, a greedy method is proposed for determining the phase shifter configuration of each subarray. We then propose to update the RIS elements relying on a complex circle manifold (CCM)-based method. The proposed dynamic subconnected structure as well as the proposed joint hybrid and passive beamforming method strike an attractive tradeoff between the bandwidth efficiency and power consumption. Our simulation results demonstrate the superiority of the proposed method compared to its traditional counterparts.

In the search for enhanced wireless communication systems, multibeam phased array receivers have gained prominence. They promise to significantly boost data rates, reduce latency, and improve reliability. However, implementing multibeam receivers with traditional beamforming techniques can be challenging due to the high computational demands and the need for multiple radio frequency (RF) chains. Hybrid beamforming combines the advantages of digital and analog beamforming to strike a balance between performance and complexity. Our research delves into the following aspects of Hybrid beamforming for multibeam phased array receivers: Reduced Hardware Complexity: By blending digital and analog beamforming, we reduce the number of required RF chains, making multibeam receivers more cost-effective. Enhanced Beam Steering: Hybrid beamforming maintains precise control over multiple beams, ensuring efficient signal reception and transmission. Real-World Applications: We discuss practical applications in 5G and beyond, satellite communications, and radar systems. The paper delves into the fundamental concepts of analog and digital beamforming, illustrating their respective strengths and limitations. It then presents the architecture of hybrid beamforming systems, emphasizing the synergistic integration of analog and digital components. Special attention is given to the design considerations of beamforming networks, antenna arrays, and the beam steering mechanism. KEYWORDS Hybrid Beamforming , Phased Array , Multi-Beam , Analog Beamforming , Digital Beamforming , Beamforming Networks , Antenna Array , Beam Steering , Spatial Multiplexing , Precoding , Channel Estimation , Interference Mitigation , Power Consumption , Millimeter Wave (mmWave) , 5G and Beyond .

This work proposes a multiuser hybrid beamforming scheme for non-orthogonal multiple access (NOMA) systems using the minimum mean square error (MMSE) approach to weighted sum rate maximization. While NOMA may be effective in terms of enhancing user fairness, hybrid beamforming is necessary to reduce the transceiver cost as the system moves towards higher frequency. The design is divided into two stages. In the first stage, a fully digital multiuser beamformer is derived by maximizing the weighted sum rate of all users under no constraint on the number of RF chains. This problem is then transformed into a weighted sum MSE minimization problem, which facilitates the use of alternating optimization to obtain an efficient local solution. In the second stage, the previously obtained multiuser beamformer is then split into RF and baseband beamformers by using orthogonal matching pursuit (OMP). A user role selection algorithm is then proposed to determine the role of strong and weak users. Simulation results are provided to demonstrate the effectiveness of the proposed schemes.

Mid-bands and massive MIMO together have become a game-changer for the 5G technology in the areas of wireless systems. It is considered as a sweet pot holding the opportunities for handling new operations covering several miles to offer large throughput and spectral efficiencies along with the massive MIMO systems. Executing massive MIMO systems using mid-band frequencies rectify to boost up the speed, capacity, and coverage areas. Hybrid beamforming is an efficient solution to design our model at 6 GHz, resulting in a smaller number of RF chains and maximizing throughput and antenna gain. In our designed experimental model, we use massive—multiple inputs and multiple outputs—OFDM ray launching design which separates the precoding at the digital baseband and then to the radio frequency analog components both at the transceiver site. Less number of RF chains reduces the system complexities and is time efficient. The experiment is carried out using the scattering and MIMO propagation channel model, and the channel simulation link is the OFDM and 16, 64, 256-QAM modulation.KeywordsMid bandMassive MIMOTDDHybrid beamformingOFDMQAM

The hybrid beamforming structure is widely used in terahertz (THz) communications due to the low hardware complexity. However, its performance is severely degraded by beam squint effects in wideband THz communications resulting from the non-frequency-specific analog beamforming. To overcome this issue, in this paper, we investigate THz multiuser communications and propose a joint subcarrier allocation and hybrid beamforming (JSH) algorithm to compensate for the beam squint effects and maximize the sum-rate of users. The JSH algorithm alternates between subcarrier allocation and hybrid beamforming. Given the hybrid beamforming, the subcarrier allocation is formulated as an assignment problem and solved using the classic Hungarian algorithm. Given the subcarrier allocation, the hybrid beamforming is solved by developing a penalty-based two-loop hybrid beamforming algorithm. Simulation results show that the proposed JSH algorithm can effectively compensate for the beam squint effects and outperforms the existing ones in terms of the multiuser sum-rate.

In order to enhance the coverage and capacity of fifth generation cellular networks (5G) which is expected to be employed soon, massive multiple-input multiple-output (m-MIMO) and millimeter-wave (mm-Wave) technologies are being developed as solutions for these challenges. However, for large-scale antenna arrays that are anticipated in MIMO technology, the utilization of traditional fully-digital MIMO beam-forming methods is not practical, requiring one radio frequency (RF) chain per antenna element, leading to high cost and high power consumption. In order to reduce the RF chains number, hybrid analog and digital beam-forming has been studied and proposed. In this paper, a hybrid beam-forming structure is proposed in a massive MIMO communication channel with multiple users, each user having different number of data streams, with additive white Gaussian noise (AWGN) interfering with the signal throughout the path. The bit error rate (BER) of each transmitter for each user will be studied and compared under different circumstances for the proposed system VS different fully digital beam-forming methods, along with the spectral efficiency of the proposed hybrid beam-forming structure for each channel compared to fully digital, or in other words optimal beam-forming. Results of these comparisons will be shown and discussed to conclude the advantages and disadvantages of the proposed scheme.

Hybrid beamforming is a viable method for lowering the complexity and expense of massive multiple-input multiple-output systems while achieving high data rates on track with digital beamforming. To this end, the purpose of the research reported in this paper is to assess the effectiveness of the three architectural beamforming techniques (Analog, Digital, and Hybrid beamforming) in massive multiple-input multiple-output systems, especially hybrid beamforming. In hybrid beamforming, the antennas are connected to a single radio frequency chain, unlike digital beamforming, where each antenna has a separate radio frequency chain. The beam formation toward a particular angle depends on the channel state information. Further, massive multiple-input multiple-output is discussed in detail along with the performance parameters like bit error rate, signal-to-noise ratio, achievable sum rate, power consumption in massive multiple-input multiple-output, and energy efficiency. Finally, a comparison has been established between the three beamforming techniques.

Massive multiple-input multiple-output (MIMO) will be employed in the 5th generation mobile communications (5G). To implement the massive MIMO, hybrid beamforming (HB) is one of the most promising techniques, because HB is composed of the analog beamforming (AB) and the digital beamforming (DB) and thus can decrease the number of baseband and radio frequency (RF) circuits significantly. Furthermore, HB can reduce a much larger amount of cost and power consumption than the full DB (FDB) configuration, which requires one baseband and RF circuit for each antenna element. This paper proposes a scheme to estimate both phases for phase rotators in AB and a precoding matrix for DB so that HB can approximate the block diagonalization (BD), which can nullify interference from the undesired users and form efficient transmit beams. For time division duplex (TDD) multiuser MIMO communications, the proposed scheme estimates the FDB channel matrix in the uplink (UL) and the phase for the phase rotators of AB in the downlink (DL). After obtaining an equivalent channel matrix from both the estimated FDB channel matrix and the AB precoding matrix, the scheme estimates the DB precoding matrix in DL from the equivalent channel matrix so that HB can approximate BD in DL. Computer simulations demonstrate that HB employing the proposed scheme can achieve DL average bit error rate (BER) performances that are little inferior to those of FDB.