Orthogonal Beamforming Research Articles

A Full-Metal Dual-Band Millimeter-Wave Antenna Array With Concomitant Multifold Orthogonal Beamforming for V2V and V2I Communications

A Full-Metal Dual-Band Millimeter-Wave Antenna Array With Concomitant Multifold Orthogonal Beamforming for V2V and V2I Communications

Orthogonal beamforming technique for massive MIMO systems

AbstractBeamforming represents a pivotal technology in massive multiple-input multiple-output (MIMO) systems, as it facilitates the regulation of transmission and reception operations. Beamforming techniques’ categorization is based either on their hardware architecture or implementation strategy. This paper proposes an orthogonal beamforming technology founded on a specific implementation method that utilizes predetermined orthogonal beams to serve users. The suggested approach incorporates numerous orthogonal beams relying on a substantial number of antennas at the base station. The primary objective of this approach is to enhance the performance of massive MIMO systems by augmenting spectral efficiency and accommodating more users. The proposed beamforming approach is well suited for millimeter frequency bands. The purpose of this paper is to explore the suggested orthogonal beamforming technology. The concept of this approach is described at first and then followed by an evaluation of its efficacy for a single user through the allocation of orthogonal beams. The suggested approach is also examined in the context of multiuser systems, and the results are compared with the adaptive ZF beamforming technique. Furthermore, the paper presents solutions to the issues that may arise in multiuser systems, for example, ensuring that each orthogonal beam is assigned to only one user. The simulations conducted in this study demonstrate that the suggested approach outperforms the ZF technique in terms of both the spectral efficiency and the number of serviced users. Specifically, the suggested approach can enhance SE by approximately 40.6% over the ZF technique, and it can support up to double the number of users when compared to the ZF approach.

An Orthogonal Beamforming Network Synthesis Method Based on Complex Givens Rotation Matrix

This letter studies the possibility of synthesizing an orthogonal beamforming network (BFN) with an arbitrary number of inputs and outputs and beam-shaping functions. The proposed synthesis approach is based on complex Givens rotation matrices and is realized through the optimized program. First, it is derived that a complex Givens rotation matrix can represent a directional coupler with corresponding power ratio and phase difference. Then, this letter presents a computer-aided program to synthesize BFN that combines matrix cascading techniques and optimization algorithms, achieving beam shaping function. For validating the proposed synthesis approach, an example of an orthogonal 2×6 BFN with flat-topped radiation patterns for diversity application is presented. The accuracy and efficiency make the proposed synthesis method beneficial in antenna array systems.

Deep learning driven beam selection for orthogonal beamforming with limited feedback

This letter studies deep learning methods for beam selection in multiuser beamforming with limited feedback. We construct a set of orthogonal random beams and allocate the beams to users to maximize the sum rate, based on limited feedback regarding the channel power on the orthogonal beams. We formulate the beam allocation problem as a classification or a regression task using a deep neural network (DNN). The results demonstrate that the DNN-based methods achieve higher sum rates than a conventional limited feedback solution in the low signal-to-noise ratio regime under Rician fading, thanks to their robustness to noisy limited feedback.

A deep learning driven hybrid beamforming method for millimeter wave MIMO system

The hybrid beamforming is a promising technology for the millimeter wave MIMO system, which provides high spectrum efficiency, high data rate transmission, and a good balance between transmission performance and hardware complexity. The most existing beamforming systems transmit multiple streams by formulating multiple orthogonal beams. However, the Neural network Hybrid Beamforming (NHB) adopts a totally different strategy, which combines multiple streams into one and transmits by employing a high-order non-orthogonal modulation strategy. Driven by the Deep Learning (DL) hybrid beamforming, in this work, we propose a DL-driven non-orthogonal hybrid beamforming for the single-user multiple streams scenario. We first analyze the beamforming strategy of NHB and prove it with better Bit Error Rate (BER) performance than the orthogonal hybrid beamforming even with the optimal power allocation. Inspired by the NHB, we propose a new DL-driven beamforming scheme to simulate the NHB behavior, which avoids time-consuming neural network training and achieves better BERs than traditional hybrid beamforming. Moreover, our simulation results demonstrate that the DL-driven non-orthogonal beamforming outperforms its traditional orthogonal beamforming counterpart in the presence of sub-connected schemes and imperfect Channel State Information (CSI).

Synthesis Method of an Orthogonal Beamforming Network With Arbitrary Ports for Shaped Beams

This article proposes a synthesis method of orthogonal beamforming networks (BFNs) with arbitrary ports. The proposed method is based on matrix decomposition theory and breakthrough the synthesized BFN number to arbitrary. It has been theoretically demonstrated that the BFN with cascading 180° hybrid couplers can synthesize shaped beams. Therefore, a BFN synthesis method that combines the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">QR</i> decomposition theory and the optimization algorithm is introduced. With the help of an optimization program, a specific power ratio of each 180° hybrid coupler in the BFN is determined. The proposed synthesis method is verified by experiments with an orthogonal <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$6\times2$ </tex-math></inline-formula> BFN with flat-topped radiation patterns. Through optimization, five 180° hybrid couplers with different power ratios synthesize the proposed BFN. Results show that two flat-topped beams with a beamwidth of (32° ± 0.3°), gain ripples less than 2.5 dB, and a sidelobe level less than 12 dB are achieved. The proposed method has the advantages of high accuracy and efficiency and a simple structure, which makes it convenient for multi-beam antenna arrays in multiple-input–multiple-output (MIMO) systems.

Orthogonal Versus Zero-Forced Beamforming in Multibeam Antenna Systems: Review and Challenges for Future Wireless Networks

Orthogonality in multibeam antennas is revisited. The difference between orthogonal beamforming and zero-forced beamforming is highlighted. The intriguing relation between orthogonality, reciprocity and losses is recapitulated. Different approaches on the design of orthogonal beamforming networks and implementation of zero-forced beamforming strategies are shown with various examples from the antenna-research-oriented literature. The use of orthogonal and zero-forced beamforming is discussed from the communication system perspective with relevant studies from diverse disciplines. Some of the future research challenges and potential benefits are outlined for the next generation satellite and cellular communication applications.

A Prototype Orthogonal Vertical Beamforming for Indoor Wireless Communications

The concept of Orthogonal Vertical Beamforming (OVB) is proposed in this paper to eliminate interference when users remain at the same angle in the horizontal plane but are positioned at different distances. This orthogonal property helps systems avoid interference in the vertical direction of the mainbeam. A fully constructed prototype tested in a real indoor environment validates the proposed concept, revealing that the proposed OVB provides higher Signal Interference plus Noise Ratio (SINR) and Packet Error Rate (PER) in the vertical plane than conventional vertical beamforming and Orthogonal Beamforming.

A 0.7–5.7 GHz Reconfigurable MIMO Receiver Architecture for Analog Spatial Notch Filtering Using Orthogonal Beamforming

A highly reconfigurable direct-conversion software-defined multiple-input multiple-output (MIMO) receiver with four RF inputs and four I/Q baseband outputs is proposed. It allows for digital MIMO but also analog interference rejection by spatial notch filtering through four flexible and simultaneous orthogonal beams. A segmented constant-Gm vector modulator (VM) with improved interference tolerance and wide RF frequency range targeting the sub-6-GHz bands is proposed. It exploits current-domain beamforming before $I$ – $V$ conversion by transimpedance amplifiers. A 0.7–5.7-GHz 22-nm fully depleted silicon-on-insulator (FD-SOI) prototype chip achieves >29 dB spatial filtering for a single notch and an ultrawideband 20-dB notch suppression bandwidth of 2.3 GHz at broadside excitation at an local oscillator (LO) frequency of 2.5 GHz. In the notches, an IIP3 of +16 dBm and B1dB of −11.5 dBm at a 41-dB gain is achieved, improving IIP3 and B1dB by 35 and 27 dB, respectively, by spatial filtering. A single-element noise figure (NF) of 5.5–7 dB is achieved on the VM constellation corners, degrading about 2 dB on the points nearby the biggest circle fitting into a square constellation. However, sub-3-dB system NF is potentially achievable, taking into account up to 6-dB improvement by the four-element beamforming. Given both gain and phase control provided by the VM, spatial patterns with up to three independent nulls can be synthesized with the four-element antenna array. The chip of 0.52 mm2 active area consumes 77–139 mW at an LO-frequency of 0.7–5.7 GHz from a 0.8-V supply.

Performance of Orthogonal Beamforming with NOMA for Smart Grid Communication in the Presence of Impulsive Noise

Smart grid networks demand reliable, efficient and real-time energy management by exchanging information. Transmitting and receiving information needs a two-way, secure, reliable and high-speed communication infrastructure, which should be capable to handle impulse noise present in power system. Power division non-orthogonal multiple access scheme can fulfill this requirement through its high spectral efficiency. In this paper, we proposed a composite multiple access model based on orthogonal beamforming (OBF) and non-orthogonal multiple access scheme for exchanging information between smart grid, smart meters (SMs) and other communication units in the presence of impulse noise. We divide a cell in sectors and implement OBF between sectors to reduce inter beams interference using orthogonalization. Within the sectors, we implement power division multiple access to utilize maximum bandwidth with the help of successive interference cancelation scheme. Furthermore, to find the effect of impulse noise on performance of proposed model we consider Gaussian and Laplacian models with Bernoulli arrival rate. Simulation and numerical findings show that the proposed method does not cause interference between SMs and offers $$3\;{\text{Mbit}}/\text{s}$$ higher data rate than the traditional OFDMA systems leading to better system capacity in case of four SMs in a sector of a cell.

Hybrid Precoding Processor for Millimeter Wave MIMO Communications

Millimeter wave (mmWave) multiple-input multiple-output system is one of the most important techniques to increase throughput for 5G communications. To overcome the severe pathloss in the mmWave channel, the hybrid analog/digital precoding technique jointly designs radio frequency (RF) beamforming vectors and a baseband precoding matrix to approach the optimal spectral efficiency with reduced RF chain power and baseband complexity. This brief presents a hybrid precoding algorithm based on multiple orthogonal beamforming codebooks and a local search scheme, which reduces computational complexity by 40% with negligible bit-error-rate performance loss compared with the state-of-the-art algorithms. The proposed hybrid precoding algorithm was also designed and implemented by using TSMC 90-nm CMOS process technology. The fabricated hybrid precoding processor chip achieves 11.1M/10.4M/6.9M/4.3M matrices per second for 1/2/3/4 data streams, respectively. Compared with a previous work, the designed processor increases throughput by 65%/55%/40%/7.5% for 1/2/3/4 data streams with only 28% of the core area.

Multipole orthogonal beamforming combined with an inverse method for coexisting multipoles with various radiation patterns

Identification of sources with non-uniform radiation patterns is attracting considerable attention these years. A multipole beamforming algorithm combined with an inverse method, is proposed to detect coexisting multipoles with various radiation patterns. Positions and strengths of sources are estimated first. The sound field of each source is represented by the eigenvector of the cross-spectral matrix of microphone array signals. Source directivity is removed by the normalization and square operations on elements of the eigenvector. Each source is represented by spherical harmonics after source localization. Types and orientations of sources can be inferred from their reconstructed radiation patterns. The proposed algorithm is verified by numerical simulations and experiments using a loudspeaker and vortex shedding from a cylinder. Compared to existing multipole beamforming algorithms, it reduces the condition number of the transfer matrix and removes the spurious sources on source maps. Positions, types and orientations of sources are estimated more accurately. The resolution of source maps is comparable to that of CLEAN-SC.

Reduction of interference using Orthogonal Vertical Beamforming in an indoor communication

The interference between users is one of the factors that limit the achievable user throughput in the current indoor communication. In this paper, an evaluation of transmit beamforming contribution is analyzed in the context of an indoor environment. The technique of the Orthogonal Vertical Beamforming (OVB) has been proposed to reduce interference in an indoor communication. The proposed concept is validated through computer simulation in term of Signal Interference plus Noise Ratio (SINR). The obtained results show that the OVB provides higher performance over the conventional vertical beamforming and Orthogonal Beamforming (OBFM) in an only vertical plane.

User Association and Scheduling Based on Auction in Multi-Cell MU-MIMO Systems

We study the user association and scheduling problem in multi-cell multi-user multiple-input multiple-output systems with dynamic traffic. Two successive linear beamforming schemes, namely, zero forcing-successive interference cancellation and adaptive orthogonal beamforming, are adopted in the uplink channel and the downlink channel, respectively. The confidence level of signal-to-interference-plus-noise ratio of a random user is analyzed, in order for base stations (BSs) to decide on the maximum number of active users while guaranteeing the worst-case quality of service. We also derive the conditional expected rate of a random user knowing its local channel state information, in order for users to evaluate the performance and select the BS. Noticing that the performance can be divided into different classes, we model the user association and scheduling problem as an auction game. The auction is equipped with a strategy-proof pricing scheme and can be conducted in a distributed fashion with a limited information exchange. Shown by the simulation, the proposed mechanism has the dominant performance in respect of social welfare, throughput, and load balancing.

Identification and analysis of the noise sources of an engine settled in a car using array-based techniques

Engine noise is one of the most important noise sources in a car. This noise is radiated to both the inside and the outside of the car. In this paper, the accuracy of the array based techniques has been compared with the one of sound intensity measurements. Then, the engine noise of a car has been measured at different rotational speeds through array based techniques. At low frequencies, statistically optimised near-field acoustical holography (SONAH) allows an accurate identification of the noise sources. At medium and high frequencies, different beamforming algorithms are compared, choosing orthogonal beamforming because of its better behaviour regarding the influence of the sidelobes and the best resolution and identification of the noise sources. The noise source maps obtained using array based techniques allow to locate in an accurate way the noise sources in the engine settled in a car when it is working at different rotational speeds, performing an efficient analysis of details of a possible noise problem. The noise sources identified are: the engine, the timing belt, the air intake system, the diesel pump and the cylinders and the crank system; all of them were afterwards analysed in detail through their noise spectra.

Orthogonal Beamforming for Multiuser Wireless Communications: Achieving higher received signal strength and throughput than with conventional beamforming

For multiuser communications, a base station (BS) simultaneously transmits data to a number of users who employ the same frequency. This can be accomplished with the help of feedback or a channel to maintain the accuracy of received data; however, what results is a high complexity system. Therefore, this article proposes an alternative beamforming method for multiuser communications called orthogonal beamforming (OBFM). A number of beams are formed in predefined directions at the same time with all beams employing the same frequency. To avoid interference from other users operating at the same frequency, all beams are orthogonal to one another. The system performance of the proposed concept is compared to the zero-forcing (ZF) algorithm. A constructed prototype is tested in a real environment, confirming that the proposed OBFM provides a higher received signal strength and a higher throughput compared with conventional beamforming. Also, the proposed systems provide a lower bit error rate (BER).

Optical wireless communication using positive real-valued orthogonal frequency-division multiplexing and optical beamforming

The relatively unsatisfactory performance of optical wireless communication (OWC) with respect to WiFi and millimeter-wave communications has formed a key issue preventing its commercialization. We experimentally demonstrate an OWC technology using a combination of positive real-valued orthogonal frequency-division multiplexing (OFDM) and optical beamforming (OB). Due to the intensity-modulation and direct-detection aspects of OWC systems, a positive real-valued OFDM signal can be suitably utilized to maximize the OWC data rate. Further, the OB technique, which can focus laser light on a desired target, can be utilized to increase the OWC data rate and transmission distance. Our experimental results show that the received optical signal power and electrical signal increase by up to 42 and 25 dB, respectively. Further, the data rate increases by a factor of 200 with OB over the conventional approach.

Partly random multiple weighting matrices selection for orthogonal random beamforming

In the multi-user multiple-input multiple-output (MIMO) system, orthogonal random beamforming (ORBF) scheme is proposed to serve multiple users simultaneously in order to achieve the multi-user diversity gain. The opportunistic space-division multiple access system (OSDMA-S) scheme performs multiple weighting matrices during the training phase and chooses the best weighting matrix to be used to broadcast data during the transmitting phase. The OSDMA-S scheme works better than the original ORBF by decreasing the inter-user interference during the transmitting phase. To save more time in the training phase, a partly random multiple weighting matrices selection scheme is proposed in this paper. In our proposed scheme, the Base Station does not need to use several unitary matrices to broadcast pilot symbol. Actually, only one broadcasting operation is needed. Each subscriber generates several virtual equivalent channels with a set of pre-saved unitary matrices and the channel status information gained from the broadcasting operation. The signal-to-interference and noise ratio (SINR) of each beam in each virtual equivalent channel is calculated and fed back to the base station for the weighting matrix selection and multi-user scheduling. According to the theoretical analysis, the proposed scheme relatively expands the transmitting phase and reduces the interactive complexity between the Base Station and subscribers. The asymptotic analysis and the simulation results show that the proposed scheme improves the throughput performance of the multi-user MIMO system.

User-Centric Downlink Cooperative Transmission With Orthogonal Beamforming Based Limited Feedback

With the increase of cell density and explosive growth of data traffic, user centric is becoming one of the design principles of next-generation cellular networks. One meaning of user centric lies in that no matter where a user is located, its demand in quality of service (QoS) will be guaranteed in high probability. One approach to achieve such an ambitious goal is allowing each user to select several preferred base stations to transmit cooperatively. In this paper, we propose a user-centric downlink cooperative transmission scheme with orthogonal beamforming based limited feedback, where the cooperative clusters of multiple users may overlap and per-cell codebooks are considered. To assist the central unit (CU) for scheduling users with guaranteed QoS and performing adaptive transmission, a method for each user to estimate its signal-to-noise-and-interference ratio is derived. Targeting to ensure the required QoS of multiple users, we propose a method to select the cooperative cluster at each user and provide a method to schedule users based on their service priorities and channel conditions at the CU, where the clusters are selected semidynamically. Simulation results show that the proposed scheme significantly increases the percentage of users with satisfactory QoS demands.

Closed-Loop Beam Alignment for Massive MIMO Channel Estimation

Training sequences are designed to probe wireless channels to obtain channel state information for block-fading channels. Optimal training sounds the channel using orthogonal beamforming vectors to find an estimate that optimizes some cost function, such as mean square error. As the number of transmit antennas increases, however, the training overhead becomes significant. This creates a need for alternative channel estimation schemes for increasingly large transmit arrays. In this work, we relax the orthogonal restriction on sounding vectors. The use of a feedback channel after each forward channel use during training enables closed-loop sounding vector design. A misalignment cost function is introduced, which provides a metric to sequentially design sounding vectors. In turn, the structure of the sounding vectors aligns the transmit beamformer with the true channel direction, thereby increasing beamforming gain. This beam alignment scheme for massive MIMO is shown to improve beamforming gain over conventional orthogonal training for a MISO channel.