Multi-beam Selection Research Articles

Coordinated Multi-Beam Transmissions for Reliable Millimeter-Wave Communications With Independent and Correlated Blockages

Millimeter-Wave (mmWave) communication has been considered as one of enabling technologies for the sixth generation (6G) network and beyond to boost the system throughput, which however is hard to provide robust and reliable transmissions since it is easy to be blocked. Coordinated multi-beam transmission has emerged as an effective way to overcome this challenge. In this paper, we first define an incomplete blockage probability and a correlated blockage probability for each user equipment (UE) to measure the robustness and reliability in coordinated multi-beam transmissions, and then formulate the coordinated multi-beam selection and transmission power allocation problem to maximize the sum rate of all UEs in consideration of the independent blockage probability and dependent blockage probability constraints of each UE in mmWave networks. To solve the considered problem efficiently, we reformulate it as a hierarchical game model and design a decentralized algorithm to search the Nash Equalibriums (NEs) of the games. Finally, we present extensive simulation results to demonstrate the effectiveness of the proposed scheme.

Concurrent multi-beam transmissions for reliable communication in millimeter-wave networks

Millimeter-wave (mmWave) communication is an important technology to meet the demand of high data rate in sixth generation (6G) wireless networks. Blockage is a major obstacle to reliable transmissions for mmWave communication. In order to prevent complete blocking of concurrent multiple beams and measure the reliability of concurrent multi-beam transmissions, beam space isolation degree (BSID) and reliability coefficient are defined, based on which a joint multi-beam selection and transmission power allocation scheme that maximizes the tradeoff utility of instantaneous achievable rate and reliability. We break the original optimization problem into two subproblems (i.e., multi-beam selection subproblem and transmission power allocation subproblem) to reduce the computational complexity, and solve them iteratively until no further improvement of the system utility, where exact potential game is used to solve the former under fixed transmission power policy, and first-order Taylor expansion and Lagrangian multiplier algorithm are utilized to solve the latter under fixed concurrent multi-beam selection strategy. Evaluation results indicate that the proposed scheme provides better sum utility and sum reliability with lower complexity, which indicates that concurrent multi-beam transmissions can improve the reliability of mmWave communication.

Intelligent Reflecting Surface Aided NOMA for Millimeter-Wave Massive MIMO With Lens Antenna Array

In this paper, we propose a downlink intelligent reflecting surface (IRS) aided non-orthogonal multiple access (NOMA) for millimeter-wave (mmWave) massive MIMO with lens antenna array, i.e., IRS-aided mmWave beamspace NOMA, where the single-antenna users without direct-link but connected to the base station (BS) with the aid of the IRS are grouped as one NOMA group. Considering the power leakage problem in beamspace channel and the per-antenna power constraint, we propose two multi-beam selection strategies for the BS-IRS link under two channel models, i.e., 2-dimension (2D) channel model and 3-dimension (3D) channel model, respectively, where two corresponding RF chain configuration strategies are designed, respectively. Then, we formulate and solve the optimization problem for maximizing the weighted sum rate by jointly optimizing the active beamforming at the BS and the passive beamforming at the IRS, where we propose the alternating optimization (AO) method to solve the above joint optimization problem. Especially, different from the stochastic method, based on the beam-splitting technique, we propose the method to initialize the feasible solution for the proposed AO method, where the conditional transmit power minimization problem is formulated and solved. Through simulations, the weighted sum rate performance of the proposed IRS-aided mmWave beamspace NOMA is verified.

Performance Evaluation of Downlink Multi-Beam Massive MIMO with Simple Transmission Scheme at Both Base and Terminal Stations

Multi-beam massive multiple-input–multiple-output (MIMO) configurations that utilize high-power beam selection in the analog parts and blind algorithms such as the constant modulus algorithm (CMA), which do not require channel state information (CSI), in the digital parts, have been proposed in the literature to improve the transmission rates and efficiency. In this paper, we evaluate the transmission performance in the downlink, with simple control at the base station (BS) and user terminal (UTs), for massive MIMO transmissions. Through computer simulations, it is shown that the analog multi-beam selection at the BS and the application of CMA at the UT with two antennas can effectively realize transmissions with high-order modulation schemes. In addition, the weight update switching by the CMA is proposed in order to obtain fast and stable performance with a realistic data size.

Beamspace SU-MIMO for Future Millimeter Wave Wireless Communications

For future networks (i.e., the fifth generation (5G) wireless networks and beyond), millimeter-wave (mmWave) communication with large available unlicensed spectrum is a promising technology that enables gigabit multimedia applications. Thanks to the short wavelength of mmWave radio, massive antenna arrays can be packed into the limited dimensions of mmWave transceivers. Therefore, with directional beamforming (BF), both mmWave transmitters (MTXs) and mmWave receivers (MRXs) are capable of supporting multiple beams in 5G networks. However, for the transmission between an MTX and an MRX, most works have only considered a single beam, which means that they do not make full potential use of mmWave. Furthermore, the connectivity of single beam transmission can easily be blocked. In this context, we propose a single-user multi-beam concurrent transmission scheme for future mmWave networks with multiple reflected paths. Based on spatial spectrum reuse, the scheme can be described as a multiple-input multiple-output (MIMO) technique in beamspace (i.e., in the beam-number domain). Moreover, this study investigates the challenges and potential solutions for implementing this scheme, including multibeam selection, cooperative beam tracking, multi-beam power allocation and synchronization. The theoretical and numerical results show that the proposed beamspace SU-MIMO can largely improve the achievable rate of the transmission between an MTX and an MRX and, meanwhile, can maintain the connectivity.

Adaptive Orthonormal Random Beamforming and Multi-Beam Selection for Cellular Systems

Channel state information (CSI) at transmitter plays an important role for multiuser MIMO broadcast channels, but full CSI at transmitter is not available for many practical systems. Previous work has proposed orthonormal random beamforming (ORBF) [16] for MIMO broadcast channels with partial channel state information (CSI) feedback, and shown that ORBF achieves the optimal sum-rate capacity for a large number of users. However, for cellular systems with moderate number of users, i.e., no more than 64, ORBF only achieves slight performance gain. Therefore, we analyze the performance of ORBF with moderate number of users and total transmit power constraint and show that ORBF scheme is more efficient under low SNR. Then we propose an adaptive ORBF scheme that selects the number of random beams for simultaneous transmission according to the average signal-to-noise ratio (SNR). Moreover, a multi-beam selection (MBS) scheme that jointly selects the number and the subset of the multiple beams is proposed to further improve the system performance for low SNR cases. The simulation results show that the proposed schemes achieve significant performance improvement when the number of users is moderate.