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Pinching antennas have been recently proposed as a promising flexible-antenna technology, which can be implemented by attaching low-cost pinching elements to dielectric waveguides. This work explores the potential of employing pinching antenna systems (PASSs) for downlink transmission in a multiuser MIMO setting. We formulate the problem of hybrid beamforming, where the digital precoder at the access point and the activated locations of the pinching elements are jointly designed to maximize the achievable weighted sum-rate. Invoking fractional programming, a novel low-complexity algorithm is developed to iteratively update the precoding matrix and the locations of the pinching antennas. We validate the proposed scheme through extensive numerical experiments. Our investigations demonstrate that using PASSs, the throughput can be significantly boosted compared to conventional fixed-location antenna systems. This enlightens the potential of the PASS as an enabling candidate for next-generation wireless networks.
21Cooperative beamforming for dual-hop amplify-and-forward multi-antenna relaying cellular networks
Cooperative beamforming for dual-hop amplify-and-forward multi-antenna relaying cellular networks
4Downlink beamforming design for mobile users in massive MIMO system
Downlink beamforming design for mobile users in massive MIMO system
A UE-Assisted Hybrid Transmission Scheme for Asynchronous Cell-Free Massive MIMO Systems With Imperfect RF Chains
A user equipment (UE)-assisted hybrid coherent and noncoherent transmission scheme is designed for cell-free massive multiple-input–multiple-output (MIMO), operating in the presence of phase offsets caused by both imperfect radio frequency (RF) chains and asynchronous reception. First, considering the effects of both factors, we derive closed-form spectral efficiency (SE) expressions for hybrid transmission under conjugate beamforming and zero-forcing (ZF) precoders. Based on these expressions, we introduce the concept of superposition gain to clarify the rationality of hybrid transmission. To leverage its advantages, we propose an access point (AP) grouping algorithm and its enhanced version, which groups the serving APs based on downlink (DL) equivalent channel at the UE side. Since the DL equivalent channel incorporates information on both RF and delay phase offsets, hybrid transmission based on this algorithm can simultaneously address both. Additionally, to implement this UE-assisted hybrid transmission with low overhead, we propose a signaling interaction strategy that extends traditional processes by introducing ZF-based DL beamforming pilot transmission for obtaining the DL equivalent channel, along with indication method for reporting the grouping results. Moreover, to further improve performance, a sequential convex approximation power allocation algorithm is proposed for hybrid transmission. Finally, simulations show that UE-assisted hybrid transmission achieves nearly fivefold improvement in 95%-likely SE over coherent transmission in the presence of both RF and delay phase offsets.
Read more7Hybrid Precoding for Secure Transmission in Reflect-Array-Assisted Massive MIMO Systems
Recently, a hybrid analog-digital architecture has been proposed for multiuser MIMO transmission in the millimeter-wave spectrum using reflect-arrays. The architecture exhibits scalability and high energy-efficiency while keeping the transmitter cost-efficient. Inspired by this architecture, we design a secure multiuser hybrid analog-digital precoding scheme. This scheme utilizes the method of regularized least-squares to shape the downlink beamformers, such that the signal received via malicious terminals is effectively suppressed. Numerical investigations depict high robustness of this scheme against the density of malicious terminals, as well as the quality of overhearing channels. Such properties along with high efficiency of the transmitter imply that the proposed scheme is an effective candidate for secure communication in multiuser millimeter-wave massive MIMO systems.
Read more3Minimal capacity loss Round-Robin scheduling algorithm for downlink beamforming multiuser MIMO systems
DOI: 10.1049/cp:20061368 ISBN: 0 86341 644 6 Location: Hangzhou, China Conference date: 6-9 Nov. 2006 Format: PDF In this paper, we propose a minimal capacity loss Round-Robin scheduling (MCLRRS) algorithm for downlink zeroforcing beamforming multiuser MIMO systems. Based on conventional round-robin scheduling, we select user with less spatially correlated channels. It guarantees full fairness of users and at the same time we can get multiuser diversity. The analysis and simulation results have both shown that MCLRRS algorithm distinctly outperforms conventional Round-Robin scheduling algorithm. (4 pages) Inspec keywords: correlation methods; MIMO communication; channel capacity; scheduling; diversity reception; array signal processing; multiuser channels; antenna arrays Subjects: Antenna arrays; Radio links and equipment
Read moreA Beamforming Pilots Scheme for Massive MIMO System
To acquire channel state information for Massive MIMO system , a downlink beamforming pilots scheme is proposed for efficient channel estimation. The channel estimation overhead of the proposed scheme is independent on the BS antenna numbers, and is only proportional to user numbers. MMSE precoding method is derived to implement the proposed scheme. Finally in simulation the proposed algorithm is compared with conventional algorithms without beaforming training in spectral efficiency performance. The simulation results show that the proposed scheme performs better than the existing schemes.
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