- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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[IEEE 2018 IEEE 10th Sensor Array and Multichannel Signal Processing Workshop (SAM) - Sheffield (2018.7.8-2018.7.11)] 2018 IEEE 10th Sensor Array and Multichannel Signal Processing Workshop (SAM) - Adaptive Near-Field Imaging with Robotic Arrays
摘要： In this paper, we are interested in phased-array imaging of an unknown area using narrowband RF signals and arrays synthesized by an unmanned vehicle. Typical phased array imaging approaches use fixed or pre-determined array configurations for imaging, which are not usually informative for the whole area. In this paper, we then propose an iterative adaptive imaging approach where we identify the uncertain regions in an initial image that need to be sensed better, find the optimal array location and orientation for such a sensing task and finally combine the new image with the initial image to obtain a better overall imaging quality. Such an approach is easily enabled by using robots to synthesize arrays. We validate our proposed approach with numerical simulations and show that an adaptive approach improves the imaging quality as compared to imaging with fixed arrays.
关键词： Near-field beamforming,Adaptive imaging,Robotic arrays
更新于2025-09-23 15:22:29
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Artificial Noise Based Beamforming for the MISO VLC Wiretap Channel
摘要： This paper investigates the secrecy performance of the multiple-input single-output (MISO) visible light communication (VLC) wiretap channel. The considered system model comprises three nodes: a transmitter (Alice) equipped with multiple fixtures of LEDs, a legitimate receiver (Bob) and an eavesdropper (Eve), each equipped with one photo-diode (PD). The VLC channel is modeled as a real-valued amplitude-constrained Gaussian channel. Eve is assumed to be randomly located in the same area as Bob. Due to this, artificial noise (AN)-based beamforming is adopted as a transmission strategy in order to degrade Eve's signal-to-noise ratio (SNR). Assuming discrete input signaling, we derive an achievable secrecy rate in a closed-form expression as a function of the beamforming vectors and the input distribution. We investigate the average secrecy performance of the system using stochastic geometry to account for the location randomness of Eve. We also adopt the truncated discrete generalized normal (TDGN) as a discrete input distribution. We present several examples through which we confirm the accuracy of the analytical results via Monte Carlo simulations. The results also demonstrate that the TDGN distribution, albeit being not optimal, yields performance close to the secrecy capacity.
关键词： MISO,Achievable secrecy rate,beamforming,TDGN,stochastic geometry,VLC
更新于2025-09-23 15:22:29
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Self Optimization Beam-Forming Null Control Based SINR Improvement
摘要： In this paper, a self optimization beamforming null control (SOBNC) scheme is proposed. There is a need of maintaining signal to interference plus noise ratio (SINR) threshold to control modulation and coding schemes (MCS) in recent technologies like Wi-Fi, Long Term Evolution (LTE) and Long Term Evolution Advanced (LTE-A). Selection of MCS depends on the SINR threshold that allows maintaining key performance index (KPI) like block error rate (BLER), bit error rate (BER) and throughput at certain level. The SOBNC is used to control the antenna pattern for SINR estimation and improve the SINR performance of the wireless communication systems. The nulling comes with a price; if wider nulls are introduced, i.e. more number of nulls are used, the 3 dB beam-width and peak side lobe level (SLL) in antenna pattern changes critically. This paper proposes a method which automatically controls the number of nulls in the antenna pattern as per the changing environment based on adaptive-network based fuzzy interference system (ANFIS) to maintain output SINR level higher or equal to the required threshold. Finally, simulation results show a performance superiority of the proposed SOBNC compared with minimum mean square error (MMSE) based adaptive nulling control algorithm and conventional fixed null scheme.
关键词： self optimization beamforming null control,adaptive neural fuzzy inference system (ANFIS),SINR improvement,digital beam-forming (DBF)
更新于2025-09-23 15:22:29
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Realization of modified Luneburg lens antenna using quasi-conformal transformation optics and additive manufacturing
摘要： We demonstrate a new method for realizing modified Luneburg lens antennas with nearly continuously graded permittivity profiles in three-dimensions. The method used a quasi-conformal transformation optics (QCTO) approach to modify the geometry and permittivity of a spherical Luneburg lens to have a flat surface for convenient integration of antenna feeds. The modified lens was then fabricated using Fused Deposition Modeling (FDM) printing with an effective media approach that employs space-filling curves. The method was validated by designing and fabricating a modified Luneburg lens antenna designed to operate in the Ka-band. The antenna performance of the sample was measured experimentally and shown to compare well to predicted results using full wave simulations. The device was able to achieve a reasonably high degree of beam steering (ie, ?55° to +55°) over the entire Ka-band. We believe this new approach provides a cost-effective and scalable means of realizing practical passive beam steering lenses that operate over a broad range of frequencies.
关键词： additive manufacturing,beamscanning,beamforming,fused deposition modeling,Luneburg lens,transformation optics
更新于2025-09-23 15:22:29
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A Generic Receiver Architecture for MIMO Wireless Power Transfer With Nonlinear Energy Harvesting
摘要： This letter investigates a multiple-input multiple-output (MIMO) wireless power transfer system under practical nonliner energy harvesting (EH) models. We propose a new generic energy receiver (ER) architecture consisting of N receive antennas and L recti?ers, for which one power splitter is inserted after each antenna to adaptively split the received radio frequency (RF) signals among the L recti?ers for ef?cient nonlinear RF-to-direct current (dc) conversion. With the proposed architecture, we maximize the total harvested dc power at the ER, by jointly optimizing the transmit energy beamforming at the energy transmitter and the power splitting ratios at the ER. Numerical results show that our proposed design by exploiting the nonlinearity of EH signi?cantly improves the harvested dc power at the ER, as compared to two conventional designs.
关键词： Wireless power transfer (WPT),non-linear energy harvesting (EH),transmit energy beamforming,adaptive power splitting
更新于2025-09-23 15:22:29
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[IEEE OCEANS 2018 MTS/IEEE Charleston - Charleston, SC, USA (2018.10.22-2018.10.25)] OCEANS 2018 MTS/IEEE Charleston - Optimal design of frequency-invariant beamformers for circular arrays
摘要： This paper proposes a optimal method designing frequency-invariant beamformers for circular arrays. First, the desired beampattern is expressed as a general complex-weighted form. Second, the weighting vectors at each frequency are accurately derived by approximating to the desired beampattern from the minimum mean square error perspective, all of which are found to be close-form functions of the desired complex weighting vectors. Third, a multiple optimization problem is formulated, and its solution gives the optimal desired weighting vector subject to different constraints. Finally, the weighting vectors at other frequencies can be directly computed based on the previously derived analytical functions. The proposed method provides flexible schemes to design different optimal frequency-invariant beamformers for circular sensor arrays. The good performance of the proposed method is demonstrated using simulations and experimental results.
关键词： circular sensor array,Frequency-invariant beamforming,multi-constraint optimization
更新于2025-09-23 15:22:29
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Hybrid Beamforming for Millimeter Wave Systems Using the MMSE Criterion
摘要： Hybrid analog and digital beamforming (HBF) has recently emerged as an attractive technique for millimeter-wave (mmWave) communication systems. It well balances the demand for sufficient beamforming gains to overcome the propagation loss and the desire to reduce the hardware cost and power consumption. In this paper, the mean square error (MSE) is chosen as the performance metric to characterize the transmission reliability. Using the minimum sum-MSE criterion, we investigate the HBF design for broadband mmWave transmissions. To overcome the difficulty of solving the multi-variable design problem, the alternating minimization method is adopted to optimize the hybrid transmit and receive beamformers alternatively. Specifically, a manifold optimization based HBF algorithm is firstly proposed, which directly handles the constant modulus constraint of the analog component. Its convergence is then proved. To reduce the computational complexity, we then propose a low-complexity general eigenvalue decomposition based HBF algorithm in the narrowband scenario and three algorithms via the eigenvalue decomposition and orthogonal matching pursuit methods in the broadband scenario. A particular innovation in our proposed alternating minimization algorithms is a carefully designed initialization method, which leads to faster convergence. Furthermore, we extend the sum-MSE based design to that with weighted sum-MSE, which is then connected to the spectral efficiency based design. Simulation results show that the proposed HBF algorithms achieve significant performance improvement over existing ones, and perform close to full-digital beamforming.
关键词： Minimum mean square error (MMSE),Alternating optimization,Manifold optimization (MO),Hybrid analog and digital beamforming (HBF),Millimeter-wave (mmWave) communications
更新于2025-09-23 15:22:29
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[IEEE 2018 9th Advanced Satellite Multimedia Systems Conference and the 15th Signal Processing for Space Communications Workshop (ASMS/SPSC) - Berlin (2018.9.10-2018.9.12)] 2018 9th Advanced Satellite Multimedia Systems Conference and the 15th Signal Processing for Space Communications Workshop (ASMS/SPSC) - Sparsity-Aided Low-Implementation cost based On-Board beamforming Design for High Throughput Satellite Systems
摘要： Soaring demand for high data rate services entails high throughput satellite (HTS) systems with multi-beam architecture, and full frequency and time resources reuse. However, interference among simultaneously served users is the fundamental factor that is needed to be addressed before enacting HTS system with this architecture. Beamforming has been proposed as a potential technique to mitigate the interference in the literature. Different types of beamforming techniques proposed including beamforming at payload (on-board), beamforming at a gateway and hybrid beamforming. On-board beamforming prevails over other techniques due to its advantages—channel information at payload is more recent than gateway and sharing overhead of channel and symbols across multiple gateways is reduced in a multi-gateway architecture to name a few. Despite these advantages, beamforming at the gateway is usually preferred due to the heavy processing cost incurred in beamforming. Beamforming processing cost can be split into two factors: design cost and implementation cost. While design cost accounts for the cost involved in the design of beamformer, implementation cost accounts for multiplications and additions involved in applying calculated beamformer coefficients to data symbols. Through our study, we noticed that the major contributing factor to processing cost is the implementation cost which accumulates for every data symbol rather than design cost which is incurred only once per channel coherence time which usually relatively longer than many data symbols. Furthermore, the implementation cost is dominated by the multiplications involved. Hence, in this work, we address the issue of implementation cost from the perspective of on-board multiplications. We formulate the problem of minimizing on-board implementation cost (multiplications) of a beamformer as a second-order cone programming problem with the help of (cid:96)1 norm constraint on the beamforming matrix subjected to a minimum signal-to-interference-noise ratio of simultaneously served users and classical total power constraint. We show the efficacy of our algorithm over the traditional power minimization method through Monte-Carlo simulations.
关键词： second-order cone programming,High throughout satellite systems,beamforming,interference
更新于2025-09-23 15:22:29
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[IEEE 2018 China International SAR Symposium (CISS) - Shanghai (2018.10.10-2018.10.12)] 2018 China International SAR Symposium (CISS) - A Novel Algorithm for Spacebome SAR DBF Based on Sparse Spatial Spectrum Estimation
摘要： A novel method of digital beam forming (DBF) based on sparse spatial spectrum estimation for spaceborne synthetic aperture radar (SAR) is proposed in this paper. This method converts the estimation of target scene elevation into the estimation of sparse spatial spectrum, which reduces the impact of the number of signal samples. Finally, the simulated results confirm the validity of the method.
关键词： Sparse Spatial Spectrum Estimation,Synthetic Aperture Radar (SAR),Digital Beamforming (DBF)
更新于2025-09-23 15:22:29
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Wireless Information and Power Transfer (Theory and Practice) || Wireless Power Transfer
摘要： Large-scale wireless networks are characterized by the existence of multi-user interference due to the concurrent transmission of the network’s terminals. In conventional networks, i.e. networks where the main focus is information transfer, interference is a critical degrading factor of a terminal’s performance. On the other hand, in networks where the main focus is wireless power transfer (WPT), interference is beneficial as it increases the harvesting efficiency. However, in both cases all wireless links are influenced by path-loss effects due to the distances between the terminals. As such, the terminals’ deployment is another important element which affects their performance. Therefore, a reasonable approach is to study radio frequency (RF) energy harvesting in large-scale networks by taking into account spatial randomness. The modeling of the geometrical characteristics of large-scale networks can be achieved with the employment of stochastic geometry, a suitable mathematical tool for studying spatial point processes [1]. Specifically, this chapter presents three sections, each dealing with a different wireless-powered communication scenario: Section 15.1 focuses on a wireless-powered cooperative network where the relays harvest energy from the source in order to convey its transmitted information; Section 15.2 deals with a simultaneous wireless information and power transfer (SWIPT) scenario, where terminals employ successive interference cancellation (SIC) techniques to boost the harvesting efficiency; Section 15.3 studies a wireless-powered communication network (WPCN) implementing a wireless-powered opportunistic beamforming (OBF) protocol. In each section closed-form mathematical expressions are provided for the considered performance metric of each scenario as well as numerical results with useful insights regarding the network’s performance.
关键词： stochastic geometry,SWIPT,opportunistic beamforming,wireless power transfer,cooperative networks
更新于2025-09-23 15:22:29