- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
In-band Full-Duplex Relay-Assisted Millimeter-Wave System Design
摘要： Millimeter-wave (mmWave) communication is a promising technology for future wireless systems due to the availability of huge unlicensed bandwidth. However, the need for large number of radio frequency (RF) chains associated with the antenna array and the corresponding increase in hardware complexity and power consumption are major stumbling blocks to its implementability. In this paper, we propose a low-complexity in-band full-duplex relay-assisted mmWave communication system design. We obtain the proposed multiple-input multiple-output analog–digital hybrid transceivers and relay filters by minimizing the overall sum-mean-square-error while mitigating the effect of residual loopback self-interference (LSI) in the system. The number of RF chains required in the proposed design is less than the number of antennas. We first present a design assuming the availability of perfect channel state information (CSI) at all the nodes. Later, we extend it to a robust design assuming a more realistic scenario, where the available CSI is imperfect. Furthermore, the LSI channel knowledge is assumed to be imperfect for both the designs rendering them robust to errors in loopback CSI. We employ sparse approximation technique to reduce the hardware complexity in the proposed system designs. The proposed algorithms are shown to converge to a limit even though the global convergence is hard to prove since the overall problem is non-convex. The hardware complexity-performance tradeoff of the proposed design is analyzed. Furthermore, the resilience of the robust design in the presence of CSI errors and the performance of both the proposed designs over various parameters are illustrated via numerical simulations.
关键词： robust design,Full-duplex,residual self-interference,millimeter-wave communication,hybrid beamforming
更新于2025-09-23 15:22:29
-
Analogue Wireless Beamforming Exploiting the Fiber-Nonlinearity of Radio Over Fiber Based C-RANs
摘要： As a key technique of supporting the fixed backbone network, radio over fiber (RoF) systems transmit the radio frequency signals over optical fiber in order to take advantage of their large available bandwidth. In this context, optical fiber aided phased antenna array (PAA) based beamforming techniques have attracted substantial research interest with the goal of improving the cell-edge coverage of cellular base stations. In this paper, we conceive a novel optical fiber aided beamforming technique based on the fiber's nonlinearity to be applied in cloud radio access network (C-RAN). In our proposed technique, the PAA elements are fed by the phase-shifted signals introduced by our highly nonlinear fiber (HNLF) aided phase-shifting solution, which results in an angular beamsteering range of around 90°. This can be exploited by sectorization in cellular networks to reduce the cochannel interference imposed. Furthermore, we exploit the proposed RoF-aided phase shifting technique in C-RAN, where our proposed system takes advantage of the centralized signal processing capability of the RoF system to conceive an all-optical processing based tunable beamforming system. While our flexible HNLF-aided phase-shifting process is confined to the central office of the C-RAN, the end users in the C-RAN cellular networks are capable of flexibly choosing the serving remote radio heads (RRHs) and employing diverse wireless transmission techniques. Through integrating our HNLF-aided phase-shifting design into the proposed C-RAN, we impose as little as 0.1 dB signal-to-noise Ratio (SNR) degradation compared to its traditional electronic counterpart, which requires extra phase-shifters.
关键词： phase-shifter,self-phase modulation,phased array antenna beamforming,C-RAN,cross-phase modulation,highly nonlinear fiber,Optical fiber,optical nonlinearity
更新于2025-09-23 15:22:29
-
Gradient Projection-Based Alternating Minimization Algorithm for Designing Hybrid Beamforming in Millimeter-Wave MIMO Systems
摘要： This study considers the use of alternating minimization (AltMin) framework as the main design principle in determining the optimal weights of hybrid digital and analog beamforming in millimeter-wave massive multiple-input multiple-output systems. However, such framework experiences analog beamformer design problem because analog beamformers are normally constructed using phase shifters (PSs), which result in non-convex constraints, and known solutions suffer from high computational complexity. We address this issue by proposing a simple yet efficient gradient projection (GP)-based AltMin (GP-AltMin) algorithm for hybrid beamforming design problems. In addition, when quantized PSs are adopted, we propose non-uniform PSs on the basis of the Lloyd-Max algorithm for minimizing the performance loss caused by quantization. Simulation results demonstrate that the proposed GP-AltMin algorithm not only has lower complexity but can also achieve spectral efficiency, which is comparable with or higher than those of state-of-the-art algorithms that use unquantized and low-resolution PSs.
关键词： gradient projection,massive MIMO,Beamforming,finite resolution phase shifters,millimeter-wave
更新于2025-09-23 15:21:21
-
Decoupling Beam Steering and User Selection for MU-MIMO 60-GHz WLANs
摘要： Multi-user transmission at 60 GHz promises to increase the throughput of next-generation WLANs via both analog and digital beamforming. To maximize the capacity, analog beams need to be jointly configured with user selection and digital weights; however, joint maximization requires prohibitively large training and feedback overhead. In this paper, we scale multi-user 60-GHz WLAN throughput via design of a low-complexity structure for decoupling beam steering and user selection such that analog beam training precedes user selection. We introduce a two-class framework comprising: 1) single-shot selection of users by minimizing overlap of their idealized beam patterns obtained from analog training and 2) interference-aware incremental addition of users via sequential training to better predict inter-user interference. We implement a programmable testbed using software-defined radios and commercial 60-GHz transceivers and conduct over-the-air measurements to collect channel traces for different indoor WLAN deployments. Measurements are conducted using a 12-element phased antenna array as well as horn antennas with different directivity gains to evaluate the performance of practical 60-GHz systems. Using trace-based emulations and high resolution 60-GHz channel models, we show that our decoupling structure experiences less than 5% performance loss compared with maximum achievable rates via joint user-beam selection.
关键词： user selection,MU-MIMO,digital beamforming,60 GHz,IEEE 802.11ay,beam steering
更新于2025-09-23 15:21:21
-
ROBUST ADAPTIVE WIDEBAND BEAMFORMING USING PROBABILITY-CONSTRAINED OPTIMIZATION
摘要： The existing robust narrowband beamformers based on probability-constrained optimization have an excellent performance as compared to several state-of-the-art robust beamforming algorithms. However, they always assume that the steering vector errors are small enough. Without this assumption, we extend the probability-constrained approach to a wideband beamformer. In addition, a novel robust wideband beamformer with frequency invariance constraints is proposed by introducing the response variation (RV) element. Our problems can be reformulated in a convex form as the iterative second order cone programming (SOCP) problem and solved effectively using well-established interior point method. Compared with existing robust wideband beamformers, a more efficient control over the beamformer’s response against the steering vector errors is achieved with an improved output signal-to-interference-plus-noise ratio (SINR).
关键词： response variation (RV),robust adaptive wideband beamforming,frequency invariance constraints,second order cone programming (SOCP),probability-constrained optimization,signal-to-interference-plus-noise ratio (SINR)
更新于2025-09-23 15:21:21
-
[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Digital Beamforming Based RFI Mitigation for Synthetic Aperture Radar
摘要： An increasing challenge for P-band Synthetic Aperture Radar (SAR) is Radio Frequency Interference (RFI). RFI results in image distortions and degrades the derived science products. This makes it critical to apply RFI removal techniques to restore the image quality. New advanced techniques can be achieved with Digital Beamforming (DBF) radars such as EcoSAR. In this paper, we present a Range-Dependent Time Minimum Variance Distortionless Response (RDTMVDR) Beamformer and apply it to EcoSAR flight data during post-processing. The antenna pattern (AP) is adaptively changed for each range line which increases the RFI suppression compared to a fixed AP for each pulse. The interferometric image quality is assessed before and after RFI suppression.
关键词： RFI,SAR,Digital Beamforming
更新于2025-09-23 15:21:21
-
Improving Spatial Resolution Using Incoherent Subtraction of Receive Beams Having Different Apodizations
摘要： In ultrasonic imaging, reduction of lateral sidelobes can result in an improved image with less distortion and fewer artifacts. In general, apodization is used to lower sidelobes in exchange for increasing the width of the mainlobe and thus decreasing lateral resolution. Null subtraction imaging (NSI) is a nonlinear image processing technique that uses different receive apodizations on copies of the same RF data to maintain low sidelobe levels while simultaneously improving lateral resolution. The images created with three different apodization functions are combined to form an image with low sidelobe levels and apparent improvements in lateral resolution compared to conventional rectangular apodization. To evaluate the performance of this technique for different imaging tasks, experiments were performed on an ATS539 phantom containing wire targets to assess lateral resolution and cylindrical anechoic and hyperechoic targets to assess contrast. NSI images were compared against rectangular apodized images and minimum variance (MV) beamformed images. In experiments, the apparent lateral resolution was observed to improve by a factor of more than 35 times when compared to rectangular apodization. Image quality was assessed by estimation of lateral resolution (-6-dB receive beamwidth), mainlobe to sidelobe ratio (MSR) and contrast-to-noise ratio (CNR). Imaging with NSI using a focal number of 2 (f/2), the -6-dB beamwidth on receive as measured from a small wire target in the ATS phantom was 0.03λ compared to 2.79λ for rectangular apodization. Sidelobes were observed to decrease by 32.9 dB with NSI compared to rectangular apodization. However, the ability to observe the contrast of anechoic and hyperechoic targets reduced when utilizing the NSI scheme, i.e., the CNR decreased from -3.05 to -1.01 for anechoic targets and 1.65 to 0.45 for the hyperechoic targets.
关键词： beamforming,apodization,plane wave imaging,Ultrasound imaging
更新于2025-09-23 15:21:21
-
[IEEE 2019 International Topical Meeting on Microwave Photonics (MWP) - Ottawa, ON, Canada (2019.10.7-2019.10.10)] 2019 International Topical Meeting on Microwave Photonics (MWP) - Heterogeneous multicore fiber for optical beamforming
摘要： We experimentally demonstrate, for the first-time to our knowledge, optical beamforming for microwave phased array antennas implemented with a heterogeneous multicore fiber link. The multicore fiber has been engineered to act as an optical sampled true time delay that allows to implement radiofrequency signal processing in a distributed way. It comprises 7 trench-assisted cores where each core is fabricated with different dimensions and core dopant concentration, as to feature a different group delay and chromatic dispersion behavior. We emulated different radio beamsteering scenarios where the beam-pointing angle is modified by tuning the optical wavelength in a 20-nm range, while squint-beam effects are avoided.
关键词： Microwave Photonics,optical beamforming networks,multicore fibers
更新于2025-09-23 15:21:01
-
[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Reducing CPV Materials Cost Through Multistage Concentration
摘要： This paper considers an energy-limited cognitive relay network, where a secondary transmitter (ST) assists to forward the traf?c from a primary transmitter (PT) to a primary receiver (PR), in exchange for serving its own secondary receiver (SR) in the same frequency. The multiple-antenna ST is assumed to be energy-constrained and powered by both information ?ow from source (PT) and dedicated energy streams from destinations (PR and SR), which is called a destination-aided wireless power transfer (DWPT) scheme. Then, the relay processing matrix, cognitive beamforming vector, and power splitter are jointly designed to maximize the rate of secondary users under the energy causality constraint and the constraint that the demanded rate of primary users is satis?ed. For the perfect channel state information (CSI) case, by adopting the semi-de?nite relax technique and the Charnes–Cooper transformation, the global optimal solution is given. To reduce the complexity, matrix decomposition, zero forcing scheme, and dual method are jointly employed to derive a suboptimal solution. For the imperfect CSI case, the S-procedure is used to transform the worst case robust problem into a tractable semi-de?nite program. Simulation results reveal that our proposed DWPT scheme is greatly preferred for both perfect and imperfect CSI cases when ST is close to PR/SR.
关键词： cognitive relay networks,power splitting,Wireless power transfer,semi-de?nite program,beamforming design
更新于2025-09-23 15:21:01
-
Design and measurement of a 5G mmW mobile backhaul transceiver at 28 GHz
摘要： High throughput and ultra low latency are the main requirements for fifth generation (5G) mobile broadband communications. Densely populated urban environments require utilization of previously underutilized millimeter wave frequency spectrum for higher data rates. The Ka-band, previously used in satellite applications, is of particular interest to terrestrial 5G mobile networks. New radio solutions are required for these frequencies, such as multiple wireless base stations organized in small cells and highly directional antennas to compensate for higher path loss. Wireless backhaul is predicted to be the most cost-effective and versatile solution to connect 5G base stations to the core network. Wireless backhaul enables flexible and easy installation of 5G base stations in ad hoc networks, supporting large crowd gatherings such as concerts and sports events. In this article, we present an architecture of a wireless backhaul transceiver, which operates on the 26.5–29.5-GHz band. The architecture described in this paper was implemented, and the performance of the receiver (Rx) array has been measured. We also present over-the-air antenna array measurement results using the Rx. The measurement results show that unequal Rx channel gains and antenna gains do not have a significant effect on the shape of the main lobe of the radiation pattern. We have measured a coherence gain of 2.7 dB from two Rx channels that is close to the theoretical value of 3.0 dB. We have achieved a conducted Rx EVM of better than 2% using a 100-MHz 16-QAM modulated signal at 26.5 GHz.
关键词： Antenna pattern,Beamforming,Millimeter wave,Radio frequency,Transceiver,5G,Antenna array,Backhaul
更新于2025-09-23 15:21:01