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oe1(光电查) - 科学论文

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  • Precoding and Detection for Broadband Single Carrier Terahertz Massive MIMO Systems Using LSQR Algorithm

    摘要： The terahertz (THz) communication utilizes the frequency spectrum above 300 GHz and is widely considered as a promising solution to the future high-speed short-range wireless communication beyond millimeter wave (mmWave) communication. While providing tens of gigahertz bandwidth, it is subjected to high propagation path loss, inter-symbol and inter-user interferences. The massive multiple-input-multiple-output (MIMO) can be applied to address these problems by cooperation between many access point (AP) antennas. However, the THz channel characteristics, including high propagation path loss, frequency selectivity and big number of samples per channel impulse response (CIR), require carefully tailored algorithm for massive MIMO signal processing. In this paper, we propose a single carrier minimum mean square error (MMSE) precoding and detection algorithm for frequency selective THz channels. The MIMO signal transmission is described with the block matrices. A gain control heuristic is introduced to reduce the complexity. The sparsity property of the channel is utilized to construct sparse channel matrices and the least square QR (LSQR) algorithm is applied to efficiently solve the problems. Besides the uniform antenna array, the hybrid array consisting of several subarrays is considered as well. Simulation results show that the massive MIMO array can provide a satisfactory performance in terms of bit error rate (BER).

    关键词： detection,massive MIMO,frequency selective channel,precoding,LSQR algorithm,block matrix,minimum mean square error,THz communication

    更新于2025-09-23 15:23:52

  • 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

  • [IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - High Performance GaAs Solar Cells Grown at High Growth Rates by Atmospheric-Pressure Dynamic Hydride Vapor Phase Epitaxy

    摘要： In this treatise, we evaluate the error-rate (ER) performance of turbo-coded multi-carrier code division multiple access scheme (MC-CDMA) for downlink (DL) transmission. The transmitter pre-processing (TP) technique is a promising signal processing technique, which is carried out at the transmitter side to reduce the burden of each mobile station (MS) in the context of DL communication. We formulate minimum mean-square-error-aided TP matrix using noisy feedback of vector-quantized estimated channel information (CI) for frequency-division duplexing system. Clearly, we estimate the CI and perform vector quantization (VQ) at each MS and transmit the index of the quantized value through dedicated low rate noisy channel. Finally, we acquire CI of all active users using known estimation algorithm in order to build TP. We realize time-frequency domain signature sequence to support more user population. In particular, we analyze the ER performance of coded MC-CDMA system with TP for Stanford University Interim channel model. The ER curve shows that coded MC-CDMA system based on TP approach provides better performance with less signal-to-noise ratio while offering low complexity of MS. In addition, performance curve shows that there is an improvement in the ER performance when perfect CI is utilized to build TP matrix compared with noise-contaminated VQ-CI.

    关键词： Code division multiple access (CDMA),minimum mean-square-error (MMSE),zero forcing (ZF),interleave division multiple access (IDMA),transmitter pre-processing (TP),vector quantization(VQ)

    更新于2025-09-23 15:19:57

  • [IEEE 2019 Compound Semiconductor Week (CSW) - Nara, Japan (2019.5.19-2019.5.23)] 2019 Compound Semiconductor Week (CSW) - Electrically injected $1.64\ \boldsymbol{\mu} \mathbf{m}$-emitting In <sub/>0.65</sub> Ga <sub/>0.35</sub> As 3-QW laser diodes grown on mismatched substrates by MOVPE

    摘要： In this treatise, we evaluate the error-rate (ER) performance of turbo-coded multi-carrier code division multiple access scheme (MC-CDMA) for downlink (DL) transmission. The transmitter pre-processing (TP) technique is a promising signal processing technique, which is carried out at the transmitter side to reduce the burden of each mobile station (MS) in the context of DL communication. We formulate minimum mean-square-error-aided TP matrix using noisy feedback of vector-quantized estimated channel information (CI) for frequency-division duplexing system. Clearly, we estimate the CI and perform vector quantization (VQ) at each MS and transmit the index of the quantized value through dedicated low rate noisy channel. Finally, we acquire CI of all active users using known estimation algorithm in order to build TP. We realize time-frequency domain signature sequence to support more user population. In particular, we analyze the ER performance of coded MC-CDMA system with TP for Stanford University Interim channel model. The ER curve shows that coded MC-CDMA system based on TP approach provides better performance with less signal-to-noise ratio while offering low complexity of MS. In addition, performance curve shows that there is an improvement in the ER performance when perfect CI is utilized to build TP matrix compared with noise-contaminated VQ-CI.

    关键词： zero forcing (ZF),transmitter pre-processing (TP),interleave division multiple access (IDMA),vector quantization(VQ),Code division multiple access (CDMA),minimum mean-square-error (MMSE)

    更新于2025-09-19 17:13:59

  • [IEEE 2018 Second International Conference on Electronics, Communication and Aerospace Technology (ICECA) - Coimbatore (2018.3.29-2018.3.31)] 2018 Second International Conference on Electronics, Communication and Aerospace Technology (ICECA) - Analysis and Evaluation of Speckle Filters by Using Polarimetric Synthetic Aperture Radar Data Through Local Statistics

    摘要： Speckle noise, a granular noise, occurs in synthetic aperture radar (SAR) data due to the interference of reflected signals with several scatterers in a resolution cell. One of the simplest techniques to suppress speckle noise from polarimetric SAR data is to use local statistics. The Lee filter employs sample mean and variance of pixels of data degraded by speckle noise, which can be multiplicative, additive, or a mixture of both, in a searching window. The refined Lee method utilizes directional windows with local minimum mean square error (LMMSE), which ensures superior maintenance of spatial resolution and features. The Lee–Sigma filter is constructed on the basis of the two-sigma probability, which effectively suppresses the speckle noise. However, insufficiencies were observed in the generation of a biased evaluation, blurring of edges, and suppression of point targets. To eliminate these insufficiencies, the improved Lee–Sigma filter was developed, which employs the minimum mean square error estimate as a priori mean. Thus, an excellent maintenance of point targets and subtle details is displayed. In this study, the Lee, refined Lee, Lee–Sigma, and improved Lee–Sigma filters were evaluated using full polarimetric data. The evaluated results indicated that the improved Lee–Sigma filter performed better than other local statistics filters.

    关键词： Speckle noise,Synthetic aperture radar,Minimum mean square error,Polarimetric synthetic aperture radar

    更新于2025-09-04 15:30:14