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A Low-Complexity Algorithm for a Reinforcement Learning-Based Channel Estimator for MIMO Systems

SENSORS 2022年第12期22卷 4379-4379页

作者： Kim, Tae-Kyoung Min, Moonsik Gachon Univ Dept Elect Engn Seongnam 13120 South Korea Kyungpook Natl Univ Sch Elect Engn Daegu 41566 South Korea Kyungpook Natl Univ Sch Elect & Elect Engn Daegu 41566 South Korea

This paper proposes a low-complexity algorithm for a reinforcement learning-based channel estimator for multiple-input multiple-output systems. The proposed channel estimator utilizes detected symbols to reduce the channel estimation error. However, the detected data symbols may include errors at the receiver owing to the characteristics of the wireless channels. Thus, the detected data symbols are selectively used as additional pilot symbols. To this end, a Markov decision process (MDP) problem is defined to optimize the selection of the detected data symbols. Subsequently, a reinforcement learning algorithm is developed to solve the MDP problem with computational efficiency. The developed algorithm derives the optimal policy in a closed form by introducing backup samples and data subblocks, to reduce latency and complexity. Simulations are conducted, and the results show that the proposed channel estimator significantly reduces the minimum-mean square error of the channel estimates, thus improving the block error rate compared to the conventional channel estimation.

关键词： multiple-input multiple-output channel estimation Markov decision process reinforcement learning

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Analysis of 2 x 2 MIMO array loaded by artificial magnetic conductor with improved gain, isolation, and bandwidth using equivalent transmission line model for indoor wireless base station

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INTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING 2022年第10期32卷 e23307-e23307页

作者： Malekpoor, Hossein Arak Univ Fac Engn Dept Elect Engn Arak *** Iran

A low profile printed dipole antenna (PDA) backed by broadband Giuseppe Peano fractal artificial magnetic conductor (AMC) is introduced for wireless communications. First, a suggested PDA with a pair of microstrip dipoles excited by an E-shaped microstrip feedline is used to expand the bandwidth in the range of 5.96-7.04 GHz (S-11 <= -10 dB). Then, the suggested Giuseppe Peano fractal AMC surface as a reflector of the antenna is inserted into the PDA to gain improved radiation efficiency. The PDA with the 6 x 6 Giuseppe Peano AMC array exhibits -10 dB measured impedance bandwidth of 4.95-7.05 GHz (35%) for wireless local area network (WLAN) and worldwide interoperability for microwave access (WiMAX) applications. The suggested PDA with AMC compared to the PDA without AMC exhibits a size reduction of 38%, enhanced gain up to 8.2 dBi, and excellent impedance matching (at least -20 dB) with directional radiation patterns. The novel AMC unit cell is realized based on the Giuseppe Peano fractal patch to operate at 6.10 GHz with an AMC bandwidth of 5.15-7.10 GHz (32%). Besides, by loading 12 x 12 AMC reflector into the four-element array of PDA, low profile wideband structure with enhanced radiation properties are achieved. The measured results show the broad bandwidths of 5-7 GHz for all elements with enhanced gains and good isolations between the elements (more than 24 dB) for multiple-input multiple-output (MIMO) systems.

关键词： artificial magnetic conductor electromagnetic band gap multiple-input multiple-output wideband AMC printed antenna

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Transceiver Impairment Mitigation by 8x2 Widely Linear MIMO Equalizer With Independent Complex Filtering on IQ Signals

IEEE PHOTONICS JOURNAL

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IEEE PHOTONICS JOURNAL 2022年第3期14卷 1页

作者： Sato, Masaki Arikawa, Manabu Noguchi, Hidemi Matsui, Junichiro Abe, Junaichi de Gabory, Emmanuel Le Taillandier NEC Corp Ltd Syst Platform Res Labs Kawasaki Kanagawa 2118666 Japan NEC Corp Ltd Network Solut Div 1 Chiba 2701198 Japan

High-order modulation formats with high symbol rates are promising candidates for meeting the growing traffic requirements of digital coherent transmission. In using these modulation formats, the impact of transceiver impairment on the signal quality becomes significant. In this paper, we propose an 8x2 widely linear (WL) multiple-input multiple-output (MIMO) equalizer with independent complex filtering on IQ signals to mitigate linear transceiver impairments. Furthermore, we extend the equalizer for digital subcarrier (SC) multiplexing. Accordingly, a 16x4 WL MIMO equalizer is also proposed to mitigate linear transceiver impairments, through application to a pair of SC inputs. Experimental results show that, for transmission of a 58-GBaud polarization-multiplexing 64 quadrature amplitude modulation (PM-64QAM) single-carrier signal, the proposed method effectively compensates for various receiver impairments and also mitigates transmitter (Tx) impairments. Q-penalties of 0.1 dB up to a 10-ps skew, 2.5-dB gain imbalance, 7.2-degree phase error, and -15-dB crosstalk in Tx were achieved for 100-km standard single-mode fiber transmission. Moreover, for a 29-GBaud PM-64QAM dual-SC signal, the proposed 16 x 4 WL MIMO equalizer shows transceiver impairment mitigation performance similar to that in the single-carrier case, even though dual-SC transmission is less tolerant of laser phase noise.

关键词： Equalizers MIMO communication Transceivers Symbols Phase locked loops Demodulation Phase noise Digital coherent transmission digital signal processing multiple-input multiple-output optical fiber communication quadrature amplitude modulation

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Shared radiator based high-isolated tri-port mobile terminal antenna group design

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INTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING 2022年第7期32卷 e23177-e23177页

作者： Huang, He Jiang, Wen Zhang, Tiancheng Zhu, Yunze Pang, Bo Hu, Wei Xidian Univ Natl Key Lab Antennas & Microwave Technol Xian Peoples R China

This article proposes a high-isolated tri-port antenna group for 5G mobile terminals based on the shared radiator and mode orthogonality technology, which is realized by exciting the two orthogonal currents through two ports on a shared loop radiator and a patch antenna orthogonal to the loop on the back of the mobile terminal. The -6 dB impedance bandwidth of the three ports in the antenna group could cover the 3.4-3.6 GHz 5G band, while the isolation is above 20 dB within the antenna group, a very compact volume. In addition, a 12 x 12 MIMO antenna is proposed by integrating four antenna groups. The MIMO antenna still has measured isolation above 18 dB and efficiency above 50% over the operation band thanks to the orthogonal decoupling design. A good multiplexing performance is also achieved with the ECC of <0.08 and peak channel capacity of 60.29 bps/Hz at 20 dB SNR.

关键词： high isolation multiple-input multiple-output shared radiator tri-port antenna group

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Performance enhancement for indoor visible light communication system with an improved inter-symbol interference model using optimized hemispherical optical-angle-diversity-receivers

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OPTICS COMMUNICATIONS 2020年 454卷 124488-000页

作者： Feng, Jingyuan Yang, Chunyong Hou, Jin Long, Hao Chen, Shaoping South Cent Univ Nationalities Hubei Key Lab Intelligent Wireless Commun Coll Elect & Informat Engn Wuhan 430074 Hubei Peoples R China

Several hemispherical optical receivers based on angle diversity technology are optimized to achieve better reception for multiple-input multiple-output (MIMO) visible light communication (VLC) system with an improved inter-symbol interference (ISI) model. The optimal parameters are obtained via analyzing the performances under different diversity dimensions, spatial distances between adjacent photodiodes (PDs) and inclination angles. The simulation results reveal that under the condition of optical angle diversity receiver (OADR) with 4 PDs, the optimal spatial distance between adjacent PDs is 0.1 m and the inclination angle is 50 degrees, respectively. Compared with common plane model of 4 PDs, the average SNR has increased by 15.2%. It is no doubt that the OADR is a kind of promising alternative for indoor visible light communications.

关键词： Visible light communication multiple-input multiple-output Angle diversity receiver Inter-symbol interference

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Complexity Reduction With a Simplified MIMO Volterra Filter for PDM-Twin-SSB PAM-4 Transmission

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JOURNAL OF LIGHTWAVE TECHNOLOGY 2020年第4期38卷 769-776页

作者： Zhu, Mingyue Zhang, Jing Hu, Shaohua Yi, Xingwen Xu, Bo Xiang, Meng Qiu, Kun Univ Elect Sci & Technol China Sch Commun & Informat Engn Educ Minist China Key Lab Opt Fiber Sensing & Commun Chengdu 611731 Peoples R China Sun Yat Sen Univ Sch Elect & Informat Technol Guangzhou 510275 Peoples R China McGill Univ Dept Elect & Comp Engn Photon Syst Grp Montreal PQ H3A 0E9 Canada

We propose and experimentally demonstrate a simplified multiple-input multiple-output Volterra filter (MIMO-VF) in a polarization division multiplexed (PDM) twin single side-band (SSB) scheme based on two offset carriers. The right side-band (RSB) and left side-band (LSB) signals of the twin-SSB in each polarization are separated by an optical filter, and the crosstalk between the RSB and LSB is mitigated in the receiver digital signal processing (DSP) by the proposed simplified MIMO-VF, which is combined with one two-stage equalizer, i.e., a linear 2 x 2 butterfly MIMO equalizer and two independent VFs. With the proposed simplified MIMO-VF, we experimentally demonstrate a 400-Gb/s four-level pulse amplitude modulation (PAM-4) signal transmission over an 80-km standard single mode fiber (SSMF). Compared with the traditional MIMO-VF, the proposed simplified MIMO-VF can retain the same transmission performance and reduce the computational complexity by approximately 57.9%.

关键词： Amplitude modulation MIMO communication Optical fiber filters Crosstalk Optical fibers multiple-input multiple-output optical comm-unication single side-band Volterra filter

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Closed-Form Power Normalization Methods for a Satellite MIMO System

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SENSORS 2022年第7期22卷 2586页

作者： Segneri, Andrea Baldominos, Alejandro Goussetis, George Mengali, Alberto Fonseca, Nelson J. G. Heriot Watt Univ Inst Sensors Signals & Syst Edinburgh EH14 4AS Midlothian Scotland European Space Agcy Telecom Syst & Tech Sect NL-2201 AZ Noordwijk Netherlands European Space Agcy Antenna & Submillimetre Waves Sect NL-2201 AZ Noordwijk Netherlands

The paper proposes a new set of normalization techniques for precoding/beamforming matrices applicable to broadband multiuser multiple-input multiple-output (MIMO) satellite systems. The proposed techniques adapt known normalization methods to account for the signal attenuation experienced by users due to the degradation of antenna gain and free space losses towards the edge of the coverage. We use, as an example, an array-fed reflector (AFR) antenna onboard a satellite in geosynchronous orbit (GEO), which provides a favorable trade-off between high-directivity, reconfigurability, and the requirement for digital processing, but suffers from high scan losses away from broadside due to optical aberrations when considered for global coverage applications. Three different precoding/beamforming techniques are employed, namely zero forcing (ZF), minimum mean squared error (MMSE), and matched filtering (MF). Low-complexity power normalization techniques digitally applied after the beamformer are introduced that, in the absence of any atmospheric effects, lead to iso-flux-like characteristics whilst satisfying the power constraint per feed. In comparison with other methods reported in the literature, mainly based on iterative algorithms, the proposed techniques consist in closed-form expressions to provide uniform signal-to-noise ratio (SNR) and signal-to-noise plus interference ratio (SNIR) across the users without significant impact on the payload sum rate. Numerical results are presented to comparatively demonstrate the achieved performance in terms of total capacity and distribution of SNR and SNIR at various noise and interference scenarios.

关键词： multiple-input multiple-output satellite communications array-fed reflectors linear precoding power normalization techniques

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A compact coplanar waveguide-fed band-notched four-port flexible ultra-wide band-multi-input-multi-output slot antenna for wireless body area network and Internet of Things applications

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INTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING 2022年第9期32卷 e23289-e23289页

作者： Du, Chengzhu Yang, Zhipeng Zhong, Shunshi Shanghai Univ Elect Power Coll Elect & Informat Engn Shanghai 200090 Peoples R China Shanghai Univ Sch Commun & Informat Engn Shanghai Peoples R China

In this letter a novel notched multi-input-multi-output (MIMO) flexible slot antenna with a C-slot is proposed and designed for wireless body area network (WBAN) and Internet of Things (IoT) applications. The proposed antenna is comprised of four similar elements with the feed line of coplanar waveguide (CPW). Antenna is printed on flexible liquid crystal polymer (LCP) substrate with compact dimensions. The proposed UWB-MIMO slot antenna can operate in range of 2.85-10.85 GHz with notched band from 4.9-6.425 GHz. The achieved notched band can filter the interference of WLAN (5.15-5.825 GHz), by adding an inverted orthogonal branch, great isolation is achieved, which is better than 24 dB over working bands. What's more, the parameters of diversity performance like gain, envelope correlation coefficient (ECC) and diversity gain (DG) are also analyzed. The actual measurement of bending test and the effect of human body indicates that the presented antenna is suitable for WBAN and IoT applications.

关键词： band-notched coplanar waveguide flexible antenna liquid crystal polymer multiple-input multiple-output WBAN Internet of Things

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Golden codeword-based generalized spatial modulation

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INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS 2022年第10期35卷 e5144-e5144页

作者： Sibanda, Nathael Xu, Hongjun Pillay, Narushan Univ KwaZulu Natal Sch Elect Elect & Comp Engn Coll Agr Engn & Sci Elect Engn Durban South Africa

Conventional-generalized spatial modulation (C-GSM) is an NTxNR multiple-input multiple-output (MIMO) spatial modulation (SM) scheme that transmits the same complex amplitude/phase modulation symbol from multiple active transmit antennas. By using two active transmit antennas during a transmission interval, C-GSM is capable of achieving high spectral efficiencies. However, as the size of the signal constellation/domain increases, the minimum Euclidean distances (ED) between the symbols decrease. Hence, this leads to a degradation of the average bit error rate (ABER) performance of the scheme. Hence, motivated to improve the error performance of C-GSM schemes, first, this study proposes a new scheme called Golden codeword-based generalized spatial modulation (GCW-GSM), which combines C-GSM and the Golden code to take advantage of the benefits of both while avoiding their drawbacks. The proposed scheme uses conventional quadrature amplitude modulation (C-QAM), and it is investigated over Rayleigh frequency-flat fading channels with additive white Gaussian noise. Second, a closed-form expression of the theoretical average bit error probability of the proposed GCW-GSM scheme is formulated. Compared to simulation results, it proves to be increasingly tight at high signal-to-noise ratio values. Finally, the proposed scheme performance over the Rayleigh-frequency-flat fading channel is compared to that over the Rician channel. An improvement in the error performance of 6dB with spectral efficiency of 10bits/s/Hz is seen in 4x4 C-16QAM GCW-GSM over 4x4 C-256QAM conventional-spatial modulation and 4x4 C-256QAM C-GSM schemes at a bit error rate (BER) of 1x10(-5). The 4x4 C-16QAM GCW-GSM scheme exhibits an improvement in the error performance of 2.9dB with spectral efficiency of 10bits/s/Hz over the 4x4 C-64QAM conventional quadrature spatial modulation scheme at a BER of 1x10(-5). Finally, the 4x4 16-QAM GCW-GSM under Rayleigh fading has a performance gain of 3 dB over 4x4 16

关键词： generalized spatial modulation Golden code multiple-input multiple-output space-time block codes spectral efficiency

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Multi-Target Localization of MIMO Radar with Widely Separated Antennas on Moving Platforms Based on Expectation Maximization Algorithm

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REMOTE SENSING 2022年第7期14卷 1670-1670页

作者： Lu, Jiaxin Liu, Feifeng Sun, Jingyi Miao, Yingjie Liu, Quanhua Beijing Inst Technol Sch Informat & Elect Beijing 100081 Peoples R China Minist Educ Key Lab Elect & Informat Technol Satellite Nav Beijing Inst Technol Beijing 100081 Peoples R China Xiaomi Commun Co Ltd Beijing 100085 Peoples R China

This paper focuses on multi-target parameter estimation of multiple-input multiple-output (MIMO) radar with widely separated antennas on moving platforms. Aiming at the superimposed signals caused by multi-targets, the well-known expectation maximization (EM) is used in this paper. Target's radar cross-section (RCS) spatial variations, different path losses and spatially-non-white noise appear because of the widely separated antennas. These variables are collectively referred to as signal-to-noise ratio (SNR) fluctuations. To estimate the echo delay/Doppler shift and SNR, the Q function of EM algorithm is extended. In addition, to reduce the computational complexity of EM algorithm, the gradient descent is used in M-step of EM algorithm. The modified EM algorithm is called generalized adaptive EM (GAEM) algorithm. Then, a weighted iterative least squares (WILS) algorithm is used to jointly estimate the target positions and velocities based on the results of GAEM algorithm. This paper also derives the Cramer-Rao bound (CRB) in such a non-ideal environment. Finally, extensive numerical simulations are carried out to validate the effectiveness of the proposed algorithm.

关键词： expectation maximization parameter estimation superimposed signals SNR fluctuations multiple-input multiple-output

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