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Compressed Channel Estimation for Near-Field XL-MIMO Using Triple Parametric Decomposition

IEEE TRANSACTIONS ON VEHICULAR techNOLOGY 2023年第11期72卷 15040-15045页

作者： Guo, Xufeng Chen, Yuanbin Wang, Ying Beijing Univ Posts & Telecommun State Key Lab Networking & Switching Technol Beijing 100876 Peoples R China

With the presence of the conventional angular-domain representation, the energy leakage effect is evident for the near-field extremely large-scale multiple-input-multiple-output (XL-MIMO) channel, which further leads to ambiguous channel power detection, significantly eroding channel estimation performance. To tackle this challenge, this paper proposes a novel Triple Parametric Decomposition (TPD) framework to facilitate compressed channel estimation in the XL-MIMO system. Specifically, we examine the case of a uniform planar array (UPA) with the geometry parameters involving a pair of azimuth-elevation angles and distances in an attempt to achieve independent decomposition by constructing their own covariance matrices. Then, by utilizing the on- and off-grid techniques, we obtain the sparse recovery of angles and distances information in the absence of energy leakage effect at reduced gridding complexity. Simulation results demonstrate that our proposed TPD achieves significant performance improvement over the state-of-the-art methods.

关键词： Antennas Channel estimation Geometry Covariance matrices Indexes Coherence Sparse matrices XL-MIMO near-field channel estimation triple parametric decomposition compressive sensing

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Web3 technologies: Challenges and Opportunities

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IEEE NETWORK 2024年第3期38卷 187-193页

作者： Liu, Weikang Cao, Bin Peng, Mugen Beijing Univ Posts & Telecommun State Key Lab Networking & Switching Technol Beijing 100876 Peoples R China Zhejiang Lab Hangzhou 311121 Peoples R China

Different from "read" based Web1 and "read-write" based Web2, "read-write-own" based Web3 is proposed as a typical user-centric Internet to open the new generation of the World Wide Web. Web3 is the internet religious fundamentalism for data rights owned by users based on identity, data, network, and service, which requires the support of full-process data protection provided by a zero-trust and zero-touch environment. However, as to the traditional layered architecture like TCP/IP, data protection is an overlaid function, which is far away from the full-process data protection requirements. To this end, in order to build a zero-trust and zero-touch environment, a Web3 architecture is presented in this article as a promising paradigm. Meanwhile, the key principles for Web3 architecture designing are discussed, covering interoperability and interpretability of data, trustworthiness throughout network lifecycle, incentive for collaboration and sharing, and human-centric experience. Moreover, in order to achieve these principles, four aspects of enabling technologies are presented, including semantic, incentive, decentralized, and spatial technologies. Finally, some main challenges and open issues are also identified as a future direction for further work.

关键词： Blockchains Data protection Security Computer architecture Collaboration Artificial intelligence Interoperability Semantic Web User centered design Decentralized applications Web3 Zero-trust Zero-touch Data rights User-centric Decentralization

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Next-Generation RIS: From Single to Multiple Functions

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IEEE WIRELESS COMMUNICATIONS LETTERS 2023年第12期12卷 1988-1992页

作者： Zheng, Ailing Ni, Wanli Wang, Wen Tian, Hui Beijing Univ Posts & Telecommun State Key Lab Networking & Switching Technol Beijing 100876 Peoples R China

In this letter, we propose a next-generation reconfigurable intelligent surface (RIS) architecture, termed multi-functional RIS (MF-RIS), which enables signal reflection, refraction and amplification simultaneously to overcome the challenges, such as half-space coverage and double-fading attenuation. In order to investigate the performance of MF-RIS, we aim at maximizing the sum-rate in an MF-RIS-aided non-orthogonal multiple access network with discrete phase shifts, where three practical operating protocols, namely energy splitting (ES), mode switching (MS), and time switching (TS), are studied. Then, an efficient iterative algorithm is developed to tackle the formulated non-convex problem, where the transmit beamforming and MF-RIS coefficients are designed jointly by solving a series of semidefinite programming problems. Simulation results show that: 1) The proposed MF-RIS-assisted NOMA network provides 57% and 41% sum-rate gains than single- and dual-functional RISs, respectively;2) The TS protocol outperforms the ES and MS counterparts.

关键词： Multi-functional RIS non-orthogonal multiple access beamforming design sum-rate maximization

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Task Allocation Under Geo-Indistinguishability via Group-Based Noise Addition

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IEEE TRANSACTIONS ON BIG DATA 2023年第3期9卷 860-877页

作者： Zhang, Pengfei Cheng, Xiang Su, Sen Wang, Ning Beijing Univ Posts & Telecommun BUPT State Key Lab Networking & Switching Technol Beijing 100876 Peoples R China

Locations are usually necessary for task allocation in spatial crowdsourcing, which may put individual privacy in jeopardy without proper protection. Although existing studies have well explored the problem of location privacy protection in task allocation under geo-indistinguishability, they potentially assume the workers could perform any tasks, which might not be practical in reality. Moreover, they usually adopt planar laplacian mechanism to achieve geo-indistinguishability, which will introduce excessive noise due to its randomness and boundlessness. To this end, we propose a task alloCAtioN approach via grOup-based noisE addition under Geo-I, referred to as CANOE. Its main idea is that each worker uploads the noisy distances between his true location and the obfuscated locations of his preferred tasks instead of uploading his obfuscated location. In particular, to alleviate the total noise when conducting grouping, we put forward an optimized global grouping with adaptive local adjustment method OGAL with convergence guarantee. To collect the noisy distances which are required for subsequent task allocation, we develop a utility-aware obfuscated distance collection method UODC with solid privacy and utility guarantees. We further theoretically analyze the privacy, utility and complexity guarantees of CANOE. Extensive analyses and experiments over two real-world datasets confirm the effectiveness of CANOE.

关键词： Task analysis Resource management Privacy Noise measurement Servers Crowdsourcing Convergence Spatial crowdsourcing task allocation privacy protection geo-indistinguishability

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Wireless Beacon Enabled Hybrid Sparse Channel Estimation for RIS-Aided mmWave Communications

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IEEE TRANSACTIONS ON COMMUNICATIONS 2023年第5期71卷 3144-3160页

作者： Guo, Xufeng Chen, Yuanbin Wang, Ying Beijing Univ Posts & Telecommun BUPT State Key Lab Networking & Switching Technol Beijing 100876 Peoples R China

The inability of reconfigurable intelligent surfaces (RISs) to signal processing has become a critical bottleneck in terms of the precise capture of cascaded channels. There exists a pair of critical issues: 1) the high-dimensional cascaded channel to be estimated, which always entails substantial pilot overhead typically proportional to RIS elements and 2) the high possibilities of false alarms and unfaithful angle detection during cascaded channel estimates, referred to as the angular distortion, particularly in the case of conventional fully-passive RIS systems. To circumvent these issues, we investigate in this paper a multi-user multiple-input multiple-output (MIMO) system assisted by a wireless beacon (WB) enabled RIS over millimeter wave (mmWave) frequency. Specifically, WB is a functionally independent hardware that attaches parasitically to the RIS using only one radio frequency chain for broadcasting pilots, allowing for the accurate acquisition of partial cascaded channel information, e.g., some of angles of arrival/departure (AoA/AoDs) and complex gains. This efficiently eliminates the angular distortion effect and thus facilitates high precision recovery of sparse cascaded mmWave channels. Then, a hybrid structured sparsity (HSS) model is presented to capture hybrid sparse priors and approximate exact posterior distributions associated with RIS-aided twin-hop channels. We conceive of channel estimation as a compressive sensing problem in contrast to its conventional copy due to the presence of an unknown sensing matrix. To tackle this problem, an expectation-maximization (EM)-based algorithm, i.e., HSS-EM, is developed in order to fully employ the sparse priors encapsulated by the proposed HSS model for a robust and accurate recovery of the cascaded channels. Numerical results validate our analytical claims and demonstrate the significant improvement in terms of the normalized mean square error (NMSE) performance over conventional designs.

关键词： Channel estimation Millimeter wave communication Distortion Radio frequency Wireless communication Sensors Hardware Reconfigurable intelligent surface millimeter wave channel estimation sparse signal recovery compressive sensing

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Multi-Functional RIS-Aided Wireless Communications

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IEEE INTERNET OF THINGS JOURNAL 2023年第23期10卷 21133-21134页

作者： Wang, Wen Ni, Wanli Tian, Hui Beijing Univ Posts & Telecommun State Key Lab Networking & Switching Technol Beijing 100876 Peoples R China

In this article, we propose a multi-functional reconfigurable intelligent surface (MF-RIS) to address the half-space coverage and double-fading attenuation issues faced by existing RISs. By simultaneously reflecting, refracting, and amplifying the incident signal, the proposed MF-RIS is capable of realizing full-space coverage with the mitigated signal degradation. The operation principle of the MF-RIS is first provided, and then an efficient beamforming scheme is proposed for MF-RIS-aided wireless communications. Simulation results show that, through combining multiple functions on one surface, the MF-RIS achieves significant throughput improvement over existing RISs.

关键词： Beamforming design multi-functional reconfigurable intelligent surface (MF-RIS) operation principle rate maximization

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Semi-Federated Learning for Collaborative Intelligence in Massive IoT Networks

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IEEE INTERNET OF THINGS JOURNAL 2023年第13期10卷 11942-11943页

作者： Ni, Wanli Zheng, Jingheng Tian, Hui Beijing Univ Posts & Telecommun State Key Lab Networking & Switching Technol Beijing 100876 Peoples R China

Implementing existing federated learning in massive Internet of Things (IoT) networks faces critical challenges, such as imbalanced and statistically heterogeneous data and device diversity. To this end, we propose a semi-federated learning (SemiFL) framework to provide a potential solution for the realization of intelligent IoT. By seamlessly integrating the centralized and federated paradigms, our SemiFL framework shows high scalability in terms of the number of IoT devices even in the presence of computing-limited sensors. Furthermore, compared to traditional learning approaches, the proposed SemiFL can make better use of distributed data and computing resources, due to the collaborative model training between the edge server and local devices. Simulation results show the effectiveness of our SemiFL framework for massive IoT networks. The code can be found at https://***/niwanli/SemiFL_IoT.

关键词： Collaborative intelligence data and device heterogeneity Internet of Things (IoT) semi-federated learning (SemiFL)

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MIMO Free-Space Optical Communications Using Photon-Counting Receivers Under Weak Links

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IEEE COMMUNICATIONS LETTERS 2023年第4期27卷 1185-1189页

作者： Wang, Siming Peng, Mugen Yuan, Renzhi Beijing Univ Posts & Telecommun State Key Lab Networking & Switching Technol Beijing 100876 Peoples R China

Spatial diversity techniques are usually used to mitigate the influence of turbulence in the free-space optical communication (FSOC) with photon-counting receivers, especially when the communication links are weak. A maximum likelihood (ML) detection can be directly applied to the outputs of photon-counting receivers. However, it is challenging to obtain an analytical error probability for the ML detection. In this letter, we derive the analytical error probability of the ML detection under both turbulent and non-turbulent cases by equivalently considering L detected photons;and the approximating error is in the order of magnitude O(?(L)b/L!), where ?(b) is the back -b ground noise. Besides, we prove that the ML detection equals a threshold detection following an equal-gain combining when the signal strengths are close to each other in non-turbulent cases. Numerical results show that L < 10 is sufficient for typical scenarios with small background noises ?(b) < 1. Besides, we demonstrate that the derived analytical error probability can achieve a higher precision and computational efficiency compared with Monte-Carlo methods.

关键词： Photonics Error probability Receivers MIMO communication Background noise Monte Carlo methods Fading channels Free-space optical communication maximum likelihood detection multiple-input multiple-output photon-counting receiver

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Swin-Loc: Transformer-Based CSI Fingerprinting Indoor Localization With MIMO ISAC System

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IEEE TRANSACTIONS ON VEHICULAR techNOLOGY 2024年第8期73卷 11664-11679页

作者： Xu, Xiaodong Zhu, Fangzhou Han, Shujun Yu, Zhongyao Zhao, Hangyu Wang, Bizhu Zhang, Ping Beijing Univ Posts & Telecommun State Key Lab Networking & Switching Technol Beijing 100876 Peoples R China Peng Cheng Lab Shenzhen 518066 Peoples R China

With multiple-input multiple-output (MIMO) technologies widely employed in mobile communication systems, wireless signals will have higher resolution in both the time and angle domains. It makes high-precision localization gain increasing attention in MIMO integrated sensing and communication (ISAC) systems. However, the decimeter-level precise indoor localization is full of challenges due to the multi-path fading and additional noise in indoor propagations. Excessive resource overhead and channel state information (CSI) fingerprint distortion in complex channel environments are the main factors that hinder indoor high-precision localization. To solve the CSI fingerprint distortion while reducing resource consumption, we propose a Swin Transformer-based CSI data-driven indoor localization framework called Swin-Loc. In the proposed Swin-Loc, a channel fingerprint extraction scheme is formulated to enhance the CSI features. Moreover, an improved Swin Transformer-based CSI network (SwinCSINet) model is proposed to improve localization precision. Experiments are conducted on the real-world CSI dataset given by the KU Leuven lab and the simulation CSI dataset generated by the DeepMIMO platform. Simulation results demonstrate that the localization precision on all datasets in the metric of root mean squared error (RMSE) is within 0.3 m, which outperforms current deep neural networks (DNNs) based schemeand attention-based scheme. Furthermore, the storage overhead of the improved SwinCSINet model is reduced to about 33$\%$ of the DNN regression model, and the real-time performance is optimized.

关键词： Location awareness Fingerprint recognition Feature extraction Transformers MIMO communication Data mining Wireless communication CSI fingerprint data-driven localization ISAC MIMO swin transformer

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Reduced Guard Interval Orthogonal Frequency Division Multiplexing: A Soft Trade-Off Solution Toward Spectral Efficiency

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IEEE COMMUNICATIONS LETTERS 2024年第12期28卷 2920-2924页

作者： Wang, Zhaoqi Xu, Ran Wu, Shihao Liu, Xiqing Peng, Mugen Beijing Univ Posts & Telecommun Sch Informat & Commun Engn State Key Lab Networking & Switching Technol Beijing 100876 Peoples R China

The guard interval, termed as cyclic prefix (CP) or zero-padding (ZP), is utilized to mitigate multipath interference in orthogonal frequency division multiplexing (OFDM) systems but at the expense of spectral efficiency. Symbol cyclic shift equalization (SCSE) is our previous proposal to address multipath propagation in CP-free OFDM systems. However, SCSE-OFDM exhibits poor bit error rate (BER) performance when the power of the shortest resolvable path is relatively low. In light of this, we carry out a reduced guard interval (RGI) OFDM scheme that achieves a soft trade-off between SCSE-OFDM and ZP-OFDM, where RGI length can be optimized using genetic algorithm. Simulation results demonstrate superior BER performance of RGI-OFDM over SCSE-OFDM and higher spectral efficiency compared to both SCSE-OFDM and ZP-OFDM. RGI-OFDM also exhibits evident advantages in harsh environments with large delay spread.

关键词： OFDM Tail Delays Symbols Spectral efficiency Receivers Interference cancellation Genetic algorithms Baseband Digital-analog conversion Orthogonal frequency division multiplexing reduced guard interval delay spread spectral efficiency

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