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Joint AP Scheduling and Precoding in RIS-Aided distributed mimo Networks: A Hierarchical DRL Framework

IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2025年第3期74卷 5264-5269页

作者： Wang, Yangjing Li, Xiao Yi, Xinping Matthaiou, Michail Jin, Shi Southeast Univ Natl Mobile Commun Res Lab Nanjing 210096 Peoples R China Queens Univ Belfast Ctr Wireless Innovat CWI Belfast BT3 9DT North Ireland

With the increasing demands for spectral and energy efficiency, distributed multiple-input multiple-output (mimo) networks assisted with reconfigurable intelligent surfaces (RISs) have attracted considerable attention. In this paper, we investigate the joint optimization of access point (AP) scheduling and precoding for RIS-aided distributed mimo networks. To make this challenging problem more tractable, we decouple the joint optimization into two hierarchical subproblems, which eventually formulate a two-timescale scheme. To further reduce the computational complexity of joint precoding, we propose a hierarchical deep reinforcement learning (HDRL) framework to maximize the system sum spectral efficiency (SE), which leads to a distributed deployment with centralized training. Simulation results show that the proposed framework yields significant reduction in the computational complexity with slight performance loss, and strong generalizability against varying system parameters.

关键词： Precoding Optimization Wireless communication Reconfigurable intelligent surfaces Processor scheduling Job shop scheduling Computational complexity Training Technological innovation Spectral efficiency AP scheduling distributed mimo hierarchical deep reinforcement learning precoding reconfigurable intelligent surface

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Location-Aware Communication for RIS-Aided distributed mimo Systems

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IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2025年第3期74卷 4445-4460页

作者： Yang, Ziang Zhang, Hongliang Di, Boya Li, Xiang Hou, Xiaolin Song, Lingyang Peking Univ Dept Elect State Key Lab Adv Opt Commun Syst & Networks Beijing 100871 Peoples R China DOCOMO Beijing Commun Labs Co Ltd Beijing 100190 Peoples R China Peking Univ Sch Elect State Key Lab Adv Opt Commun Syst & Networks Beijing 100871 Peoples R China Peking Univ Sch Elect & Comp Engn Shenzhen Grad Sch Shenzhen 518055 Peoples R China

In reconfigurable intelligent surface (RIS)-aided distributed multiple-input multiple-output (D-mimo) systems, instantaneous channel state information (CSI) is essential for the optimization of the RIS phase shifts. However, the D-mimo systems often involve numerous RISs and access points (APs), requiring the transmission of a significant amount of pilots for CSI estimation, thus resulting in high signaling overhead. To mitigate the high signaling overhead associated with CSI estimation, this paper introduces a location-aware communication method that only relies on large-scale fading information. Two new challenges have arisen in the proposed location-aware communication method. First, it is challenging to design a user position estimation method to achieve fast and accurate localization. Second, it is hard to handle the location uncertainty brought by the estimation error when performing beamforming. In response to the above challenges, we first design a space-time cooperative beam training-based localization method to achieve a favorable trade-off between localization accuracy and time cost. Subsequently, to handle the location uncertainty, by taking historical error distribution into consideration, we formulate a distributionally robust optimization (DRO)-based problem for sum-rate maximization. Numerical evaluations demonstrate the effectiveness of our proposed localization method, which can achieve sub-meter accuracy with low beam training overhead. Furthermore, the proposed DRO-based beamforming method can improve the sum-rate by 11.4% compared to the robust optimization and non-robust schemes.

关键词： Location awareness Training Optimization Array signal processing Accuracy Wireless communication Reconfigurable intelligent surfaces mimo communication Uncertainty Fingerprint recognition Reconfigurable intelligent surface (RIS) distributed mimo wireless localization distributionally robust optimization (DRO)

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Data-Aided Regularization of Direct-Estimate Combiner in distributed mimo Systems

Data-Aided Regularization of Direct-Estimate Combiner in Dis...

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2025 IEEE International Conference on Acoustics, Speech, and Signal Processing, ICASSP 2025

作者： Gouda, Bikshapathi Atzeni, Italo Tölli, Antti Centre for Wireless Communications University of Oulu Finland

ISBN: (纸本)9798350368741

This paper explores the data-aided regularization of the direct-estimate combiner in the uplink of a distributed multiple-input multiple-output system. The network-wide combiner can be computed directly from the pilot signal received at each access point, eliminating the need for explicit channel estimation. However, the sample covariance matrix of the received pilot signal that is used in its computation may significantly deviate from the actual covariance matrix when the number of pilot symbols is limited. To address this, we apply a regularization to the sample covariance matrix using a shrinkage coefficient based on the received data signal. Initially, the shrinkage coefficient is determined by minimizing the difference between the sample covariance matrices obtained from the received pilot and data signals. Given the limitations of this approach in interference-limited scenarios, the shrinkage coefficient is iteratively optimized using the sample mean squared error of the hard-decision symbols, which is more closely related to the actual system's performance, e.g., the symbol error rate (SER). Numerical results demonstrate that the proposed regularization of the direct-estimate combiner significantly enhances the SER, particularly when the number of pilot symbols is limited. © 2025 IEEE.

关键词： Direct-estimate combiner distributed mimo interference rejection regularization

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distributed mimo Broadcasting: Reverse Compute-and-Forward and Signal-Space Alignment

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2017年第1期16卷 581-593页

作者： Yang, Tao Univ Technol Sydney Global Big Data Technol Ctr Ultimo NSW 2007 Australia

We study a downlink distributed mimo system where a central unit (CU) broadcasts messages to K' users through K distributed BSs. The CU is connected to the BSs via K independent rate-constrained fronthaul (FH) links. The distributed BSs collectively serve the users through the air. We propose a new network coding based distributed mimo broadcasting scheme, using reverse compute-and-forward and signal-space alignment. At the CU, a network coding generator matrix is employed for pre network coding of the users' messages. The network coded messages are forwarded to the BSs, where the FH rate-constraint determines the actual number of network-coded messages forwarded to the BSs. At the BSs, linear precoding matrices are designed to create a number of bins, each containing a bunch of spatial streams with aligned signal-spaces. At each user, post physical-layer network coding is employed to compute linear combinations over the NC messages with respect to the bins, which reverses the prenetwork coding and recovers the desired messages. We derive an achievable rate of the proposed scheme based on the existence of NC generator matrix, signal-space alignment precoding matrices, and nested lattice codes. Improved rate and degrees of freedom over existing interference alignment and compress-and-forward schemes are shown. Numerical results demonstrate the performance improvement, e.g., by as much as 70% increase in throughput over benchmark schemes.

关键词： Cloud RAN CoMP mimo distributed mimo broadcast channel physical-layer network coding compute-and-forward interference alignment

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distributed mimo Networks With Rotary ULAs for Indoor Scenarios Under Rician Fading

IEEE OPEN JOURNAL OF THE COMMUNICATIONS SOCIETY

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IEEE OPEN JOURNAL OF THE COMMUNICATIONS SOCIETY 2024年 5卷 6367-6380页

作者： Tominaga, Eduardo N. Lopez, Onel L. A. Svensson, Tommy Souza, Richard D. Alves, Hirley Univ Oulu Ctr Wireless Commun Oulu 90570 Finland Chalmers Univ Technol Commun Syst Grp S-41296 Gothenburg Sweden Univ Fed Santa Catarina Dept Elect & Elect Engn BR-88040370 Florianopolis Brazil

The Fifth-Generation (5G) wireless communications networks introduced native support for Machine-Type Communications (MTC) use cases. Nevertheless, current 5G networks cannot fully meet the very stringent requirements regarding latency, reliability, and number of connected devices of most MTC use cases. Industry and academia have been working on the evolution from 5G to Sixth Generation (6G) networks. One of the main novelties is adopting distributed Multiple-Input Multiple-Output (D-mimo) networks. However, most works studying D-mimo consider antenna arrays with no movement capabilities, even though some recent works have shown that this could bring substantial performance improvements. In this work, we propose the utilization of Access Points (APs) equipped with Rotary Uniform Linear Arrays (RULAs) for this purpose. Considering a spatially correlated Rician fading model, the optimal angular position of the RULAs is jointly computed by the central processing unit using particle swarm optimization as a function of the location of the active devices. Considering the impact of imperfect location estimates, our numerical results show that the RULAs's optimal rotation brings substantial performance gains in terms of mean per-user spectral efficiency. The improvement grows with the strength of the line-of-sight components of the channel vectors. Given the total number of antenna elements, we study the trade-off between the number of APs and the number of antenna elements per AP, revealing an optimal number of APs for the cases of APs equipped with static ULAs and RULAs.

关键词： Antenna arrays Vectors Antennas Wireless communication Uplink Signal to noise ratio 5G mobile communication Rician channels Location awareness Central Processing Unit 6G distributed mimo location-based beamforming machine-type communications particle swarm optimization

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distributed mimo Demonstrated with 5G Radio Access Prototype

Distributed MIMO Demonstrated with 5G Radio Access Prototype

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European Conference on Networks and Communications (EuCNC)

作者： Halvarsson, Bjorn Karam, Elias Nystrom, Martin Pirinen, Roger Simonsson, Arne Zhang, Qiang Okvist, Peter Ericsson AB Stockholm Sweden Ericsson Res Stockholm Sweden

ISBN: (纸本)9781509028931

This paper presents measurement results from a distributed 4x4 multiple-input multiple-output (mimo) trial. The measurements were performed using a 5G radio access prototype including two transmission points (TPs) and a mobile terminal over 200 MHz bandwidth at 15 GHz carrier frequency. The TPs and the mobile terminal each consists of multiple antennas, enabling spatial multiplexing. In the present paper, improvements from using 4x4 mimo transmission with dual TPs are being assessed and compared with 4x4 mimo transmission from one single TP. A significant increase in throughput was demonstrated with distributed mimo where the two TPs were transmitting unique streams in parallel. This significantly improved the spatial multiplexing capacity in line-of-sight and increased the rank significantly beyond the two polarization dimensions. In the performed tests this improved the throughput from 1.1 Gbps (5.7 bps/Hz) to 2.5 Gbps (12.6 bps/Hz).

关键词： 5G distributed mimo prototype 15 GHz dual transmission

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distributed mimo Network for 5G Enhanced Mobile Broadband 12

Distributed MIMO Network for 5G Enhanced Mobile Broadband

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Conference on Broadband Access Communication Technologies XII

作者： Adachi, Fumiyuki Boonkajay, Amnart Saito, Tomoyuki Seki, Yuta Tohoku Univ Res Org Elect Commun Aoba Ku 2-1-1 Katahira Sendai Miyagi 9808577 Japan

ISBN: (数字)9781510616042

ISBN: (纸本)9781510616042

One of important applications in 5G mobile communications is the enhanced mobile broadband (eMBB). A promising approach for achieving 5G eMBB under the limited radio bandwidth and energy is an introduction of a small-cell structured network. An advanced utilization of multi-input multi-output (mimo) transmission is also another possible approach. First, the conceptual structure of distributed mimo network is introduced. A number of distributed antennas (DAs) are deployed over a macro-cell area and they are connected to a macro-cell base station (MBS) via optical mobile fronthaul. Then, we present the recent advances in distributed mimo cooperative transmission, i.e., space-time block coded transmit diversity (STBC-TD) for improving the link capacity of a macro-cell edge area, minimum mean square error multiuser multiplexing combined with singular value decomposition (MMSE-SVD) for increasing the sum capacity, and blind selective mapping (SLM) for reducing the transmit signal peak-to-average power ratio (PAPR).

关键词： 5G distributed mimo optical mobile fronthaul cooperative transmission space-time block coded transmit diversity MMSE multiplexing singular value decomposition selected mapping

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distributed mimo Systems for 6G

Distributed MIMO Systems for 6G

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Joint European Conference on Networks and Communications / 6G Summit (EuCNC/6G Summit)

作者： Haliloglu, Omer Yu, Han Madapatha, Charitha Guo, Hao Kadan, Fehmi Emre Wolfgang, Andreas Puerta, Rafael Frenger, Pal Svensson, Tommy Ericsson Res Turkiye Istanbul Turkiye Ericsson Res Sweden Kista Sweden Qamcom Res & Technol AB Gothenburg Sweden Chalmers Univ Technol Gothenburg Sweden

ISBN: (纸本)9798350311020

This study focuses on distributed mimo (D-mimo) systems and provides a discussion about their role in next generation networks. The paradigm shift to distributed networks offers great potential to address the 6G requirements, through macro diversity. As 6G scenarios and use cases continue to emerge, new challenges are likely to arise that may affect the widespread implementation of D-mimo. To address those, different deployment options have been proposed for roll-out considerations. They are composed of several sub-components that can be categorized as (i) wireless or wired fronthaul/backhaul, (ii) analog or digital signals, (iii) distributed or centralized processing, and (iv) coherent or non-coherent transmission. To facilitate standardization efforts, we provide 3GPP-aligned terminology for network nodes, multipoint transmission and reception schemes. In order to enable large-scale implementation of D-mimo systems, it is important to determine the needed amount of distribution, develop practical solutions for high-frequency bands, and ways to convey data that meet the transport requirements. On this regard, we discuss key enablers and present simulation results for D-mimo systems towards 6G. In particular, we present solutions for D-mimo networks in dynamic scenarios related to channel estimation and layer-1 mobility considering coherent and non-coherent joint transmission, and analog fronthaul implementation using analogradio-over-fiber that are promising for high (upper mm-Wave and (sub-)THz) carrier frequencies, as well as integrated access and backhaul, network-controlled repeaters, and reconfigurable intelligent surfaces that are possible enablers for cost-efficient network densification at both low (cm-Wave, lower mm-Wave) and high carrier frequencies.

关键词： 6G distributed mimo D-mimo cell-free massive mimo 5G network controlled repeaters NCR integrated access and backhaul reconfigurable intelligent surfaces RIS L1 mobility non-coherent transmission channel estimation IAB analog fronthaul

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distributed mimo for 6G sub-Networks in the Unlicensed Spectrum

Distributed MIMO for 6G sub-Networks in the Unlicensed Spect...

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IEEE Conference on Standards for Communications and Networking (CSCN)

作者： Elwekeil, Mohamed Giordano, Lorenzo Galati Baracca, Paolo Buzzi, Stefano Nokia Munich Germany Univ Cassino & Southern Lazio Cassino Italy Consorzio Nazl Interuniv Telecomunicaz Parma Italy Politecn Milan Milan Italy

ISBN: (纸本)9798350395389

In this paper, we consider the sixth generation (6G) sub-networks, where hyper reliable low latency communications (HRLLC) requirements are expected to be met. We focus on a scenario where multiple sub-networks are active in the service area and assess the feasibility of using the 6 GHz unlicensed spectrum to operate such deployment, evaluating the impact of listen before talk (LBT). Then, we explore the benefits of using distributed multiple input multiple output (mimo), where the available antennas in every sub-network are distributed over a number of access points (APs). Specifically, we compare different configurations of distributed mimo with respect to centralized mimo, where a single AP with all antennas is located at the center of every sub-network. Our simulation results show the effectiveness of employing distributed mimo for future sub-networks in the 6 GHz unlicensed spectrum when adaptive transmission power reduction (APR) is used.

关键词： 6G in-X sub-networks hyper reliable low latency communications (HRLLC) distributed mimo unlicensed spectrum

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distributed mimo Uplink Capacity under Transform Coding Fronthaul Compression

Distributed MIMO Uplink Capacity under Transform Coding Fron...

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IEEE International Conference on Communications (IEEE ICC)

作者： Wiffen, Fred Bocus, Mohammud Z. Doufexi, Angela Nix, Andrew Univ Bristol Commun Syst & Networks Res Grp Bristol Avon England Toshiba Res Europe Ltd Bristol Avon England

ISBN: (纸本)9781538680889

In this work we analyse the capacity of the distributed mimo uplink when transform coding is applied locally at each remote radio head (RRH) to compress fronthaul traffic. Assuming the use of optimal scalar compression, we derive a closed form capacity expression for the distributed mimo uplink under Gaussian signalling, which is shown to be a function of both local and global channel eigendecompositions. We then outline two rate allocation schemes for efficiently allocating the available fronthaul to the compressed scalars, based on either local or global channel state information (CSI). Numerical results under Rayleigh fading conditions are presented which show that transform coding can provide a significant compression gain relative to direct signal quantisation, which grows as the number of antennas deployed at each RRH increases. Results also show that allocating fronthaul based on global CSI significantly improves performance, especially as the number of RRHs deployed increases.

关键词： distributed mimo fronthaul compression transform coding cell-free C-RAN

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