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14th International Conference on Advanced Technologies, Systems and Services in Telecommunications (TELSIKS)

作者： Riera-Palou, Felip Femenias, Guillem Univ Balearic Isl Mobile Commun Grp Mallorca Illes Balears Spain

ISBN: (纸本)9781728108780

Cell-free Massive MIMO (CF-M-MIMO) networks have recently emerged as a promising architectural solutions to satisfy the requirements of future networks (i.e., beyond 5G, 6G). The CF-M-MIMO paradigm advocates for the irregular deployment of a large number of access points (AP) throughout the network coverage area, all connected to a central processing unit (CPU), with the aim of bringing the radio access front-end closer to the users. Indeed, the cell-free topology can be interpreted as a fully distributed implementation of the Massive MIMO (M-MIMO) technology that is currently permeating the rollout of 5G. Interestingly, the large body of theoretical results derived for M-MIMO over the last decade can be recast in the CF-M-MIMO framework yet the distributed nature of the system needs to be carefully factored in. This paper aims at highlighting the different trade-offs affecting various performance metrics in CF-M-MIMO networks. In particular, the influence and consequences of using different precoding strategies, various power allocation techniques and pilot allocation strategies will be discussed and assessed. Moreover, a novel technique, termed user-subset selection, is shown to significantly improve the performance of maxmin power allocation at the cost of penalty in the form of an outage probability.

关键词： Cell-free Massive MIMO zero-forcing precoding Normalized conjugate precoding Maxmin performance Maxmin-sumrate

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Pseudo-Inverse vs Generalized Inverse for C-RAN Downlink precoding

Pseudo-Inverse vs Generalized Inverse for C-RAN Downlink Pre...

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IEEE Global Communications Conference (GLOBECOM) on Advanced Technology for 5G Plus

作者： Mojahedian, Mohammad M. Mosayebi, Reza Lozano, Angel Univ Pompeu Fabra Barcelona Spain

ISBN: (纸本)9781728182988

This paper tackles the problem of zero-forcing (ZF) precoding for the downlink of centralized radio-access networks operating in a cell-free fashion. While the customary workhorse of ZF precoding is the channel pseudo-inverse, because of the separate power constraint at each participating access point, the pseudo-inverse is not optimum. Rather, it can be improved upon by other inverses that allow conveying stronger signals (or, equivalently, consuming less power) while respecting the same ZF conditions. Motivated by the enormous disparity in computational cost between simple pseudo-inversion and general inversion, we ascertain the performance disadvantage of the former in a wide range of conditions. The welcome conclusion is that pseudo-inversion is close-to-optimum for all operational regimes of interest.

关键词： C-RAN cell-free networks ultradense networks zero-forcing precoding pseudo-inverse generalized inverse

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precoding DESIGN FOR THE MIMO-ROC DOWNLINK 44

PRECODING DESIGN FOR THE MIMO-ROC DOWNLINK

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44th IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP)

作者： Rizzello, Valentina Joham, Michael Matera, Andrea Utschick, Wolfgang Spagnolini, Umberto Tech Univ Munich Inst Signal Proc D-80333 Munich Germany Politecn Milan DEIB I-20133 Milan Italy

ISBN: (纸本)9781479981311

MIMO Radio-over-Copper (MIMO-RoC) is a transport system for indoor coverage that leverages the pre-existing building's copper cabling infrastructure. In MIMO-RoC, the overall channel from the Base Band Units (BBU) to the end-user is the cascade of a MIMO-radio over a MIMO-cable channel and the analog fronthaul together with a wireless channel enables the transport to the mobile users. The entire system poses two main challenges: i) design low-complexity and flexible allocation strategies between wired and wireless resources;ii) design interference cancellation techniques tailored to the mutually coupled wired-wireless interference. While the former has been extensively investigated, the optimal design of precoding algorithms for the MIMO-RoC downlink is still an open issue and is covered here. In particular, in this paper, the Linear Successive Allocation (LISA) algorithm has been revised and adapted to the MIMO amplify-and-forward (AF) structure of MIMO-RoC. Numerical results validate the proposed method considering a realistic radio environment with 100m copper cable remotization.

关键词： MIMO Radio Over Copper C-RAN LISA zero-forcing precoding

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Performance Analysis of Multistream Receive Spatial Modulation in the MIMO Broadcast Channel

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2016年第3期15卷 1808-1820页

作者： Stavridis, Athanasios Di Renzo, Marco Haas, Harald Univ Edinburgh Sch Engn Inst Digital Commun Li Fi Res & Dev Ctr Edinburgh EH9 3JL Midlothian Scotland Univ Paris Saclay Univ Paris 11 Cent Supelec Lab Signaux & SystCNRS F-91192 Gif Sur Yvette France

In this paper, Multi-Stream Receive-Spatial Modulation (MSR-SM) for application to the Multiple-Input Multiple-Output (MIMO) broadcast channel is introduced and studied. MSR-SM is a closed-loop transmission scheme, which applies the concept of multistream space modulation at the receiver side. An accurate mathematical framework for the evaluation of the Bit Error Rate (BER) is proposed. In addition, the diversity order and coding gain of the new architecture are derived. Note that the proposed analytical framework takes into account both the small-scale fading and the system topology, and is directly applicable to the conventional MIMO broadcast channel. Compared with the state-of-the-art MIMO transmission in the broadcast channel, it is mathematically shown that MSR-SM achieves the same diversity order and a better coding gain, in the high Signal-to-Noise Ratio (SNR) regime. Finally, the proposed mathematical framework and the new findings are validated via Monte Carlo simulation results.

关键词： Broadcast channel MIMO communication performance analysis spatial modulation zero-forcing precoding

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zero-forcing Beamforming in Multiuser MISO Downlink Systems Under Per-Antenna Power Constraint and Equal-Rate Metric

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2013年第1期12卷 228-236页

作者： Lee, Sang-Rim Kim, Jin-Sung Moon, Sung-Hyun Kong, Han-Bae Lee, Inkyu Korea Univ Sch Elect Engn Seoul South Korea

In this paper, we analyze the average sum rate of downlink multi-antenna systems with zero-forcing beamforming (ZFBF). In practical implementations, each antenna is equipped with its own power amplifier and is limited individually by linearity of the amplifier. Thus, this paper adopts a more realistic per-antenna power constraint instead of conventional sum-power constraint on transmit antennas. To this end, we first show that a distribution of the received signal-to-noise ratio (SNR) of the ZFBF scheme with per-antenna power constraint and equal-rate metric can be approximated as a minimum of chi-square random variables. Based on this result, we present an accurate formula of the average sum rate in a closed form. Furthermore, employing extreme value theory, an expression of the asymptotic average sum rate with large numbers of transmit antennas and users is derived from the limiting distribution of the received SNR. Simulation results verify the validity of our analysis even with not so large numbers of transmit antennas and users.

关键词： Broadcast channel zero-forcing precoding per-antenna power constraints

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A Study on Dynamic Clustering for Large-Scale Multi-User MIMO Distributed Antenna Systems with Spatial Correlation

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IEICE TRANSACTIONS ON COMMUNICATIONS 2016年第4期E99B卷 928-938页

作者： Zhao, Ou Murata, Hidekazu Kyoto Univ Grad Sch Informat Kyoto 6068501 Japan

Distributed antenna systems (DASs) combined with multi-user multiple-input multiple-output (MU-MIMO) transmission techniques have recently attracted significant attention. To establish MU-MIMO DASs that have wide service areas, the use of a dynamic clustering scheme (CS) is necessary to reduce computation in precoding. In the present study, we propose a simple method for dynamic clustering to establish a single cell large-scale MU-MIMO DAS and investigate its performance. We also compare the characteristics of the proposal to those of other schemes such as exhaustive search, traditional location-based adaptive CS, and improved norm-based CS in terms of sum rate improvement. Additionally, to make our results more universal, we further introduce spatial correlation to the considered system. Computer simulation results indicate that the proposed CS for the considered system provides better performance than the existing schemes and can achieve a sum rate close to that of exhaustive search but at a lower computational cost.

关键词： dynamic clustering multi-user MIMO distributed antenna systems spatial correlation sum rate zero-forcing precoding

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Access Point Switch ON/OFF Strategies for Green Cell-Free Massive MIMO Networking

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IEEE ACCESS 2020年 8卷 21788-21803页

作者： Femenias, Guillem Lassoued, Narjes Riera-Palou, Felip Univ Balearic Isl Mobile Commun Grp Palma De Mallorca 07122 Spain Univ Carthage INNOVCOM Res Lab Gabes 6031 Tunisia

The combination of user-centric network densification and distributed massive multiple-input multiple-output (MIMO) operation has recently brought along a new paradigm in the wireless communications arena, referred to as cell-free massive MIMO networking. In these networks, a large number of distributed access points (APs), coordinated by a central processing unit (CPU), cooperate to coherently serve a large number of mobile stations (MSs) in the same time/frequency resource. Similar to what has been traditionally done with conventional cellular networks, cell-free massive MIMO networks will be dimensioned to provide the required quality of service (QoS) to MSs under heavy traffic load conditions, and thus they might be underutilized during low traffic load periods, leading to an inefficient use of both spectral and energy resources. Aiming at the implementation of green cell-free massive MIMO networks, this paper proposes and analyzes the performance of different AP switch ON/OFF (ASO) strategies designed to dynamically turn ON/OFF some of the APs based on the number and/or location of the active MSs in the network. The proposed framework considers line-of-sight (LOS) and non-line-of-sight (NLOS) links between APs and MSs, the use of different antenna array architectures at the access points (APs), suitably characterized by array-dependent spatial correlation matrices, and specific power consumption models for APs, MSs and fronthaul links between the APs and the CPU. Numerical results show that the use of properly designed ASO strategies in cell-free massive MIMO networks clearly improve the achievable energy efficiency. Moreover, they also reveal the existing trade-offs among the achievable energy efficiency, the available network-state information, and the hardware configuration (i.e., number of APs, number of transmit antennas per AP, and number of MSs).

关键词： AP ON OFF switching green networking cell-free massive MIMO zero-forcing precoding

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Securing cognitive radio with a combined approach of beamforming and cooperative jamming

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IET COMMUNICATIONS 2017年第1期11卷 1-9页

作者： Liu, Weigang Sarkar, Md. Zahurul Islam Ratnarajah, Tharmalingam Du, Huiqin Univ Edinburgh Inst Digital Commun Sch Engn Edinburgh EH9 3JL Midlothian Scotland Jinan Univ Coll Informat Sci & Technol Guangzhou 510632 Guangdong Peoples R China

The authors consider secret communication through a relay-assisted cognitive interference channel in which primary and secondary base stations (SBSs), respectively, communicate with the primary and secondary receivers (PU-Rx and SU-Rx) in the presence of multiple eavesdroppers. An SBS is allowed to transmit simultaneously with the primary base station (PBS). They propose three cooperative jamming (CJ) schemes based on the available channel state information at the base stations and the relay. The proposed CJ schemes are designed to create additional interference in the direction of eavesdroppers without creating any interference to the PU-Rx and the SU-Rx. A combined approach of beamforming and zero-forcing precoding is developed at the PBS, the SBS and the relay to cancel out jamming interference at the PU-Rx and the SU-Rx. The secrecy rate of SU-Rx is calculated with the constraint of maintaining interference temperature at the PU-Rx under a certain threshold. Compared with the direct transmission schemes that are available in the literature, the authors' results show that the approach which combined beamforming and CJ significantly improves the secrecy rate of the cognitive interference channel.

关键词： array signal processing jamming cognitive radio interference suppression relay networks (telecommunication) precoding cognitive radio security combined beamforming approach cooperative jamming relay-assisted cognitive interference channel secondary base stations SBSs primary base stations secondary receivers primary receivers SU-Rx secrecy rate PU-Rx multiple eavesdroppers cooperative jamming schemes CJ schemes channel state information zero-forcing precoding jamming interference cancellation interference temperature

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Overhead-Performance Tradeoff for MISO Broadcast Channels With zero-forcing Precoder

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2020年第2期19卷 995-1007页

作者： Liu, Guangyi Feng, Hao Wang, Qi Cimini, Leonard J. Univ Delaware Elect & Comp Engn Dept Newark DE 19716 USA Google San Francisco CA 94105 USA

By applying a rate-distortion approach, we investigate the relationship between the amount of overhead and the system performance from an information-theoretic point of view. Though the purpose of rate-distortion theory is to find a lower bound on lossy source coding problems, the concepts of distortion and rate can be extended to communication performance measures and the quality of feedback overhead, respectively. In this article, we study the overhead-performance tradeoff for a downlink MU-MISO channel system with limited feedback. The required feedback bits for characterizing the channel state information is represented as a function of tolerable rate loss. The proposed method to derive this tradeoff is valid for any number of transmit antennas and users, and can help in designing practical systems where the impact of channel feedback overhead cannot be neglected. Comparing the obtained rate-distortion curves with vector quantization, it can be concluded that, for each user, by feeding back different numbers of bits for different channel power gains, the optimal performance can be achieved.

关键词： Rate-distortion Wireless communication MISO communication Downlink Source coding Vector quantization MU-MISO limited feedback rate-distortion theory zero-forcing precoding quantization

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An energy-efficient joint antenna and user selection algorithm for multi-user massive MIMO downlink

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IET COMMUNICATIONS 2018年第3期12卷 255-260页

作者： Olyaee, Maryam Eslami, Mohsen Haghighat, Javad Shiraz Univ Technol Dept Elect Elect Shiraz Iran

Massive multiple-input multiple-output (MIMO) technology employs hundreds of antennas at the base station (BS) of a cellular system. Activating hundreds of antennas requires hundreds of radio-frequency (RF) chains that lead to high cost and high energy consumption. Antenna selection techniques reduce the number of RF chains while curtailing the resulting performance loss. In this study, the authors consider massive-MIMO downlink with zero-forcing (ZF) precoding in a single cell. In ZF precoding with antenna selection, the number of users must always be less than or equal to the number of selected antennas, which may require adopting user selection (scheduling) algorithms. They propose a joint user and antenna selection algorithm to increase BS's energy efficiency (EE) and show that its performance is very close to that of the optimum exhaustive-search based scheme. Using an analytical approximation for EE of the proposed scheme in asymptotically large numbers of users region, they find the optimum number of antennas to be selected.

关键词： antenna arrays MIMO communication cellular radio energy conservation energy consumption precoding telecommunication scheduling telecommunication power management energy-efficient joint antenna user selection algorithm multiuser massive MIMO downlink massive multiple-input multiple-output technology base station cellular system radio-frequency chains RF chains energy consumption performance loss zero-forcing precoding ZF precoding scheduling algorithms BS energy efficiency optimum exhaustive-search based scheme analytical approximation

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