| 1. |
- Alegría, Juan Vidal, et al.
(författare)
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Modular binary tree architecture for distributed large intelligent surface
- 2021
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Ingår i: International Conference on Acoustics, Speech, and Signal Processing (ICASSP). - 1520-6149. - 9781728176055 - 9781728176062 ; 2021-June, s. 4865-4869
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Konferensbidrag (refereegranskat)abstract
- Large intelligent surface (LIS) is a technology that extends massive MIMO by considering an even greater number of antennas distributed throughout vast areas. In order to be able to implement this technology, it is crucial to consider decentralized architectures so as to make the whole system scalable. We consider a LIS divided into several LIS panels of smaller size, which can be located far away from each other. We present a modular architecture that allows combining different LIS panels using a binary tree. This architecture is also valid in a cell-free massive MIMO scenario. We make use of a newly defined matrix decomposition, the WAX decomposition, to define the modules that are used within our architecture. We also study the lossless dimensionality reduction in the data to be processed, which can be achieved using our proposed architecture.
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| 2. |
- Alegria, Juan Vidal, et al.
(författare)
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Trade-Offs in Decentralized Multi-Antenna Architectures: The WAX Decomposition
- 2021
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Ingår i: IEEE Transactions on Signal Processing. - 1053-587X. ; 69, s. 3627-3641
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Tidskriftsartikel (refereegranskat)abstract
- Current research on multi-antenna architectures is trending towards increasing the amount of antennas in the base stations (BSs) so as to increase the spectral efficiency. As a result, the interconnection bandwidth and computational complexity required to process the data using centralized architectures is becoming prohibitively high. Decentralized architectures can reduce these requirements by pre-processing the data before it arrives at a central processing unit (CPU). However, performing decentralized processing introduces also cost in complexity/interconnection bandwidth at the antenna end which is in general being ignored. This paper aims at studying the interplay between level of decentralization and the associated complexity/interconnection bandwidth requirement at the antenna end. To do so, we propose a general framework for centralized/decentralized architectures that can explore said interplay by adjusting some system parameters, namely the number of connections to the CPU (level of decentralization), and the number of multiplications/outputs per antenna (complexity/interconnection bandwidth). We define a novel matrix decomposition, the WAX decomposition, that allows information-lossless processing within our proposed framework, and we use it to obtain the operational limits of the interplay under study. We also look into some of the limitations of the WAX decomposition.
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| 3. |
- Alegria, Juan Vidal, et al.
(författare)
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Trade-offs in quasi-decentralized massive MIMO
- 2020
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Ingår i: 2020 IEEE International Conference on Communications Workshops, ICC Workshops 2020 - Proceedings. - 9781728174402
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Konferensbidrag (refereegranskat)abstract
- Typical massive multiple-input multiple-output (MIMO) architectures consider a centralized approach, in which all baseband data received by each antenna has to be sent to a central processing unit (CPU) to be processed. Due to the enormous amount of antennas expected in massive MIMO base stations (BSs), the number of connections to the CPU required in centralized massive MIMO is not scalable. In recent literature decentralized approaches have been proposed to reduce the number of connections between the antennas and the CPU. However, the reduction in the connections to the CPU requires more outputs per antenna to be generated. We study the trade-off between number of connections to the CPU and number of outputs per antenna. We propose a generalized architecture that allows exploitation of this trade-off, and we define a novel matrix decomposition that allows information-lossless filtering within our proposed architecture.
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| 4. |
- Bengtsson, Erik L, et al.
(författare)
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Simulation of Multiple-Antenna Terminal Performance in Massive MIMO Systems based on Indoor Measurements
- 2020
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Ingår i: IEEE Transactions on Vehicular Technology. - 0018-9545. ; 69:1, s. 418-427
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Tidskriftsartikel (refereegranskat)abstract
- In massive MIMO systems the uplink pilot signalstransmitted by a terminal define the channel seen by the basestation. This gives the terminal some degree of freedom selectingan uplink pilot transmission strategy. In this paper, we investigatethe benefit of different pilot transmission strategies when increasingthe number of antennas in the terminal. Building on previouswork on a simulation framework for Multiple-antenna terminalsin 5G massive MIMO systems, this paper presents simulatedperformance results for various transmission schemes. The resultsare calibrated to reflect a real communication situation in a largeauditorium. Emulating the measurement set-up, we show that theframework can be tuned to generate channel distributions thatmatch measured data. Under generalized conditions, we performsimulations for different terminal transmission-strategies, bothrelated to single stream and multiple streams. All evaluations arebased on terminals with four antennas integrated into real SonyXperia smartphone-chassis, tuned to 3.7 GHz. The measurementsare conducted by using the Lund University Massive MIMOtestbed with its 100 antennas. The results clearly show theadvantage of increasing the antenna-count also at the terminalside in massive MIMO systems.
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| 5. |
- Cai, Xuesong, et al.
(författare)
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A Switched Array Sounder for Dynamic Millimeter-Wave Channel Characterization: Design, Implementation and Measurements
- 2024
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Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X.
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Tidskriftsartikel (refereegranskat)abstract
- A prerequisite for the design and evaluation of wireless systems is the understanding of propagation channels. While abundant propagation knowledge exists for bands below 6 GHz, the same is not true for millimeter-wave frequencies. In this paper, we present the design, implementation and measurement-based verification of a re-configurable 27.5-29.5 GHz channel sounder. Based on the switched array principle, our design is capable of characterizing 128×256 dynamic double-directional dual-polarized channels with snapshot times of around 600 ms. This is in sharp contrast to measurement times on the order of tens-of-minutes of sounders by rotating horn antennas. The antenna arrays at both link ends are calibrated in an anechoic chamber with high angular sampling intervals of 3 degrees in azimuth and elevation domains, which enables de-embedding the system responses of the sounder from the propagation channels. This is complemented with a bandwidth of up to 2 GHz, i.e., nanosecond-level delay resolution. The short measurement times and stable radio frequency design facilitate real-time processing of the received wavefronts to enhance measurement dynamic range. After disclosing the sounder design and implementation, we demonstrate its capabilities by presenting a measurement campaign at 28 GHz in an indoor lab environment.
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| 6. |
- Callebaut, Gilles, et al.
(författare)
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6G Radio Testbeds: Requirements, Trends, and Approaches
- 2024
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Ingår i: IEEE Microwave Magazine. - 1527-3342 .- 1557-9581. ; 25:4, s. 14-31
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Tidskriftsartikel (refereegranskat)abstract
- The proof of the pudding lies in eating, and that is why 6G testbeds are essential in the progress toward the next generation of wireless networks. Theoretical research toward 6G wireless networks proposes advanced technologies to serve new applications and drastically improve energy performance. Testbeds are indispensable to validate these new technologies under more realistic conditions. This article clarifies the requirements for 6G radio testbeds, reveals trends, and introduces approaches toward their development.
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| 7. |
- Cheng, Sijia, et al.
(författare)
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A Hardware-in-the-Loop Simulator for mmWave Massive MIMO Using PYNQ Framework
- 2023
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Ingår i: 2023 IEEE 66th International Midwest Symposium on Circuits and Systems, MWSCAS 2023. - : Institute of Electrical and Electronics Engineers (IEEE). - 9798350302103 ; , s. 698-702
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Konferensbidrag (refereegranskat)abstract
- Massive multiple-input multiple-output (MIMO) plays an important role in beyond 5G systems to support high data rate and low latency, especially operating at millimeter-wave frequency bands. In traditional software-based simulators, the simulation time increases exponentially with the number of base station antennas and served users. We propose a hardware-in-loop simulator that combines the flexible software and fast and accurate hardware with Python Productivity for Zynq (PYNQ) framework. The simulation of massive MIMO detection is accelerated by 4 orders of magnitudes with bit-accurate result. With the help of the developed simulator, we explore the design trade-offs between system performance and hardware cost for in-flight-cabin use cases.
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| 8. |
- Cheng, Sijia, et al.
(författare)
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MmWave Massive MIMO Processing in Demanding Environments - An Aircraft Cabin Deployment Study
- 2023
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Ingår i: Conference Record of the 57th Asilomar Conference on Signals, Systems and Computers, ACSSC 2023. - 1058-6393. - 9798350325744 ; , s. 1631-1635
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Konferensbidrag (refereegranskat)abstract
- Massive multiple-input multiple-output (MIMO) technology will continue playing an important role in beyond 5G wireless systems. Fully digital beamforming at the millimeter wave (mmWave) spectrum enables applications that require high data rates and low latency. This paper investigates the development and deployment of mmWave massive MIMO systems in an in-flight cabin environment, from both system performance and hardware implementation aspects. Ray-tracing methods with realistic geometry coefficients captured from commercial airplane models are used to represent this in-door dense environment. A hardware-in-the-loop simulator running on the AMD/Xilinx PYNQ FPGA is leveraged to conduct fast design space exploration. The outcomes of our investigation provide insights and guidelines in strategies for implementing and deploying mmWave massive MIMO systems in-flight cabins, for instance, how to place and distribute access points to enhance coverage and serve quality and the appropriate quantization strategy balancing hardware cost and signal processing quality.
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| 9. |
- Chung, Minkeun, et al.
(författare)
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Demo : Millimeter-Wave Massive MIMO Testbed with Hybrid Beamforming
- 2020
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Ingår i: 2020 IEEE Wireless Communications and Networking Conference Workshops, WCNCW 2020 - Proceedings. - 9781728151786
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Konferensbidrag (refereegranskat)abstract
- Massive multiple-input multiple-out (MIMO) is vital in millimeter-wave (mmWave) bands to obtain large array gains. However, there are practical challenges, such as high hardware cost and power consumption in such systems. A promising solution to these problems is to adopt a hybrid beamforming architecture. This architecture has a much lower number of transceiver (TRx) chains than the total antenna number, resulting in cost- and energy- efficient systems. In this demo, we present a real- time mmWave (28GHz) massive MIMO testbed with hybrid beamforming. This testbed has a 64- antenna/16-TRx unit for beam-selection, which can be expanded to larger array sizes in a modular way. For testing everything from baseband processing algorithms to scheduling and beam-selection in real propagation environment, we extend the capability of an existing 100-antenna/100-TRx massive MIMO testbed (below 6GHz), built upon software-defined radio technology, to a flexible mmWave massive MIMO system.
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| 10. |
- Chung, Min Keun, et al.
(författare)
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LuMaMi28 : Real-Time Millimeter-Wave Multi-User MIMO Systems with Antenna Selection
- 2023
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Ingår i: IEEE Transactions on Wireless Communications. - 1536-1276. ; 22:11, s. 7944-7960
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents LuMaMi28, a real-time 28GHz multi-user (MU) multiple-input multiple-output (MIMO) testbed. In this testbed, the base station has 16 transceiver chains with a fully-digital beamforming architecture (with different pre-coding algorithms) and simultaneously supports multiple user equipments (UEs) with spatial multiplexing. The UEs are equipped with a beam-switchable antenna array for real-time antenna selection where the one with the highest channel magnitude, out of four pre-defined beams, is selected. For the beam-switchable antenna array, we consider two kinds of UE antennas, with different beam-width and different peak-gain. Based on this testbed, we provide measurement results for millimeter-wave (mmWave) MU-MIMO performance in different real-life scenarios with static and mobile UEs. We explore the potential benefit of the mmWave MU-MIMO systems with antenna selection based on measured channel data, and discuss the performance results through real-time measurements.
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