| 1. |
- Callebaut, Gilles, et al.
(författare)
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Massive MIMO goes Sub-GHz : Implementation and Experimental Exploration for LPWANs
- 2020
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Ingår i: Conference Record of the 54th Asilomar Conference on Signals, Systems and Computers, ACSSC 2020. - 1058-6393. - 9780738131269 ; 2020-November, s. 1101-1105
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Konferensbidrag (refereegranskat)abstract
- Low-Power Wide-Area Networks operating in the unlicensed bands are being deployed to connect a rapidly growing number of Internet-of-Things devices. While the unlicensed sub-GHz band offers favorable propagation for long-range connections, measurements show that the energy consumption of the nodes is still mostly dominated by the wireless transmission affecting their autonomy. We investigate the potential benefits of deploying massive MIMO technology to increase system reliability and at the same time support low-energy devices with good coverage at sub-GHz frequencies. The impact of different antenna configurations and propagation conditions is analyzed. Both actual average experienced array gain and channel hardening are examined. The assessment demonstrates the effect of channel hardening as well as the potential benefits of the experienced array gain. These measurements serve as a first assessment of the channel conditions of massive MIMO at sub-GHz frequencies and are, to the best of our knowledge, the first of its kind.
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| 2. |
- Chung, Min Keun, et al.
(författare)
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Millimeter-Wave Massive MIMO Testbed with Hybrid Beamforming
- 2020
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Ingår i: Conference Record of the 54th Asilomar Conference on Signals, Systems and Computers, ACSSC 2020. - 1058-6393. - 9780738131269 ; 2020-November, s. 309-313
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Konferensbidrag (refereegranskat)abstract
- Massive multiple-input multiple-out (MIMO) technology 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 paper, 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 environments, 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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| 3. |
- Muneer, Sidra, et al.
(författare)
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Handling PA Nonlinearity in Massive MIMO : What are the Tradeoffs between System Capacity and Power Consumption
- 2020
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Ingår i: Conference Record of the 54th Asilomar Conference on Signals, Systems and Computers, ACSSC 2020. - 1058-6393. - 9780738131269 ; 2020-November, s. 974-978
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Konferensbidrag (refereegranskat)abstract
- Massive MIMO enables a very high spectral efficiency by spatial multiplexing and opens opportunities to reduce transmit power per antenna. On the other side, it also introduces new challenges in tackling the power amplifier nonlinearity due to the increased number of antennas. The behavior of Out-of-Band radiation from PAs in Massive MIMO is non-trivial depending upon the applied precoding scheme, propagation environment, and how the users are distributed spatially. In this paper, we analyze the in-band and Out-of-Band power distribution in space for a Massive MIMO base station with nonlinear power amplifiers. We also study the tradeoff between amplifier power consumption and system performance (in terms of error vector magnitude at intended receivers) for PAs with different backoff operating levels. The spatial analysis of Out-of-Band under more realistic channel conditions is more reflective of the situation, to determine system emission requirements. The tradeoff between performance and power consumption will provide a basis for future investigations into the design of efficient Massive MIMO systems, taking nonlinearities into account.
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| 4. |
- Pereira, Andreia, et al.
(författare)
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The Impact of Terminal Mobility on the Performance of a Panel-Based Large Intelligent Surface
- 2020
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Ingår i: Conference Record of the 54th Asilomar Conference on Signals, Systems and Computers, ACSSC 2020. - 1058-6393. - 9780738131269 ; 2020-November, s. 569-573
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Konferensbidrag (refereegranskat)abstract
- A Large Intelligent Surface (LIS) is a recently pro-posed concept that relies on the integration of a vast number of antenna-elements over an entire surface able to transmit and/or receive information, especially suitable for high speed indoor communications and massive internet of things (IoT) applications. In this paper, we study the impact of terminal mobility on the performance of a panel-based LIS, considering different resource allocation approaches (including panel selection and/or panel-terminal association) and small panel areas. Such configuration represents a clear advantage in terms of flexibility, together with the fact that, from an economy of scale perspective, the production of this type of configuration choosing smaller areas seems more foreseeable.Our performance results show that there is no need to have a contagious distribution of panels, instead they can be physically separated according to a given distribution. It is also observed that, keeping a regularly fixed or predefined panel scheme, leading only to panel-terminal association, are able to fight against the unpredictability of terminal movements and overcome the computational complexity imposed by the optimum approach (that includes both panel selection and terminal-panel allocation stages), presenting maximum rate losses of 16-30%.
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| 5. |
- Sandra, Michiel, et al.
(författare)
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Internet of Buoys : An Internet of Things Implementation at Sea
- 2020
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Ingår i: 2020 54th Asilomar Conference on Signals, Systems and Computers, ACSSC 2020. - 1058-6393. - 9780738131269 ; 2020-November, s. 1096-1100
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Konferensbidrag (refereegranskat)abstract
- Internet of Things (IoT) applications are emerging in many different areas, including maritime environments. One of the applications in this area is the monitoring of buoys at sea. To realize wireless tracking of buoys, an accurate prediction of the path loss in an open-sea environment is essential. So far, channel measurements at sea have mainly been conducted with antennas placed a couple of meters above the sea surface, which is higher than the buoys themselves. Therefore, we investigated the validity of the published channel models at sea by means of path loss measurements using a LoRa link with a transmitter antenna height of 0.35 m and a base station antenna height of 2.65 m and 5.2 m. Our results show that the round earth loss model is not accurate at these antenna heights. The ITU-R P.2001-3 model and a model by Bullington show a better agreement with our measurements. However, the difference between our two measurement campaigns shows that more investigation is needed on the dependence of the path loss on the sea state. Additionally, the availability of Sigfox, Narrowband Internet of Things and The Things has been explored. We found that that these can be used for IoT applications in the tested area at low antenna heights.
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| 6. |
- Aabel, Lise, 1992, et al.
(författare)
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Distributed Massive MIMO via all-Digital Radio Over Fiber
- 2020
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Ingår i: Conference Record - Asilomar Conference on Signals, Systems and Computers. - 1058-6393. ; 2020-November, s. 319-323
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Konferensbidrag (refereegranskat)abstract
- A crucial challenge in the implementation of distributed massive multiple-input multiple-output (MIMO) architectures is to provide phase coherence while, at the same time, limit the complexity of the remote-radio heads (RRHs), which is important for cost-efficient scalability. To address this challenge, we present in this paper a phase-coherent distributed MIMO architecture, based on off-the-shelf, low-cost components. In the proposed architecture, up- and down-conversion are carried out at the central unit (CU). The RRHs are connected to the CU by means of optical fibers carrying oversampled radio-frequency (RF) 1-bit signals. In the downlink, the 1-bit signal is generated via sigma-delta modulation. At the RRH, the RF signal is recovered from the 1-bit signal through a bandpass filter and a power amplifier, and then fed to an antenna. In the uplink, the 1-bit signal is generated by a comparator whose inputs are the low-noise-amplified received RF signal and a suitably designed dither signal. The performance of the proposed architecture is evaluated with satisfactory results both via simulation and measurements from a testbed.
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| 7. |
- Arslan, Mehmet Ali, et al.
(författare)
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Partitioning and Mapping Dynamic Dataflow Programs
- 2012
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Ingår i: [Host publication title missing]. - 1058-6393. ; , s. 1452-1456
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Konferensbidrag (refereegranskat)abstract
- Partitioning and mapping are important design decisions in exploiting the parallelism of programs that are to be run on systems with multiple processing elements. In this paper we introduce a fast, incremental approach for mapping dynamic dataflow programs to multiprocessor systems. We use causation traces and architecture descriptions as input for the mapping process that devises several heuristics for reaching a short makespan for the given trace. We evaluate our approach by comparing our results to two different lower bounds and another algorithm used often in solving mapping problems: simulated annealing.
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| 8. |
- Atzeni, Italo, et al.
(författare)
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Low-Resolution Massive MIMO Under Hardware Power Consumption Constraints
- 2021
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Ingår i: Conference Record - Asilomar Conference on Signals, Systems and Computers. - 1058-6393. - 9781665458283
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Konferensbidrag (refereegranskat)abstract
- We consider a fully digital massive multipleinput multiple-output architecture with low-resolution analogto-digital/digital-to-analog converters (ADCs/DACs) at the base station (BS) and analyze the performance trade-off between the number of BS antennas, the resolution of the ADCs/DACs, and the bandwidth. Assuming a hardware power consumption constraint, we determine the relationship between these design parameters by using a realistic model for the power consumption of the ADCs/DACs and the radio frequency chains. Considering uplink pilot-aided channel estimation, we build on the Bussgang decomposition to derive tractable expressions for uplink and downlink ergodic achievable sum rates. Numerical results show that the ergodic performance is boosted when many BS antennas with very low resolution (i.e., 2 to 3 bits) are adopted in both the uplink and the downlink.
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| 9. |
- Becirovic, Ema, et al.
(författare)
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Reciprocity Aided CSI Feedback for Massive MIMO
- 2020
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Ingår i: 2020 54TH ASILOMAR CONFERENCE ON SIGNALS, SYSTEMS, AND COMPUTERS. - : IEEE. - 9780738131269 ; , s. 1022-1027
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Konferensbidrag (refereegranskat)abstract
- A potential showstopper for reciprocity-based beamforming is that the uplink SNR often is much smaller than the downlink SNR, making it hard to estimate channels on the uplink. We analyze this problem by considering a "grid-of-beams world" with a finite number of possible channel realizations. We assume that the terminal can accurately detect the channel and we propose a method of improving the channel detection from uplink pilots by designing a mapping between the channel and the pilots. We find a simple metric that is to be minimized to maximize performance. Further, we propose an algorithm that draws pilot sequences from a distribution aimed to minimize the metric. We see that we can come close to optimal performance, which requires long sequences, with significantly shorter sequences.
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| 10. |
- Bencheikh Lehocine, Chouaib, 1993, et al.
(författare)
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Sensitivity analysis of beamforming techniques for periodic broadcast V2V communication
- 2021
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Ingår i: Conference Record - Asilomar Conference on Signals, Systems and Computers. - 1058-6393. ; Volume 2021-October, s. 61-66
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Konferensbidrag (refereegranskat)abstract
- In this work, we extend the results of two previously proposed transmit beamforming techniques for periodic, broadcast, vehicle-to-vehicle communication with a common fixed broadcast period, to the scenario where vehicular users (VUs) use different, and potentially varying broadcast periods. The two techniques, analog beamforming network (ABN) of phase shifters and antenna switching network (ASN), were previously developed in accordance with a multiple antenna receiver that employs an analog combining network (ACN) of phase shifters. To accommodate the use of multiple broadcast periods, we propose the design of phase shifter parameters of ABN-ACN and ASN-ACN systems using a design period Td. Then, we analytically derive sets of broadcast periods that sustain optimality, in the sense that the sum signal-to-noise ratio (SNR) of Kconsecutive packets for any receiving VU is maximized. Next, we provide guidelines on how to set Td to ensure a sufficient granularity of the sets of optimal broadcast periods. Finally, we investigate using numerical computations the effect of certain design choices on the sensitivity of ABN/ASN-ACN systems to small variations of the broadcast period.
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