| 1. |
- Bernal, Ximena E., et al.
(författare)
-
Empowering Latina scientists
- 2019
-
Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 363:6429, s. 825-826
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
|
|
| 2. |
- Balatsoukas-Stimming, Alexios, et al.
(författare)
-
Neural-Network Optimized 1-bit Precoding for Massive MU-MIMO
- 2019
-
Ingår i: IEEE Workshop on Signal Processing Advances in Wireless Communications, SPAWC. ; 2019-July
-
Konferensbidrag (refereegranskat)abstract
- Base station (BS) architectures for massive multiuser (MU) multiple-input multiple-output (MIMO) wireless systems are equipped with hundreds of antennas to serve tens of users on the same time-frequency channel. The immense number of BS antennas incurs high system costs, power, and interconnect bandwidth. To circumvent these obstacles, sophisticated MU precoding algorithms that enable the use of 1-bit DACs have been proposed. Many of these precoders feature parameters that are, traditionally, tuned manually to optimize their performance. We propose to use deep-learning tools to automatically tune such 1-bit precoders. Specifically, we optimize the biConvex 1-bit PrecOding (C2PO) algorithm using neural networks. Compared to the original C2PO algorithm, our neural-network optimized (NNO-)C2PO achieves the same error-rate performance at 2× lower complexity. Moreover, by training NNO-C2PO for different channel models, we show that 1-bit precoding can be made robust to vastly changing propagation conditions.
|
|
| 3. |
- Castaneda, Oscar, et al.
(författare)
-
1-bit Massive MU-MIMO Precoding in VLSI
- 2017
-
Ingår i: IEEE Journal on Emerging and Selected Topics in Circuits and Systems. - : Institute of Electrical and Electronics Engineers (IEEE). - 2156-3365 .- 2156-3357. ; 7:4, s. 508-522
-
Tidskriftsartikel (refereegranskat)abstract
- Massive multi-user (MU) multiple-input multiple-output (MIMO) will be a core technology in fifth-generation (5G) wireless systems as it offers significant improvements in spectral efficiency compared to existing multi-antenna technologies. The presence of hundreds of antenna elements at the base station (BS), however, results in excessively high hardware costs and power consumption, and requires high interconnect throughput between the baseband-processing unit and the radio unit. Massive MU-MIMO that uses low-resolution analog-to-digital and digital-toanalog converters (DACs) has the potential to address all these issues. In this paper, we focus on downlink precoding for massive MU-MIMO systems with 1-bit DACs at the BS. The objective is to design precoders that simultaneously mitigate MU interference and quantization artifacts. We propose two nonlinear 1-bit precoding algorithms and corresponding very large-scale integration (VLSI) designs. Our algorithms rely on biconvex relaxation, which enables the design of efficient 1-bit precoding algorithms that achieve superior error-rate performance compared with that of linear precoding algorithms followed by quantization. To showcase the efficacy of our algorithms, we design VLSI architectures that enable efficient 1-bit precoding for massive MU-MIMO systems, in which hundreds of antennas serve tens of user equipments. We present corresponding field-programmable gate array (FPGA) reference implementations to demonstrate that 1-bit precoding enables reliable and high-rate downlink data transmission in practical systems.
|
|
| 4. |
- Castaneda, Oscar, et al.
(författare)
-
Finite-alphabet MMSE equalization for all-digital massive MU-MIMO mmWave communications
- 2020
-
Ingår i: IEEE Journal on Selected Areas in Communications. - 0733-8716 .- 1558-0008. ; 38:9, s. 2128 -2141
-
Tidskriftsartikel (refereegranskat)abstract
- We propose finite-alphabet equalization, a new paradigm that restricts the entries of the spatial equalization matrix to low-resolution numbers, enabling high-throughput, low-power, and low-cost hardware equalizers. To minimize the performance loss of this paradigm, we introduce FAME, short for finite-alphabet minimum mean-square error (MMSE) equalization, which is able to significantly outperform a naïve quantization of the linear MMSE matrix. We develop efficient algorithms to approximately solve the NP-hard FAME problem and showcase that near-optimal performance can be achieved with equalization coefficients quantized to only 1-3 bits for massive multi-user multiple-input multiple-output (MU-MIMO) millimeter-wave (mmWave) systems. We provide very-large scale integration (VLSI) results that demonstrate a reduction in equalization power and area by at least a factor of 3.9× and 5.8×, respectively.
|
|
| 5. |
- Castaneda, Oscar, et al.
(författare)
-
Finite-Alphabet Wiener Filter Precoding for mmWave Massive MU-MIMO Systems
- 2019
-
Ingår i: Conference Record - Asilomar Conference on Signals, Systems and Computers. - 1058-6393. ; 2019-November, s. 178-183
-
Konferensbidrag (refereegranskat)abstract
- Power consumption of multi-user (MU) precoding is a major concern in all-digital massive MU multiple-input multiple-output (MIMO) base-stations with hundreds of antenna elements operating at millimeter-wave (mmWave) frequencies. We propose to replace part of the linear Wiener filter (WF) precoding matrix by a finite-alphabet WF precoding (FAWP) matrix, which enables the use of low-precision hardware that consumes low power and area. To minimize the performance loss of our approach, we present methods that efficiently compute FAWP matrices that best mimic the WF precoder. Our results show that FAWP matrices approach infinite-precision error-rate and error-vector magnitude performance with only 3-bit precoding weights, even when operating in realistic mmWave channels. Hence, FAWP is a promising approach to substantially reduce power consumption and silicon area in all-digital mmWave massive MU-MIMO systems.
|
|
| 6. |
- Castañeda, Oscar, et al.
(författare)
-
Hardware-Friendly Two-Stage Spatial Equalization for All-Digital mmWave Massive MU-MIMO
- 2020
-
Ingår i: Conference Record - Asilomar Conference on Signals, Systems and Computers. - 1058-6393. ; 2020-November, s. 388-392
-
Konferensbidrag (refereegranskat)abstract
- Next generation wireless communication systems are expected to combine millimeter-wave communication with massive multi-user multiple-input multiple-output technology. All-digital base-station implementations for such systems need to process high-dimensional data at extremely high rates, which results in excessively high power consumption. In this paper, we propose two-stage spatial equalizers that first reduce the problem dimension by means of a hardware-friendly, low-resolution linear transform followed by spatial equalization on a lower-dimensional signal. We consider adaptive and non-adaptive dimensionality reduction strategies and demonstrate that the proposed two-stage spatial equalizers are able to approach the performance of conventional linear spatial equalizers that directly operate on high-dimensional data, while offering the potential to reduce the power consumption of spatial equalization.
|
|
| 7. |
- Castañeda, Oscar, et al.
(författare)
-
High-Bandwidth Spatial Equalization for mmWave Massive MU-MIMO with Processing-in-Memory
- 2020
-
Ingår i: IEEE Transactions on Circuits and Systems II: Express Briefs. - 1549-7747 .- 1558-3791. ; 67:5, s. 891-895
-
Tidskriftsartikel (refereegranskat)abstract
- All-digital basestation (BS) architectures enable superior spectral efficiency compared to hybrid solutions in massive multi-user MIMO systems. However, supporting large bandwidths with all-digital architectures at mmWave frequencies is challenging as traditional baseband processing would result in excessively high power consumption and large silicon area. The recently-proposed concept of finite-alphabet equalization is able to address both of these issues by using equalization matrices that contain low-resolution entries to lower the power and complexity of high-throughput matrix-vector products in hardware. In this brief, we explore two different finite-alphabet equalization hardware implementations that tightly integrate the memory and processing elements: (i) a parallel array of multiply-accumulate (MAC) units and (ii) a bit-serial processing-in-memory (PIM) architecture. Our all-digital VLSI implementation results in 28nm CMOS show that the bit-serial PIM architecture reduces the area and power consumption up to a factor of 2× and 3×, respectively, when compared to a parallel MAC array that operates at the same throughput.
|
|
| 8. |
- Castañeda, Oscar, et al.
(författare)
-
Resolution-Adaptive All-Digital Spatial Equalization for mmWave Massive MU-MIMO
- 2021
-
Ingår i: IEEE Workshop on Signal Processing Advances in Wireless Communications, SPAWC. ; 2021-September, s. 386-390
-
Konferensbidrag (refereegranskat)abstract
- All-digital basestation (BS) architectures for millimeter-wave (mmWave) massive multi-user multiple-input multiple-output (MU-MIMO), which equip each radio-frequency chain with dedicated data converters, have advantages in spectral efficiency, flexibility, and baseband-processing simplicity over hybrid analog-digital solutions. For all-digital architectures to be competitive with hybrid solutions in terms of power consumption, novel signal-processing methods and baseband architectures are necessary. In this paper, we demonstrate that adapting the resolution of the analog-to-digital converters (ADCs) and spatial equalizer of an all-digital system to the communication scenario (e.g., the number of users, modulation scheme, and propagation conditions) enables orders-of-magnitude power savings for realistic mmWave channels. For example, for a 256-BS-antenna 16-user system supporting 1 GHz bandwidth, a traditional baseline architecture designed for a 64-user worst-case scenario would consume 23 W in 28 nm CMOS for the ADC array and the spatial equalizer, whereas a resolution-adaptive architecture is able to reduce the power consumption by 6.7×.
|
|
| 9. |
- Castañeda, Oscar, et al.
(författare)
-
Soft-Output Finite Alphabet Equalization for mmWave Massive MIMO
- 2020
-
Ingår i: ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings. - 1520-6149. ; 2020-May, s. 1764-1767
-
Konferensbidrag (refereegranskat)abstract
- Nxt-generation wireless systems are expected to combine millimeter-wave (mmWave) and massive multi-user multiple-input multiple-output (MU-MIMO) technologies to deliver high data-rates. These technologies require the basestations (BSs) to process high-dimensional data at extreme rates, which results in high power dissipation and system costs. Finite-alphabet equalization has been proposed recently to reduce the power consumption and silicon area of uplink spatial equalization circuitry at the BS by coarsely quantizing the equalization matrix. In this work, we improve upon finite-alphabet equalization by performing unbiased estimation and soft-output computation for coded systems. By simulating a massive MU-MIMO system that uses orthogonal frequency-division multiplexing and per-user convolutional coding, we show that soft-output finite-alphabet equalization delivers competitive error-rate performance using only 1 to 3 bits per entry of the equalization matrix, even for challenging mmWave channels.
|
|
| 10. |
- Castaneda, Oscar, et al.
(författare)
-
VLSI Design of a 3-bit Constant-Modulus Precoder for Massive MU-MIMO
- 2018
-
Ingår i: Proceedings - IEEE International Symposium on Circuits and Systems. - 0271-4310. ; 2018-May
-
Konferensbidrag (refereegranskat)abstract
- Fifth-generation (5G) cellular systems will build on massive multi-user (MU) multiple-input multiple-output (MIMO) technology to attain high spectral efficiency. However, having hundreds of antennas and radio-frequency (RF) chains at the base station (BS) entails prohibitively high hardware costs and power consumption. This paper proposes a novel nonlinear precoding algorithm for the massive MU-MIMO downlink in which each RF chain contains an 8-phase (3-bit) constantmodulus transmitter, enabling the use of low-cost and powerefficient analog hardware. We present a high-throughput VLSI architecture and show implementation results on a Xilinx Virtex-7 FPGA. Compared to a recently-reported nonlinear precoder for BS designs that use two 1 -bit digital-to-analog converters per RF chain, our design enables up to 3:75 dB transmit power reduction at no more than a 2.7x increase in FPGA resources.
|
|
| 11. |
- Daza-Caicedo, Sandra, et al.
(författare)
-
Measuring the impact of practices of social appropriation of science and technology: a proposal for a set of indicators
- 2017
-
Ingår i: História, Ciências, Saúde-Manguinhos. - : FUNDACO OSWALDO CRUZ. - 0104-5970 .- 1678-4758. ; 24:1, s. 145-164
-
Tidskriftsartikel (refereegranskat)abstract
- We propose a set of qualitative indicators for monitoring practices of social appropriation of science and technology. The design of this set is based on the Maloka case, but it can be of use to multiple actors involved in the social appropriation of science and technology (referred to by its Spanish acronym, ASCyT). The introduction discusses the concept of ASCyT. The first section provides a review of the literature about measuring activities that link science and society. The second section explains why it is important to develop this type of measurement. The third section lays out the methodology used in designing the indicators. The fourth section explains the set of indicators and the fifth reflects on that process.
|
|
| 12. |
- Jacobsson, Sven, 1990, et al.
(författare)
-
Nonlinear Precoding for Phase-Quantized Constant-Envelope Massive MU-MIMO-OFDM
- 2018
-
Ingår i: 2018 25TH INTERNATIONAL CONFERENCE ON TELECOMMUNICATIONS (ICT). - 9781538623213 ; , s. 367-372
-
Konferensbidrag (refereegranskat)abstract
- We propose a nonlinear phase-quantized constant-envelope precoding algorithm for the massive multi-user (MU) multiple-input multiple-output (MIMO) downlink. Specifically, we adapt the squared-infinity norm Douglas-Rachford splitting (SQUID) precoder to systems that use oversampling digital-to-analog converters (DACs) at the base station (BS) and orthogonal frequency-division multiplexing (OFDM) to communicate over frequency-selective channels. We demonstrate that the proposed SQUID-OFDM precoder is able to generate transmit signals that are constrained to constant envelope, which enables the use of power-efficient analog radio-frequency circuitry at the BS. By quantizing the phase of the resulting constant-envelope signal, we obtain a finite-cardinality transmit signal that can be synthesized by low-resolution (e.g., 1-bit) DACs. We use error-rate simulations to demonstrate the superiority of SQUID-OFDM over linear-quantized precoders for massive MU-MIMO-OFDM systems.
|
|
| 13. |
- Maldonado Castaneda, Oscar
(författare)
-
Making HPV Vaccines Efficient: Cost-Effectiveness Analysis and the Economic Assemblage of Healthcare in Colombia
- 2018
-
Ingår i: Science & Technology Studies. - Tampere, Finland : Finnish Society for Science and Technology Studies. - 2243-4690. ; 31:2
-
Tidskriftsartikel (refereegranskat)abstract
- Cost-effectiveness analysis is a strategy of calculation whose main objective is to compare for making decisions about the best, the most efficient solution (costs vs benefits) to a particular problem. Cost-effectiveness analysis not only provides a framework to compare healthcare interventions which in practice seem incommensurable; it also performs a set of assumptions regarding the nature of healthcare and individuals behaviour. This article analyses the role of cost-effectiveness analysis as a device to produce value in the introduction of human papillomavirus vaccines to Colombia. In different institutional pathways and decision-making scenarios cost-effectiveness has been the key issue that justified the inclusions and exclusions that such technology entails. Cost-effectiveness justified the definition of girls as the population target and the exclusion of boys from the risks and benefits of this technology. Cost-effectiveness analysis has been a key instrument in the sexualising and desexualising of cervical cancer and human papillomavirus vaccines through the rationalisation of economic benefits.
|
|
| 14. |
- Maldonado Castaneda, Oscar
(författare)
-
Price-effectiveness: pharmacoeconomics, value and the right price for HPV vaccines
- 2017
-
Ingår i: Journal of Cultural Economy. - : ROUTLEDGE JOURNALS, TAYLOR & FRANCIS LTD. - 1753-0350 .- 1753-0369. ; 10:2, s. 163-177
-
Tidskriftsartikel (refereegranskat)abstract
- Drawing on a pragmatist approach to pricing, this article discusses the impact of cost-effectiveness analysis (CEA) in the pricing strategies of pharmaceutical companies. Through an analysis of the human papillomavirus (HPV) vaccination, this article illustrates the strategic appropriation of evidence-based medicine (narratives and practices) that pharmaceutical companies have undertaken to enhance the value of their products. While governments are concentrated on the measurement of costs and efficiency (cost-effectiveness), companies attempt to find the threshold of effectiveness that supports their estimation of value. I have called such mode of calculation, price-effectiveness. Pharmaceutical companies engage in different ways with CEA in devising their own price strategies. First, CEA is used as an instrument to raise HPV vaccines as a matter of interest for health authorities. Second, companies produce models to maximise the effectiveness of their products. Third, the expense side of CEA has opened an opportunity to represent some conditions as diseases in order to increase the potential value of the vaccine, expressed in a higher price. Debates and practices of pricing offer a unique opportunity to trace how particular forms of quantification have become the common ground in the demonstration of value in healthcare and the adaptation of companies.
|
|
| 15. |
- Marti, Gian, et al.
(författare)
-
Hybrid Jammer Mitigation for All-Digital mmWave Massive MU-MIMO
- 2021
-
Ingår i: Conference Record - Asilomar Conference on Signals, Systems and Computers. - 1058-6393. - 9781665458283 ; 2021-October
-
Konferensbidrag (refereegranskat)abstract
- Low-resolution analog-to-digital converters (ADCs) simplify the design of millimeter-wave (mmWave) massive multi-user multiple-input multiple-output (MU-MIMO) base-stations, but increase vulnerability to jamming attacks. As a remedy, we propose HERMIT (short for Hybrid jammER MITigation), a method that combines a hardware-friendly adaptive analog transform with a corresponding digital equalizer: The analog transform removes most of the jammer’s energy prior to data conversion; the digital equalizer suppresses jammer residues while detecting the legitimate transmit data. We provide theoretical results that establish the optimal analog transform as a function of the user equipments' and the jammer’s channels. Using simulations with mmWave channel models, we demonstrate the superiority of HERMIT compared both to purely digital jammer mitigation as well as to a recent hybrid method that mitigates jammer interference with a nonadaptive analog transform.
|
|
| 16. |
- Navarro, Mario A., et al.
(författare)
-
Improving the optimization performance by an adaptable design : A dynamic selection of operators via criteria-based matrix for evolutionary algorithms
- 2022
-
Ingår i: 2022 IEEE Congress on Evolutionary Computation (CEC). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781665467087
-
Konferensbidrag (refereegranskat)abstract
- The balance between exploration and exploitation is an important feature in Evolutionary Algorithms (EA). The use of different operators permits to explore the search space and exploit the most prominent regions. This article introduces a dynamic operator selection method that considers different criteria at the same time. The proposed approach uses a dynamic decision matrix (DyDM) to identify which operators must be used at each iteration based on how the algorithm behaves. The DyDM considers specific information as the diversity of the algorithm to avoid stagnation, the actual iteration to work accordingly, and the fitness to direct the search. The proposed approach is called Dynamic Decision Matrix Optimizer (DyDMO) and it has been compared with different well-known algorithms tested on the CEC 2017 benchmark functions. The comparative analysis and non-parametric statistical tests validate how DyDMO im-proves the quality of the solutions and is more stable than its comnetitors.
|
|
| 17. |
- Rivera-Monroy, Victor H., et al.
(författare)
-
Salinity and Chlorophyll a as Performance Measures to Rehabilitate a Mangrove-Dominated Deltaic Coastal Region : the Cienaga Grande de Santa Marta-Pajarales Lagoon Complex, Colombia
- 2011
-
Ingår i: Estuaries and Coasts. - : Springer Science and Business Media LLC. - 1559-2723 .- 1559-2731. ; 34:1, s. 1-19
-
Tidskriftsartikel (refereegranskat)abstract
- Salinity, water temperature, and chlorophyll a (chl-a) biomass were used as performance measures in the period 1999-2001 to evaluate the effect of a hydrological rehabilitation project in the Cienaga Grande de Santa Marta (CGSM)-Pajarales lagoon complex, Colombia where freshwater diversions were initiated in 1995 and completed in 1998. The objective of this study was to evaluate how diversions of freshwater into previously hypersaline (>80) environments changed the spatial and temporal distribution of environmental characteristics. Following the diversion, 19 surveys and transects using a flow-through system were surveyed in the CGSM-Pajarales complex to continuously measure selected water quality parameters. Geostatistical analysis indicates that hydrology and salinity regimes and water circulation patterns in the CGSM lagoon are largely controlled by freshwater discharge from the Fundacion, Aracataca, and Sevilla Rivers. Residence times in the CGSM lagoon were similar before (15.5+/-3.8 days) and after (14.2+/-2.0 days) the rehabilitation project and indicated that the system is flushed regularly. In contrast, chl-a biomass was highly variable in the CGSM-Pajarales lagoon complex and not related to discharge patterns. Mean annual chl-a biomass (44-250 mu g L(-1)) following the diversion project was similar to values recorded since the 1980s and still remains among the highest reported in coastal systems around the world owing to its unique hydrology regulated by the Magdalena River and Sierra Nevada de Santa Marta watersheds and the high teleconnection to the El Nino Southern Oscillation (ENSO). Our results confirm that the reduction in salinity in the CGSM lagoon and Pajarales complex during 1999-2000 was largely driven by high precipitation (2500 mm) induced by the ENSO-La Nina rather than by the freshwater diversions.
|
|
