| 1. |
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- 2019
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Journal article (peer-reviewed)
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| 2. |
- Klionsky, Daniel J., et al.
(author)
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Guidelines for the use and interpretation of assays for monitoring autophagy
- 2012
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In: Autophagy. - : Informa UK Limited. - 1554-8635 .- 1554-8627. ; 8:4, s. 445-544
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Research review (peer-reviewed)abstract
- In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field.
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| 3. |
- Acatauassu, Diogo, et al.
(author)
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KHM cable model parameters for ITU-T G.Fast reference loops
- 2016
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In: 2015 IEEE Conference on Standards for Communications and Networking, CSCN 2015. - 9781479989287 ; , s. 168-173
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Conference paper (peer-reviewed)abstract
- G.Fast is a new standard for fixed broadband access that aims at achieving bit rates of 1 Gb/s over short copper loops. In order to give support to simulation, design and performance evaluation tests, the G.Fast recommendation presents examples of some wiring topologies and reference loops describing configurations expected to be found in real G.Fast deployments. Our work describes results of modeling some types of lines adopted in these reference loops by means of a low complexity and causal parametric cable model. The results indicate that the modeling approach proposed in this work is accurate for all the analyzed cases, which include high quality, medium quality and low quality cables.
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| 4. |
- Acatauassu, Diogo, et al.
(author)
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Simple and Causal Copper Cable Model Suitable for G.fast Frequencies
- 2014
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In: IEEE Transactions on Communications. - 0090-6778. ; 62:11, s. 4040-4051
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Journal article (peer-reviewed)abstract
- G.fast is a new standard from the International Telecommunication Union, which targets 1 Gb/s over short copper loops using frequencies up to 212 MHz. This new technology requires accurate parametric cable models for simulation, design, and performance evaluation tests. Some existing copper cable models were designed for the very high speed digital subscriber line spectra, i.e., frequencies up to 30 MHz, and adopt assumptions that are violated when the frequency range is extended to G.fast frequencies. This paper introduces a simple and causal cable model that is able to accurately characterize copper loops composed by single or multiple segments, in both frequency and time domains. Results using G.fast topologies show that, apart from being accurate, the new model is attractive due to its low computational cost and closed-form expressions for fitting its parameters to measurement data.
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| 5. |
- Acatauassu, Diogo, et al.
(author)
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Simple and Causal Twisted-Pair Channel Models for G.fast Systems
- 2013
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In: [Host publication title missing].
-
Conference paper (peer-reviewed)abstract
- The use of a hybrid copper and fiber architecture is attractive in both fixed access and mobile backhauling scenarios. This trend led the industry and academia to start developing the fourth generation broadband system, which aims at achieving bitrates of 1 Gbps over short copper loops. In this context, accurate models of short twisted-pair cables operating at relatively high frequencies are key elements. This work describes new parametric cable models that incorporate four important characteristics: support of frequencies up to 200 MHz, few parameters, causal impulse responses and require relatively easy fitting procedures. The results show that the models achieve good accuracy for single segments, which are the expected topology for G.fast deployments.
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| 6. |
- Conceicao, Filipe, et al.
(author)
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Empowering industry 4.0 and autonomous drone scouting use cases through 5G-DIVE solution
- 2021
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In: 2021 Joint European Conference on Networks and Communications and 6G Summit, EuCNC/6G Summit 2021. - 2575-4912. - 9781665415262 ; , s. 265-270
-
Conference paper (peer-reviewed)abstract
- The 5G Edge Intelligence for Vertical Experimentation (5G-DIVE) project aims at demonstrating the technical merits and business value proposition of 5G technologies in two vertical pilots, namely the Industry 4.0 (I4.0) and Autonomous Drones Scout (ADS) pilots. This paper presents an overview of the overall 5G-DIVE solution and reports the results of the initial validation campaign of the selected use case, featuring 5G connectivity, distributed Edge computing, and artificial intelligence. The initial results for the I4.0 provide a baseline for next step validation campaign targeting a broader scale 5G implementation, while the ADS results provides promising results for enhancing the autonomous navigation in real-time.
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| 7. |
- Fonseca, Maria Nilma, et al.
(author)
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DCT-based compression scheme for OFDM baseband signals
- 2018
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In: 2018 Wireless Days, WD 2018. - 9781538656327 ; 2018-April, s. 92-97
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Conference paper (peer-reviewed)abstract
- The requirements on the data rates of communication systems increase roughly an order of a magnitude at each new generation. This increase can be especially noticeable for the new centralized radio access networks (C-RAN) scenarios, considered for meeting the requirements of the fifth generation (5G) wireless systems. The general C-RAN architecture normally assumes data transmission in the form of digitized baseband, i.e. I/Q samples. This paper proposes a relatively low-complexity compression scheme for LTE OFDM baseband samples based on transform coding, using the discrete cosine transform (DCT). The compression method is evaluated in both downlink and uplink. The results show that this process can be configured to achieve compression ratio according with the load, for example, in the range of 5:1 to 31:1, with error vector magnitudes (EVMs) lower than 2.8%.
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| 8. |
- Hazra, Saptarshi, et al.
(author)
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Demo : Multi-Radio Access Technology IoT Gateway
- 2020
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In: Proceedings of the 2020 International Conference on Embedded Wireless Systems and Networks. - : Junction Publishing. ; , s. 189-191
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Conference paper (other academic/artistic)abstract
- We present VGATE, a softwarised, multiple-RAT IoT gateway. The baseband of IEEE 802.15.4, LoRa and NB-IoT are implemented with software-defined radio in containers that can execute in an edge computing platform. The demo shows simultaneous multi-channel access and simultaneous execution of multiple RATs in a shared infrastructure.
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| 9. |
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| 10. |
- Hazra, Saptarshi, et al.
(author)
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Handling inherent delays in virtual IoT gateways
- 2019
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In: Proceedings - 15th Annual International Conference on Distributed Computing in Sensor Systems, DCOSS 2019. - : Institute of Electrical and Electronics Engineers Inc.. - 9781728105703 - 9781728105710 ; , s. 58-65
-
Conference paper (peer-reviewed)abstract
- Massive deployment of diverse ultra-low power wireless devices in different application areas has given rise to a plethora of heterogeneous architectures and communication protocols. It is challenging to provide convergent access to these miscellaneous collections of communicating devices. In this paper, we propose VGATE, an edge-based virtualized IoT gateway for bringing these devices together in a single framework using SDRs as technology agnostic radioheads. SDR platforms, however, suffer from large unpredictable delays. We design a GNU Radio-based IEEE 802.15.4 experimental setup using LimeSDR, where the data path is time-stamped at various points of interest to get a comprehensive understanding of the characteristics of the delays. Our analysis shows that GNU Radio processing and LimeSDR buffering delays are the major delays. We decrease the LimeSDR buffering delay by decreasing the USB transfer size but show that this comes at the cost of increased processing overhead. We modify the USB transfer packet size to investigate which USB transfer size provides the best balance between buffering delay and processing overhead across two different host computers. Our experiments show that for the best measured configuration the mean and jitter of latency decreases by 37% and 40% respectively for the host computer with higher processing resources. We also show that the throughput is not affected by these modifications.
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| 11. |
- Huang, Yezi, et al.
(author)
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Enabling DSL and Radio on the Same Copper Pair
- 2015
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In: 2015 IEEE International Conference on Communications (ICC). - 9781467364324 ; , s. 1031-1035
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Conference paper (peer-reviewed)abstract
- To increase indoor coverage for mobile services, we propose a residential small cell infrastructure making use of the existing copper plant. The system is cabinet-based, collocated with VDSL2 and uses small pieces of spectrum next to VDSL2. Inspired by the Ericsson Radio Dot System, it challenges the femtocell paradigm offering full macro functionality in the small cells. An interesting service potential is offered albeit the added mobile traffic capacity is moderate as it is limited by the copper fronthaul.
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| 12. |
- Huang, Yezi, et al.
(author)
-
Fast Mitigation of Sudden Termination Changes in Wideband Wireline Systems
- 2016
-
In: IEEE Transactions on Communications. - 0090-6778. ; 64:6, s. 2610-2621
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Journal article (peer-reviewed)abstract
- Vectoring enables cooperative crosstalk mitigation in wideband wireline systems. A sudden termination change within a vectored group alters the entire perceived channel matrix and thus disturbs the vectoring operation since the precoder, which is tuned to the channel before the change, is no longer up to date. We analyze the resulting residual crosstalk and its impact on performance degradation during showtime for both linear and non-linear precoding systems. To cover, a new channel matrix must be estimated to update the precoder accordingly. We use a model-based approach to track a vector instead of estimating the full matrix. Based on this vector, simplified precoder updating methods for both precoding systems are presented accounting for a sudden line deactivation or (re)activation in a vectored group. As an alternative to the state-of-the-art methods, the proposed procedures significantly reduce the complexity of both channel estimation and precoder updating and minimize the disturbed period for active users.
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| 13. |
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| 14. |
- Huang, Yezi, et al.
(author)
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Functional Split of Zero-Forcing Based Massive MIMO for Fronthaul Load Reduction
- 2018
-
In: IEEE Access. - 2169-3536. ; 6, s. 6350-6359
-
Journal article (peer-reviewed)abstract
- The evolution towards centralized radio access network (C-RAN) for 5G is driven by the need for improved network performance and reduced total-cost-of-ownership (TCO). In CRAN, physically separated remote radio units (RRUs) and baseband units (BBUs) are connected via fronthaul (FH) links, which are capacity constrained. When base-station antennas are upgraded to support massive MIMO techniques, an intra PHY split between RRU and BBU becomes favorable to avoid the dramatic rate growth on the FH links. In this paper, we present a new uplink functional split alternative that decomposes the massive MIMO processing, on the basis of zero-forcing (ZF) equalization, into two phases: dimension-reduction phase and interference cancellation phase, which are implemented in RRU and BBU respectively. Compared with the traditional C-RAN architecture having all baseband processing in the BBU, the new scheme largely alleviates the FH load by reducing the number of FH streams to be equal to the number of MIMO user layers. Compared with an existing split that places all MIMO processing in RRU, the new scheme reduces the RRU complexity without compromising the post-processing performances.
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| 15. |
- Huang, Yezi, et al.
(author)
-
LTE Over Copper - Potential and Limitations
- 2015
-
In: 2015 IEEE 26th Annual International Symposium on Personal, Indoor, and Mobile Radio Communications (PIMRC). - 9781467367820 ; , s. 1339-1343
-
Conference paper (peer-reviewed)abstract
- The densification of mobile networks in order to meet increased capacity demands is ongoing, needed and costly. A few papers have been published based on the insight that the fixed broadband networks offer a multitude of sites, for instance our homes, for potential small cell deployment providing backhaul capacity and power without site costs. However, in order to reach economical large-scale benefits, we explore the case when radio systems are deployed in coexistence with DSL. In this paper, we establish the feasibility of such a concept under constraints invoked by state-of-the-art and emerging systems (3GPP, VDSL2 and G.fast) and make statements about the required architecture. We also point out that the enthusiasm of previously published results should be lowered a notch.
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| 16. |
- Huang, Yezi, et al.
(author)
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Mitigating Disorderly Leaving Events in G.fast
- 2015
-
In: 2015 IEEE International Conference on Communications (ICC). ; , s. 939-944
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Conference paper (peer-reviewed)abstract
- Vectoring is a vital component of wideband wire- line communication systems. A disorderly leaving event (DLE) disturbs the vectoring operation since the precoder, which was designed for the channel before the change, is no longer up to date. Measurements indicate that the impact of a DLE can be serious for frequencies beyond 30 MHz, which corresponds to the band used by emerging wideband communication systems over short multi-pair copper cables such as G.fast. As an alternative to the state-of-the-art update procedure, this paper presents an approach to mitigating the DLE problem. By interpreting DLE with the FEXT-reflected-NEXT (FRN) model, we propose a scheme that enables the showtime lines to return to disturbance-free transmission once the loss of signal on a certain line is detected while updating the precoder as a background process. Furthermore, the estimation complexity for a K-user vectoring group is reduced from O(K^2) to O(K).
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| 17. |
- Huang, Yezi, et al.
(author)
-
Rate-Boosting Using Strong Crosstalk in Next Generation Wireline Systems
- 2016
-
In: 2015 IEEE Global Communications Conference (GLOBECOM). - 9781467395267 ; , s. 1-6
-
Conference paper (peer-reviewed)abstract
- Next-generation wireline systems may exploit fre- quencies up to several hundred MHz on short lines. Strong crosstalk coupling, comparable to the direct paths, is one of the main channel characteristics at high frequencies. Instead of fully cancelling all crosstalk, we utilize strong crosstalk paths to boost data-rate for active users. Two linear precoding schemes, based on maximum ratio-combining (MRC) and convex optimization, respectively, are proposed and applied to a common network topology. The precoding schemes exploit constructive crosstalk signals on unused lines or in unused parts of the spectrum on neighboring lines to boost data-rate while still complying with the regulated spectral power limits per line. More than 500 Mbps throughput gain per active user can be achieved compared to state-of-the-art linear precoding.
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| 18. |
- Huang, Yezi, et al.
(author)
-
Time-Domain Precoding for LTE-over-Copper Systems
- 2016
-
In: 2016 IEEE International Conference on Communications (ICC). - 9781479966646 - 9781479966653 ; , s. 1-6
-
Conference paper (peer-reviewed)abstract
- Crosstalk cancellation is a crucial issue for traditional digital subscriber line systems. For LTE-over-copper systems, however, the need for crosstalk cancellation varies depending on the analog fronthauling architecture and its parameters. A crosstalk handler that is decoupled as much as possible from the rest of the system architecture is thus preferred. Therefore, we propose a time-domain precoding scheme specifically in downstream direction to separate the precoding unit from the LTE signal flow, and perform crosstalk cancellation in an on-demand manner. Estimation of all direct and crosstalk paths is assisted by LTE cell-specific reference signals. The time-domain precoder transforms the interference channel into a crosstalk-free channel with identical direct paths, which allows for low-complexity inter-symbol interference mitigation. We evaluate the concept in terms of signal-to-noise ratio provided for LTE signals using measured wireline channel data.
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| 19. |
- Lei, Wanlu
(author)
-
A study of wireless communications with reinforcement learning
- 2022
-
Doctoral thesis (other academic/artistic)abstract
- The explosive proliferation of mobile users and wireless data traffic in recent years pose imminent challenges upon wireless system design. The trendfor wireless communications becoming more complicated, decentralized andintelligent is inevitable. Lots of key issues in this field are decision-makingrelated problems such as resource allocation, transmission control, intelligentbeam tracking in millimeter Wave (mmWave) systems and so on. Reinforcement learning (RL) was once a languishing field of AI for solving varioussequential decision-making problems. However, it got revived in the late 80sand early 90s when it was connected to dynamic programming (DP). Then,recently RL has progressed in many applications, especially when underliningmodels do not have explicit mathematical solutions and simulations must beused. For instance, the success of RL in AlphaGo and AlphaZero motivatedlots of recent research activities in RL from both academia and industries.Moreover, since computation power has dramatically increased within thelast decade, the methods of simulations and online learning (planning) become feasible for implementations and deployment of RL. Despite of its potentials, the applications of RL to wireless communications are still far frommature. Therefore, it is of great interest to investigate RL-based methodsand algorithms to adapt to different wireless communication scenarios. Morespecifically, this thesis with regards to RL in wireless communications can beroughly divided into the following parts:In the first part of the thesis, we develop a framework based on deepRL (DRL) to solve the spectrum allocation problem in the emerging integrated access and backhaul (IAB) architecture with large scale deploymentand dynamic environment. We propose to use the latest DRL method by integrating an actor-critic spectrum allocation (ACSA) scheme and a deep neuralnetwork (DNN) to achieve real-time spectrum allocation in different scenarios. The proposed methods are evaluated through numerical simulations andshow promising results compared with some baseline allocation policies.In the second part of the thesis, we investigate the decentralized RL algorithms using Alternating direction method of multipliers (ADMM) in applications of Edge IoT. For RL in a decentralized setup, edge nodes (agents)connected through a communication network aim to work collaboratively tofind a policy to optimize the global reward as the sum of local rewards. However, communication costs, scalability and adaptation in complex environments with heterogeneous agents may significantly limit the performance ofdecentralized RL. ADMM has a structure that allows for decentralized implementation and has shown faster convergence than gradient-descent-basedmethods. Therefore, we propose an adaptive stochastic incremental ADMM(asI-ADMM) algorithm and apply the asI-ADMM to decentralized RL withedge computing-empowered IoT networks. We provide convergence properties for proposed algorithms by designing a Lyapunov function and prove thatthe asI-ADMM has O(1=k) + O(1=M) convergence rate where k and M are thenumber of iterations and batch samples, respectively.The third part of the thesis considers the problem of joint beam training and data transmission control of delay-sensitive communications overvimmWave channels. We formulate the problem as a constrained Markov Decision Process (MDP), which aims to minimize the cumulative energy consumption over the whole considered period of time under delay constraints.By introducing a Lagrange multiplier, we reformulate the constrained MDPto an unconstrained one. Then, we solve it using the parallel-rollout-basedRL method in a data-driven manner. Our numerical results demonstrate thatthe optimized policy obtained from parallel rollout significantly outperformsother baseline policies in both energy consumption and delay performance.The final part of the thesis is a further study of the beam tracking problem using supervised learning approach. Due to computation and delay limitation in real deployment, a light-weight algorithm is desired in the beamtracking problem in mmWave networks. We formulate the beam tracking(beam sweeping) problem as a binary-classification problem, and investigatesupervised learning methods for the solution. The methods are tested in bothsimulation scenarios, i.e., ray-tracing model, and real testing data with Ericsson over-the-air (OTA) dataset. It showed that the proposed methods cansignificantly improve cell capacity and reduce overhead consumption whenthe number of UEs increases in the network.
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| 20. |
- Lei, Wanlu, et al.
(author)
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Adaptive Beam Sweeping With Supervised Learning
- 2022
-
In: IEEE Wireless Communications Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 2162-2337 .- 2162-2345. ; 11:12, s. 2650-2654
-
Journal article (peer-reviewed)abstract
- Utilizing millimeter-wave (mmWave) frequencies for wireless communication in mobile systems is challenging since continuous tracking of the beam direction is needed. For the purpose, beam sweeping is performed periodically. Such approach can be sufficient in the initial deployment of the network when the number of users is small. However, a more efficient solution is needed when lots of users are connected to the network due to higher overhead consumption. We explore a supervised learning approach to adaptively perform beam sweeping, which has low implementation complexity and can improve cell capacity by reducing beam sweeping overhead. By formulating the beam tracking problem as a binary classification problem, we applied supervised learning methods to solve the formulated problem. The methods were tested on two scenarios: ray-tracing outdoor scenario and over-the-air (OTA) testing dataset from Ericsson. Both experimental results show that the proposed methods significantly increase cell throughput comparing with existing exhaustive sweeping and periodical sweeping strategies.
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| 21. |
- Lei, Wanlu, et al.
(author)
-
Adaptive Beam Tracking With Supervised Learning
-
Other publication (other academic/artistic)abstract
- Utilizing millimeter-wave (mmWave) frequencies forwireless communication in mobile systems is challenging sincecontinuous tracking of the beam direction is needed. For the purpose, beam sweeping is performed periodically. Such approachcan be sufficient in the initial deployment of the network whenthe number of users is small. However, a more efficient solutionis needed when lots of users are connected to the network due tohigher overhead consumption. We explore a supervised learningapproach to adaptively perform beam sweeping, which has lowimplementation complexity and can improve cell capacity byreducing beam sweeping overhead. By formulating the beamtracking problem as a binary classification problem, we appliedsupervised learning methods to solve the formulated problem.The methods were tested on two scenarios: ray-tracing outdoorscenario and over-the-air (OTA) testing dataset from Ericsson.Both experimental results show that the proposed methodssignificantly increase cell throughput comparing with existingexhaustive sweeping and periodical sweeping strategies.
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| 22. |
- Lei, Wanlu, et al.
(author)
-
Joint Beam Training and Data Transmission Control for mmWave Delay-Sensitive Communications : A Parallel Reinforcement Learning Approach
- 2022
-
In: IEEE Journal of Selected Topics in Signal Processing. - : Institute of Electrical and Electronics Engineers (IEEE). - 1932-4553. ; 16:3, s. 447-459
-
Journal article (peer-reviewed)abstract
- Future communication networks call for new solutions to support their capacity and delay demands by leveraging potentials of the millimeter wave (mmWave) frequency band. However, the beam training procedure in mmWave systems incurs significant overhead as well as huge energy consumption. As such, deriving an adaptive control policy is beneficial to both delay-sensitive and energy-efficient data transmission over mmWave networks. To this end, we investigate the problem of joint beam training and data transmission control for mmWave delay-sensitive communications in this paper. Specifically, the considered problem is firstly formulated as a constrained Markov Decision Process (MDP), which aims to minimize the cumulative energy consumption over the whole considered period of time under delay constraint. By introducing a Lagrange multiplier, we transform the constrained MDP into an unconstrained one, which is then solved via a parallel-rollout-based reinforcement learning method in a data-driven manner. Our numerical results demonstrate that the optimized policy via parallel-rollout significantly outperforms other baseline policies in both energy consumption and delay performance.
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| 23. |
- Medeiros, Eduardo, et al.
(author)
-
Crosstalk Mitigation for LTE-over-Copper in Downlink Direction
- 2016
-
In: IEEE Communications Letters. - 1089-7798. ; 20:7, s. 1425-1428
-
Journal article (peer-reviewed)abstract
- Radio-over-copper is a niche idea that has potential to become a cornerstone in the deployment of dense 5G networks. We address one of the remaining hurdles and present an architecture for transparent crosstalk mitigation in LTE-over-copper systems. By taking advantage of reference symbols present in the downlink LTE signals we propose two methods for estimating the copper channel. System performance is evaluated using channel measurements and error vector magnitude calculations with promising results.
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| 24. |
- Medeiros, Eduardo, et al.
(author)
-
How Vectoring in G.fast May Cause Neighborhood Wars
- 2014
-
In: [Host publication title missing]. - 9781479920037 ; , s. 3865-3870
-
Conference paper (peer-reviewed)abstract
- Emerging wireline transmission systems such as G.fast use bands up to around 200 MHz on short cables. A key enabler for achieving the aspired throughput of several hundred Mbit/s is joint processing of transmit signals in downstream direction as well as joint processing of receive signals in upstream direction through techniques referred to as vectoring. A new challenge in such systems are sudden and severe changes in the channel matrix caused by changing terminations on lines outside the vectoring group. Such events can be caused by users disconnecting their modems, turning them on or off, or on-/off- hook events on lines that still support the plain old telephony service. This work presents channel measurements capturing the impact of termination changes caused by modems or handsets. An analysis of the impact of these sudden changes on the signal- to-noise-power-ratio in vectoring systems reveals that throughput and stability can be seriously degraded. The potential of decision- directed channel tracking based on least squares estimation is investigated.
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| 25. |
- Medeiros, Eduardo, et al.
(author)
-
Modeling Alien-Line Impedance Mismatch in Wideband Vectored Wireline Systems
- 2014
-
In: IEEE Communications Letters. - 1089-7798. ; 18:9, s. 1527-1530
-
Journal article (peer-reviewed)abstract
- Sudden changes of channel coefficients in a wideband vectored wireline system (such as G.fast) due to changes in the terminating impedance of lines outside the vectored group can seriously degrade stability and throughput. This letter presents a model that predicts the impact of termination mismatch based exclusively on crosstalk data for the properly-terminated state. Experimental results confirm a tight fit between model and mea- surements. The model allows analysis of system performance and stability without dedicated crosstalk measurements for mismatch cases.
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| 26. |
- Müller, Francisco, et al.
(author)
-
Optimizing Power Normalization for G.fast Linear Precoder by Linear Programming
- 2014
-
In: 2014 IEEE International Conference on Communications, ICC 2014. - 9781479920037 ; , s. 4060-4065
-
Conference paper (peer-reviewed)abstract
- The use of vectoring for crosstalk cancellation in the new ITU-T G.fast standard for next generation DSL systems becomes essential for efficient utilization of the extended bandwidth (up to 200 MHz). In VDSL2 (up to 30 MHz), a zero-forcing-based linear precoder is used in downstream which approaches single-line performance. However, at high frequencies, the linear precoder may amplify the signal power substantially since the crosstalk channel is much stronger than at lower frequencies. Performance could be significantly degraded by power normalization to keep the PSD below the mask. In this work, we extended a per-line power normalization scheme by linear programming (LP) optimization. By simulations using measured cable data it is shown how the LPbased scheme further improves the linear precoder and it is also capable of balancing the data rate between lines. Further, the simulations also show the non-linear Tomlinson-Harashima precoder performs better than the linear precoders.
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| 27. |
- Ramalho, Leonardo, et al.
(author)
-
An LPC-based fronthaul compression scheme
- 2017
-
In: IEEE Communications Letters. - 1089-7798. ; 21:2, s. 318-321
-
Journal article (peer-reviewed)abstract
- Several new architectures are under investigation for cloud radio access networks, assuming distinct splits of functionality among the network elements. Consequently, the research on radio data compression for the fronthaul is based on assumptions that correspond to a wide variety of tradeoffs among data rate, signal distortion, latency, and computational cost. This letter describes a method for LTE downlink point-topoint signal compression based on linear prediction and Huffman coding, which is suitable for low cost encoding and decoding units with stringent restrictions on power consumption. The proposed method can work at various compression factors, such as 3.3:1 at an average EVM of 0.9%, or 4:1 at an average EVM of 2.1%.
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| 28. |
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| 29. |
- Zhang, Chao, et al.
(author)
-
A Virtualized LoRa Testbed and Experimental Results for Resource Pooling
- 2021
-
In: 7th IEEE World Forum on Internet of Things, WF-IoT 2021. - 9781665444316 ; , s. 871-876
-
Conference paper (peer-reviewed)abstract
- Traditional network architecture design of Low Power Wide Area Networks (LPWAN) is incapable of dynamically scaling resources based on the served traffic and requires manual procedures for network capacity upgrades. Today's over-provisioning approach based on proprietary hardware (HW) would not be cost and energy efficient to cope with the ever-increasing scale of Internet of Things (IoT) devices in future. The concept of virtualized radio access network (vRAN) by softwarizing and virtualizing communication stacks to a cloud environment is seen as a potential solution to provide web-scale scalability with the benefit of automation and resource pooling, which would significantly increase the resource utilization efficiency. In this work, we developed a LoRa-based testbed to investigate the resource pooling perspective for virtualized physical layer (PHY) functions in a Cloud environment. The testbed is first experimentally validated by comparing the single-cell emulation results and the test results with real LoRa devices. The results show that the testbed can generate the same traffic pattern as real LoRa devices, where two cases show similar resource usages. Then the multi-cell experiments show that one PHY function instance can serve many full-traffic LoRa cells, which showcases a great potential of resource pooling for LoRa networks.
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