| 1. |
- Agheli, Pouya, et al.
(författare)
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Goal-Oriented Multiple Access Connectivity for Networked Intelligent Systems
- 2024
-
Ingår i: IEEE Communications Letters. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 1089-7798 .- 1558-2558. ; 28:8, s. 1795-1799
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Tidskriftsartikel (refereegranskat)abstract
- We design a self-decision goal-oriented multiple access scheme, where sensing agents observe a common event and individually decide to communicate the event's attributes as updates to the monitoring agents, to satisfy a certain goal. Decisions are based on the usefulness of updates, generated under uniform, change- and semantics-aware acquisition, as well as statistics and updates of other agents. We obtain optimal activation probabilities and threshold criteria for decision-making under all schemes, maximizing a grade of effectiveness metric. Alongside studying the effect of different parameters on effectiveness, our simulation results show that the self-decision scheme may attain at least 92% of optimal performance.
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| 2. |
- Agheli, Pouya, et al.
(författare)
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Semantic Filtering and Source Coding in Distributed Wireless Monitoring Systems
- 2024
-
Ingår i: IEEE Transactions on Communications. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 0090-6778 .- 1558-0857. ; 72:6, s. 3290-3304
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Tidskriftsartikel (refereegranskat)abstract
- The problem of goal-oriented semantic filtering and timely source coding in multiuser communication systems is considered here. We study a distributed monitoring system in which multiple information sources, each observing a physical process, provide status update packets to multiple monitors having heterogeneous goals. Two semantic filtering schemes are first proposed as a means to admit or drop arrival packets based on their goal-dependent importance, which is a function of the intrinsic and extrinsic attributes of information and the probability of occurrence of each realization. Admitted packets at each sensor are then encoded and transmitted over block-fading wireless channels so that served monitors can timely fulfill their goals. A truncated error control scheme is derived, which allows transmitters to drop or retransmit undelivered packets based on their significance. Then, we formulate the timely source encoding optimization problem and analytically derive the optimal codeword lengths assigned to the admitted packets which maximize a weighted sum of semantic utility functions for all pairs of communicating sensors and monitors. Our analytical and numerical results provide the optimal design parameters for different arrival rates and highlight the improvement in timely status update delivery using the proposed semantic filtering, source coding, and error control schemes.
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| 3. |
- Agheli, Pouya, et al.
(författare)
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Semantic Source Coding for Two Users with Heterogeneous Goals
- 2022
-
Ingår i: 2022 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM 2022). - : IEEE. - 9781665435406 - 9781665435413 ; , s. 4983-4988
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Konferensbidrag (refereegranskat)abstract
- We study a multiuser system in which an information source provides status updates to two monitors with heterogeneous goals. Semantic filtering is first performed to select the most useful realizations for each monitor. Packets are then encoded and sent so that each monitor can timely fulfill its goal. In this regard, some realizations are important for both monitors, while every other realization is informative for only one monitor. We determine the optimal real codeword lengths assigned to the selected packet arrivals in the sense of maximizing a weighted sum of semantics-aware utility functions for the two monitors. Our analytical and numerical results provide the optimal design parameters for different arrival rates and highlight the improvement in timely status update delivery using semantic filtering and source coding.
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| 4. |
- Agheli, Pouya, et al.
(författare)
-
Semantics-Aware Source Coding in Status Update Systems
- 2022
-
Ingår i: 2022 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS WORKSHOPS (ICC WORKSHOPS). - : IEEE. - 9781665426718 - 9781665426725 ; , s. 169-174
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Konferensbidrag (refereegranskat)abstract
- We consider a communication system in which the destination receives status updates from an information source that observes a physical process. The transmitter performs semantics-empowered filtering as a means to send only the most "important" samples to the receiver in a timely manner. As a first step, we explore a simple policy where the transmitter selects to encode only a fraction of the least frequent realizations of the observed random phenomenon, treating the remaining ones as not not informative. For this timely source coding problem, we derive the optimal codeword lengths in the sense of maximizing a semantics-aware utility function and minimizing a quadratic average length cost. Our numerical results show the optimal number of updates to transmit for different arrival rates and encoding costs and corroborate that semantic filtering results in higher performance in terms of timely delivery of important updates.
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| 5. |
- Björnson, Emil, Professor, 1983-, et al.
(författare)
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Deploying Dense Networks for Maximal Energy Efficiency : Small Cells Meet Massive MIMO
- 2016
-
Ingår i: IEEE Journal on Selected Areas in Communications. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 0733-8716 .- 1558-0008. ; 34:4, s. 832-847
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Tidskriftsartikel (refereegranskat)abstract
- What would a cellular network designed for maximal energy efficiency look like? To answer this fundamental question, tools from stochastic geometry are used in this paper to model future cellular networks and obtain a new lower bound on the average uplink spectral efficiency. This enables us to formulate a tractable uplink energy efficiency (EE) maximization problem and solve it analytically with respect to the density of base stations (BSs), the transmit power levels, the number of BS antennas and users per cell, and the pilot reuse factor. The closed-form expressions obtained from this general EE maximization framework provide valuable insights on the interplay between the optimization variables, hardware characteristics, and propagation environment. Small cells are proved to give high EE, but the EE improvement saturates quickly with the BS density. Interestingly, the maximal EE is achieved by also equipping the BSs with multiple antennas and operate in a "massive MIMO" fashion, where the array gain from coherent detection mitigates interference and the multiplexing of many users reduces the energy cost per user.
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| 6. |
- Björnson, Emil, Professor, 1983-, et al.
(författare)
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Designing Wireless Broadband Access for Energy Efficiency : Are Small Cells the Only Answer?
- 2015
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Ingår i: 2015 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATION WORKSHOP (ICCW). - : IEEE. - 9781467363051 ; , s. 136-141
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Konferensbidrag (refereegranskat)abstract
- The main usage of cellular networks has changed from voice to data traffic, mostly requested by static users. In this paper, we analyze how a cellular network should be designed to provide such wireless broadband access with maximal energy efficiency (EE). Using stochastic geometry and a detailed power consumption model, we optimize the density of access points (APs), number of antennas and users per AP, and transmission power for maximal EE. Small cells are of course a key technology in this direction, but the analysis shows that the EE improvement of a small-cell network saturates quickly with the AP density and then "massive MIMO" techniques can further improve the EE.
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| 7. |
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| 8. |
- Björnson, Emil, Professor, 1983-, et al.
(författare)
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Energy-Efficient Future Wireless Networks : A Marriage between Massive MIMO and Small Cells
- 2015
-
Ingår i: 2015 IEEE 16TH INTERNATIONAL WORKSHOP ON SIGNAL PROCESSING ADVANCES IN WIRELESS COMMUNICATIONS (SPAWC). - : IEEE. - 9781479919314 ; , s. 211-215
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Konferensbidrag (refereegranskat)abstract
- How would a cellular network designed for high energy efficiency look like? To answer this fundamental question, we model cellular networks using stochastic geometry and optimize the energy efficiency with respect to the density of base stations, the number of antennas and users per cell, the transmit power levels, and the pilot reuse. The highest efficiency is neither achieved by a pure small-cell approach, nor by a pure massive MIMO solution. Interestingly, it is the combination of these approaches that provides the highest energy efficiency; small cells contributes by reducing the propagation losses while massive MIMO enables multiplexing of users with controlled interference.
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| 9. |
- Björnson, Emil, et al.
(författare)
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Massive MIMO Systems With Non-Ideal Hardware : Energy Efficiency, Estimation, and Capacity Limits
- 2014
-
Ingår i: IEEE Transactions on Information Theory. - : IEEE Press. - 0018-9448 .- 1557-9654. ; 60:11, s. 7112-7139
-
Tidskriftsartikel (refereegranskat)abstract
- The use of large-scale antenna arrays can bring substantial improvements in energy and/or spectral efficiency to wireless systems due to the greatly improved spatial resolution and array gain. Recent works in the field of massive multiple-input multiple-output (MIMO) show that the user channels decorrelate when the number of antennas at the base stations (BSs) increases, thus strong signal gains are achievable with little interuser interference. Since these results rely on asymptotics, it is important to investigate whether the conventional system models are reasonable in this asymptotic regime. This paper considers a new system model that incorporates general transceiver hardware impairments at both the BSs (equipped with large antenna arrays) and the single-antenna user equipments (UEs). As opposed to the conventional case of ideal hardware, we show that hardware impairments create finite ceilings on the channel estimation accuracy and on the downlink/uplink capacity of each UE. Surprisingly, the capacity is mainly limited by the hardware at the UE, while the impact of impairments in the large-scale arrays vanishes asymptotically and interuser interference (in particular, pilot contamination) becomes negligible. Furthermore, we prove that the huge degrees of freedom offered by massive MIMO can be used to reduce the transmit power and/or to tolerate larger hardware impairments, which allows for the use of inexpensive and energy-efficient antenna elements.
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| 10. |
- Björnson, Emil, 1983-
(författare)
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Multiantenna Cellular Communications : Channel Estimation, Feedback, and Resource Allocation
- 2011
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The use of multiple antennas at base stations and user devices is a key component in the design of cellular communication systems that can meet the capacity demands of tomorrow. The downlink transmission from base stations to users is particularly limiting, both from a theoretical and a practical perspective, since user devices should be simple and power-efficient, and because many applications primarily create downlink traffic (e.g., video streaming). The potential gain of employing multiple antennas for downlink transmission is well recognized: the total data throughput increases linearly with the number of transmit antennas if the spatial dimension is exploited for simultaneous transmission to multiple users. In the design of practical cellular systems, the actual benefit of multiuser multiantenna transmission is limited by a variety of factors, including acquisition and accuracy of channel information, transmit power, channel conditions, cell density, user mobility, computational complexity, and the level of cooperation between base stations in the transmission design. The thesis considers three main components of downlink communications: 1) estimation of current channel conditions using training signaling; 2) efficient feedback of channel estimates; and 3) allocation of transmit resources (e.g., power, time and spatial dimensions) to users. In each area, the thesis seeks to provide a greater understanding of the interplay between different system properties. This is achieved by generalizing the underlying assumptions in prior work and providing both extensions of previous outcomes and entirely new mathematical results, along with supporting numerical examples. Some of the main thesis contributions can be summarized as follows. A framework is proposed for estimation of different channel quantities using a common optimized training sequence. Furthermore, it is proved that each user should only be allocated one data stream and utilize its antennas for receive combining and interference rejection, instead of using the antennas for reception of multiple data streams. This fundamental result is proved under both exact channel acquisition and under imperfections from channel estimation and limited feedback. This also has positive implications on the hardware and system design. Next, a general mathematical model is proposed for joint analysis of cellular systems with different levels of base station cooperation. The optimal multicell resource allocation can in general only be found with exponential computational complexity, but a systematic algorithm is proposed to find the optimal solution for the purpose of offline benchmarking. A parametrization of the optimal solution is also derived, creating a foundation for heuristic low-complexity algorithms that can provide close-to-optimal performance. This is exemplified by proposing centralized and distributed multicell transmission strategies and by evaluating these using multicell channel measurements.
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| 11. |
- Björnson, Emil, et al.
(författare)
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Receive Combining vs. Multi-Stream Multiplexing in Downlink Systems With Multi-Antenna Users
- 2013
-
Ingår i: IEEE Transactions on Signal Processing. - : IEEE Signal Processing Society. - 1053-587X .- 1941-0476. ; 61:13, s. 3431-3446
-
Tidskriftsartikel (refereegranskat)abstract
- In downlink multi-antenna systems with many users, the multiplexing gain is strictly limited by the number of transmit antennas and the use of these antennas. Assuming that the total number of receive antennas at the multi-antenna users is much larger than, the maximal multiplexing gain can be achieved with many different transmission/reception strategies. For example, the excess number of receive antennas can be utilized to schedule users with effective channels that are near-orthogonal, for multi-stream multiplexing to users with well-conditioned channels, and/or to enable interference-aware receive combining. In this paper, we try to answer the question if the data streams should be divided among few users (many streams per user) or many users (few streams per user, enabling receive combining). Analytic results are derived to show how user selection, spatial correlation, heterogeneous user conditions, and imperfect channel acquisition (quantization or estimation errors) affect the performance when sending the maximal number of streams or one stream per scheduled user-the two extremes in data stream allocation. While contradicting observations on this topic have been reported in prior works, we show that selecting many users and allocating one stream per user (i.e., exploiting receive combining) is the best candidate under realistic conditions. This is explained by the provably stronger resilience towards spatial correlation and the larger benefit from multi-user diversity. This fundamental result has positive implications for the design of downlink systems as it reduces the hardware requirements at the user devices and simplifies the throughput optimization.
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| 12. |
- Boccardi, Federico, et al.
(författare)
-
Spectrum Pooling in MmWave Networks : Opportunities, Challenges, and Enablers
- 2016
-
Ingår i: IEEE Communications Magazine. - : IEEE. - 0163-6804 .- 1558-1896. ; 54:11, s. 33-39
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Tidskriftsartikel (refereegranskat)abstract
- Motivated by the specific characteristics of mmWave technologies, we discuss the possibility of an authorization regime that allows spectrum sharing between multiple operators, also referred to as spectrum pooling. In particular, considering user rate as the performance measure, we assess the benefit of coordination among networks of different operators, study the impact of beamforming at both base stations and user terminals, and analyze the pooling performance at different frequency carriers. We also discuss the enabling spectrum mechanisms, architectures, and protocols required to make spectrum pooling work in real networks. Our initial results show that, from a technical perspective, spectrum pooling at mmWave has the potential to use the resources more efficiently than traditional exclusive spectrum allocation to a single operator. However, further studies are needed in order to reach a thorough understanding of this matter, and we hope that this article will help stimulate further research in this area.
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| 13. |
- Chen, Zheng, et al.
(författare)
-
Cooperative Caching and Transmission Design in Cluster-Centric Small Cell Networks
- 2017
-
Ingår i: IEEE Transactions on Wireless Communications. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 1536-1276 .- 1558-2248. ; 16:5, s. 3401-3415
-
Tidskriftsartikel (refereegranskat)abstract
- Wireless content caching in small cell networks (SCNs) has recently been considered as an efficient way to reduce the data traffic and the energy consumption of the backhaul in emerging heterogeneous cellular networks. In this paper, we consider a cluster-centric SCN with combined design of cooperative caching and transmission policy. Small base stations (SBSs) are grouped into disjoint clusters, in which in-cluster cache space is utilized as an entity. We propose a combined caching scheme, where part of the cache space in each cluster is reserved for caching the most popular content in every SBS, while the remaining is used for cooperatively caching different partitions of the less popular content in different SBSs, as a means to increase local content diversity. Depending on the availability and placement of the requested content, coordinated multi-point technique with either joint transmission or parallel transmission is used to deliver content to the served user. Using Poisson point process for the SBS location distribution and a hexagonal grid model for the clusters, we provide analytical results on the successful content delivery probability of both transmission schemes for a user located at the cluster center. Our analysis shows an inherent tradeoff between transmission diversity and content diversity in our cooperation design. We also study the optimal cache space assignment for two objective functions: maximization of the cache service performance and the energy efficiency. Simulation results show that the proposed scheme achieves performance gain by leveraging cache-level and signal-level cooperation and adapting to the network environment and user quality-of-service requirements.
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| 14. |
- Chen, Zheng, et al.
(författare)
-
Decentralized Opportunistic Access for D2D Underlaid Cellular Networks
- 2018
-
Ingår i: IEEE Transactions on Communications. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 0090-6778 .- 1558-0857. ; 66:10, s. 4842-4853
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we propose a decentralized access control scheme for interference management in device-to-device (D2D) underlaid cellular networks. Our method combines signal-to-interference ratio (SIR)-aware link activation with cellular guard zones in a system, where D2D links opportunistically access the licensed cellular spectrum when the activation conditions are satisfied. Analytical expressions for the success/coverage probability of both cellular and D2D links are derived. We characterize the impact of the guard zone radius and the SIR threshold on the D2D potential throughput and cellular coverage. A tractable approach is proposed to find the SIR threshold and guard zone radius that maximize the potential throughput of the D2D communication while ensuring sufficient coverage probability for the cellular uplink users. Simulations validate the accuracy of our analytical results and show the performance gain of the proposed scheme compared to prior state-of-the-art solutions.
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| 15. |
- Chen, Zheng, et al.
(författare)
-
Energy Harvesting in Delay-Aware Cognitive Shared Access Networks
- 2017
-
Ingår i: IEEE Workshop on Emerging Energy Harvesting Solutions for 5G Networks (5G-NRG). - : IEEE Press. - 9781509015252 - 9781509015269 ; , s. 168-173
-
Konferensbidrag (refereegranskat)abstract
- In this work, we study the effect of energy harvesting in a cognitive shared access network with delay constraints on the primary user. We model the distribution of secondary nodes by a homogeneous Poisson point process (PPP), while the primary user is located at fixed location. The secondary users are assumed to have always packets to transmit whilst the primary transmitter has bursty traffic. We assume an energy harvesting zone around the primary transmitter and a guard zone around the primary receiver. The secondary users are transmitting in a random access manner, however, transmissions of secondary nodes are restricted by their battery status and location. Targeting at achieving the maximum secondary throughput under primary delay constraints, we analyze the impact of various parameters on the performance of the considered network. Our results provide insights into the optimization of access protocol parameters for the energy harvesting-based cognitive shared access network with delay constraints.
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| 16. |
- Chen, Zheng, et al.
(författare)
-
Probabilistic Caching in Wireless D2D Networks: Cache Hit Optimal Versus Throughput Optimal
- 2017
-
Ingår i: IEEE Communications Letters. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 1089-7798 .- 1558-2558. ; 21:3, s. 584-587
-
Tidskriftsartikel (refereegranskat)abstract
- Departing from the conventional cache hit optimization in cache-enabled wireless networks, we consider an alternative optimization approach for the probabilistic caching placement in stochastic wireless D2D caching networks taking into account the reliability of D2D transmissions. Using tools from stochastic geometry, we provide a closed-form approximation of cache-aided throughput, which measures the density of successfully served requests by local device caches, and we obtain the optimal caching probabilities via numerical optimization. Compared with the cache-hit-optimal case, the optimal caching probabilities obtained by cache-aided throughput optimization show notable gain in terms of the density of successfully served user requests, particularly in dense user environments.
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| 17. |
- Chen, Zheng, et al.
(författare)
-
Throughput Analysis of Smart Objects with Delay Constraints
- 2016
-
Ingår i: 2016 IEEE 17TH INTERNATIONAL SYMPOSIUM ON A WORLD OF WIRELESS, MOBILE AND MULTIMEDIA NETWORKS (WOWMOM). - : IEEE. - 9781509021857
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we analyze a shared access network with one primary device and randomly distributed smart objects with secondary priority. Assuming random traffic at the primary device and saturated queues at the smart objects with secondary priority, an access protocol is employed to adjust the random access probabilities of the smart objects depending on the congestion level of the primary. We characterize the maximum throughput of the secondary network with respect to delay constraints on the primary. Our results highlight the impact of system design parameters on the delay and throughput behavior of the shared access network with massive number of connected objects.
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| 18. |
- Chen, Zheng, et al.
(författare)
-
Throughput With Delay Constraints in a Shared Access Network With Priorities
- 2018
-
Ingår i: IEEE Transactions on Wireless Communications. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 1536-1276 .- 1558-2248. ; 17:9, s. 5885-5899
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we analyze a shared access network with a fixed primary node and randomly distributed secondary nodes whose spatial distribution follows a poisson point process. The secondary nodes use a random access protocol allowing them to access the channel with probabilities that depend on the queue size of the primary node. Assuming a system with multipacket reception receivers, having bursty packet arrivals at the primary and saturated traffic at the secondary nodes, our protocol can be tuned to alleviate congestion at the primary. We analyze the throughput of the secondary network and the primary average delay, as well as the impact of the secondary node access probability and transmit power. We formulate an optimization problem to maximize the throughput of the secondary network under delay constraints for the primary node; in the case of no congestion control, the optimal access probability can be provided in closed form. Our numerical results illustrate the effect of network operating parameters on the performance of the proposed priority-based shared access protocol.
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| 19. |
- Daei, Sajad, et al.
(författare)
-
Blind Asynchronous Goal-Oriented Detection for Massive Connectivity
- 2023
-
Ingår i: 2023 21st International Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks, WiOpt 2023. - : Institute of Electrical and Electronics Engineers Inc.. ; , s. 167-174
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Konferensbidrag (refereegranskat)abstract
- Resource allocation and multiple access schemes are instrumental for the success of communication networks, which facilitate seamless wireless connectivity among a growing population of uncoordinated and non-synchronized users. In this paper, we present a novel random access scheme that addresses one of the most severe barriers of current strategies to achieve massive connectivity and ultra reliable and low latency communications for 6G. The proposed scheme utilizes wireless channels’ angular continuous group-sparsity feature to provide low latency, high reliability, and massive access features in the face of limited time-bandwidth resources, asynchronous transmissions, and preamble errors. Specifically, a reconstruction-free goal oriented optimization problem is proposed which preserves the angular information of active devices and is then complemented by a clustering algorithm to assign active users to specific groups. This allows to identify active stationary devices according to their line of sight angles. Additionally, for mobile devices, an alternating minimization algorithm is proposed to recover their preamble, data, and channel gains simultaneously, enabling the identification of active mobile users. Simulation results show that the proposed algorithm provides excellent performance and supports a massive number of devices. Moreover, the performance of the proposed scheme is independent of the total number of devices, distinguishing it from other random access schemes. The proposed method provides a unified solution to meet the requirements of machine-type communications and ultra reliable and low latency communications, making it an important contribution to the emerging 6G networks.
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| 20. |
- Fountoulakis, Emmanouil, et al.
(författare)
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Goal-Oriented Policies for Cost of Actuation Error Minimization in Wireless Autonomous Systems
- 2023
-
Ingår i: IEEE Communications Letters. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 1089-7798 .- 1558-2558. ; 27:9, s. 2323-2327
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Tidskriftsartikel (refereegranskat)abstract
- We consider the minimization of the cost of actuation error under resource constraints for real-time tracking in wireless autonomous systems. A transmitter monitors the state of a discrete random process and sends updates to a receiver over an unreliable wireless channel. The receiver then takes actions according to the estimated state of the source. For each discrepancy between the real state of the source and the estimated one, we consider a different cost of actuation error. This models the case where some states, and consequently the corresponding actions to be taken, are more important than others. We provide two algorithms, a first one reaching an optimal solution but of high complexity, and a second low-complexity one that provides a suboptimal solution. Our simulation results evince that the performance of the two algorithms are quite close.
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| 21. |
- Kountouris, Marios, et al.
(författare)
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Approximating the Interference Distribution in Large Wireless Networks
- 2014
-
Ingår i: 2014 11TH INTERNATIONAL SYMPOSIUM ON WIRELESS COMMUNICATIONS SYSTEMS (ISWCS). - : IEEE. - 9781479958634 ; , s. 80-84
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Konferensbidrag (refereegranskat)abstract
- The spatial locations of transmitters play a cardinal role in evaluating the aggregate interference and hence the performance of large wireless networks. The most widely used approach for modeling the network geometry is the Poisson point process (PPP), mainly due to its analytical tractability. However, point process models with repulsion and inhibition, such as the Matern hardcore process, the Strauss process, the Ginibre point process, and the Poisson cluster process, are more accurate and realistic models than the PPP for actual heterogeneous cellular network (HetNets) deployments. Nevertheless, the limited analytical tractability of the aforementioned point processes makes it difficult or even impossible to obtain closed-form analytical expressions for network performance. In this paper, we provide a framework for approximating the interference distribution in wireless networks with spatial randomness. Specifically, the distribution of aggregate interference is approximated by known probability density functions, as a means to provide simple and tractable expressions for key performance metrics, i.e. coverage probability, area spectral efficiency, and average rate. We show the effectiveness of the proposed approach in analyzing large wireless networks with nodes exhibiting attraction and inhibition.
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| 22. |
- Kountouris, Marios, et al.
(författare)
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QoS Provisioning in Large Wireless Networks
- 2018
-
Ingår i: 16th International Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks (WiOpt). - : IEEE. - 9783903176003 - 9781538646212
-
Konferensbidrag (refereegranskat)abstract
- Quality of service (QoS) provisioning in next-generation mobile communications systems entails a deep understanding of the delay performance. The delay in wireless networks is strongly affected by the traffic arrival process and the packet service process, which in turn depends on the medium access mechanisms and the signal-to-interference-plus-noise ratio (SINR). In this work, we analyze the delay of large wireless networks, where the sources are distributed as a Poisson point process. We provide analytical expressions for the service process and derive delay violation probability bounds using tools from stochastic network calculus and stochastic geometry. Furthermore, we analyze the delay performance under statistical queueing constraints imposed as limitations on buffer violation probabilities. The impact of QoS requirements, network geometry and spatial density of interferers on the throughput and delay performance is identified. Our results provide useful guidelines for resource allocation and system dimensioning to guarantee stringent delay requirements.
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| 23. |
- Kountouris, Marios, et al.
(författare)
-
Series Editorial: Network Softwarization and Management
- 2021
-
Ingår i: IEEE Communications Magazine. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 0163-6804 .- 1558-1896. ; 59:6, s. 96-102
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Tidskriftsartikel (refereegranskat)abstract
- This series focuses on softwarization, management, and their integration in communication networks and services. "Network Softwarization" advocates for network architectures that separate the software implementing network functions, protocols and services from the hardware running them. "Network Management" aims to integrate fault, configuration, accounting, performance, and security capabilities in the network and to support self-management features, integral automation, and autonomic capabilities, empowering the network with inbuilt cognition and intelligence. The critical role that software and management are increasingly playing in telecommunications is enabling unprecedented levels of abstraction, disaggregation, operation, integration, robustness, optimization, intelligence, precision delivery, programmability, and cost and complexity reduction in the network infrastructures and services. Such an approach is resulting in even greater attainment of non-functional characteristics (e.g., qualities of the operation of a network, rather than specific behaviors including flexibility, integrability, interoperability, operational guarantees, deployability, auditability and control, reliability, adaptability, elasticity, effectiveness, extensibility, automation and autonomicity).
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| 24. |
- Pappas, Nikolaos, et al.
(författare)
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Age of Information of Multiple Sources with Queue Management
- 2015
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Ingår i: 2015 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC). - : IEEE. - 9781467364324 ; , s. 5935-5940
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Konferensbidrag (refereegranskat)abstract
- We consider a system of multiple sources generating status update packets, which need to be sent by a single transmitter to a destination over a network. In the model we study, the packet generation time may vary at each source, and the packets go through the network with a random delay. Each update carries a time stamp of its generation, allowing the destination to calculate for each source the so called Age of Information, which measures the timeliness of each status update arriving. Considering that queuing delay can unnecessarily increase the age of a critical status update, we propose here a queue management technique, in which we maintain a queue with only the latest status packet of each source, overwriting any previously queued update from that source. This simple technique drastically limits the need for buffering and can be applied in systems where the history of source status is not relevant. We show that this scheme results in significantly less transmissions compared to the standard M/M/1 queue model. Furthermore, the proposed technique reduces the per source age of information, especially in settings not using queue management with high status update generation rates.
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| 25. |
- Pappas, Nikolaos, et al.
(författare)
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Delay Violation Probability and Age of Information Interplay in the Two-user Multiple Access Channel
- 2019
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Ingår i: 2019 IEEE 20TH INTERNATIONAL WORKSHOP ON SIGNAL PROCESSING ADVANCES IN WIRELESS COMMUNICATIONS (SPAWC 2019). - : IEEE. - 9781538665282
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we study the interplay between delay violation probability and average Age of Information (AoI) in a two-user wireless multiple access channel with multipacket reception (MPR) capability. We consider a system in which users have heterogeneous traffic characteristics: one has stringent delay constraints, while the other measures a source and transmits status updates in order to keep the AoI low. We show the effect of sensor sampling rate on the delay violation probability and that of the service rate of the delay-sensitive user on information freshness.
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| 26. |
- Pappas, Nikolaos, et al.
(författare)
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Effect of Energy Harvesting on Stable Throughput in Cooperative Relay Systems
- 2016
-
Ingår i: Journal of Communications and Networks. - : KOREAN INST COMMUNICATIONS SCIENCES (K I C S). - 1229-2370 .- 1976-5541. ; 18:2, s. 261-269
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, the impact of energy constraints on a two hop network with a source, a relay and a destination under random medium access is studied. A collision channel with erasures is considered, and the source and the relay nodes have energy harvesting capabilities and an unlimited battery to store the harvested energy. Additionally, the source and the relay node have external traffic arrivals and the relay forwards a fraction of the source nodes traffic to the destination; the cooperation is performed at the network level. An inner and an outer bound of the stability region for a given transmission probability vector are obtained. Then, the closure of the inner and the outer bound is obtained separately and they turn out to be identical. This work is not only a step in connecting information theory and networking, by studying the maximum stable throughput region metric but also it taps the relatively unexplored and important domain of energy harvesting and assesses the effect of that on this important measure.
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| 27. |
- Pappas, Nikolaos, et al.
(författare)
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Performance analysis of distributed cooperation under uncoordinated network interference
- 2014
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Ingår i: 2014 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP). ; , s. 6181-6185
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Konferensbidrag (refereegranskat)abstract
- Managing interference is a major technical challenge in large wireless networks. Distributed cooperation techniques, such as Interference Alignment (IA), exploit the available spatial degrees of freedom of the interference channel holding promise of enhanced spectral efficiency. Most prior results, however, consider isolated network settings, neglecting the interference from nodes that are not participating in the cooperation scheme. This paper analyzes the performance of IA in the presence of uncoordinated interference from a heterogeneous network. Specifically, we analyze perfect downlink IA in a fixed-size cell, where the interfering nodes are distributed according to a spatial point process, and compare it with a non-cooperative MIMO scheme. Furthermore, the performance gains by using a guard zone between the IA cluster and the interference field are evaluated and design guidelines for the necessary isolation distance from out-of-cluster interferers are provided.
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| 28. |
- Pappas, Nikolaos, et al.
(författare)
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Relay-Assisted Multiple Access With Full-Duplex Multi-Packet Reception
- 2015
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Ingår i: IEEE Transactions on Wireless Communications. - : Institute of Electrical and Electronics Engineers (IEEE). - 1536-1276 .- 1558-2248. ; 14:7, s. 3544-3558
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Tidskriftsartikel (refereegranskat)abstract
- The effect of full-duplex cooperative relaying in a random access multiuser network is investigated here. First, we model the self-interference incurred due to full-duplex operation, assuming multi-packet reception capabilities for both the relay and the destination node. Traffic at the source nodes is considered saturated and the cooperative relay, which does not have packets of its own, stores a source packet that it receives successfully in its queue when the transmission to the destination has failed. We obtain analytical expressions for key performance metrics at the relay, such as arrival and service rates, stability conditions, and average queue length, as functions of the transmission probabilities, the self interference coefficient, and the links outage probabilities. Furthermore, we study the impact of the relay node and the self-interference coefficient on the per-user and aggregate throughput, and the average delay per packet. We show that perfect self-interference cancelation plays a crucial role when the SINR threshold is small, since it may result to worse performance in throughput and delay comparing with the half-duplex case. This is because perfect self-interference cancelation can cause an unstable queue at the relay under some conditions.
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| 29. |
- Pappas, Nikolaos, et al.
(författare)
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Stable Throughput Region of the Two-User Broadcast Channel
- 2018
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Ingår i: IEEE Transactions on Communications. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 0090-6778 .- 1558-0857. ; 66:10, s. 4611-4621
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we consider the two-user broadcast channel and we characterize its stable throughput region. We start the analysis by providing the stability region for the general case without any specific considerations on transmission and reception mechanisms. We also provide conditions for the stable throughput region to be convex. Subsequently, we study the case where the transmitter uses superposition coding and we consider two special cases for the receivers. The first one is when both receivers treat interference as noise. The second is when the user with a better channel uses successive decoding and the other receiver treats interference as noise.
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| 30. |
- Pappas, Nikolaos, et al.
(författare)
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Stable Throughput Region of the Two-User Interference Channel
- 2019
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Ingår i: Ad hoc networks. - : ELSEVIER SCIENCE BV. - 1570-8705 .- 1570-8713. ; 85, s. 19-31
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Tidskriftsartikel (refereegranskat)abstract
- We consider the two-user interference channel where two independent pairs communicate concurrently and investigate its stable throughput region. First, the stability region is characterized for the general case, i.e., without any specific consideration on the transmission and reception structures. Second, we explore two different interference harnessing strategies at the receiver: treating interference as noise and successive interference cancellation. Furthermore, we provide conditions for the convexity of the stability region and for which a certain receiver strategy leads to broader stability region. The impact of multiple transmit antennas on the stability region is briefly discussed. Finally, we study the effect of random access on the stability region of the two-user interference channel. (C) 2018 Elsevier B.V. All rights reserved.
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| 31. |
- Pappas, Nikolaos, et al.
(författare)
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The Stability Region of the Two-User Broadcast Channel
- 2016
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Ingår i: 2016 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC). - : IEEE. - 9781479966646
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Konferensbidrag (refereegranskat)abstract
- In this paper, we characterize the stability region of the two-user broadcast channel. First, we obtain the stability region in the general case. Second, we consider the particular case where each receiver treats the interfering signal as noise, as well as the case in which the packets are transmitted using superposition coding and successive decoding is employed at the strong receiver.
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| 32. |
- Pappas, Nikolaos, et al.
(författare)
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Throughput of a Cognitive Radio Network under Congestion Constraints: A Network-Level Study
- 2014
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Ingår i: 2014 9TH INTERNATIONAL CONFERENCE ON COGNITIVE RADIO ORIENTED WIRELESS NETWORKS AND COMMUNICATIONS (CROWNCOM). - : IEEE. - 9781631900037 ; , s. 162-166
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Konferensbidrag (refereegranskat)abstract
- In this paper we analyze a cognitive radio network with one primary and one secondary transmitter, in which the primary transmitter has bursty arrivals while the secondary node is assumed to be saturated (i.e. always has a packet waiting to be transmitted). The secondary node transmits in a cognitive way such that it does not impede the performance of the primary node. We assume that the receivers have multipacket reception (MPR) capabilities and that the secondary node can take advantage of the MPR capability by transmitting simultaneously with the primary under certain conditions. We obtain analytical expressions for the stationary distribution of the primary node queue and we also provide conditions for its stability. Finally, we provide expressions for the aggregate throughput of the network as well as for the throughput at the secondary node.
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| 33. |
- Popovski, Petar, et al.
(författare)
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A Perspective on Time Toward Wireless 6G
- 2022
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Ingår i: Proceedings of the IEEE. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9219 .- 1558-2256. ; 110:8, s. 1116-1146
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Tidskriftsartikel (refereegranskat)abstract
- With the advent of 5G technology, the notion of latency got a prominent role in wireless connectivity, serving as a proxy term for addressing the requirements for real-time communication. As wireless systems evolve toward 6G, the ambition to immerse the digital into physical reality will increase. Besides making the real-time requirements more stringent, this immersion will bring the notions of time, simultaneity, presence, and causality to a new level of complexity A growing body of research points out that latency is insufficient to parameterize all real-time requirements. Notably, one such requirement that received significant attention is information freshness, defined through the Age of Information (AoI) and its derivatives. In general, the metrics derived from a conventional black-box approach to communication network design are not representative of new distributed paradigms, such as sensing, learning, or distributed consensus. The objective of this article is to investigate the general notion of timing in wireless communication systems and networks, and its relation to effective information generation, processing, transmission, and reconstruction at the senders and receivers. We establish a general statistical framework of timing requirements in wireless communication systems, which subsumes both latency and AoI. The framework is made by associating a timing component with the two basic statistical operations: decision and estimation. We first use the framework to present a representative sample of the existing works that deal with timing in wireless communication. Next, it is shown how the framework can be used with different communication models of increasing complexity, starting from the basic Shannon one-way communication model and arriving at communication models for consensus, distributed learning, and inference. Overall, this article fills an important gap in the literature by providing a systematic treatment of various timing measures in wireless communication and sets the basis for design and optimization for the next-generation real-time systems.
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| 34. |
- Salimnejad, Mehrdad, et al.
(författare)
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Real-Time Reconstruction of Markov Sources and Remote Actuation Over Wireless Channels
- 2024
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Ingår i: IEEE Transactions on Communications. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 0090-6778 .- 1558-0857. ; 72:5, s. 2701-2715
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we study the real-time tracking and reconstruction of an information source with the purpose of actuation. A device monitors the state of the information source and transmits status updates to a receiver over a wireless erasure channel. We consider two models for the source, namely an $N$ -state Markov chain and an $N$ -state Birth-Death Markov process. We investigate several joint sampling and transmission policies, including a semantics-aware one, and we study their performance for a set of metrics. Specifically, we investigate the real-time reconstruction error and its variance, the cost of actuation error, the consecutive error, and the cost of memory error. These metrics capture different characteristics of the system performance, such as the impact of erroneous actions and the timing of errors. In addition, we propose a randomized stationary sampling and transmission policy and we derive closed-form expressions for the aforementioned metrics. We then formulate two optimization problems. The first optimization problem aims to minimize the time-averaged reconstruction error subject to time-averaged sampling cost constraint. Then, we compare the optimal randomized stationary policy with uniform, change-aware, and semantics-aware sampling policies. Our results show that in the scenario of constrained sampling generation, the optimal randomized stationary policy outperforms all other sampling policies when the source is rapidly evolving. Otherwise, the semantics-aware policy performs the best. The objective of the second optimization problem is to obtain an optimal sampling policy that minimizes the average consecutive error with a constraint on the time-averaged sampling cost. Based on this, we propose a wait-then-generate sampling policy which is simple to implement.
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| 35. |
- Salimnejad, Mehrdad, et al.
(författare)
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Real-time Remote Reconstruction of a Markov Source and Actuation over Wireless
- 2023
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Ingår i: 2023 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS WORKSHOPS, ICC WORKSHOPS. - : IEEE. - 9798350333077 - 9798350333084 ; , s. 1386-1391
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Konferensbidrag (refereegranskat)abstract
- In this work, we study the problem of real-time tracking and reconstruction of an information source with the purpose of actuation. A device monitors an N-state Markov process and transmits status updates to a receiver over a wireless erasure channel. We consider a set of joint sampling and transmission policies, including a semantics-aware one, and we study their performance with respect to relevant metrics. Specifically, we investigate the real-time reconstruction error and its variance, the consecutive error, the cost of memory error, and the cost of actuation error. Furthermore, we propose a randomized stationary sampling and transmission policy and derive closed-form expressions for all aforementioned metrics. We then formulate an optimization problem for minimizing the real-time reconstruction error subject to a sampling cost constraint. Our results show that in the scenario of constrained sampling generation, the optimal randomized stationary policy outperforms all other sampling policies when the source is rapidly evolving. Otherwise, the semantics-aware policy performs the best.
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| 36. |
- Salimnejad, Mehrdad, et al.
(författare)
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State-aware Real-time Tracking and Remote Reconstruction of a Markov Source
- 2023
-
Ingår i: Journal of Communications and Networks. - : KOREAN INST COMMUNICATIONS SCIENCES (K I C S). - 1229-2370 .- 1976-5541. ; 25:5, s. 657-669
-
Tidskriftsartikel (refereegranskat)abstract
- The problem of real-time remote tracking and reconstruction of a two-state Markov process is considered here. A transmitter sends samples from an observed information source to a remote monitor over an unreliable wireless channel. The receiver, in turn, performs an action according to the state of the reconstructed source. We propose a state-aware randomized stationary sampling and transmission policy which accounts for the importance of different states of the information source, and their impact on the goal of the communication process. We then analyze the performance of the proposed policy, and compare it with existing goal-oriented joint sampling and transmission policies, with respect to a set of performance metrics. Specifically, we study the real-time reconstruction error, the cost of actuation error, the consecutive error, and a new metric, coined importance aware consecutive error. In addition, we formulate and solve a constrained optimization problem that aims to obtain the optimal sampling probabilities that minimize the average cost of actuation error. Our results show that in the scenario of constrained sampling generation, the optimal state-aware randomized stationary policy outperforms all other sampling policies for fast evolving sources, and, under certain conditions, for slowly varying sources. Otherwise, a semantics-aware policy performs better only when the source is slowly varying.
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| 37. |
- Shalmashi, Serveh, et al.
(författare)
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Energy Efficiency and Sum Rate Tradeoffs for Massive MIMO Systems with Underlaid Device-to-Device Communications
- 2016
-
Ingår i: EURASIP Journal on Wireless Communications and Networking. - : Springer. - 1687-1472 .- 1687-1499.
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we investigate the coexistence of two technologies that have been put forward for the fifth generation (5G) of cellular networks, namely, network-assisted device-to-device (D2D) communications and massive MIMO (multiple-input multiple-output). Potential benefits of both technologies are known individually, but the tradeoffs resulting from their coexistence have not been adequately addressed. To this end, we assume that D2D users reuse the downlink resources of cellular networks in an underlay fashion. In addition, multiple antennas at the BS are used in order to obtain precoding gains and simultaneously support multiple cellular users using multiuser or massive MIMO technique. Two metrics are considered, namely the average sum rate (ASR) and energy efficiency (EE). We derive tractable and directly computable expressions and study the tradeoffs between the ASR and EE as functions of the number of BS antennas, the number of cellular users and the density of D2D users within a given coverage area. Our results show that both the ASR and EE behave differently in scenarios with low and high density of D2D users, and that coexistence of underlay D2D communications and massive MIMO is mainly beneficial in low densities of D2D users.
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| 38. |
- Shalmashi, Serveh, et al.
(författare)
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Energy Efficiency and Sum Rate when Massive MIMO meets Device-to-Device Communication
- 2015
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Ingår i: Proc. of the IEEE International Conference on Communications (ICC). - : Institute of Electrical and Electronics Engineers (IEEE). ; , s. 627-632
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Konferensbidrag (refereegranskat)abstract
- This paper considers a scenario of short-range communication, known as device-to-device (D2D) communication, where D2D users reuse the downlink resources of a cellular network to transmit directly to their corresponding receivers. In addition, multiple antennas at the base station (BS) are used in order to simultaneously support multiple cellular users using multiuser or massive MIMO. The network model considers a fixed number of cellular users and that D2D users are distributed according to a homogeneous Poisson point process (PPP). Two metrics are studied, namely, average sum rate (ASR) and energy efficiency (EE). We derive tractable expressions and study the tradeoffs between the ASR and EE as functions of the number of BS antennas and density of D2D users for a given coverage area.
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| 39. |
- Shokri-Ghadikolaei, Hossein, et al.
(författare)
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The Impact of beamforming and coordination on spectrum pooling in mmWave Cellular networks
- 2016
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Ingår i: Signals, Systems and Computers, 2016 50th Asilomar Conference on. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781538639542
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Konferensbidrag (refereegranskat)abstract
- Spectrum pooling is not typically used in current cellular networks, because it only provides a slight performance improvement while requiring heavy coordination among different cellular operators. However, these problems can be potentially overcome in millimeter-wave (mmWave) networks, thanks to the use of beamforming both at base stations and at user equipments. In this paper, we develop a joint beamforming and cell association optimization problem to characterize the performance gain that can be obtained when spectrum pooling is used, as a function of the underlying beamforming and coordination strategies. Our performance analysis reveals that beamforming can substantially reduce the need for coordination and simplify the implementation of spectrum pooling. These benefits are more prominent at higher mmWave frequencies (for example, 73 GHz) due to the possibility of having antenna arrays with more elements within the radome. The results of this paper provides useful insights on the feasibility of spectrum pooling at mmWave networks.
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| 40. |
- Siniarski, Bartlomiej, et al.
(författare)
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ROBUST-6G: Smart, Automated, and Reliable Security Service Platform for 6G
- 2024
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Ingår i: International Conference on Ubiquitous and Future Networks, ICUFN. - 2165-8536 .- 2165-8528. ; , s. 384-389
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Konferensbidrag (refereegranskat)abstract
- In the progressive development towards 6G, the ROBUST-6G initiative aims to provide fundamental contributions to developing data-driven, AIIML-based security solutions to meet the new concerns posed by the dynamic nature of forth-coming 6G services and networks in the future cyber-physical continuum. This aim has to be accompanied by the transversal objective of protecting AIIML systems from security attacks and ensuring the privacy of individuals whose data are used in AI-empowered systems. ROBUST-6G will essentially investigate the security and robustness of distributed intelligence, enhancing privacy and providing transparency by leveraging explainable AIIML (XAI). Another objective of ROBUST-6G is to promote green and sustainable AIIML methodologies to achieve energy efficiency in 6G network design. The vision of ROBUST-6G is to optimize the computation requirements and minimize the consumed energy while providing the necessary performance for AIIML-driven security functionalities; this will enable sustainable solutions across society while suppressing any adverse effects. This paper aims to initiate the discussion and to highlight the key goals and milestones of ROBUST-6G, which are important for investigation towards a trustworthy and secure vision for future 6G networks.
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| 41. |
- Stathakis, Efthymios, 1984-
(författare)
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On Interference Management With Incomplete Side Information
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The evolution towards next generation wireless networks has to serve high expectations and demands, therefore ongoing research has to tackle problems that have hitherto received less attention. A decisive step in this direction is to consolidate cohabitation paradigms into the envisioned communication protocols. There hasbeen increasing interest in enabling, possibly heterogeneous, entities to coexist harmoniously;recent studies have established theoretical gains that stem from coordinated interference embedding into various network architectures. To further bridgethe gap between theory and practice we need to explore uncharted dimensions of interference networks and, in particular, the limitations that arise in realistic scenarios. In this thesis, we consider the performance optimization and analysis of interference networks where the participating links have equal or unequal quality-of-service priorities. Link priorities are widely applied in the context of cognitive radio systems and are reflected in the metrics and the relative weights that are assigned to each link in the network. To integrate conditions that are encountered in practical systems we assume scenarios where the link of interest does not know perfectly the relevant design parameters, namely the channels, but instead has an estimate. We propose and analyze metrics that are suitable proxies for performance assessment in the considered scenarios and as a case-study we establish a framework for enhanced parameter acquisition.In the first part of this thesis, comprising the first three technical chapters, we focus on single-user system design within the interference network. In these chapters, the main goal is to optimize the design or analyze the performance, or even carry out both tasks, for the target link. We consider metrics that are widely adopted for performance assessment in wireless communications such as the instantaneous achievable rate (Chapter 2), its ergodic counterpart (Chapter 3), or the probability of decoding outage (Chapter 4). Our setups are fortuitous in that they have direct application to the well-known underlay cognitive radio framework. However, we provision for a wider context by occasionally casting the discussion at the more general level of cellular networks, as in Chapter 3. The presence of other communication links is reflected in the constraints that bound the outgoing interference power of the desired system, in each respective scenario, towards the unintended nodes. Limiting the inflicted interference is a way of mapping the remaining participants’ quality-of-service and subsequently their priority in the network. To capture realistic conditions, we pursue the aforementioned design targets under the assumption that the system of interest has incomplete knowledge of the channels that are involved in the problem formulation, namely in the objective and the constraints. One of our contributions is that we propose formulations that are tailored to the type of the available channel side-information and suitable for the, pertinent to the model, performance assessment. In several cases, we provide novel analytical solutions to the associated optimization problems and establish insights that naturally extend existing results into our scenarios.In the second thematic part, which maps to Chapter 5 of the thesis, we generalize our investigation to the joint design of multi-user interference networks. In this chapter, we seek to optimize the performance of all links simultaneously and in away that is beneficial for all the participants in the network. Under this premise, trade-offs inevitably arise and sets of solutions that are Pareto-optimal become the desirable goal. Even though this area is well-documented, the assumption of incomplete channel state information introduces a new dimension into the analysis; to settle the arising shortcoming we stipulate and tailor to our setup the definition of the outage rate-region, which essentially is a blend of the metrics used in the previous chapters. Thus the theoretical findings and results presented in this chapter generalize gracefully the content of the preceding part, which can be obtained as a snapshot of the generic model of Chapter 5. The analysis conducted in this chapter, along with the conclusions we draw, indicate that we can successfully replace orthogonal transmission schemes with cohabitation protocols.Throughout the thesis we appeal to the availability of incomplete channel-state information to render our models more realistic. However, the acquisition of any necessary exterior parameters is not explicitly accounted for, in the first two parts. To fill this gap, we present in Chapter 6 a short case-study, which is applicable to some of the setups considered in the thesis. In particular, we investigate enhancement techniques for improving the estimation of the instantaneous signal-to-noise ratio, when viewed as a deterministic parameter. Albeit its narrow scope, this study brings forth some interesting ideas for enhancing the quality of the available side-information.
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| 42. |
- Subramanyam Thoota, Sai, et al.
(författare)
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Site-specific millimeter-wave compressive channel estimation algorithms with hybrid MIMO architectures
- 2021
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Ingår i: ITU Journal on Future and Evolving Technologies. - : International Telecommunication Union. - 2616-8375. ; 2:4
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we present and compare three novel model-cum-data-driven channel estimation procedures in a millimeter-wave Multi-Input Multi-Output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) wireless communication system. The transceivers employ a hybrid analog-digital architecture. We adapt techniques from a wide range of signal processing methods, such as detection and estimation theories, compressed sensing, and Bayesian inference, to learn the unknown virtual beamspace domain dictionary, as well as the delay-and-beamspace sparse channel. We train the model-based algorithms with a site-specific training dataset generated using a realistic ray tracing-based wireless channel simulation tool. We assess the performance of the proposed channel estimation algorithms with the same site's test data. We benchmark the performance of our novel procedures in terms of normalized mean squared error against an existing fast greedy method and empirically show that model-based approaches combined with data-driven customization unanimously outperform the state-of-the-art techniques by a large margin. The proposed algorithms were selected as the top three solutions in the "ML5G-PHY Channel Estimation Global Challenge 2020" organized by the International Telecommunication Union.
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