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1.	Al-Hraishawi, Hayder, et al. (författare) Energy Harvesting from Jamming Attacks in Multi-User Massive MIMO Networks 2023 Ingår i: IEEE Transactions on Green Communications and Networking. - : Institute of Electrical and Electronics Engineers (IEEE). - 2473-2400. ; 7:3, s. 1181-1191 Tidskriftsartikel (refereegranskat)abstract Fifth-generation (5G) and beyond communication systems offer new functionalities and significant performance improvements but that comes at the cost of tougher energy requirements on user devices. Addressing this issue while reducing the environmental impact of the substantial increase in energy consumption can be achieved through energy-neutral systems that operate using energy harvested from radio frequency (RF) transmissions. In this direction, this work examines the concept of utilizing an unconventional source for RF energy harvesting. Specifically, the performance of an RF energy harvesting scheme for multi-user massive multiple-input multiple-output (MIMO) is investigated in the presence of multiple active jammers. The key idea is to exploit the jamming transmissions as an energy source to be harvested by the legitimate users. To this end, the feasibility of this concept is studied via system performance analysis for a training-based massive MIMO encompasses imperfectly estimated channel state information (CSI) at the base-station and employing the time-switching protocol. In particular, the achievable uplink sum rate expressions are derived in closed-form for two different antenna configurations at the base-station. Two optimal time-switching schemes are also proposed based on maximum sum rate and user-fairness criteria. The essential trade-off between the harvested energy and achievable sum rate in time-switching protocol are quantified in closed-form as well. Our analysis reveals that the proposed energy harvesting scheme from jamming signals is viable and can boost massive MIMO uplink performance by exploiting the surrounding RF signals of the jamming attacks for increasing the amount of harvested energy at the served users. Finally, numerical results validate the theoretical analyses and the effectiveness of the derived closed-form expressions through simulations.
2.	Alabbasi, Abdulrahman, et al. (författare) Optimal Processing Allocation to Minimize Energy and Bandwidth Consumption in Hybrid CRAN 2018 Ingår i: IEEE Transactions on Green Communications and Networking. - : Institute of Electrical and Electronics Engineers (IEEE). - 2473-2400. ; 2:2, s. 545-555 Tidskriftsartikel (refereegranskat)abstract Cloud radio access network (CRAN) architecture is proposed to save energy, facilitate coordination between radio units, and achieve scalable solutions to improve radio network's performance. However, stringent delay and bandwidth constraints are incurred by fronthaul in CRAN [the network segment connecting RUs and digital units (DUs)]. Therefore, we propose a hybrid cloud radio access network architecture, where a DU's functionalities can be virtualized and split at several conceivable points. Each split option results in two-level deployment of the processing functions (central site level and remote site level) connected by a transport network, called midhaul. We study the interplay of energy efficiency and midhaul bandwidth consumption under optimal processing allocation. We jointly minimize the power and midhaul bandwidth consumption in H-CRAN, while satisfying network constraints, i.e., processing and midhaul bandwidth capacity. We enable power saving functionalities by shutting down different network components. The proposed model is formulated as a constraint programming problem. The proposed solution shows that 42 percentile of midhaul bandwidth savings can be achieved compared to the fully centralized CRAN; and 35 percentile of power consumption saving can be achieved compared to the case where all the network functions are distributed at the edge.
3.	Allipuram, Sujatha, et al. (författare) Performance Analysis of a MIMO System With Bursty Traffic in the Presence of Energy Harvesting Jammer 2022 Ingår i: IEEE TRANSACTIONS ON GREEN COMMUNICATIONS AND NETWORKING. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 2473-2400. ; 6:2, s. 1157-1172 Tidskriftsartikel (refereegranskat)abstract This paper explores the role of multiple antennas in mitigating jamming attacks for the Rayleigh fading environment with exogenous random traffic arrival. The jammer is assumed to have energy harvesting ability where energy arrives according to Bernoulli process. The outage probabilities are derived with different assumptions on the number of antennas at the transmitter and receiver. The outage probability for the Alamouti space-time code is also derived. The work characterizes the average service rate for different antenna configurations taking into account of random arrival of data and energy at the transmitter and jammer, respectively. In many practical applications, latency and timely updates are of importance, thus, delay and Average Age of Information (AAoI) are the meaningful metrics to be considered. The work characterizes these metrics under jamming attack. The impact of finite and infinite energy battery size at the jammer on various performance metrics is also explored. Two optimization problems are considered to explore the interplay between AAoI and delay under jamming attack. Furthermore, our results show that Alamouti code can significantly improve the performance of the system even under jamming attack, with less power budget. The paper also demonstrates how the developed results can be useful for multiuser scenarios.
4.	Azari, Amin, 1988-, et al. (författare) Energy and Resource Efficiency by User Traffic Prediction and Classification in Cellular Networks 2022 Ingår i: IEEE Transactions on Green Communications and Networking. - : Institute of Electrical and Electronics Engineers (IEEE). - 2473-2400. ; 6:2, s. 1082-1095 Tidskriftsartikel (refereegranskat)abstract There is a lack of research on the analysis of peruser traffic in cellular networks, for deriving and following traffic-aware network management. In fact, the legacy design approach, in which resource provisioning and operation control are performed based on the cell-aggregated traffic scenarios, are not so energy- and cost-efficient and need to be substituted with user-centric predictive analysis of mobile network traffic and proactive network resource management. Here, we shed light on this problem by designing traffic prediction tools that utilize standard machine learning (ML) tools, including long shortterm memory (LSTM) and autoregressive integrated moving average (ARIMA) on top of per-user data. We present an expansive empirical evaluation of the designed solutions over a real network traffic dataset. Within this analysis, the impact of different parameters, such as the time granularity, the length of future predictions, and feature selection are investigated. As a potential application of these solutions, we present an ML-powered Discontinuous reception (DRX) scheme for energy saving. Towards this end, we leverage the derived ML models for dynamic DRX parameter adaptation to user traffic. The performance evaluation results demonstrate the superiority of LSTM over ARIMA in general, especially when the length of the training time series is high enough, and it is augmented by a wisely-selected set of features. Furthermore, the results show that adaptation of DRX parameters by online prediction of future traffic provides much more energy-saving at low latency cost in comparison with the legacy cell-wide DRX parameter adaptation.
5.	Azari, Amin, et al. (författare) Energy-Efficient and Reliable IoT Access Without Radio Resource Reservation 2021 Ingår i: IEEE TRANSACTIONS ON GREEN COMMUNICATIONS AND NETWORKING. - : Institute of Electrical and Electronics Engineers (IEEE). - 2473-2400. ; 5:2, s. 908-920 Tidskriftsartikel (refereegranskat)abstract One of the major challenges for Internet-of-Things applications is that the existing cellular technologies do not support the uplink IoT traffic in an energy-efficient manner. There are two principal ways for serving the uplink IoT traffic: grant-based (i.e., scheduled) and grant-free (i.e., random access). Grant-based access provides fine-grained control of reliability and latency at the cost of energy consumption required for signaling. Grant-free access removes the signaling overhead at the cost of looser control of performance in terms of reliability and latency. However, a precise analysis of reliability, latency and energy performance of grant-free access (GFA) is largely missing. This article focuses on a GFA-type protocol, in which a device transmits several packet replicas, asynchronously with respect to the other devices. Using stochastic geometry, we derive closed-form expressions for reliability, delay, and energy consumption, which can be used to identify the tradeoffs among these performance parameters. In order to improve the performance of the protocol, we develop a receiver that leverages the random timing and frequency offsets among the devices in order to facilitate resolution of collisions. This is complemented by a per-device adaptive scheme that controls the number of transmitted replicas. The evaluation confirms the validity of the analysis and the potential of the proposed solution, identifying operating regions in which GFA outperforms the grant-based access.
6.	Azari, Amin, 1988-, et al. (författare) On the Latency-Energy Performance of NB-IoT Systems in Providing Wide-Area IoT Connectivity 2019 Ingår i: IEEE Transactions on Green Communications and Networking. - 2473-2400. Tidskriftsartikel (refereegranskat)abstract Narrowband Internet-of-Things (NB-IoT) offers a significant link budget improvement in comparison with the legacy networks by introducing different coverage classes, allowing repeated transmissions, and tuning the repetition order based on the path-loss in communications. However, those repetitions necessarily increase energy consumption and latency in the whole NB-IoT system. The extent to which the whole system is affected depends on the scheduling of the uplink and downlink channels. We address this question, not treated previously, by developing a tractable model of NB-IoT connectivity, comprising message exchanges in random-access, control, and data channels. The model is then used to analyze the impact of channel scheduling and interaction of coverage classes on the performance of IoT devices through the derivation of the expected latency and battery lifetime. These results are subsequently employed in determining the optimized operation points, i.e., (i) scheduling of data and control channels for a given set of users and respective coverage classes, or (ii) determining the optimal set of coverage classes and served users per coverage class for a given scheduling strategy. Simulations results show the validity of the analysis and confirm that channel scheduling and coexistence of coverage classes significantly affect latency and battery lifetime performance of NB-IoT devices.
7.	Bashar, Manijeh, et al. (författare) Energy Efficiency of the Cell-Free Massive MIMO Uplink with Optimal Uniform Quantization 2019 Ingår i: IEEE Transactions on Green Communications and Networking. - : IEEE. - 2473-2400. ; 3:4, s. 971-987 Tidskriftsartikel (refereegranskat)abstract A cell-free Massive multiple-input multiple-output (MIMO) uplink is considered, where the access points (APs) are connected to a central processing unit (CPU) through limited-capacity wireless microwave links. The quantized version of the weighted signals are available at the CPU, by exploiting the Bussgang decomposition to model the effect of quantization. A closed-form expression for spectral efficiency is derived taking into account the effects of channel estimation error and quantization distortion. The energy efficiency maximization problem is considered with per-user power, backhaul capacity and throughput requirement constraints. To solve this non-convex problem, we decouple the original problem into two sub-problems, namely, receiver filter coefficient design, and power allocation. The receiver filter coefficient design is formulated as a generalized eigenvalue problem whereas a successive convex approximation (SCA) and a heuristic sub-optimal scheme are exploited to convert the power allocation problem into a standard geometric programming (GP) problem. An iterative algorithm is proposed to alternately solve each sub-problem. Complexity analysis and convergence of the proposed schemes are investigated. Numerical results indicate the superiority of the proposed algorithms over the case of equal power allocation.
8.	Biswas, Sinchan, 1988-, et al. (författare) On Optimal Quantized Non-Bayesian Quickest Change Detection with Energy Harvesting 2020 Ingår i: IEEE Transactions on Green Communications and Networking. - : Institute of Electrical and Electronics Engineers (IEEE). - 2473-2400. ; 4:2, s. 433-447 Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract In this paper, we consider a problem of decentralized non-Bayesian quickest change detection using a wireless sensor network where the sensor nodes are powered by harvested energy from the environment. The underlying random process being monitored by the sensors is subject to change in its distribution at an unknown but deterministic time point and the sensors take samples (sensing) periodically, compute the likelihood ratio based on the distributions before and after the change, quantize it and send it to a remote fusion centre (FC) over fading channels for performing a sequential test to detect the change. Due to the unpredictable and intermittent nature of harvested energy arrivals, the sensors need to decide whether they want to sense, and at what rate they want to quantize their information before sending them to the FC, since higher quantization rates result in higher accuracy and better detection performance, at the cost of higher energy consumption. We formulate an optimal sensing and quantization rate allocation problem (in order to minimize the expected detection delay subject to false alarm rate constraint) based on the availability (at the FC) of non-causal and causal information of sensors’ energy state information, and channel state information between the sensors and the FC. Motivated by the asymptotically inverse relationship between the expected detection delay (under a vanishingly small probability of false alarm) and the Kullback-Leibler (KL) divergence measure at the FC, we maximize an expected sum of the KL divergence measure over a finite horizon to obtain the optimal sensing and quantization rate allocation policy, subject to energy causality constraints at each sensor. The optimal solution is obtained using a typical dynamic programming based technique, and based on the optimal quantization rate, the optimal quantization thresholds are found by maximizing the KL information measure per slot. We also provide suboptimal threshold design policies using uniform quantization and an asymptotically optimal quantization policy for higher number of quantization bits. We provide an asymptotic approximation for the loss due to quantization of the KL measure, and also consider an alternative optimization problem with minimizing the expected sum of the inverse the KL divergence measure as the cost per time slot. Numerical results are provided comparing the various optimal and suboptimal quantization strategies for both optimization problem formulations, illustrating the comparative performance of these strategies at different regimes of quantization rates.
9.	Chang, Z., et al. (författare) Energy-Efficient and Secure Resource Allocation for Multiple-Antenna NOMA With Wireless Power Transfer 2018 Ingår i: IEEE Transactions on Green Communications and Networking. - 2473-2400. ; 2:4, s. 1059-1071 Tidskriftsartikel (refereegranskat)abstract Non-orthogonal multiple access (NOMA) is considered as one of the promising techniques for providing high data rates in the fifth generation mobile communication. By applying successive interference cancellation schemes and superposition coding at the NOMA receiver, multiple users can be multiplexed on the same subchannel. In this paper, we investigate resource allocation algorithm design for an OFDM-based NOMA system empowered by wireless power transfer (WPT). In the considered system, users who need to transmit data can only be powered by the WPT. With the consideration of an existing eavesdropper, the objective is to obtain secure and energy efficient transmission among multiple users by optimizing time, power and subchannel allocation. Moreover, we also take into consideration for the practical case that the statistics of the channel state information of the eavesdropper is not available. In order to address the optimization problem and its high computational complexity, we propose an iterative algorithm with guaranteed convergence to deliver an upper bound and a suboptimal solution in more general cases. For some special cases, we identify the optimality condition that ensures the global optimum in our algorithm. Extensive simulation studies demonstrate the competitiveness and effectiveness of the proposed algorithmic solution over conventional OFDMA systems as well as over other existing NOMA resource allocation schemes.
10.	Chen, Zheng, et al. (författare) Dynamic Resource Allocation in Co-Located and Cell-Free Massive MIMO 2020 Ingår i: IEEE Transactions on Green Communications and Networking. - : IEEE. - 2473-2400. ; 4:1, s. 209-220 Tidskriftsartikel (refereegranskat)abstract In this paper, we study joint power control and scheduling in uplink massive multiple-input-multiple-output (MIMO) systems with randomly arriving data traffic. We consider both co-located and Cell-Free (CF) Massive MIMO, where the difference lies in whether the antennas are co-located at the base station or spread over a wide network area. The data is generated at each user according to an individual stochastic process. Using Lyapunov optimization techniques, we develop a dynamic scheduling algorithm (DSA), which decides at each time slot the amount of data to admit to the transmission queues and the transmission rates over the wireless channel. The proposed algorithm optimizes the long-term user throughput under various fairness policies while keeping the transmission queues stable. Simulation results show that the state-of-the-art power control schemes developed for Massive MIMO with infinite backlogs can fail to stabilize the system even when the data arrival rates are within the network capacity region. Our proposed DSA shows advantage in providing finite delay with performance optimization whenever the network can be stabilized. © 2017 IEEE.
11.	Chiaraviglio, Luca, et al. (författare) Minimum Cost Design of Cellular Networks in Rural Areas with UAVs, Optical Rings, Solar Panels and Batteries 2019 Ingår i: IEEE Transactions on Green Communications and Networking. - 2473-2400. ; 3 Tidskriftsartikel (refereegranskat)abstract Bringing the cellular connectivity in rural zones is a big challenge, due to the large installation costs that are incurred when a legacy cellular network based on fixed Base Stations (BSs) is deployed. To tackle this aspect, we consider an alternative architecture composed of UAV-based BSs to provide cellular coverage, ground sites to connect the UAVs with the rest of the network, Solar Panels (SPs) and batteries to recharge the UAVs and to power the ground sites, and a ring of optical fiber links to connect the installed sites. We then target the minimization of the installation costs for the considered UAV-based cellular architecture, by taking into account the constraints of UAVs coverage, SPs energy consumption, levels of the batteries and the deployment of the optical ring. After providing the problem formulation, we derive an innovative methodology to ensure that a single ring of installed optical fibers is deployed. Moreover, we propose a new algorithm, called DIARIZE, to practically tackle the problem. Our results, obtained over a set of representative rural scenarios, show that DIARIZE performs very close to the optimal solution, and in general outperforms a reference design based on fixed BSs.
12.	Cui, Enfang, et al. (författare) Improving Power Stability of Energy Harvesting Devices with Edge Computing Assisted Time Fair Energy Allocation 2021 Ingår i: IEEE Transactions on Green Communications and Networking. - 2473-2400. ; 5:1, s. 540-551 Tidskriftsartikel (refereegranskat)abstract Due to the time-varying characteristics of energy harvesting sources, it is a challenge for energy harvesting to provide stable energy output. In this paper, the time fair energy allocation (TFEA) problem is investigated, and an utility maximization framework is proposed to guarantee both time fairness and energy efficiency of energy allocation. Then we propose a prediction based energy allocation scheme. First, a deep learning predictor is used to predict the harvested energy. Second, we transform the TFEA problem into an Euclidean shortest path problem and propose a fast time fair energy allocation algorithm (FTF) based on inflection points search. Our algorithm can significantly decrease the iteration number of the shortest path search and reduce the computation time. In addition, we propose an edge computing assisted energy allocation framework, in which the computing tasks are offloaded to edge gateways. The proposed scheme is evaluated in the scenario of metro vehicles health monitoring. Experiment results show that the time consumption of FTF is at least 92.2% lower than traditional algorithms, while the time fairness of FTF is the best. The total time cost and energy cost of our edge computing scheme is also competitive compared with traditional local computing schemes.
13.	da Silva, Carlos Natalino, et al. (författare) Joint Optimization of Failure Management Costs, Electricity Costs, and Operator Revenue in Optical Core Networks 2017 Ingår i: IEEE Transactions on Green Communications and Networking. - : IEEE Press. - 2473-2400 .- 2473-2400. ; PP:99 Tidskriftsartikel (refereegranskat)abstract We focus on the problem of maximizing profitability in an optical core network by acting on the power states of Optical Line Amplifiers (OLAs) and Line Cards (LCs) operating under varying traffic. Specifically, the profitability metric considered in this work takes into account the electricity costs of OLAs and LCs, the failure management costs derived from the application of power states to the network devices, and the operator revenue. After proving that all terms of the considered profitability function are deeply inter-correlated, we formulate the optimization problem of maximizing the network profitability in an optical core network with multi-period traffic. By solving the proposed formulation on a realistic scenario, we show that it is possible to wisely trade between the considered costs and revenue, and achieve higher network profitability than in the case in which the single terms are considered in isolation, e.g., only electricity consumption or only Failure Management Costs (FMC).
14.	Dazhi, Michael N., et al. (författare) Energy-Efficient Service-Aware Multi-Connectivity Scheduler for Uplink Multi-Layer Non-Terrestrial Networks 2023 Ingår i: IEEE Transactions on Green Communications and Networking. - : Institute of Electrical and Electronics Engineers (IEEE). - 2473-2400. ; 7:3, s. 1326-1341 Tidskriftsartikel (refereegranskat)abstract This paper introduces the concept of energy efficiency (EE) in the uplink with the capability of multi-connectivity (MC) in a multi-orbit non-terrestrial network (NTN), where user terminals (UTs) can be simultaneously served by more than one satellite to achieve higher peak throughput at reduced energy consumption. This concept also considers the service classification of the users, so that network dimensioning is performed in order to satisfy the quality of service (QoS) requirement of users. MC can increase throughput, but this entails increased power consumption at user terminal for uplink transmissions. To this end, an energy-efficient service-aware multi-connectivity (EE-SAMC) scheduling algorithm is developed in this paper to improve the EE of uplink communications. EE-SAMC uses available radio resources and propagation information to intelligently define a dynamic resource allocation pattern, that optimally routes traffic so as to reduce the energy consumption at the UT while ensuring QoS is maximized. EE-SAMC is designed based on the formulation of a non-convex combinatorial problem, it is solved in two ways involving firstly an optimization solution and secondly a heuristic approach. The effectiveness of EE-SAMC is compared with random allocation, round robin and heuristic schedulers in terms of EE, throughput and delay; EE-SAMC outperforms all schedulers.
15.	Edfors, Ove, et al. (författare) Interference-free OFDM embedding of wake-up signals for low-power wake-up receivers 2020 Ingår i: IEEE Transactions on Green Communications and Networking. - 2473-2400. ; 4:3, s. 669-677 Tidskriftsartikel (refereegranskat)abstract The use of ultra-low power wake-up receivers (WuRx) can significantly reduce idle listening energy cost. To tailor a WuRx scheme to orthogonal frequency division multiplexing (OFDM) based systems, such as LTE-MTC or IEEE 802.11, the wake-up signal (WUS) also needs to follow OFDM principles to avoid interfering with other transmissions in the same shared bandwidth. Here, we address this particular issue and propose an approach where the OFDM transmitter is modified to also transmit WUSs designed for non-coherent low-power WuRxs, on a subset of the carriers, thus embedding the WUS correctly and ensuring orthogonality. The approach is evaluated for different system parameters and channel conditions. Its applicability across a wide range of OFDM-based systems is examined.
16.	Gautam, S., et al. (författare) Feasible Point Pursuit and Successive Convex Approximation for Transmit Power Minimization in SWIPT-Multigroup Multicasting Systems 2021 Ingår i: IEEE Transactions on Green Communications and Networking. - : Institute of Electrical and Electronics Engineers (IEEE). - 2473-2400. Tidskriftsartikel (refereegranskat)
17.	K. S., Sanila, et al. (författare) Energy Efficient Multi User Spatial Modulated NOMA for mmWave Communications 2023 Ingår i: IEEE Transactions on Green Communications and Networking. - : Institute of Electrical and Electronics Engineers (IEEE). - 2473-2400. ; 7:3, s. 1285-1296 Tidskriftsartikel (refereegranskat)
18.	Khan, Suleman, et al. (författare) Post Quantum Secure Handover Mechanism for Next Generation Aviation Communication Networks 2024 Ingår i: IEEE Transactions on Green Communications and Networking. - : Institute of Electrical and Electronics Engineers (IEEE). - 2473-2400. ; , s. 1-17 Tidskriftsartikel (refereegranskat)abstract The L-band Digital Aeronautical Communications System (LDACS) is a key advancement for next-generation aviation networks, enhancing Communication, Navigation, and Surveillance (CNS) capabilities. It operates with VHF Datalink mode 2 (VDLm2) and features a seamless handover mechanism to maintain uninterrupted communication between aircraft and ground stations (GSs), improving safety and efficiency in air traffic management (ATM). However, LDACS’ handover process encounters significant security risks due to inadequate authentication and key agreement between aircraft and ground station controllers (GSCs) during handovers. This vulnerability threatens communications’ confidentiality, integrity, and authenticity, posing risks to flight safety and sensitive data. Therefore, developing and implementing a robust security framework to protect aviation communications is essential. In response, we have proposed a security solution specifically designed to protect LDACS handovers. Our solution uses a mutual authentication and key agreement mechanism tailored for LDACS handovers, ensuring robust security for all types of handovers, including Intra GSC -Intra Aeronautical Telecommunication Network (ATN), Inter GSC -Intra ATN, and Inter GSC -Inter ATN. Our approach utilizes post-quantum cryptography to protect aviation communication systems against potential post-quantum threats, such as unauthorized access to flight data, interception of communication, and spoofing of aircraft identity. Furthermore, our proposed solution has undergone a thorough informal security analysis to ensure its effectiveness in addressing handover challenges and offering robust protection against various threats. It seamlessly integrates with the LDACS framework, delivering low Bit Error Rate (BER) and latency levels, making it a highly reliable approach in practice.
19.	Khan, Wali Ullah, et al. (författare) Integration of NOMA with Reflecting Intelligent Surfaces : A Multi-cell Optimization with SIC Decoding Errors 2023 Ingår i: IEEE Transactions on Green Communications and Networking. - : Institute of Electrical and Electronics Engineers (IEEE). - 2473-2400. ; 7:3, s. 1554-1565 Tidskriftsartikel (refereegranskat)abstract Reflecting intelligent surfaces (RIS) has gained significant attention due to its high energy and spectral efficiency in next-generation wireless networks. By using low-cost passive reflecting elements, RIS can smartly reconfigure the signal propagation to extend the wireless communication coverage. On the other hand, non-orthogonal multiple access (NOMA) has been proven as a key air interface technique for supporting massive connections over limited resources. Utilizing the superposition coding and successive interference cancellation (SIC) techniques, NOMA can multiplex multiple users over the same spectrum and time resources by allocating different power levels. This paper proposes a new optimization scheme in a multi-cell RIS-NOMA network to enhance the spectral efficiency under SIC decoding errors. In particular, the power budget of the base station and the transmit power of NOMA users while the passive beamforming of RIS is simultaneously optimized in each cell. Due to objective function and quality of service constraints, the joint problem is formulated as non-convex, which is very complex and challenging to obtain the optimal global solution. To reduce the complexity and make the problem tractable, we first decouple the original problem into two sub-problems for power allocation and passive beamforming. Then, the efficient solution of each sub-problem is obtained in two-steps. In the first-step of For power allocation sub-problem, we transform it to a convex problem by the inner approximation method and then solve it through a standard convex optimization solver in the second-step. Accordingly, in the first-step of passive beamforming, it is transformed into a standard semi-definite programming problem by successive convex approximation and different of convex programming methods. Then, penalty based method is used to achieve a Rank-1 solution for passive beamforming in second-step. Numerical results demonstrate the benefits of the proposed optimization scheme in the multi-cell RIS-NOMA network.
20.	Mafi, Yousef, et al. (författare) Ultra-Low-Power IoT Communications : A novel address decoding approach for wake-up receivers 2022 Ingår i: IEEE Transactions on Green Communications and Networking. - : Institute of Electrical and Electronics Engineers (IEEE). - 2473-2400. ; 6:2, s. 1107-1121 Tidskriftsartikel (refereegranskat)abstract Providing energy-efficient Internet of Things (IoT) connectivity has attracted significant attention in fifth-generation (5G) wireless networks and beyond. A potential solution for realizing a long-lasting network of IoT devices is to equip each IoT device with a wake-up receiver (WuR) to have always-accessible devices instead of always-on devices. WuRs typically comprise a radio frequency demodulator, sequence decoder, and digital address decoder and are provided with a unique authentication address in the network. Although the literature on efficient demodulators is mature, it lacks research on fast, low-power, and reliable address decoders. As this module continuously monitors the received ambient energy for potential paging of the device, its contribution to WuR’s power consumption is crucial. Motivated by this need, a low-power, reliable address decoder is developed in this paper. We further investigate the integration of WuR in low-power uplink/downlink communications and, using system-level energy analysis; we characterize operation regions in which WuR can contribute significantly to energy saving. The device-level energy analysis confirms the superior performance of our decoder. The results show that the proposed decoder significantly outperforms the state-of-the-art with power consumption of 60 nW, at cost of compromising negligible increase in decoding delay.
21.	Manjate, Juvencio Arnaldo, et al. (författare) Can Energy-Aware Routing Improve the Energy Savings of Energy-Efficient Ethernet? 2018 Ingår i: IEEE Transactions on Green Communications and Networking. - : Institute of Electrical and Electronics Engineers (IEEE). - 2473-2400. ; 2:3, s. 787-794 Tidskriftsartikel (refereegranskat)abstract Telecommunication networks are over-provisioned with redundant resources in order to cope with traffic load during peak hours and to quickly recover from failures. However, much of the resources are underutilized during long periods of time, but still consuming full energy. With the growing concerns of energy waste and greenhouse gas emissions, the network design principles tend to shift towards allocation of resources on-demand for energy-efficiency. In this paper, we analyze and evaluate the performance of two different energy-saving techniques, namely energy saving topology control (ESTOP) and energy-efficient Ethernet (EEE). We investigate the energy-saving characteristics of ESTOP+EEE; the combination of ESTOP and EEE. The evaluation is conducted in OMNet++ with realistic and synthetic network topologies under varying traffic conditions. The results indicate that the combination has a significant potential for saving energy, compared to running ESTOP or EEE alone, but that the amount of energy savings depends on topology, traffic load, and the chosen target connectivity level for ESTOP. In particular, the results show that the target connectivity level needs to be carefully matched to the topology and the current traffic situation, suggesting that ESTOP+EEE would be suitable where the target connectivity level is dynamically adjusted according to traffic variations.
22.	Mishra, Deepak, 1990-, et al. (författare) Transmit Precoding and Receive Power Splitting for Harvested Power Maximization in MIMO SWIPT Systems 2018 Ingår i: IEEE Transactions on Green Communications and Networking. - : Institute of Electrical and Electronics Engineers (IEEE). - 2473-2400. ; 2:3, s. 774-786 Tidskriftsartikel (refereegranskat)abstract We consider the problem of maximizing the harvested power in Multiple Input Multiple Output (MIMO) Simultaneous Wireless Information and Power Transfer systems with power splitting reception. Different from recently proposed designs, with our optimization problem formulation we target for the jointly optimal transmit precoding and receive uniform power splitting ratio maximizing the harvested power, while ensuring that the quality-of-service requirement of the MIMO link is satisfied. We assume practical radio-frequency Energy Harvesting (EH) receive operation that results in a non-convex optimization problem for the design parameters, which we first formulate in an equivalent generalized convex problem that we then solve optimally. We also derive the globally optimal transmit precoding design for ideal reception. Furthermore, we present analytical bounds for the key variables of both considered problems along with tight high signal-to-noise ratio approximations for their optimal solutions. Two algorithms for the efficient computation of the globally optimal designs are outlined. The first requires solving a small number of non-linear equations, while the second is based on a two-dimensional (2-D) search having linear complexity. Computer simulation results are presented validating the proposed analysis, providing key insights on various system parameters, and investigating the achievable EH gains over benchmark schemes.
23.	Mukherjee, Priyadarshi, et al. (författare) Exploiting Temporal Correlation in Wireless Channel for Energy-Efficient Communication 2017 Ingår i: IEEE Transactions on Green Communications and Networking. - : Institute of Electrical and Electronics Engineers (IEEE). - 2473-2400. ; 1:4, s. 381-394 Tidskriftsartikel (refereegranskat)abstract Widespread adoption of Internet-of-Things (IoT) technology depends on cost-affordability of the devices and convenience of their usage in terms of long life. Energy-efficiency of the miniaturized wireless IoT devices is a key to the cost and convenience factors. While there have been a few prior studies on wireless channel adaptive communication strategies, in this paper we relook at the problem aiming at effectively characterizing the wireless fading channel and devising energy-efficient link-layer retransmission strategy suitable for IoT devices. In particular, we propose a new channel-adaptive strategy that depends on the rate of variation of wireless channel irrespective of the underlying channel fading distribution. We further show that the concept of average fade duration dependent retransmission is a special case of the proposed strategy. Extensive simulations show that the proposed scheme most effectively characterizes the temporal variations of wireless channel in comparison with the other existing schemes. Performance of the proposed retransmission strategy is compared with the competitive protocols using the Markov model. Numerical results demonstrate that, the proposed scheme offers a gain of about 9% in terms data throughput and about 12% in terms of energy efficiency in comparison to its nearest existing benchmark scheme.
24.	Ngo, Hien Quoc, et al. (författare) On the Total Energy Efficiency of Cell-Free Massive MIMO 2018 Ingår i: IEEE Transactions on Green Communications and Networking. - : IEEE. - 2473-2400. ; 2:1, s. 25-39 Tidskriftsartikel (refereegranskat)abstract We consider the cell-free massive multiple-input multiple-output (MIMO) downlink, where a very large number of distributed multiple-antenna access points (APs) serve many single-antenna users in the same time-frequency resource. A simple (distributed) conjugate beamforming scheme is applied at each AP via the use of local channel state information (CSI). This CSI is acquired through time-division duplex operation and the reception of uplink training signals transmitted by the users. We derive a closed-form expression for the spectral efficiency taking into account the effects of channel estimation errors and power control. This closed-form result enables us to analyze the effects of backhaul power consumption, the number of APs, and the number of antennas per AP on the total energy efficiency, as well as, to design an optimal power allocation algorithm. The optimal power allocation algorithm aims at maximizing the total energy efficiency, subject to a per-user spectral efficiency constraint and a per-AP power constraint. Compared with the equal power control, our proposed power allocation scheme can double the total energy efficiency. Furthermore, we propose AP selections schemes, in which each user chooses a subset of APs, to reduce the power consumption caused by the backhaul links. With our proposed AP selection schemes, the total energy efficiency increases significantly, especially for large numbers of APs. Moreover, under a requirement of good quality-of-service for all users, cell-free massive MIMO outperforms the colocated counterpart in terms of energy efficiency.
25.	Ntontin, Konstantinos, et al. (författare) Time- and Unit-Cell Splitting Comparison for the Autonomous Operation of Reconfigurable Intelligent Surfaces 2023 Ingår i: IEEE Transactions on Green Communications and Networking. - : Institute of Electrical and Electronics Engineers (IEEE). - 2473-2400. ; 7:3, s. 1566-1582 Tidskriftsartikel (refereegranskat)abstract In this work, we analytically compare the performance of the time- and unit cell-splitting protocols for satisfying the energy needs of reconfigurable intelligent surfaces (RISs) through wireless energy harvesting from information signals. We first compute the RIS energy consumption per frame for both protocols and subsequently formulate an optimization problem that maximizes the average rate under the constraint of meeting the RIS long-term energy consumption demands. Analytical solutions to the optimal allocation of resources that involve a single integral are provided for both protocols in the case of random transmitter-RIS links that are subject to Rician or Nakagami-m fading distributions. Moreover, closed-form solutions are provided for the case of deterministic transmitter-RIS links. In addition, increasing and decreasing monotonic trends are revealed, based on analysis, for the ratio of the achievable rates of the presented protocols with respect to the RIS energy consumption. Finally, numerical results validate the analytical findings and reveal that the unit cell-splitting protocol exhibits a notably higher average rate performance compared with its time-splitting counterpart throughout the feasible range of RIS energy consumption values. However, this comes at a cost of a notably reduced signal-to-noise ratio as the RIS energy demands increase.
26.	Ntontin, Konstantinos, et al. (författare) Wireless Energy Harvesting for Autonomous Reconfigurable Intelligent Surfaces 2023 Ingår i: IEEE TRANSACTIONS ON GREEN COMMUNICATIONS AND NETWORKING. - : Institute of Electrical and Electronics Engineers (IEEE). - 2473-2400. ; 7:1, s. 114-129 Tidskriftsartikel (refereegranskat)abstract In the current contribution, we examine the feasibility of fully-energy-autonomous operation of reconfigurable intelligent surfaces (RIS) through wireless energy harvesting (EH) from incident information signals. Towards this, we first identify the main RIS energy-consuming components and present a suitable and accurate energy-consumption model that is based on the recently proposed integrated controller architecture and includes the energy consumption needed for channel estimation. Building on this model, we introduce a novel RIS architecture that enables EH through RIS unit-cell (UC) splitting. Subsequently, we introduce an EH policy, where a subset of the UCs is used for beamsteering, while the remaining UCs absorb energy. In particular, we formulate a subset al.ocation optimization problem that aims at maximizing the signal-to-noise ratio (SNR) at the receiver without violating the RIS's energy consumption demands. As a problem solution, we present low-complexity heuristic algorithms. The presented numerical results reveal the feasibility of the proposed architecture and the efficiency of the presented algorithms with respect to both the optimal and very high-complexity brute-force approach and the one corresponding to random subset selection. Furthermore, the results reveal how important the placement of the RIS as close to the transmitter as possible is, for increasing the harvesting effectiveness.
27.	Pizzo, Andrea, et al. (författare) Network Deployment for Maximal Energy Efficiency in Uplink with Multislope Path Loss 2018 Ingår i: IEEE Transactions on Green Communications and Networking. - : Institute of Electrical and Electronics Engineers (IEEE). - 2473-2400. ; 2:3, s. 735-750 Tidskriftsartikel (refereegranskat)abstract This work aims to design the uplink (UL) of a cellular network for maximal energy efficiency (EE). Each base station (BS) is randomly deployed within a given area and is equipped with M antennas to serve K user equipments (UEs). A multislope (distance-dependent) path loss model is considered and linear processing is used, under the assumption that channel state information is acquired by using pilot sequences (reused across the network). Within this setting, a lower bound on the UL spectral efficiency and a realistic circuit power consumption model are used to evaluate the network EE. Numerical results are first used to compute the optimal BS density and pilot reuse factor for a Massive MIMO network with three different detection schemes, namely, maximum ratio combining, zero-forcing (ZF) and multicell minimum mean-squared error. The numerical analysis shows that the EE is a unimodal function of BS density and achieves its maximum for a relatively small density of BS, irrespective of the employed detection scheme. This is in contrast to the single-slope (distance-independent) path loss model, for which the EE is a monotonic non-decreasing function of BS density. Then, we concentrate on ZF and use stochastic geometry to compute a new lower bound on the spectral efficiency, which is then used to optimize, for a given BS density, the pilot reuse factor, number of BS antennas and UEs. Closed-form expressions are computed from which valuable insights into the interplay between optimization variables, hardware characteristics, and propagation environment are obtained.
28.	Prasad, Ganesh, et al. (författare) Joint Optimization Framework for Operational Cost Minimization in Green Coverage-Constrained Wireless Networks 2018 Ingår i: IEEE Transactions on Green Communications and Networking. - : Institute of Electrical and Electronics Engineers (IEEE). - 2473-2400. ; 2:3, s. 693-706 Tidskriftsartikel (refereegranskat)abstract In this paper, we investigate the joint optimization of base station (BS) location, its density, and transmit power allocation to minimize the overall network operational cost required to meet an underlying coverage constraint at each user equipment (UE), which is randomly deployed following the binomial point process (BPP). As this joint optimization problem is nonconvex and combinatorial in nature, we propose a non-trivial solution methodology that effectively decouples it into three individual optimization problems. Firstly, by using the distance distribution of the farthest UE from the BS, we present novel insights on optimal BS location in an optimal sectoring type for a given number of BSs. After that we provide a tight approximation for the optimal transmit power allocation to each BS. Lastly, using the latter two results, the optimal number of BSs that minimize the operational cost is obtained. Also, we have investigated both circular and square field deployments. Numerical results validate the analysis and provide practical insights on optimal BS deployment. We observe that the proposed joint optimization framework, that solves the coverage probability versus operational cost tradeoff, can yield a significant reduction of about 65% in the operational cost as compared to the benchmark fixed allocation scheme.
29.	Saraiva, J. V., et al. (författare) Energy Efficiency Maximization Under Minimum Rate Constraints in Multi-Cell MIMO Systems with Finite Buffers 2021 Ingår i: IEEE Transactions on Green Communications and Networking. - : Institute of Electrical and Electronics Engineers (IEEE). - 2473-2400. ; 5:1, s. 174-189 Tidskriftsartikel (refereegranskat)abstract Having recognized the dramatic increase in the number of mobile devices and infrastructure nodes, standards organizations and regulatory bodies have adopted energy efficiency (EE) as a key performance metric for fifth-generation networks. Recent works on multiple input multiple output (MIMO) systems have suggested that it is important to use finite-buffer models, because they may lead to better transceiver designs and more accurate performance analyses than full-buffer traffic models. Therefore, this paper addresses the MIMO transceiver design problem for EE maximization in the downlink of finite-buffer multicell systems. Unlike previous works, our problem formulation takes into account per-user minimum rate requirements. We arrive at a nonconvex fractional optimization problem, which is hard to tackle. By exploiting the properties of fractional programming, and using Dinkelbach’s method, the resulting fractional form optimization problem is transformed to an equivalent optimization problem in subtractive form. Next, the nonconvexity of this problem is handled using successive convex approximation, leading to iterative centralized and decentralized resource allocation solutions. Finally, considering a realistic channel model with space, frequency and time correlations, numerical results confirm the effectiveness of the proposed algorithms and indicate significant performance gains in terms of achieved EE over existing solutions for full and finite-buffer models. IEEE
30.	Seifullaev, Ruslan, et al. (författare) Event-Triggered Transmission Policies For Harvesting Powered Sensors With Time-Varying Models 2021 Ingår i: IEEE transactions on green communications and networking. - : Institute of Electrical and Electronics Engineers (IEEE). - 2473-2400. ; 5:4, s. 2139-2149 Tidskriftsartikel (refereegranskat)abstract We consider a wireless control system where sensors transmit their measurements to a controller over a fading channel. We assume that each sensor is equipped with a rechargeable battery and can harvest energy from the environment or other energy sources. To predict the harvested energy, we consider a stationary Markovian model conditioned on a scenario and estimate the unknown parameters based on empirical measurements. The transmission energy is assumed to be inversely proportional to the communication channel gain, which is described by a compound distribution. To increase energy efficiency, we use a continuous event-trigger allowing the sensors to transmit new data only when certain conditions are satisfied. Finally, we analyze the exponential stability of the closed-loop nonlinear system with multiple sector-bounded nonlinearities based on the input-delay method and Lyapunov–Krasovskii technique.
31.	Wazar, Asan, et al. (författare) BER Analysis of a Backscatter CommunicationSystem With Non-Orthogonal Multiple Access 2021 Ingår i: IEEE Transaction on Green Communications and Networking. - : IEEE. - 2473-2400. ; 5:2, s. 574-586 Tidskriftsartikel (refereegranskat)abstract Backscatter communication (BackCom) has been emerging as a prospective candidate in tackling lifetime management problems for massively deployed Internet-of-things (IoT) devices, which suffer from battery related issues, i.e., replacements, charging, and recycling. This passive sensing approach allows a backscatter sensor node (BSN) to transmit information by reflecting the incident signal from a carrier emitter without8 initiating its transmission. To multiplex multiple BSNs, power domain non-orthogonal multiple access (NOMA) is fully exploited in this work. In this paper, we present the design and analysis of a NOMA enhanced bistatic BackCom system for a battery less smart communication paradigm. Specifically, we derive the closed-form bit error rate (BER) expressions for a cluster of two devices in a bistatic BackCom system employing NOMA with imperfect successive interference cancellation under Nakagami-m fading channel. The obtained expressions are utilized to evaluate the reflection coefficients of devices needed for the most favorable system performance along with the performance comparison with orthogonal multiple access-time domain multiple access scheme (OMA-TDMA).
32.	You, Lei, et al. (författare) Learning-Assisted Optimization for Energy-Efficient Scheduling in Deadline-Aware NOMA Systems 2019 Ingår i: IEEE Transactions on Green Communications and Networking. - : Institute of Electrical and Electronics Engineers (IEEE). - 2473-2400. ; 3:3, s. 615-627 Tidskriftsartikel (refereegranskat)abstract In this paper, we study a class of minimum-energy scheduling problems in non-orthogonal multiple access (NOMA) systems. NOMA is adopted to enable efficient channel utilization and interference mitigation, such that base stations can consume minimal energy to empty their queued data in presence of transmission deadlines, and each user can obtain all the requested data timely. Due to the high computational complexity in resource scheduling and the stringent execution-time constraints in practical systems, providing a time-efficient and high-quality solution to 5G real-time systems is challenging. The conventional iterative optimization approaches may exhibit their limitations in supporting online optimization. We herein explore a viable alternative and develop a learning-assisted optimization framework to improve the computational efficiency while retaining competitive energy-saving performance. The idea is to use deep-learning-based predictions to accelerate the optimization process in conventional optimization methods for tackling the NOMA resource scheduling problems. In numerical studies, the proposed optimization framework demonstrates high computational efficiency. Its computational time is insensitive to the input size. The framework is able to provide optimal solutions as long as the learning-based predictions satisfy a derived optimality condition. For the general cases with imperfect predictions, the algorithmic solution is error-tolerable and performance scaleable, leading the energy-saving performance close to the global optimum.
33.	Yuan, Weijie, et al. (författare) Guest Editorial Special Issue on Integrated Sensing and Communications for Future Green Networks 2023 Ingår i: IEEE Transactions on Green Communications and Networking. - 2473-2400. ; 7:1, s. 354-355 Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)

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