Energy Efficiency In Wireless Networks Research Articles

Improved Channel Utilization with Energy Efficiency in Wireless Networks

Improved Channel Utilization with Energy Efficiency in Wireless Networks

QoS-aware User Load Management with Beamforming for Energy Efficiency in Wireless Networks

QoS-aware User Load Management with Beamforming for Energy Efficiency in Wireless Networks

Wireless Max–Min Utility Fairness With General Monotonic Constraints by Perron–Frobenius Theory

This paper presents a systematic approach for solving wireless max–min utility fairness optimization problems in multiuser wireless networks with general monotonic constraints. These problems are often challenging to solve due to their nonconvexity. By establishing a connection between this class of optimization problems and the class of conditional eigenvalue problems that can be addressed by a generalized nonlinear Perron–Frobenius theory, we show how these problems can be solved optimally using an iterative algorithm that converges geometrically fast. The mathematical development in this paper unifies previous work and allows us to handle a broader class of competitive utility functions with general nonlinear monotonic constraints. Several representative applications illustrate the effectiveness of the proposed framework, including the max–min quality-of-service subject to robust interference temperature constraints in cognitive radio networks, the min–max weighted mean-square error subject to signal-to-interference-and-noise ratio constraints in multiuser downlink systems, the max–min throughput subject to nonlinear power constraints in energyefficient wireless networks, the max–min sigmoid utility in multimedia wireless networks, and the min–max outage probability subject to outage constraints in heterogeneous wireless networks. Numerical results are presented to demonstrate the fast-convergence behavior of the algorithms to the optimal fixed-point solution characterized by our generalized nonlinear Perron–Frobenius theoretic framework.

Energy Allocation and Cooperation for Energy-Efficient Wireless Two-Tier Networks

In this paper, we consider the resource allocation in two-tier wireless systems in which small-cell base stations harvest energy from renewable sources in addition to the conventional power grid. Moreover, we assume that each cell has access to an energy storage system with a limited battery capacity. We introduce new mechanisms that enable an efficient allocation of the available energy over time across the network. In doing so, we take into account the time-varying fading channel, the inter-cell interference and the fluctuations of harvested energy. In particular, we propose convergent offline algorithms to maximize the network energy efficiency while satisfying an average sum-rate constraint at each cell. Furthermore, we extend the resource allocation scheme by enabling an energy cooperation between the cells. By cooperating, they can exchange their harvested energy through a smart-grid power infrastructure. Using numerical simulations, we verify the convergence of the proposed algorithms and analyze the efficacy of the resource allocation and energy cooperation schemes.

Cross-layer designs for energy efficient wireless body area networks: a review

Cross-layer design is considered a powerful alternative to solve the complexities of wireless communication in wireless body area networks (WBAN), where the classical communication model has been shown to be inaccurate. Regarding the energy consumption problem, we have prepared a current survey of the most relevant scientific publications on energy-efficient cross-layer design for WBAN. In this paper, we provide a comprehensive review of the advances in cross-layer approaches, protocols and optimizations aimed at increasing the network lifetime by saving energy in WBANs. Subsequently, we discuss the relevant aspects and shortcomings of these energy-efficient cross-layer techniques and point out the open research issues and challenges in WBAN cross-layer design. In this survey, we propose a taxonomy for cross-layer approaches to fit them into categories based on the protocols involved in the cross-layer scheme. A novel classification is included to clarify the theoretical concepts behind each cross-layer scheme; and to group similar approaches by establishing their differences from the other strategies reviewed. Our conclusion considers the aspects of mobility and channel modeling in WBAN scenarios as the directions of future cross-layer research for WBAN and telemedicine applications.

Cross-layer designs for energy efficient wireless body area networks: a review

This paper presents an experimental evaluation of the structural integrity of the lumbar section (L2-L3-L4) considering a damaged intervertebral disc. In this study porcine specimens were used due to the similarity of the mechanical properties those of the human spine. The lumbar section L2-L3-L4 was tested under compression. Five cases were analyzed; in the first one, the lumbar section consisted of healthy intervertebral discs. For the other four cases the disc located between L2 and L3 was divided into four quadrants: front, back, left and right. For each of these cases, a damage condition was induced by making an incision from the annular fibers to the pulpous nucleus, covering each quadrant; the back elements (pedicles and facet joint) were removed and only the vertebral bodies and discs were tested. As a damaged intervertebral disc is unable to properly perform its mechanical function, the load transferred from L2 to L3 through the disc is no longer optimal. The actual stress field on L3, considering the damaged disc, was obtained using reflective photoelasticity for each one of the before mentioned study cases. The results show that the induced damage in the intervertebral discs increases the stresses on L3 considerably when compared to the case of an undamaged disc, being the most critical when the damage is located in the back quadrant of the disc. In the other three cases, the damaged disc does not reduce the structural integrity of the vertebral body significantly. However, the inter-vertebrae space is reduced as a result of the damage thus compromising the structural integrity of the studied lumbar section.

Stability Analysis of Slotted Aloha With Opportunistic RF Energy Harvesting

Energy harvesting (EH) is a promising technology for realizing energy-efficient wireless networks. In this paper, we utilize the ambient RF energy, particularly interference from neighboring transmissions, to replenish the batteries of the EH enabled nodes. However, RF energy harvesting imposes new challenges into the analysis of wireless networks. Our objective in this paper is to investigate the performance of a slotted Aloha random access wireless network consisting of two types of nodes, namely Type I, which has unlimited energy supply and Type II, which is solely powered by an RF energy harvesting circuit. The transmissions of a Type I node are recycled by a Type II node to replenish its battery. We characterize an inner bound on the stable throughput region under half-duplex and full-duplex energy harvesting paradigms as well as for the finite capacity battery case. Additionally, we analyze the case where RF energy harvesting serves as a backup for an unlimited energy source. We present numerical results that validate our analytical results, and demonstrate their utility for the analysis of the exact system.

Has Time Come to Switch From Duty-Cycled MAC Protocols to Wake-Up Radio for Wireless Sensor Networks?

Duty-cycled Medium Access Control (MAC) protocols certainly improve the energy efficiency of wireless networks. However, most of these protocols still suffer from severe degrees of overhearing and idle listening. These two issues prevent optimum energy usage, a crucial aspect in energy-constrained wireless networks such as wireless sensor networks (WSNs). Wake-up radio (WuR) systems drastically reduce these problems by completely switching off the nodes' microcontroller unit (MCU) and main radio transceiver until a secondary, extremely low-power receiver is triggered by a particular wireless transmission, the so called wake-up call. Unfortunately, most WuR studies focus on theoretical platforms and/or custom-built simulators. Both these factors reduce the associated usefulness of the obtained results. In this paper, we model and simulate a real, recent, and promising WuR hardware platform developed by the authors. The simulation model uses time and energy consumption values obtained in the laboratory and does not rely on custom-built simulation engines, but rather on the OMNET++ simulator. The performance of the WuR platform is compared to four of the most well-known and widely employed MAC protocols for WSN under three real-world network deployments. The paper demonstrates how the use of our WuR platform presents numerous benefits in several areas, from energy efficiency and latency to packet delivery ratio and applicability, and provides the essential information for serious consideration of switching duty-cycled MAC-based networks to WuR.

A Novel Power Consumption Model for Effective Energy Efficiency in Wireless Networks

Designing energy-efficient delay-aware communication networks have become an inevitable trend in 5G wireless networks. In this letter, we present an energy-efficient and delay-aware cross-layer resource allocation in SISO wireless systems. To achieve this goal, we apply the notion of effective energy efficiency (EEE), defined as the ratio of the system effective capacity (EC) over the total power consumption. Unlike previous works, we introduce a new average power consumption model which accounts for the data link layer, allowing for the probability of emptying the buffer during the transmission timeframe. This leads to a new definition of EEE, which results in better performance in terms of both EEE and EC.

Energy Efficient Resource Allocation for Mixed RF/VLC Heterogeneous Wireless Networks

Developing energy efficient wireless communication networks has become crucial due to the associated environmental and financial benefits. Visible light communication (VLC) has emerged as a promising candidate for achieving energy efficient wireless communications. Integrating VLC with radio frequency (RF)-based wireless networks has improved the achievable data rates of mobile users. In this paper, we investigate the energy efficiency benefits of integrating VLC with RF-based networks in a heterogeneous wireless environment. We formulate and solve the problem of power and bandwidth allocation for energy efficiency maximization of a heterogeneous network composed of a VLC system and an RF communication system. Then, we investigate the impact of the system parameters on the energy efficiency of the mixed RF/VLC heterogeneous network. Numerical results are conducted to corroborate the superiority in performance of the proposed hybrid system. The impact of hybrid system parameters on the overall energy efficiency is also quantified.

Energy Efficiency of Distributed Signal Processing in Wireless Networks: A Cross-Layer Analysis

In order to meet the growing mobile data demand, future wireless networks will be equipped with a multitude of access points (APs). Besides the important implications for the energy consumption, the trend towards densification requires the development of decentralized and sustainable radio resource management techniques. It is critically important to understand how the distribution of signal processing operations affects the energy efficiency of wireless networks. In this paper, we provide a cross-layer framework to evaluate and compare the energy efficiency of wireless networks under different levels of distribution of the signal processing load: (i) hybrid, where the signal processing operations are shared between nodes and APs, (ii) centralized, where signal processing is entirely implemented at the APs, and (iii) fully distributed, where all operations are performed by the nodes. We find that in practical wireless networks, hybrid signal processing exhibits a significant energy efficiency gain over both centralized and fully distributed approaches.

Freenet: Spectrum and energy harvesting wireless networks

The dramatic growth in mobile data traffic is resulting in spectrum crunch, and is also leading to exorbitant energy consumption. Thus, it is desirable to liberate mobile and wireless networks from the constraint of spectrum scarcity and to rein in growing energy consumption. This article introduces FreeNet, figuratively synonymous with “Free Network,” which engineers spectrum and energy harvesting techniques to alleviate spectrum and energy constraints by sensing and harvesting spare spectrum for data communications and utilizing renewable energy as power supplies, respectively. Hence, FreeNet increases the spectrum and energy efficiency of wireless networks and enhances network availability. As a result, FreeNet can be deployed to alleviate network congestion in urban areas, provision broadband services in rural areas, and upgrade emergency communication capacity. This article provides a brief analysis of the design of FreeNet that accommodates the dynamics of the spare spectrum and employs renewable energy.

Performance Evaluation and Measurement for Energy Efficient Wireless Networks

Growth of high-data-rate applications is increasing day by day, more energy is consumed in wireless networks to guarantee quality of service. The data rate expected to meet in latest 4G is up to 1Gbps.In**creasing energy efficiency in wireless communications network has attracted the attention recently. In this research different performance metrics that are to be measure and analyze viz. no. of nodes used,power transmission by nodes, wireless channel type, energy efficiency(in bits/joule) data rate in bits per channel use, SNR(signal-to-noise ratio), power transmission(Pt), subcarrier bandwidth, protocol & throughput. The various performance measurements are on the basis of optimal metrics analysis for the wireless communication system to be selected. The parameters measured and reported are power transmission of 5-10dB, energy efficiency in bits per Joule as 4×1020, data rate in bits per channel use as 4, SNR as 10dB, probability of error as 10-4, distance between nodes as 100m, FFT size as 512, protocol as Medium Access Control (MAC), throughput as 50%.

On balancing energy efficiency for network operators and mobile users in dynamic planning

The high energy consumption of network operators and mobile users has raised environmental, financial, and quality-of-experience concerns. These concerns have renewed the research efforts in developing green communication strategies for energy efficient wireless network operation. Network operators employ dynamic planning to save energy at low call traffic load by switching off some of their base stations (BSs), and mobile users are served by the remaining active BSs. The existing research investigates energy efficiency of dynamic planning approaches only from the network operator perspective. Dynamic planning, if not carefully designed, can lead to higher energy consumption for the mobile users in the uplink, which in turn degrades the uplink service quality due to mobile terminals' battery depletion. In this article we propose a dynamic planning framework with balanced energy efficiency that accounts for the energy consumption of the mobile users in the uplink as well as that of the network operators in the downlink. We discuss the associated challenges and implementation issues. A dynamic planning approach based on a multi-time scale decision process is proposed to achieve the balanced energy efficiency framework. Numerical results demonstrate the improved energy efficiency performance for the uplink mobile users as compared with the traditional dynamic planning approach.

Cross-Layer Resource Allocation With Elastic Service Scaling in Cloud Radio Access Network

Cloud radio access network (C-RAN) aims to improve spectrum and energy efficiency of wireless networks by migrating conventional distributed base station functionalities into a centralized cloud baseband unit (BBU) pool. We propose and investigate a cross-layer resource allocation model for C-RAN to minimize the overall system power consumption in the BBU pool, fiber links and the remote radio heads (RRHs). We characterize the cross-layer resource allocation problem as a mixed-integer nonlinear programming (MINLP), which jointly considers elastic service scaling, RRH selection, and joint beamforming. The MINLP is however a combinatorial optimization problem and NP-hard. We relax the original MINLP problem into an extended sum-utility maximization (ESUM) problem, and propose two different solution approaches. We also propose a low-complexity Shaping-and-Pruning (SP) algorithm to obtain a sparse solution for the active RRH set. Simulation results suggest that the average sparsity of the solution given by our SP algorithm is close to that obtained by a recently proposed greedy selection algorithm, which has higher computational complexity. Furthermore, our proposed cross-layer resource allocation is more energy efficient than the greedy selection and successive selection algorithms.

Special issue on energy‐efficient wireless communication networks with QoS

Special issue on energy‐efficient wireless communication networks with QoS

Placement Of Energy Aware Wireless Mesh Nodes For E-Learning In Green Campuses

Energy efficiency solutions are more vital for Green Mesh Network (GMN) campuses. Today students are benefited using these e-learning methodologies. Renewable energies such as solar, wind, hydro has tremendous applications on energy efficient wireless networks for sustaining the ever growing traffic demands. One of the major issues in designing a GMN is minimizing the number of deployed mesh routers and gateways and satisfying the sustainable QOS based energy constraints. During low traffic periods the mesh routers are switched to power save or sleep mode. In this paper we have mathematically formulated a single objective function with multi constraints to optimize the energy. The objective is to place minimum number of Mesh routers and gateways in a set of candidate location. The mesh nodes are powered using the solar energy to meet the traffic demands. Two global optimisation algorithms are compared in this paper to optimize the energy sustainability, to guarantee seamless connectivity.

An Energy Saving Strategy for LTE-A Multiantenna Systems

Long Term Evolution - Advanced (LTE-A) supports closed-loop Multiple Input Multiple Output (MIMO) techniques to improve its performance, but in order to exploit multiuser (MU) MIMO channel capabilities, the design of an efficient Medium Access Control (MAC) scheme that supports MU-MIMO is still an open issue in the literature. This paper proposes a novel energy efficient MAC scheme for LTE-A, which aims to achieve simultaneous downlink transmissions to multiple users, through the deployment of a low complexity beamforming technique at the physical layer. Our proposed scheme takes advantage from the multiuser gain of the MIMO channel and the multiplexing gain of the Multibeam Opportunistic Beamforming (MOB) technique, to improve the system throughput and the energy efficiency of wireless networks. We provide a closed form mathematical expression of the energy efficiency, where the results from the proposed scheme achieve a considerable energy saving at the Base Station (eNB).

Recent advances in energy-efficient networks and their application in 5G systems

This article provides an overview on research in energy-efficient wireless networks during the past decade and discusses its potential applications toward the fifth generation cellular systems. After analyzing the trade-off between spectrum efficiency and energy efficiency, various research results are summarized within a framework of energy-efficient resource allocation with optimization as a common tool. Then potential energy efficiency improving approaches in both physical layer and deployment aspects are provided. Finally, energy efficiency related open problems in massive multiple-input multiple- output, device-to-device communications, ultra dense networks, and other emerging technologies are identified.

A distributed virtual MIMO coalition formation framework for energy efficient wireless networks

In this paper, we consider a distributed virtual multiple-input multiple-output (MIMO) coalition formation algorithm. Energy savings are obtained in the reverse link by forming multi-antenna virtual arrays for information transmission. Virtual arrays are formed by finding a stable match between two sets of single antenna devices such as mobile stations (MSs) and relay stations (RSs) based on a game theoretic approach derived from the concept of the college admissions problem. Thus, power savings are obtained through multi-antenna arrays by implementing the concepts of spatial diversity and spatial multiplexing for reverse link transmission. We focus on optimizing the overall consumed power rather than the transmitted power of MSs and RSs. Furthermore, it is shown analytically and by simulation that when the overall consumed power is considered, the energy efficiency of the single antennas devices is not always improved by forming a virtual MIMO array. Hence, single antenna devices may prefer to transmit on their own when channel conditions are favorable. In addition, the simulation results show that the framework we propose provides comparable energy savings and a lower implementation complexity when compared to a centralized exhaustive search approach.