Special issue on energy‐efficient wireless communication networks with QoS
Victor C. M. Leung, Shihab A. Jimaa, Peng‐Yong Kong, Michael Chai · International Journal of Communication Systems · 2015
Welcome to this special issue of the International Journal of Communication Systems (IJCS). This special issue is devoted to the recent advances in wireless networking technologies to achieve energy efficiency without compromising quality of service (QoS). Nowadays, we are witnessing a huge increase in the number of mobile subscribers. Forecasts in the tremendous growth of the telecommunications market call for a substantial increase in the per subscriber data rate and the roll out of additional base stations for next generation mobile networks. An undesired consequence is the growth of networks' energy consumption that causes increases in not only the global carbon dioxide (CO2) emissions but also the operational costs for operators. This has triggered the need to innovate in the field of energy-efficient communications, as wireless network infrastructures as a whole have contributed a significant portion of the total CO2 emissions of telecommunication systems. As such, energy-efficient wireless networks can play an important role in helping to alleviate the global warming. However, the design of energy-efficient networking techniques must not affect the service quality perceived by a user. It is a major challenge to be able to reduce power consumption and maintain good service quality at the same time. The challenges in the design of network architectures and protocols for energy-efficient wireless communications with QoS have motivated a significant amount of research in this area. The aim of this special issue is to present a collection of high-quality research papers that report the latest research advances in these areas. By gathering the relevant cutting-edge works, this special issue identifies the unique challenges and the efficient solutions in the area of energy-efficient wireless networks with QoS. Original contributions on the design, analysis, implementation, demonstration, application, and standardization of energy-efficient wireless networking technologies with QoS were solicited for this special issue. Among the 26 submissions received through the open call, we have selected 14 papers for inclusion in this special issue after extensive reviews and revisions. The selected papers could be classified into three categories with four or five papers in each category: (1) wireless sensors, mesh, and heterogeneous networks; (2) energy efficiency; and (3) QoS. A detailed overview of the selected papers is given in the succeeding text. This part describes the recent advances in energy-efficient wireless sensors, mesh, and heterogeneous networks. The first paper, Directional Antennas MAC Protocol for Energy-efficient Wireless Sensor Networks with Mobile Sink, presents a novel Semi-Markov Decision Process-based model that is constructed for energy-efficient wireless sensor networks with a mobile sink using directional antennas. Optimal values of the sum of expected total discounted energy consumption are achieved. The second paper, A Gravitational Search Algorithm for Solving the Relay Node Placement Problem in Wireless Sensor Networks, tackles the Relay Node Placement Problem, that is, the addition of relay nodes to traditional Wireless Sensor Networks as a way to optimize such networks, assuming two important factors: energy consumption and average coverage. All the results obtained are studied through a widely accepted statistical methodology and two metrics (hyper volume and set coverage). The third paper, Energy Efficiency and Traffic Offloading in Wireless Mesh Networks with Delay Bounds, develops a mathematical model of a wireless access network based on the IEEE 802.11 standard and enriched with features such as caching and mesh networking and solves it optimally by means of integer linear programming. Also the paper provides an investigation on the benefits of adding traffic aggregation features to the mathematical model. The fourth paper, Dynamic Programming based Pico Base Station Sleep Mode Control in Heterogeneous Networks, proposes a sleeping mode control for low-power wireless node, that is, pico base station (PBS) in heterogeneous networks, to save energy cost with adaptation to the time-varying traffic load. The complexity of the proposed scheme is only in linear order instead of exponential complexity with conventional scheme. Furthermore, the proposed algorithm is verified in dynamic traffic environment that comprises two kinds of hot-spot area covered by PBSs. There are five selected papers in this part. The first paper, Power Allocation in the Energy Harvesting Full-Duplex Gaussian Relay Channels, proposes a general model to study the full-duplex non-coherent decode-and-forward Gaussian relay channel with energy harvesting (EH) nodes, called NC-EH-RC, in three cases: (i) no energy transfer (ET); (ii) one-way ET from the source (S) to the relay (R); and (iii) two-way ET. The authors considered the problem of optimal power allocation in NC-EH-RC in order to maximize the total transmitted bits from S to the destination in a given time duration. The second paper, Energy-Efficient Power Allocation for Cognitive Radio Networks with Minimal Rate Requirements, investigates the energy-efficient power allocation problem in Orthogonal Frequency Division Multiplexing (OFDM)-based relaying Cognitive Radio (CR) networks. Authors developed a general framework to maximize the overall Energy Efficiency (EE) of the CR system, under the constraints of transmission power budget, traffic demands, as well as the interference constraints of the primary users. Numerical results validated that the proposed method can exploit the overall EE of CR systems, while the algorithm converges efficiently and stably. The third paper, An Efficient Energy-Aware Predictive Clustering approach for Vehicular Ad Hoc Networks, proposes an efficient energy-aware predictive clustering scheme for vehicles. Efficient algorithms are designed for future mobility predictions and average variations of vehicles on the road. The algorithms estimate the clustering duration and total vehicles in the cluster. The performance of the designed algorithms is studied using extensive simulations by varying the number of vehicles and cluster durations in comparison with existing benchmarked scheme in the literature. The results obtained show that the proposed scheme is superior in comparison with the existing scheme of its category. The fourth paper selected is Theoretical Study and Performance Evaluation of Energy-Efficient Macro-assisted Data-only Carrier for Next Generation 5G System. In this paper, a new Control-plane and User-plane C/U split architecture of Data-only Carrier (DoC) system is analyzed comprehensively from various aspects, such as overhead costs, coverage probability, spectral efficiency and EE for the first time. Based on the model of stochastic geometry, the influences of density and power of small cell and cell range expansion factors are all taken into account to compare the DoC architecture with the baseline Long Term Evolution (LTE) system. Numerical results show that the DoC system can greatly reduce the overhead costs and help to achieve higher throughput gain and better coverage performance over the conventional LTE system. The fifth paper, Timer-based Power Management for Infrastructure IEEE 802.11 WLAN with Unreliable Wireless Links, presents the Timer-based Power Management (TPM) applied in the infrastructure IEEE 802.11 Wireless Local Area Network (WLAN) with Unreliable Wireless Links (UWLs), referred to as TPM-UWL. A novel stochastic analysis model is developed for TPM-UWL, based on which the probabilities that a mobile station (STA) is at active, dozing, and idle states are obtained. Additionally, the number of buffered frames at the Access Point and the sleeping STA, the STA's average power consumption, and a frame's average delay under TPM-UWL are derived. Further, the optimization problem that minimizes power consumption under the constraints of delay and buffer size is presented, which enables an STA to set its maximum number of retransmissions and the values of the idle and doze timers in the medium access control layer such that power consumption is minimized while the constraints of delay and buffer size are satisfied. The third part comprises five selected papers that focusses on the issues related to the QoS. The first paper is Energy Efficiency Optimization for Downlink OFDMA System in Heterogeneous Network with QoS Constraints. This paper optimizes energy efficiency (EE) for downlink OFDMA system in HetNet, taking into account realistic network power consumption model. Also it investigates the energy efficiency (EE) maximization using convex optimization theory where primary optimization criterion is data rate in a downlink multiuser HetNet. Given QoS (data rate) requirement, for maximizing EE, a constrained based optimization problem is devised. The considered optimization problem is transformed into a convex optimization problem by redefining the constraint using cubic inequality, which results in an efficient iterative resource allocation algorithm. In each iteration, the transformed problem is solved by using dual decomposition with a projected gradient method. Analytical insights and numerical results exhibit the potency of the devised scheme for the targeted complex wireless systems. The second paper, QoS-Driven Resource Allocation in Green OFDMA Wireless Networks, presents a QoS-driven energy-efficient power and subcarrier allocation in green Orthogonal Frequency Division Multiple Access (OFDMA) networks. The proposed scheme aims at maximizing the effective energy efficiency (EEE), defined as overall effective capacity per total power consumption, subject to given user delay-QoS requirements and an average sum transmit power constraints. Authors analytically obtains the uniquely global optimal power and subcarrier using fractional programming which transforms the fractional program into an equivalent parametric convex program that has a tractable solution. Analytical results show that the optimal solution has the same structure as effective capacity maximization and overall power minimization solutions. Simulation results show that there exists a trade-off between EEE and delay. Furthermore, the proposed resource allocation provides significant EEE gains over both the independent resource allocation and overall power minimization scheme. The third paper, QoS-Aware Energy-Efficient Resource Allocation in OFDM-Based Heterogeneous Cellular Networks, presents an iterative energy-efficient scheduling scheme (IEESS) for downlink OFDM-based HetNets with quality-of-service consideration. Authors formulate the problem as a nonlinear fractional programming problem aiming to maximize the QoS-aware energy efficiency (QEE) in HetNets. In order to solve this problem, authors first transform it into a parametric programming problem, which takes QEE as an evolved parameter in the iterative procedure of IEESS. In each iteration, for the given value of QEE, subchannel and power assignment sub-problem is a nonlinear NP-hard problem. And hence they adopt dual decomposition method for obtaining the optimal assignment of subchannels and power of the sub-problem for the given value of QEE. Simulation results depict that both outer QEE parameter search and inner subgradient search can converge in a few iterations and the resultant solutions outperform the equal power allocation scheme and capacity maximization scheme in terms of QEE. The fourth paper, A QoS-Aware Green Cooperative Compressed Sensing Scheme in IEEE 802.22 WRAN, introduces compressed sensing (CS) theory into Distributed antennas-wireless regional area network (DA-WRAN) and proposes a QoS-Aware Green Cooperative Compressed Sensing (QAGCCS) scheme, which aims to maximize energy efficiency of DA-WRAN under its basic QoS constraints of packet drop probability, sensing delay and total throughput. In the proposed scheme, the expression for accuracy of compressed signal recovery under certain sparsity is fitted into exponential function and the number of compressed samples number is taken account into the energy efficiency optimization for the first time. To solve the formulated nonlinear multivariate optimal problem, a sub-optimal algorithm based on particle swarm optimization (PSO) is presented. Also, the performances of the proposed scheme are simulated and discussed and the simulation results show that the performance on energy efficiency of the proposed scheme is about 17.5%-33.3% better than contrasting algorithms without compromising CPEs' QoS. The last paper, A Novel Energy-Efficient Cross-Application-Layer Platform with QoS-Security Support, presents an iterative energy-efficient scheduling scheme (IEESS) for downlink OFDM-based HetNets with quality-of-service (QoS) consideration. Authors formulates the problem as a nonlinear fractional programming problem aiming to maximize the QoS-aware energy efficiency (QEE) in HetNets. In order to solve this problem, authors first transform it into a parametric programming problem, which takes QEE as an evolved parameter in the iterative procedure of IEESS. In each iteration, for the given value of QEE, subchannel and power assignment sub-problem is a nonlinear NP-hard problem. And hence, they adopt dual decomposition method for obtaining the optimal assignment of subchannels and power of the sub-problem for the given value of QEE. Simulation results show that both outer QEE parameter search and inner subgradient search can converge in a few iterations, and the resultant solutions outperform the equal power allocation scheme and capacity maximization scheme in terms of QEE. In conclusion, this issue of IJCS offers a ground-breaking view into the recent advances in energy-efficient wireless communication networks with QoS. The popularity of submissions indicates that energy-efficient wireless communication networks is a world-wide focus. Finally, we would like to express our gratitude to the Editor-in-Chief of the IJCS, Dr. Mohammad Obaidat, for his advice, patience, and encouragement from the beginning until the final stage in the realization of this special issue. We thank all the anonymous reviewers who have spent much of their valuable time reviewing all the papers. Their timely and thoughtful reviews and comments greatly helped the authors in improving their presented works and enabled us to select the best papers for this special issue. We also thank all the authors who have submitted their papers for consideration for this special issue. We hope that you will enjoy reading the great selection of papers in this special issue.