Power-conscious design of wireless circuits and systems

The great importance of power consciousness is well understood in mobile wireless communications. However, with growing experience the fundamental principles underlying power conscious design of RF circuits, systems, and networks are only now becoming known. Using as example ultralow-power wireless devices for messaging such as paging receivers and wireless sensor networks, the first part of this paper presents the relationship between current consumption and dynamic range of low-noise amplifiers, mixers, oscillators, and active filters. The second part of the paper covers issues of modulation, protocols, and networking that would be required in dense networks of wireless sensors, which communicate using very little energy. These ideas are expected to find use in most forms of digital wireless communications     

Throughput maximization in electromagnetic energy harvesting cognitive radio sensor networks

In the near future, billions of wireless devices are expected to be operational. To enable the required machine to machine communications, two major problems must be addressed. How to obtain the required spectrum efficiency, and how to deliver the required power to these devices. The most promising answers to these questions are cognitive radio and energy harvesting, respectively. Energy harvesting enables deployment of sensors and devices without having to worry about their battery lifetime. Cognitive radio increases the utilization of spectrum by accessing unused spectrum dynamically. Energy harvesting from electromagnetic waves is suitable for these low power, low cost devices used in machine to machine communications because only minimal additional hardware is required for such energy harvesting. With this idea as the starting point, we first present an analysis on how much throughput can be obtained from a cognitive, electromagnetic energy harvesting wireless network. Then, we show when and how cooperation among network nodes may increase performance. We believe that our results will provide insight for the development of future cooperative cognitive energy harvesting networks. Copyright © 2015 John Wiley & Sons, Ltd.     

Evolution and future trends of research in cognitive radio: a contemporary survey

The cognitive radio (CR) paradigm for designing next‐generation wireless communications systems is becoming increasingly popular, and different aspects of it are being implemented in currently available wireless systems. In the last decade, a significant amount of research efforts has been made to solve CR challenges, and several standards related to CR and dynamic spectrum access have been developed. Also, there have been advances in software‐defined radio platforms to implement the CR systems. In this article, we provide a comprehensive survey on the evolution of CR research covering aspects such as spectrum sensing, measurements and statistical modeling of spectrum usage, physical layer aspects such as waveform and modulation design, multiple access, resource allocation and power control, cognitive learning, adaptation and self‐configuration, multihop transmission and routing, and robustness and security in CR networks. Also, state‐of‐the‐art research on the economics of CR networks, CR simulation tools, testbeds and hardware prototypes, CR applications, and CR standardization efforts is summarized. Emerging trends on CR research and open research challenges related to the cost‐effective and large‐scale deployment of CR systems are outlined. Copyright © 2013 John Wiley & Sons, Ltd.     

Energy-Efficiency-Based Power Allocation Scheme in Multi-user Single-DF-Relay Cognitive Networks

Due to the enhancement in both spectral efficiency and energy efficiency, cognitive radio (CR) being combined with relay cooperation technique is deemed as a promising way to realize green-broadband communication in the fifth generation (5G) networks. In this paper, for such CR-relay networks operating in underlay mode, when multiple secondary cognitive users (SUs) share a common cognitive relay in decode-and-forward manner to complete their physical transmissions, system power consumption is investigated. For the scenarios where the co-channel interference to primary users and the peak transmit power of SUs and cognitive relay are constrained, the problem of power allocation in CR-relay network is formulated to minimizing sum-system-consumption. Then, based on the principle that power-consumption minimization is equivalent to energy-efficiency maximization, a novel power allocation scheme is proposed. Further numerical simulation is used to verify the optimality of the proposed power allocation scheme.

     

Context-aware cooperative testbed for energy analysis in beyond 4G networks

The complexity of heterogeneous wireless networks in synergy with battery powered mobile devices is driving new stringent requirements in terms of power efficiency to ensure that battery life, environmental and thermal criteria can be met. Modern mobile devices are equipped with multiple interfaces, which allow them to exploit the benefits offered by heterogeneous networking environments, but on the other hand, drain battery swiftly. In this paper, architecture for a context-based node and a testbed platform for the analysis of energy consumption of heterogeneous cooperative communications are presented. The demonstrative testbed comprises a WiFi Access Point, which provides WiFi coverage in the infrastructure mode, as well as nodes capable of communicating through short-range ultra-wideband WiMedia. The testbed includes a context aware module that provides and stores information related to different nodes in the system. The paper shows how context information can be used to save the energy of mobile devices and extend their battery lifetime using short-range communications. The testbed is used as a proof-of-concept for the practical implementation of the cooperative communications concept. The obtained results show that significant amount of energy can be saved using context information along cooperation among multiple interfaces, in comparison to direct communications.     

基于多域协同的绿色无线通信系统体系构架

绿色无线通信是全球经济低碳化的一个重要组成部分,日益受到关注。无线通信的核心指标是以满足通信容量为目标的功率效率和频谱效率,传统的无线通信系统大多侧重于频谱效率,而绿色无线通信则需在侧重功率效率的同时,兼顾功率效率与频谱效率的折中。本文介绍了绿色无线通信的现状,分析了无线通信系统体系构架对于发展绿色通信的重要性,提出了基于多域协同研究绿色无线通信系统体系构架的有效方法,并在此基础上初步探讨了绿色无线通信系统体系构架的核心技术。     

基于能效的解码转发中继OFDM链路自适应功率分配方案研究

在能效问题中,设备本身的电路功耗已成为不可忽略的一部分,故将中继引入无线网络之后势必会带来更严重的电路功耗.该文基于解码转发(DF)中继OFDM频率选择性链路,结合电路所耗功率,提出一种最优能效功率分配方法,求得DF中继链路能效上界,同时分析了速率和功率限制对能效的影响.仿真结果表明,该文所提基于能效的功率分配算法可求出最大化能效的最优功率解,并能在保证较高速率的同时获得最好的系统能效.     

Rakeness with block sparse Bayesian learning for efficient ZigBee‐based EEG telemonitoring

Future healthcare systems are shifted toward long‐term patient monitoring using embedded ultra‐low power devices. In this paper, the strengths of both rakeness‐based compressive sensing (CS) and block sparse Bayesian learning (BSBL) are exploited for efficient electroencephalogram (EEG) transmission/reception over wireless body area networks. A binary sensing matrix based on the rakeness concept is used to find the most energetic signal directions. A balance is achieved between collecting energy and enforcing restricted isometry property to capture the underlying signal structure. Correct presentation of the EEG oscillatory activity, EEG wave shape, and main signal characteristics is provided using the discrete cosine transform based BSBL, which models the intra‐block correlation. The IEEE 802.15.4 wireless communication technology (ZigBee) is employed, since it targets low data rate communications in an energy efficient manner. To alleviate noise and channel multipath effects, a recursive least square based equalizer is used, with an adaptation algorithm that continually updates the filter weights using successive input samples. For the same compression ratio (CR), results indicate that the proposed system permits a higher reconstruction quality compared with the standard CS algorithm. For higher CRs, lower dimensional projections are allowed, meanwhile guaranteeing a correct reconstruction. Thus, low computational high quality data compression/reconstruction are achieved with minimal energy expenditure at the sensors nodes.     

Relay characteristic impact on energy consumption in heterogeneous sensor network

Indoor heterogeneous wireless sensor networks are considered in this paper. We analyze the power consumption for multihop communications with non-regenerative relays. Since sensor nodes are battery operated, energy consumption is a crucial issue. We determine the optimal relay gains and transmitted power that minimize the dissipated power for a given quality of service in a narrow band fading channel. Our work includes two main contributions: firstly, we study the energy consumption taking into account hardware aspects, especially the relays’ efficiency. In an AWGN channel, carefully analyzing the energy gain as a function of the position, we show that relay characteristics have an important impact on the multihop link consumption budget. We then use a Rice channel model based on simulations and further study the hardware impact on energy saving.     

On co-channel and adjacent channel interference mitigation in cognitive radio networks

Cognitive radio (CR) is an emerging wireless communications paradigm of sharing spectrum among licensed (or, primary) and unlicensed (or, CR) users. In CR networks, interference mitigation is crucial not only for primary user protection, but also for the quality of service of CR user themselves. In this paper, we consider the problem of interference mitigation via channel assignment and power allocation for CR users. A cross-layer optimization framework for minimizing both co-channel and adjacent channel interference is developed; the latter has been shown to have considerable impact in practical systems. Cooperative spectrum sensing, opportunistic spectrum access, channel assignment, and power allocation are considered in the problem formulation. We propose a reformulation–linearization technique (RLT) based centralized algorithm, as well as a distributed greedy algorithm that uses local information for near-optimal solutions. Both algorithms are evaluated with simulations and are shown quite effective for mitigating both types of interference and achieving high CR network capacity.     

Mobile device‐centric access point monitoring scheme for handover decision triggering in heterogeneous networks

Because of the low throughput and the high packet error rate in wireless communications, the network traffic often converges at access points (APs), which take a role of connecting wired and wireless communication interfaces, and APs are usually bottleneck points in wireless networks. In heterogeneous networks, various networks are around mobile devices. Furthermore, today's mobile devices have various wireless network capabilities. Thus, mobile devices should be able to understand network situations autonomously and use a wide range of network options in heterogeneous networks. However, since current mobile devices cannot know the connected AP's network condition, they continue to use the AP, which provides poor‐quality networks even though there are other available APs and networks nearby. To resolve the aforementioned problems, we propose MAPS , the low‐power AP monitoring scheme for handover decision triggering in heterogeneous networks. Using MAPS , a mobile device can trigger a handover decision properly through predicting the connected AP's network condition accurately without any cooperation from other devices. Furthermore, MAPS does not require any modification on existing network systems, and the mobile device can use MAPS with simple application installation. Through diverse simulations, actual experiments, and power consumption analysis, we validate that MAPS can detect the busy AP effectively and is suitable for mobile devices because of low power consumption.     

Energy Efficient Cooperation with Chip-Interleaved Transceivers in WSNs Over Frequency-Selective Fading Channels

Cooperative diversity techniques have been utilized to improve the energy efficiency of wireless sensor networks (WSNs) operating over flat fading channels in a considerable number of literature. However, wireless channels of WSNs operating in indoor environments are supposed to be characterised by frequency-selective fading. Theoretical analysis of energy efficient cooperative communications in WSNs operating in indoor environments are rarely addressed. Therefore, this paper studies the energy efficient cooperative communications in WSNs operating over frequency-selective fading channels. Closed-form bit error rate expressions are derived for systems over frequency-selective fading channels. In order to fully explore the energy conservation potential of cooperative communications, solutions of the optimal transmit power allocation and the partner node selection are provided. Moreover, it is proven that the communication quality can be greatly improved by using chip-interleaving techniques in WSNs subject to flat fading channels. Thus, this paper investigates the energy-saving potential of chip-interleaved transceivers in WSNs subject to frequency-selective fading. Numerical results show that significant energy savings can be achieved via cooperations with chip-interleaved transceivers in WSNs operating in indoor environments.

     

Exploiting location awareness toward improved wireless system design in cognitive radio

Rapid advances in digital technology allow people to have a single wireless device that has multiple functions such as communication, computing, and entertainment. These functions are generally embedded into the devices as add-on hardware components such as sensors, digital cameras, and so on. Currently, the functions operate independent of each other, since there is no unit that controls and coordinates the add-on hardware. However, with the aid of a cognitive engine, CR can take advantage of each component to improve its communications. In this work, location awareness is exploited to improve the wireless communication system design in CR. It is shown that several crucial wireless channel parameters are environment-dependent. In order for CR to relate a corresponding empirical model with an environment, the classification of propagation environments is outlined as well. The methods of characterizing the propagation environment for CR are also discussed. In addition, it is described how CR can carry out all these steps with the aid of a KRS along with RKRL and complete its adaptation cycle. CR networks are also discussed, including disseminating the location awareness information, propagation characteristics, and their effects on the network itself.     

一种基于网络编码协作的高能效无线传感器网络机制

Energy-efficient communications is crucial for wireless sensor networks (WSN) where energy consumption is constrained. The transmission and reception energy can be saved by applying network coding to many wireless communications systems. In this paper, we present a coded cooperation scheme which employs network coding to WSN. In the scheme, the partner node forwards the combination of the source data and its own data instead of sending the source data alone. Afterward, both of the system block error rates (BLERs) and energy performance are evaluated. Experiment results show that the proposed scheme has higher energy efficiency. When Noise power spectral density is -171dBm/Hz, the energy consumption of the coded cooperation scheme is 81.1% lower than that of the single-path scheme, 43.9% lower than that of the cooperation scheme to reach the target average BLER of 10-2. When the channel condition is getting worse, the energy saving effect is more obvious.     

Sustainable Spectrum Allocation Strategy for 5G Mobile Network

These days, 5G wireless communication are being created for different modern IoT (Internet of Things) applications around the world, arising with the IoT. All things considered, it is feasible to send energy efficient innovation in a manner that advances the drawn out sustainability of networks. Next-generation heterogeneous wireless communication is composed of different base stations. In this network, sustainable spectrum allocation is required to maximize the bandwidth utilization along with a reduction in power consumption. This paper proposes an algorithm for allocating an optimized spectrum to clusters in a multi-cluster environment for sustainable 5G environment using particle swarm optimization (PSO). The proposed strategy is applicable for 3G, 4G, and 5G mobile networks. Mobile devices enter and leave the cluster randomly and stay within the cluster for an uncertain amount of time. During that period the user demands may vary. Consequently, various bandwidth allocations are required. For such cases, static allocation might result in inefficient utilization of bandwidth, wastage of power, and degrade user satisfaction. The proposed algorithm will optimize the spectrum allocated to a cluster from time to time to solve this problem and produce an optimized solution within a given deadline. PSO based proposed scalable spectrum allocation method is applicable for the different frequency range for each cluster, hence scalable from 3G telecommunication to 5G-mobile edge technology. The convergence of the strategy is analyzed. From simulation analysis, it is observed that the proposed strategy reduces power consumption by approximately 8%, 11%, and 6% in 3G, 4G, and 5G communications respectively than the existing scheme.

     

Power Control for Cognitive Radio Networks: A Game Theoretic Approach

In communication industry one of the most rapidly growing area is wireless technology and its applications. The efficient access to radio spectrum is a requirement to make this communication feasible for the users that are running multimedia applications and establishing real-time connections on an already overcrowded spectrum. In recent times cognitive radios (CR) are becoming the prime candidates for improved utilization of available spectrum. The unlicensed secondary users share the spectrum with primary licensed user in such manners that the interference at the primary user does not increase from a predefined threshold. In this paper, we propose an algorithm to address the power control problem for CR networks. The proposed solution models the wireless system with a non-cooperative game, in which each player maximize its utility in a competitive environment. The simulation results shows that the proposed algorithm improves the performance of the network in terms of high SINR and low power consumption.

     

基于大规模MIMO和D2D技术的混合网络能量效率研究

文章研究了基于大规模多输入多输出（multiple-input multiple-output,MIMO）和端到端（device-to-device,D2D）技术的双层混合网络及其能量效率,面向D2D用户（D2D user,DU）提出了无线能量采集方案。在该混合网络模型中,宏蜂窝基站由大规模MIMO天线阵列构成,D2D网络覆盖在宏蜂窝之上,与蜂窝网共享频谱。为了保证D2D通信,系统配置了由小规模MIMO天线构成的专用能量发射基站（power beacon,PB）,其通过迫零预编码向能量约束的D2D发射机传送能量;同时,为了提高网络的能量效率,DU还可以从附近蜂窝网用户（cellular user,CU）的射频（radio frequency,RF）干扰信号中采集能量。对此混合网模型和能量采集方案,文章通过假设网络中CU、DU以及PB的位置服从独立泊松点过程和利用随机几何分析方法,基于反功率控制方案得到了网络中任一D2D发射机通过采集足够能量来建立通信链路的概率,其以简单的积分形式给出。分析和数值结果表明,文章提出的无线能量采集方案由于PB的配置保证了D2D通信的可靠性;同时又因为充分利用了附近CU的RF干扰信号,有效提高了D2D用户采集足够能量的概率,节约了PB的能量,改善了系统的能量效率。      

Low Power Downlink MAC Protocols for Infrastructure Wireless Sensor Networks

This paper addresses low power medium access control (MAC) protocols for the downlink channel of infrastructure wireless sensor networks. Access points are assumed to be energy unconstrained. The trade-off between the power consumption of the sensor nodes and the transmission delay is analyzed, focusing on low traffic. We describe WiseMAC (Wireless Sensor MAC), a new protocol for the downlink of infrastructure wireless sensor networks. Another original contribution is the presentation and analysis of PTIP (Periodic Terminal Initiated Polling). Here, polling is used in the reversed direction as compared to common polling protocols. WiseMAC and PTIP are compared with PSM (Power Save Mode), the power save protocol used in both the IEEE 802.11 and IEEE 802.15.4 ZigBee standards. Analytical expressions are derived for the power consumption and the transmission delay for each protocol, as a function of the wake-up period. It is shown that WiseMAC provides, with low bit rate radio transceivers, a significantly lower power consumption than PSM. Although less energy efficient than WiseMAC and PSM, it is shown that PTIP can, thanks to its implementation simplicity, become attractive for applications tolerating large transmission delays.Amre El-Hoiydi received the electrical engineer degree from the Swiss Federal Institute of Technology in Zurich (ETHZ), Switzerland, in 1994. In 1995, he was a teaching assistant at the Swiss Federal Institute of Technology in Lausanne (EPFL), working on mobility management for low earth orbit mobile satellite communication systems. In 1996, he joined CSEM (Neuchâtel, Switzerland). Since then, he has been working on several research and development projects dealing with various aspects of wireless communications. In the ACTS RAINBOW and FRAMES projects, he was involved with the network and air interface aspects of 3rd generation cellular systems. In the ESPRIT INFOGATE and IST OPENROUTER projects, he worked on electronic design and embedded programming of Linux based wireless LAN gateways. His current research focus is low power communication protocols for wireless sensor networks.Jean-Dominique Decotignie is head of the real-time and networking group at the Swiss Center for Electronics and Microsystems (CSEM) in Neuchâtel. He is professor at the School of Computer and Communication Sciences of EPFL (Swiss Federal Institute of Technology in Lausanne) and teaches real-time systems as well as hardware and software design. From 1977 to 1982, he has worked at EPFL and the University of Tokyo in the area of optical communications. In 1983, he joined the Industrial Computer Engineering Lab. at EPFL where he became Assistant Professor in 1992. From 1989 to 1992, he has been the head of an interdisciplinary project on Computer Integrated Manufacturing at EPFL. Since January 1997, he is with CSEM. His current research interests include industrial and real-time local area networks, distributed control systems and software engineering for real-time systems as well as real-time wireless networks.     

Green Resource Allocation for Multiple OFDMA Based Networks: A Survey

Orthogonal frequency division multiple access (OFDMA) is a popular and widely accepted multiple access technique to provide high data rate services in a mobile environment in the area of wireless communications. OFDMA can provide better flexibility in allocating the radio spectra by utilizing subcarrier allocations, scheduling, and energy control to obtain multi-dimension diversity gains. Due to its resource allocation flexibility, OFDMA has been widely used as a green air interface technology for the emerging broadband wireless access networks. This paper extensively addresses the integration of green OFDMA to the future air interface technologies, for instance:two-tier cellular, multi radio access technologies (RATs), FemtoCell, and relay networks. The main focus of the paper is to review and analyze the current OFDMA techniques to address the green resource allocation in multiuser diversity, where the critical constraints are the computational complexity, energy efficiency, and the sub-channel assignment. The future trend of OFDMA based networks will aim to maximize the energy efficiency of the exclusive channel assignment through a joint sub-channel and power allocation to accommodate high data traffic networks specially the relay based 5G cellular networks.     

Radio-over-Fibre access for sustainable Digital Cities

Pervasive broadband access will transform cities to the net social, environmental and economic benefit of the e-City dweller as did the introduction of utility and transport network infrastructures. Yet without action, the quantity of greenhouse gas emissions attributable to the increasing energy consumption of access networks will become a serious threat to the environment. This paper introduces the vision of a ‘sustainable Digital City’ and then considers strategies to overcome economic and technical hurdles faced by engineers responsible for developing the information and communications technology (ICT) network infrastructure of a Digital City. In particular, ICT energy consumption, already an issue from an operating cost perspective, is responsible for 3 % of global energy consumption and is growing unsustainably. A grand challenge is to conceive of networks, systems and devices that together can cap wireless network energy consumption whilst accommodating growth in the number of subscribers and the bandwidth of services. This paper provides some first research directions to tackle this grand challenge. A distributed antenna system with radio frequency (RF) transport over an optical fibre (or optical wireless in benign environments) distribution network is identified as best suited to wireless access in cluttered urban environments expected in a Digital City from an energy consumption perspective. This is a similar architecture to Radio-over-Fibre which, for decades, has been synonymous with RF transport over analogue intensity-modulated direct detection optical links. However, it is suggested herein that digital coherent optical transport of RF holds greater promise than the orthodox approach. The composition of the wireless and optical channels is then linear, which eases the digital signal processing tasks and permits robust wireless protocols to be used end-to-end natively which offers gains in terms of capacity and energy efficiency. The arguments are supported by simulation studies of distributed antenna systems and digital coherent Radio-over-Fibre links.