Energy Efficiency Optimization in Relay-Assisted Networks with Energy Harvesting Relay Constraints

In this paper we consider data transmission in a decode-and-forward(DF)relay-assisted network in which the relay is energy harvesting(EH) powered while the base station(BS) is power-grid powered.Our purpose is to maximize the BS's energy efficiency(EE) while making full use of the relay's renewable energy and satisfying the specific average throughput requirements.In contrast to existing literature on energy harvesting system which only considers the radio transmission power,we take the static circuit power into account as well.We formulate the EE optimization problem and prove that the EE of the BS and relay are both quasiconvex in the instantaneous transmission rate.Then we divide the complex optimization problem into two point-to-point link level optimization parts and propose an energyefficient resource allocation(EERA) scheme in which power control and sleep mode management are jointly used.The simulation results demonstrate that EERA may achieve good energy saving effects.We also compare the EE of an energy harvesting relay system with a power-grid powered one and provide more insight into the EE problem of energy harvesting relay system.

Energy Efficiency Analysis of Cellular Networks with Cooperative Relays via Stochastic Geometry

Cooperative relaying is a promising technology that can improve the spectral and energy efficiency of cellular networks. However, the deployed relays consume a lot of energy and system resources. To improve the energy efficiency of the relay-assisted cellular networks, this paper considers the use of energy harvesting(EH) on relay nodes. A random sleeping strategy is also introduced in macro base stations(MBS) as a possible method to reduce energy consumption. In this paper, an analytical model is proposed to investigate the energy efficiency of cellular networks with EH relays and sleep mode strategy. Numerical results confirm a significant energy efficiency gain of the proposed networks comparing to the cellular networks with non-EH relays and MBSs without sleep mode strategy. The effects of the density and transmit power of MBSs on energy efficiency are also given through simulations.

Performance evaluation of a two-way relay network with energy harvesting^and hardware noises

In this paper,we propose a Two-Way Cognitive Relay Network(TWCRN)where the secondary users operate on an underlay mode to access the licensed bands.In the proposed protocols,two secondary sources transmit their data to a relay in the first time slot,and then the relay would forward the received information to both sources in the remaining time.Moreover,the relay is self-powered by harvesting energy from ambient Radio Frequency(RF)signals,using the Time Switching(TS)and the Power Switching(PS)method.This paper concentrates on eval-uating the performance of the secondary networks under the impact of hardware impairments and co-channel interference from the primary networks.In particular,based on the secondary transmitters'constraint power,we derive the closed-form expressions of the outage probability and the throughput over Rayleigh fading channels in two cases:TS and PS.We also investigate the energy efficiency issue and the locally optimal position of the relay to maximize the system throughput,which provides much information to install the relay location.Finally,our derivations are verified by Monte Carlo simulation.

Energy efficient and delay aware ternary-state transceivers for aerial base stations

In recent times, Aerial Base Stations(AeBSs) are being investigated to provide wireless coverage to terrestrial radio terminals. There are many advantages of using aerial platforms to provide wireless coverage, including larger coverage in remote areas and better line-of-sight conditions, etc. Energy is a scarce resource for the AeBSs, hence the wise management of energy is quite beneficial for the aerial network. In this context, we study the means of reducing the total energy consumption by designing and implementing an energy efficient AeBSs as presented in this paper. Implementing the sleep mode in the Base Stations (BSs) has been proven to be a very good approach for improving the energy efficiency and we propose a novel strategy for further improving energy efficiency by considering ternary state transceivers for AeBSs. Using the three state model, we propose a Markov Decision Process (MDP) based algorithm, which intelligently switches among three states of the transceivers based on the offered traffic meanwhile maintaining a prescribed minimum channel rate per user. We define a reward function for the MDP, which helps us to get an optimal policy for selecting a particular mode for the transceivers of the AeBS. Considering an AeBS with transceivers whose states are changeable, we perform simulations to analyse the performance of the algorithm. Our results show that, compared with the always active model, around 40% gain in the energy efficiency is achieved by using our proposed MDP algorithm together with the three-state transceivers model. We also show the energy-delay tradeoff in order to design an efficient AeBS.

解码转发全双工能量收集最大的多认知中继网络能效谱效权衡

在无线携能(SWIPT)支持下的全双工多认知中继网络中,为使能效谱效最大,选择能量收集最大的中继进行解码转发,以此形成一个能效谱效权衡最优化问题,采用变量变换和凹凸过程优化方法将该问题转换为凸优化问题。当权衡因子为0时,该优化问题等价于使谱效(SE)最大的优化问题;当权衡因子为1时,该优化问题等价于使系统消耗的能量最小问题。为求解该优化问题,提出一种可以直接得到使能效(EE)最大的权衡因子的改进算法,通过联合源节点发射功率和功率分割因子进行优化。所提算法分为两步:首先固定功率分割因子,得到使EE最优的源节点发射功率和权衡因子;其次,固定最优的源节点发射功率,利用能效谱效与功率分割因子之间的关系,求得最优的功率分割因子。仿真实验结果表明,相较于剩余其他中继组成的网络,能量收集最大的中继网络在EE和SE上都更优。在能效谱效方面,与只优化发射功率的方法相比,所提算法的EE提高了63%以上,SE提高了30%以上;所提算法EE和SE与穷举法相差不大,同时算法收敛较快。

Influences of Environmental Motion Modes on the Efficiency of Ultrathin Flexible Piezoelec trie Energy Harvesters

Harvesting energy from ambient vibration sources with ultrathin flexible piezoelectric energy harvesters(PEHs)for battery-free electronics has received attention in recent years.However,the excitation modes in the environment and human body motion are more complicated than the ideal harmonic modes employed in previous theoretical analyses,and their influence on the efficiency of PEHs has received little attention.In this study,these environmental excitation modes are classified into three types,i.e.,the triangular,sinusoidal,and square wave modes,with varied duty ratios.We derived theoretically the output power of flexible PEHs under these excitation modes and establish a simple scaling law,in which the normalized output power depends only on two combined normalized parameters,i.e.,the intrinsic system parameter and the excitation mode.Results reveal that the output power of PEHs changes dramatically for different excitation modes with varied duty ratios even when all the other parameters including excitation ampli tude,excitation frequency,elec trical parameter,and geometrical and material parameters of the PEHs are identical.This paper may provide a systematic understanding in the effect of exc计ation modes on the output power of flexible PEHs and promote the realization of energy harvesting from the complex environmental and human body motions.

An Energy-Aware Geographical Forwarding Protocol Utilizing Adaptive Sleeping in Wireless Sensor Networks

This paper proposes a novel energy-aware geographical forwarding protocol utilizing adaptive sleeping, in which each node selects its relay based on a new criterion that is based on its residual energy reserves and its geographical location to guarantes energy efficiency. In addition, this paper presents an adaptive sleep mechanism fully integrated into the new relay criterion, in which each node sleeps for a variable duration based on its residual energy reserves. Simulation results show that the proposed protocol significantly reduces the energy consumption of the network and improves its balance, especially when on heavy traffic load in dense networks. Our protocol is 20 times better in balancing the energy consumption compared with geographical random forwarding protocol.

GB 21520-2023显示器能效限定值及能效等级标准变化解析

本文主要从GB 21520-2023标准的修订内容及新旧标准的主要变化方面进行解读。详细介绍了新旧标准适用范围的差异,分析了显示器能效技术提升情况,以及新旧标准在能效测试方法方面的差异。最后结合产品的实际测试数据,分析了新标准对显示器测试结果判定的影响。

IEEE 802.16j中继站睡眠模式改进算法

IEEE 802.16j标准在IEEE 802.16e标准的基础上引入了中继站。中继站睡眠模式是能量节省的重要手段。其中各参数的选取关系到RS睡眠模式的效果——平均能量消耗和平均帧时延。用概率统计的方法构建了IEEE 802.16jRS睡眠模式下的能量消耗模型和帧时延模型,通过对睡眠模式各窗口参数的分析,提出了根据业务流动态改变窗口参数的算法,并且对改进前后的算法进行了仿真分析。

基于交叉层设计的IEEE802.16e休眠机制

针对IEEE802.16e标准休眠模式中无线接入设备过多的监听下行信道问题,建议了一种交叉层设计方法,设置休眠参数的动态算法。将MAC层提取的休眠时间数值与物理层固定值相结合,形成休眠调度参数。通过建立马尔可夫链模型,分析了建议的算法能更多节省电池供电的移动台有限能量。NS2仿真实验验证了该算法比标准的节能性能最大可提高30%。

802.16e系统中一种针对多用户实时业务的改进休眠算法

在802.16e系统中,当具有实时业务的多个移动站点(MS)同时进入休眠模式时,重叠的侦听窗口上数据调度的竞争将会影响MS的节能效率。该文对这种实时业务下多MS同时进入休眠模式的场景进行分析,提出了一种改进的休眠算法。该算法通过调整新加入连接休眠模式的启动时间,使得各MS的侦听窗口尽量分散,实现系统负载在OFDM帧上较为均匀的分布,从而提高网络的平均节能效果。仿真结果表明所提出算法不仅能够提高系统平均的节能效率,还能够降低系统的信令开销,同时在整体上提高系统的QoS保障。

802.16e系统中一种节能的实时业务数据调度算法

在802.16e系统中,当多个拥有实时业务的MS同时处在休眠模式时,BS的调度结果不仅决定了这些实时业务的QoS,还会影响到网络的平均节能效率.针对这个问题提出了一种新的节能数据调度算法.该算法具有两个方面的技术特点:1)通过调整新加入的MS休眠模式的启动时间,使得各MS的侦听窗口尽量分散并实现系统负载在OFDM帧上较为均匀的分布,以平滑BS调度器的输入;2)对目前广泛使用的实时业务调度算法EDF进行改进,提高处在休眠状态的MS的数据调度优先级.仿真结果表明,该算法在保证系统QoS的同时,不仅能够较大地提高了网络的平均节能效率,还降低了系统的整体信令开销.

IEEE 802.16j中继站睡眠模式的研究

IEEE 802.16j标准在IEEE 802.16d/e标准的基础上引入了中继站。由于有的中继站具有便携、游牧,甚至移动的特性,往往采用电池或者太阳能供电的方式,中继站的能量节省问题也随之而来。中继站睡眠模式作为能量节省的重要手段,对其进行研究是十分必要和有用的。介绍了IEEE802.16jRS睡眠机制,并构建了中继站睡眠模式下的能量消耗模型和帧时延模型。然后用概率统计的方法对模型进行了仿真,并就各参数对平均能量消耗和平均帧时延的影响进行了分析。

无线携能通信中一种能效优先的缓存队列机制中继选择方案

针对无线携能(SWIPT)中在节点能量受限情况下的缓存队列机制半双工(HD)中继选择的问题,研究了SWIPT中能效优先的缓存队列机制中继节点选择方案和所提策略的系统能效。给出了基于能效优先的缓存队列机制SWIPT最佳接收/转发中继节点选择方案。数值仿真结果表明,所提策略可以有效降低SWIPT网络的中断概率,实现缓存队列SWIPT中能效与中断性能的折中。

QoS约束下多层异构蜂窝网中基于分层休眠的节能机制研究

针对多层异构蜂窝网中资源分配和节能问题,本文基于随机几何模型利用分布式配对算法实现了用户连接和资源分配的联合优化,并利用分层休眠机制提升了系统的整体能效。首先,采用随机几何工具对不同类型的基站进行建模,在建立模型的基础上提出用户QoS约束下的最小化系统总功耗的联合优化方案,然后将该方案分解简化为用户连接资源分配和基站休眠两个子问题,并分别利用稳定配对算法和基于投票法的分层休眠机制加以解决。仿真和分析结果表明本文方法可以显著提升系统能效,与已有的休眠策略相比具有更低的用户平均中断比。

无线能量收集协作系统的节能中继选择方法

在无线能量收集协作通信系统中,针对中继处可能出现的能量瓶颈,提出优化源节点和中继的传输功率的节能中继选择方法。利用源节点与中继之间发射功率的比例关系计算源节点的发射功率,选择信道容量最大的中继链路进行数据转发,并考虑源节点与中继的发射功率约束。在此基础上,推导系统的平均信道容量和中断性能。仿真结果表明,该方法可显著提高系统能量效率,节约源节点的能量消耗。

基于无线携能的双向中继星地网络系统性能分析

随着卫星通信技术的发展和用户需求的增加,星地混合网络以其性能优势和空间优势吸引了大量学者的关注,然而,实现高速率高质量通信的同时也会降低双向中继星地网络的生存时间。因此,能量受限一直阻碍着星地混合网络的实际应用,针对这一问题提出了一种基于无线携能的双向中继星地网络系统传输方法。首先推导了卫星终端和用户终端的可达速率,其次引入无线携能技术,推导出双向中继星地网络系统的能量效率,并利用蒙特卡洛仿真,对该系统的能量性能进行了分析。仿真结果表明,无线携能技术能够有效地降低系统能量消耗,依据实际通信环境合理设置中继发射功率将有助于提高系统能量效率。

基于非线性能量收集的全双工认知中继网络的联合优化方法

针对信息传输过程的时间消耗和信道估计误差对网络能效的影响,提出了一种基于非线性能量收集的全双工认知中继网络的联合优化方法。所提方法是在中继采用非线性能量收集并考虑非完美信道状态信息(CSI)的情况下,首先通过将能效非凸优化问题转化为两个凸的子优化问题,从而求出次用户和中继的传输功率以及收集的能量;其次,在保证主用户干扰门限以及最优传输功率非负的情况下,求出传输的信道容量范围;最后,将传输功率代入表达式得到关于时间的目标函数,并利用海森矩阵证明该目标函数为凸函数,进而求出最优传输时间以及功率分割因子,最终得出能效最优解。实验结果表明,在相同条件下,所提联合优化方法的能效相较于仅优化传输功率的能效提升了约84.3%;同时验证了信道估计误差因子为0.01时,所提方法的网络能效降低了约1.9%。

中继网络中基于能量效率的动态用户接入算法

为了解决中继网络中基于能量效率的用户接入问题,将用户数据需求严格受限下基于能量效率最优的动态用户接入问题建模为一个整数优化问题,该问题类似于一个NP-hard的多维背包问题.首先,采用穷搜法分析了该问题最优解的复杂度.然后,提出了一种低复杂度、高效的基于能量效率的动态用户接入算法(UAEEM).该算法在保证用户数据需求严格受限的前提下,按照系统射频端和电路端的能量效率最大原则,动态调整用户归属和中继的工作状态,以实现网络能量效率最大化.最后,通过仿真实验验证所提算法性能.结果表明,UAEEM算法能显著提高系统的能量效率、降低系统的计算复杂度,且其性能接近最优解.

未来网络休眠机制的研究

目前传统网络架构显得越来越臃肿,以致于产生很多的问题,其中能耗问题显得越来越突出。为了解决这些问题,不是对已有的网络架构做修补,而是革命性地更改网络体系架构。国内外已经有部分项目提出了未来网络体系架构,并且在一些新型的网络体系架构下提出了休眠机制,旨在降低能耗。主要介绍了未来网络架构下的休眠方案,同时对节点级休眠方案进行仿真和比较,为以后的研究做铺垫。