Energy-efficient Rate Adaptation MAC Protocol for Ad Hoc Wireless Networks

In this paper, two novel energy-efficient rate adaptation schemes are presented. The proposed protocols use the Distributed Power Control (DPC) algorithm to predict the channel state and determine the necessary transmission power which optimizes the energy consumption. The first proposed rate adaptation scheme heuristically alters the modulation rate to balance the energy-efficiency and the required throughput which is estimated with queue fill ratio. Moreover, the back-off scheme is incorporated to mitigate congestion and reduce packet losses due to buffer overflows thus minimizing energy consumption. Consequently, the nodes will conserve energy when the traffic is low, offer higher throughput when needed and save energy during congestion by limiting transmission rates. The second rate adaptation scheme employs dynamic programming (DP) principle to analytically select modulation rate and a burst size to be used during transmission. The proposed quadratic cost-function minimizes the energy consumption while alleviating network congestions and buffer overflows. The proposed DP solution renders a Riccati equation ultimately providing an optimal rate selection. The simulation results indicate that an increase in throughput by 96% and energy-efficiency by 131% is observed when compared to other available protocols, for example Receiver Based AutoRate (RBAR).

WSN节能设计研究现状

传感器网（WSN）综合了传感器技术、嵌入式计算技术、通信技术等，在人无法或很难到达的地方具有很高的利用价值。传感器网络能够应用于军事和民用方面，然而传感器网络中的节点数量众多，体积小，能量受限，因此如何降低节点的能量消耗。延长网络的寿命显的极为重要。文章介绍了传感器网络的结构，总结了传感器网络中的节能算法和协议，并提出了今后发展的方向。     

WSN节能设计研究现状

传感器网络(WSN)综合了传感器技术、嵌入式计算技术、通信技术等,在人无法或很难到达的地方具有很高的利用价值。传感器网络能够应用于军事和民用方面,然而传感器网络中的节点数量众多,体积小,能量受限,因此如何降低节点的能量消耗,延长网络的寿命显的极为重要。文章介绍了传感器网络的结构,总结了传感器网络中的节能算法和协议,并提出了今后发展的方向。     

Cluster Size Optimization in Sensor Networks with Decentralized Cluster-Based Protocols

Network lifetime and energy-efficiency are viewed as the dominating considerations in designing cluster-based communication protocols for wireless sensor networks. This paper analytically provides the optimal cluster size that minimizes the total energy expenditure in such networks, where all sensors communicate data through their elected cluster heads to the base station in a decentralized fashion. LEACH, LEACH-Coverage, and DBS comprise three cluster-based protocols investigated in this paper that do not require any centralized support from a certain node. The analytical outcomes are given in the form of closed-form expressions for various widely-used network configurations. Extensive simulations on different networks are used to confirm the expectations based on the analytical results. To obtain a thorough understanding of the results, cluster number variability problem is identified and inspected from the energy consumption point of view.     

Distributed computing for carbon footprint reduction by exploiting low-footprint energy availability

Low carbon footprint energy sources such as solar and wind power typically suffer from unpredictable or limited availability. By globally distributing a number of these renewable sources, these effects can largely be compensated for. We look at the feasibility of this approach for powering already distributed data centers in order to operate at a reduced total carbon footprint. From our study we show that carbon footprint reductions are possible, but that these are highly dependent on the approach and parameters involved. Especially the manufacturing footprint and the geographical region are critical parameters to consider. Deploying additional data centers can help in reducing the total carbon footprint, but substantial reductions can be achieved when data centers with nominal capacity well below maximum capacity redistribute processing to sites based on renewable energy availability.     

Thermodynamic perfectibility based analysis of energy-efficiency standards for air conditioning products in China

There are presently different types of air conditioning products in China such as room air conditioners, variable speed room air conditioners, unity air conditioners, multi-connected air-condition (heat pump) unit, chilled water air conditioning systems. For these air conditioning products, evaluation indexes have been created, respectively including energy efficiency ratio (EER), coefficient of performance (COP), seasonal energy efficiency ratio (SEER) and integrated part load value (IPLV), and their energy efficiency standards have been established. Based on thermodynamic perfectibility, this paper makes the compatible analysis of the energy efficiency and thermodynamic perfectibility gradient of energy efficiency standards for different air conditioning products. According to testing conditions of evaluation indexes, these air conditioning products are classified into two groups, the standard rating conditions group (EER, COP) and the variable working condition group (SEER, IPLV). The results show the thermodynamic perfectibility of different air conditioning products grade as the same level for energy efficiency standards in each group differ from one another. Besides, the average thermodynamic perfectibility gradient of energy efficiency levels for air conditioning product in the standard rating conditions group is basically the same, and that of variable speed room air conditioners and multi-connected air-condition (heat pump) unit are the highest and lowest, respectively.     

谢菲尔德大学社会科学信息合作楼

本文从项目背景、建筑设计、技术策略和用户反馈几个主要方面介绍了以研究交流功能为主的谢菲尔德大学社会科学信息合作楼,希望通过研究这个成功的实例,深入了解建筑设计、生态环境和使用者之间的密切关系。     

Evening office lighting – visual comfort vs. energy efficiency vs. performance?

During the study presented in this article, we compared two highly energy-efficient lighting scenarios for evening office lighting (i.e. electric lighting that is typically used for approxiamately 2 h in the evening). The first of these lighting scenarios (referred to as “Reference”-scenario, Lighting Power Density or LPD of 4.5 W/m²) has been successfully in use in many office rooms of the Solar Energy and Building Physics Laboratory’s experimental building, located on the campus of the Swiss Federal Institute of Technology in Lausanne, for several years. The second lighting scenario (referred to as “Test”-scenario, Lighting Power Density of 3.9 W/m²) is more energy-efficient, creates higher workplane illuminances but leads to an increased risk of discomfort glare. The aim of this study was to meticulously compare the two lighting scenarios in order to find a lighting solution for evening office lighting that offers an optimal trade-off between energy-efficiency, visual comfort and visual performance.     

可控性节能建筑设计

节能建筑有两个重要特征,地区差异性和过程控制性。该文根据可控性原理提出建筑总体环境布局、建筑空间、围护结构及构件的可控性节能设计方法。