An ant swarm-inspired energy-aware routing protocol for wireless ad-hoc networks

Primitive routing protocols for ad-hoc networks are “power hungry” and can therefore consume considerable amount of the limited amount of battery power resident in the nodes. Thus, routing in ad-hoc networks is very much energy-constrained. Continuous drainage of energy degrades battery performance as well. If a battery is allowed to intermittently remain in an idle state, it recovers some of its lost charge due to the charge recovery effect, which, in turn, results in prolonged battery life.In this paper, we use the ideas of naturally occurring ants’ foraging behavior (Dorigo and Stuetzle, 2004) [1] and based on those ideas, we design an energy-aware routing protocol, which not only incorporates the effect of power consumption in routing a packet, but also exploits the multi-path transmission properties of ant swarms and, hence, increases the battery life of a node. The efficiency of the protocol with respect to some of the existing ones has been established through simulations. It has been observed that the energy consumed in the network, the energy per packet in the case of EAAR are 60% less compared to MMBCR and the packets lost is only around 12% of what we have in AODV, in mobility scenarios.     

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.     

无线传感器网络中定向扩散协议的改进算法

定向扩散算法周期性地扩散探测分组时,会给网络带来很大负载,严重影响了数据分组的传输性能。该文提出了一种基于梯度的受限扩散算法。通过分析邻居梯度,计算扩散的广度和深度,进而选取最优的转发节点集进行扩散。仿真结果表明受限扩散算法在保证较低能量消耗的前提下,大大缩短了扩散持续的时间和数据分组端到端时延。     

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。     

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.     

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.     

Greening campus WLANs: Energy-relevant usage and mobility patterns

The past years have witnessed a significant increase in the number of WLANs deployed in most of the enterprises, campuses and public areas to provide high-speed Internet connectivity. These WLANs typically consist of APs densely installed to assure enough capacity to meet users demand during the peak period of activity. At the same time, it translates into a serious energy wastage during low-utilization periods, when capacity is not needed at the APs. To reduce this wastage, many proposed solutions consist of adapting the active capacity to the actual needs, introducing switching strategies able to turn on and off the APs. The effectiveness and potential benefit of these strategies strongly depend on the user behavior and traffic patterns.In this paper, we focus our analysis on the real usage characteristics of a dense WLAN (such as users’ behavior and users’ mobility patterns) in a university campus and evaluate potential energy savings and benefits achievable when introducing AP on/off switching strategies. We discuss different strategies, in which decisions are based either on: (1) historical behavior in the campus, or on (2) current AP utilization. In addition, considering the large overlapping coverage available in dense WLANs, we investigate users’ mobility patterns to derive further improvements to AP switching strategies. The results show that, due to the repetitiveness of users’ patterns and large differences in WLAN usage between days and nights, as well as between weekdays and weekends, large savings of up to 40% can be easily achieved. Moreover, by fine-tuning the strategies in different areas of the campus, additional savings are possible. The deployment of these strategies leads to energy saving and, as a practical consequence, to a remarkable reduction of electricity costs.     

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).