Load Metric Research Articles

ERCP: Energy-Efficient and Reliable-Aware Clustering Protocol for Wireless Sensor Networks.

Wireless Sensor Networks (WSNs) have been around for over a decade and have been used in many important applications. Energy and reliability are two of the major problems with these kinds of applications. Reliable data delivery is an important issue in WSNs because it is a key part of how well data are sent. At the same time, energy consumption in battery-based sensors is another challenge. Therefore, efficient clustering and routing are techniques that can be used to save sensors energy and guarantee reliable message delivery. With this in mind, this paper develops an energy-efficient and reliable clustering protocol (ERCP) for WSNs. First, an efficient clustering technique is proposed for sensor nodes' energy savings considering different clustering parameters, including the link quality metric, the energy, the distance to neighbors, the distance to the sink node, and the cluster load metric. The proposed routing protocol works based on the concept of a reliable inter-cluster routing technique that saves energy. The routing decisions are made based on different parameters, such as the energy balance metric, the distance to the sink node, and the wireless link quality. Many experiments and analyses are examined to determine how well the ERCP performs. The experiment results showed that the ECRP protocol performs much better than some of the recent algorithms in both homogeneous and heterogeneous networks.

Developing Secure Multipath Routing (AODV-SMR) Protocol Framework Based Multipath Network Routing Protocol

Mobile ad hoc networks (MANETs) are wireless networks, which consist of mobile nodes that communicate over wireless media. MANETs are typically characterized by high mobility and frequent link failures. Since routing protocols are crucial for the success of MANETs, multipath routing can be employed to reduce link failure so that alternate paths will be available. This paper aims to develop and evaluate the performance of a new multipath routing protocol based on the ad hoc on-demand distance vector (AODV) routing protocol. It is an on-demand multipath routing protocol named ad hoc on-demand distance vector-secure multipath routing (AODV-SMR). The on-demand multipath routing protocol was evaluated against three performance metrics: packet delivery ratio, average end-to-end delay and normalized routing load. The simulation results, obtained using an OMNET++ simulator, showed that the proposed protocol exhibits significant improvement in the packet delivery ratio. It also outperformed the ad hoc on-demand multipath distance vector (AOMDV) protocol in the average end-to-end delay, and outperformed AODV in the normalized routing load metric.

Cascading Failures Analysis of Wireless Sensor Networks With Varying Routing Schemes

In practical wireless sensor networks (WSNs), routing schemes determine the message-forwarding direction of sensor nodes, which have a significant impact on the cascading process of WSNs. However, the existing cascading failure models fail to consider the impact of routing schemes. Therefore, in this work, we propose an actual cascading failure model for WSNs considering routing factors. In this model, a sink-oriented load metric is proposed to characterize the actual load distribution of WSNs, and four load redistribution mechanisms (i.e., latency-sensitive global routing, congestion-sensitive global routing, capacity-sensitive local routing and latency-sensitive local routing) are proposed to mimic the most commonly used routing schemes. Through extensive simulations, we have obtained some meaningful results: 1) there is a critical threshold for node capacity. When the node capacity is greater than the threshold, the lifting effects of capacity expansion are saturated; 2) there is a cascade interval for the attack range. Cascading failures occur only if the attack range is within this interval; 3) among the four routing schemes, congestion-sensitive global routing has the strongest cascading robustness; 4) flat-structured topology is the most robust, followed by clustering topology, and finally scale-free topology. The obtained results can provide theoretical support for improving the cascading robustness of WSNs.

Interference, Traffic Load and Delay Aware Routing Metric for Wireless Mesh Network

The self-organizing property of the wireless mesh network (WMN) has made them suitable for implementing various networking application, such as video surveillance. In WMN, routing prot ...

In-situ service load monitoring of automotive electronic systems using silicon-based piezoresistive stress sensor

It is expected that more and more complex (integrated) automotive electronics will be adopted in systems. These advanced electronics are critical for passenger safety. Documenting the in-situ loading is, thus, very important for accurate reliability prognostics. In this study, we propose a piezoresistive stress sensor to detect the in-situ loading of an automotive electronic control unit (ECU). A load metric directly related to the in-situ loading is defined by considering the in-situ stress values of twelve measurement cells in each sensor. The sensor and the proposed load metric are implemented to document the in-situ loading that results from the local coefficient of thermal expansion mismatch between the electrical components and printed circuit board (PCB) in advanced ECUs. The validity of the proposed metric is corroborated by failure analysis of solder joints of multilayer ceramic capacitors (MLCCs).

Duodenal bacterial load as determined by quantitative polymerase chain reaction in asymptomatic controls, functional gastrointestinal disorders and inflammatory bowel disease.

Small intestinal bacterial overgrowth may play a role in gastrointestinal and non-gastrointestinal diseases. To use quantitative polymerase chain reaction (qPCR) to determine and compare bacterial loads of duodenal biopsies in asymptomatic controls, and patients with functional gastrointestinal disorders (FGIDs) and inflammatory bowel disease (IBD) including ulcerative colitis (UC) and Crohn's disease (CD). To define effects of gastric acid inhibition on bacterial load, explore links of bacterial load and gastrointestinal symptoms in response to a standardised nutrient challenge and compare bacterial load with glucose breath test results. In 237 patients (63 controls, 84 FGID and 90 IBD), we collected mucosal samples under aseptic conditions during endoscopy extracted and total DNA. Bacterial load metric was calculated utilising qPCR measurements of the bacterial 16S rRNA gene, normalised to human beta-actin expression. Standard glucose breath test and nutrient challenge test were performed. The duodenal microbial load was higher in patients with FGID (0.22±0.03) than controls (0.07±0.05; P=0.007) and patients with UC (0.01±0.05) or CD (0.02±0.09), (P=0.0001). While patients treated with proton pump inhibitors (PPI) had significantly higher bacterial loads than non-users (P<0.05), this did not explain differences between patient groups and controls. Bacterial load was significantly (r=0.21, P<0.016) associated with the symptom response to standardised nutrient challenge test. Methane, but not hydrogen values on glucose breath test were associated with bacterial load measured utilising qPCR. Utilising qPCR, a diagnosis of FGID and treatment with PPI were independently associated with increased bacterial loads. Increased bacterial loads are associated with an augmented symptom response to a standardised nutrient challenge.

Interactive Learning of Assembly Processes using Digital Assistance

Abstract Due to an increasing demand for individualized products and the resulting high variability in manufacturing processes, flexibility and cognitive skills of human workers are highly important for manual assembly processes. Nowadays, novice workers are often trained by colleagues or foremen in addition to and alongside their main work. Since time is usually scarce and the procedure can be highly variable, one solution for the companies can be the introduction of digital assistance systems. Hence, the focus of this contribution is the initial learning procedure of the assembly of a new and complex product. Therefore, a user study was conducted in close cooperation with an industrial partner to compare the traditional way of training to the self-paced learning with a digital assistance system. During the execution of the user study, objective data was recorded to allow precise measurements of the individual learning progress. Furthermore, the subjective learning experience was assessed using a customized questionnaire and a standardized task load metric. The evaluation of the study results suggests that learning autonomously with a digital assistance system leads to similar performance curves as learning the process through a personal explanation.

Channel load based interference‐aware scheduling in military communication environment

SummaryThis work is focused to improve the military communication by introducing Channel Load based Average Link Interference Estimation (CLAIE) which will assess the channel load level of every route path, thus the interference reduced communication can be guaranteed. Channel load metric is capable of identifying interference superior to the previous metrics specified in IEEE 802.11 networks. This routing metric attains greater performance, when measured in the environment affected with interference, which contains inadequate radio channel resources such as wireless mesh network. This research offers a sequence of formulas in order to calculate link‐interference, path‐interference, and node‐interference and, in addition, to choose the paths containing the least average link‐interference amid the source and target, and an interference‐aware routing protocol is presented. Paths identified by this protocol are likely to evade the places containing greater interferences, decreasing the amount of retransmissions of packet and collisions, bringing about greater network throughput and increased lifespan. We present this average link interference‐aware routing. The overall methodology is deployed in military communication environment. In the NS2 simulation environment, the complete assessment of the research technique is implemented and proved that the presented research technique gives improved result.

Congestion detection for QoS-enabled wireless networks and its potential applications

We propose a mechanism for monitoring load in quality of service (QoS)-enabled wireless networks and show how it can be used for network management as well as for dynamic pricing. Mo- bile network traffic, especially video, has grown exponentially over the last few years and it is anticipated that this trend will continue into the future. Driving factors include the availability of new af- fordable, smart devices, such as smart-phones and tablets, together with the expectation of high quality user experience for video as one would obtain at home. Although new technologies such as long term evolution (LTE) are expected to help satisfy this demand, the fact is that several other mechanisms will be needed to manage overload and congestion in the network. Therefore, the efficient management of the expected huge data traffic demands is critical if operators are to maintain acceptable service quality while making a profit. In the current work, we address this issue by first investi- gating how the network load can be accurately monitored and then we show how this load metric can then be used to provide creative pricing plans. In addition, we describe its applications to features like traffic offloading and user satisfaction tracking.

Load Density Analysis of Mobile Zigbee Coordinator in Hexagonal Configuration

Mobility is one of the major new paradigms of the current Internet, and this is driving most of the research activity in networking throughout the World. The Mobility of Wireless Sensor Networks (WSN) has become a hot research theme in recent years due to its wide range of applications ranging from medical research to military. The widely adopted standard for wireless sensor network platform is IEEE 802.15.4/ZigBee. The IEEE 802.15.4/ZigBee is considered the “technology of choice” due to low-power, cost-effective communication and the reliability they provide. In this paper, we perform extensive network evaluation, to study the Effect of coordinator mobility on ZigBee mesh network, using OPNET Modeler. In mobile coordinator, the type of the trajectory along with the node density and the traffic are the major factors that decide the system performance. The results obtained from the wide analysis of ZigBee mesh network shows variation when the routers are placed at Hexagonal configuration with a mobile coordinator. In this paper, variations in load metric is analyzed in hexagonal configuration by enabling and disabling ACK. Thus the status of ACK also plays a critical role in analysing load metrics.

A novel load metric with enhanced ability of distinguishing different load status

This paper has proposed a new metric for characterizing the load of a uniprocessor computer. This metric is defined as a ratio of the average waiting time experienced by computing tasks to the average idle time of the processor. This definition is based on two important observations. As the load becomes heavier, the average idle time of a processor becomes shorter, and the average waiting time experienced by computing tasks becomes longer. The new load metric aims to have an enhanced ability in distinguishing different load status. The valid comparison of different load status using the new load metric is subject to the satisfaction of certain conditions: a majorization has to be satisfied between two processes of the measures (idle time or waiting time). The ability of the new load metric on distinguishing different load status has been validated through numerical simulations. The results showed that the new load metric can facilitate balancing the load among multiple servers better than the conventional load metric of average utilization, when they are used as the task assignment criteria.

On gLite WMS/LB monitoring and Management through WMSMonitor

The Workload Management System is the gLite service supporting the distributed production and analysis activities of various HEP experiments. It is responsible of dispatching computing jobs to remote computing facilities by matching job requirements and the resource status information collected from the Grid information services. Given the distributed and heterogeneous nature of the Grid, the monitoring of the job lifecycle and of the aggregate workflow patterns generated by multiple user communities, and the reliability of the service are of great importance. In this paper we deal with the problem of WMS monitoring and management. We present the architecture and implementation of the WMSMonitor, a tool for WMS monitoring and management, which has been designed to meet the needs of various WMS user categories: administrators, developers, advanced Grid users and performance testers. The tool was successfully deployed to monitor the progress of WMS job submission activities during HEP computing challenges. We also describe how, for each WMS in a cluster, WMSMonitor produces status indexes and a load metric that can be used for automated notification of critical events via Nagios, or for ranking of service instances deployed in load balancing mode.

Client‐driven load balancing through association control in IEEE 802.11 WLANs

AbstractThe growth of IEEE 802.11 wireless local area networks (WLANs) (Wi‐Fi) brings new possibilities of getting connected in public spaces, known as Hot Spots. Current client‐access point associations are an interesting research topic because in these scenarios, users tend to be ‘gregarious’ and essentially static. Under IEEE 802.11 standards, association and roaming decisions are made by client devices and most implementations are based on signal strength measurements; i.e. a client station selects the access point (AP) that provides the strongest signal, which leads to an uneven distribution of clients and load between neighbouring APs. As it can be observed in practical scenarios, the default AP‐client association scheme followed in IEEE WLANs, produces unfair situations. This work provides means to effectively alleviate this performance issue and also gives details for a feasible implementation. In this paper we analyse how new IEEE 802.11 standards will allow new radio measurements to provide more efficient association decisions. We propose a new load metric that will produce client‐driven associations that ensure greater fairness and throughput. Copyright © 2008 John Wiley &amp; Sons, Ltd.

Effective Load Metric and Efficient Initial Job Placement for Dynamic Load Balancing in Cluster

High performance clusters are being configured specially to give data centers that require extreme performance, the processing power they need. In Cluster Computing Environment the data latency time has significant impact on the performance, when the data is accessed across clusters. Instead of processing power, memory and I/O have become the new bottleneck in achieving efficient load balance at higher performance for cluster computer systems. Initial job placement and load balancing are the key aspects affecting the performance. In this research, data access patterns, memory and CPU utilization and locality of memory are combined to consider as load metric in the load balancing aspect across cluster. A scheduling algorithm based on this metric has been proposed to dynamically balance the load in the cluster. Initial job placement for a job in the cluster considers data access patterns and for load balance aspect metric constitutes CPU, memory utilization including locality of memory. Experimental results show performance improvement to considerable levels with the implementation of the concept, specifically when the cost of data access from other clusters is higher and is proportionate to the amount of data.

동적 부하 분산 시스템에서 효율적인 작업 크기 계산을 통한 성능 개선

클러스터와 같은 분산 시스템에서 초기 작업 배치 시, 할당할 프로세스의 자원 요구량을 정확히 예측하여 작업을 분배할 수 있다면 보다 나은 시스템 성능을 얻을 수 있게 된다. 이 때 임의의 작업을 적절한 호스트에 배치하기 위해서 자원 기반 초기 작업 배치 (resource-based initial job placement) 기법은 그 작업의 자원 사용량을 미리 예측할 필요가 있다. 하지만 잘못된 자원 예측은 동적 부하 분산 시스템의 성능을 크게 떨어뜨리는 원인이 된다. 따라서 본 논문에서는 잘못된 예측에 의한 문제를 해결하기 위해 새로운 부하 기준을 제안한다. 새로운 부하 기준을 사용한 자원 기반 초기 작업 배치 기법은 프로세스의 유형에 관한 사전 지식 없이도 동작하는 장점을 가진다. 실험을 통해 본 논문은 동적 부하 분산 시스템에서 제안하는 방식이 기존의 방식에 비해 향상된 성능을 가짐을 보인다. In distributed systems like cluster systems, in order to get more performance improvement, the initial task placement system precisely estimates and correctly assigns the resource requirement by the process. The resource-based initial job placement scheme needs the prediction of resource usage of a task in order to fit it to the most suitable hosts. However, the wrong prediction of resource usage causes serious performance degradation in dynamic load balancing systems. Therefore, in this paper, to resolve the problem due to the wrong prediction, we propose a new load metric. By the new load metric, the resource-based initial job placement scheme can work without priori knowledge about the type of process. Simulation results show that the dynamic load balancing system using the proposed approach achieves shorter execution times than the conventional approaches.

Impact of topology on Bluetooth Scatternet

To utilize Bluetooth as a layer 2 multi‐hop subnet for global IP network, there are two missing protocols in current Bluetooth stack: network formation and routing. In this paper, we propose our network formation and routing protocols optimized for such Bluetooth subnset usage scenarios to fill this gap. In this paper, we first present some observations on performance degradations of Bluetooth PAN due to network topologies and topology change when radio independant protocols are implemented. And then we analyze the reason of performance degradation. Based on our analysis, we first propose a flexible scatternet formation algorithm under conference scenario for multi‐hop communication. By using proposed method, scatternet can be formed flexibly with star, mesh, or linked line based on several parameters like number of maximum piconets that a gateway Bluetooth device can participate, and whether loops are needed in the resulting scatternet to achieve better network performance. To utilize topology information in multi‐hop communication, we propose a Cross‐layer Optimized Routing for Bluetooth (CORB) CORB is a QoS‐extended AODV routing protocol with mainly two optimizations between networking layer and underlying Bluetooth MAC layer. The first optimization is to use a new load metric. (LM) in QoS routing protocol instead of number of hops in conventional best effort routing. LM is derived from estimation of nodes’ link bandwidth, which reflects the different roles of nodes in Bluetooth scatternet. This proposal helps routing protocol to bypass heavily loaded nodes, and find route with larger bandwidth. The second optimization is to adjust LM and some MAC layer parameters in response to the unstable network topology caused by movement and change of indoor radio condition. Finally, We present some simulation and experiment results based on implementation, which prove the effectiveness of our protocols.

Declustering and load-balancing methods for parallelizing geographic information systems

Declustering and load balancing are important issues in designing a high performance geographic information system (HPGIS), which is a central component of many interactive applications such as real time terrain visualization. The current literature provides efficient methods for declustering spatial point data. However, there has been little work toward developing efficient declustering methods for collections of extended objects, like chains of line segments and polygons. We focus on the data partitioning approach to parallelizing GIS operations. We provide a framework for declustering collections of extended spatial objects by identifying the following key issues: (1) work load metric; (2) spatial extent of the work load; (3) distribution of the work load over the spatial extent; and (4) declustering method. We identify and experimentally evaluate alternatives for each of these issues. In addition, we also provide a framework for dynamically balancing the load between different processors. We experimentally evaluate the proposed declustering and load balancing methods on a distributed memory MIMD machine (Cray T3D). Experimental results show that the spatial extent and the work load metric are important issues in developing a declustering method. Experiments also show that the replication of data is usually needed to facilitate dynamic load balancing, since the cost of local processing is often less than the cost of data transfer for extended spatial objects. In addition, we also show that the effectiveness of dynamic load balancing techniques can be improved by using declustering methods to determine the subsets of spatial objects to be transferred during runtime.