JSQE: Joint Surveillance Quality and Energy Conservation for Barrier Coverage in WSNs
0
Citation
22
Reference
10
Related Paper
Abstract:
Barrier coverage is a fundamental issue in wireless sensor networks (WSNs). Most existing works have developed centralized algorithms and applied the Boolean Sensing Model (BSM). However, the critical characteristics of sensors and environmental conditions have been neglected, which leads to the problem that the developed mechanisms are not practical, and their performance shows a large difference in real applications. On the other hand, the centralized algorithms also lack scalability and flexibility when the topologies of WSNs are dynamically changed. Based on the Elfes Sensing Model (ESM), this paper proposes a distributed Joint Surveillance Quality and Energy Conservation mechanism (JSQE), which aims to satisfy the requirements of the desired surveillance quality and minimize the number of working sensors. The proposed JSQE first evaluates the sensing probability of each sensor and identifies the location of the weakest surveillance quality. Then, the JSQE further schedules the sensor with the maximum contribution to the bottleneck location to improve the overall surveillance quality. Extensive experiment results show that our proposed JSQE outperforms the existing studies in terms of surveillance quality, the number of working sensors, and the efficiency and fairness of surveillance quality. In particular, the JSQE improves the surveillance quality by 15% and reduces the number of awake sensors by 22% compared with the relevant TOBA.Bottleneck detection in manufacturing is the key to improving production efficiency and stability in order to improve capacity. Yet common bottleneck detection methods in industry and academia lack either accuracy or practicability, or both, for dynamic systems. The new methodology is conducted by the observation of processes and inventories. Blocked processes and full inventories indicate a downstream bottleneck. Starved processes and empty inventories indicate an upstream bottleneck. Through subsequent observations of multiple process states and inventory levels within a system, it is possible to determine the direction of the bottleneck at the given time and hence to find the momentary bottleneck in the system. The shifting of bottlenecks can be observed directly. Work-sampling techniques can be used to obtain a long-term picture of the dynamically shifting bottleneck. The new methodology does not require any calculations, statistics, or time measurements. Hence the method is suited for practical use by shop floor supervisors and clerks. The direct observation of the bottleneck also gives additional information about the underlying causes of the bottlenecks, simplifying the improvement of the system capacity. Extensive field testing of the method received positive feedback not only from management but also shop floor operators. The method is already in use at the Robert Bosch GmbH, where it is known as the bottleneck walk.
Cite
Citations (32)
Identification
Traffic system
Cite
Citations (11)
A variety of established approaches exist for the detection of dynamic bottlenecks. Furthermore, the prediction of bottlenecks is experiencing a growing scientific interest, quantifiable by the increasing number of publications in recent years. Neglected, on the other hand, is the diagnosis of occurring bottlenecks. Detection methods may determine the current location of a bottleneck, while predictive approaches may indicate the location of an upcoming bottleneck. However, mere knowledge of current and future bottlenecks does not enable concrete actions to be taken to avoid the bottlenecks, nor does it open up any immediate advantage for manufacturing companies. Since small and medium-sized companies in particular have limited resources, they cannot implement improvement measures for every bottleneck that occurs. Due to the shifts of dynamic bottlenecks, the selection of the mostsuitable stations in the value stream becomes more difficult. This paper therefore contributes to the neglected field of bottleneck diagnosis. First, we propose two data-driven metrics, relative bottleneck frequency and relative bottleneck severity, which allow a quantitative assessment of the respective bottleneck situations. For validation purposes, we apply these metrics in nine selected scenarios generated using discrete event simulation in a value stream with a serial manufacturing line. Finally, we evaluate and discuss the results.
Cite
Citations (0)
The performance of a manufacturing or logistic system is determined by its constraints. Therefore, in order to improve the performance, it is necessary to improve the constraints, also known as the bottlenecks. Finding the bottlenecks, however, is not easy. We compare the two most common bottleneck detection methods, based on the utilization and the waiting time, with the shifting bottleneck detection method developed by us, for AGV systems. We find that the two conventional methods have many shortcomings compared to the shifting bottleneck detection method. In the example presented here, conventional methods are either unable to detect the bottleneck at all or detect the bottleneck incorrectly. The shifting bottleneck detection method not only finds the bottlenecks but also determines the magnitude of the primary and secondary bottlenecks.
Cite
Citations (54)
Buffer (optical fiber)
Cite
Citations (11)
Cite
Citations (3)
Programming autograding at scale is a requirement for many online learning applications. This paper is a case study report of the hunt for the bottleneck that was hindering the multicore scalability of one such autograder - EvalPro. EvalPro is the autograding module of our in-house online learning application Bodhitree, and is used regularly for program autograding in our introductory programming course. A baseline experiment found that the maximum autograding throughput provided by EvalPro did not increase much beyond that provided with 8 cores. We however had larger servers (e.g. 64 core machines) for use for a scaled up deployment of the application. To address this issue, we followed an empirical approach first, hypothesizing various bottlenecks and checking whether removing them increased scalability. We followed this with profiling experiments on microbenchmarks that finally helped us identify the bottleneck: an off-the-shelf program not a part of our application, but was simply used by our application. Our main conclusions from the study are that bottleneck identification studies remain complex and time consuming and must be done systematically, and that stable well-known, off the shelf programs may also not display multi-core scalability, as they may not have been built for such a purpose.
Multi-core processor
Profiling (computer programming)
Cite
Citations (0)
ACID-compliant DBMSs are said to be difficult to scale their performance by using many more processors, which means that they are difficult to enjoy the benefits of recent manycore systems that wide-spread use of multi-core processors has made practicable. Since DBMSs are indispensable in most of IT systems, scalability issues should be addressed to fulfill the demand of handling large quantity of data. This paper proposes a viable approach for solving scalability issue, in which lock-related bottleneck will be identified from event trace based measurements and scalability will be improved by replacing the bottleneck-lock with fine-grained locks. This paper also describes a case study on the application of the proposed method, in which the scalability of a many-core system in executing DBT-1 transactions with MySQL adopting the InnoDB storage engine has been successfully improved. Since applying the proposed method produced the increase in maximum throughput of the 16- CPU system by 1.6 times, the method is promising, as long as lock-related bottlenecks are of concern.
Lock (firearm)
Multi-core processor
TRACE (psycholinguistics)
Cite
Citations (1)
The performance of a manufacturing or logistic system is determined by its constraints. Therefore, in order to improve the performance, it is necessary to improve the constraints, also known as the bottlenecks. Finding the bottlenecks, however, is not easy. This paper compares the two most common bottleneck detection methods, based on the utilization and the waiting time, with the shifting bottleneck detection method developed by us, for AGV systems. We find that the two conventional methods have many shortcomings compared to the shifting bottleneck detection method. In the example presented here, conventional methods are either unable to detect the bottleneck at all or detect the bottleneck incorrectly. The shifting bottleneck detection method not only finds the bottlenecks but also determines the magnitude of the primary and secondary bottlenecks.
Cite
Citations (10)
As a weak point, bottleneck plays a crucial role in improving the property of the whole water system. In this paper, sensitivity computation formula is defined and corresponding mathematical model is established to confirm the bottleneck of water network. And the case proves that the bottleneck streams and units can be easily confirmed by the method in this paper.
Cite
Citations (0)