Browsing by Subject "Wireless Sensor Networks"

Now showing 1 - 9 of 9

Open Access
Active set partitioning scheme for extending the lifetime of large wireless sensor networks
(2010) Kalkan, Mustafa
Wireless Sensor Networks consist of spatially distributed and energy-constrained autonomous devices called sensors to cooperatively monitor physical or environmental conditions such as temperature, sound, vibration, pressure or pollutants at different locations. Because these sensor nodes have limited energy supply, energy efficiency is a critical design issue in wireless sensor networks. Having all the nodes simultaneously work in the active mode, results in an excessive energy consumption and packet collisions because of high node density in the network. In order to minimize energy consumption and extend network life-time, this thesis presents a centralized graph partitioning approach to organize the sensor nodes into a number of active sensor node sets such that each active set maintains the desired level of sensing coverage and forms a connected network to perform sensing and communication tasks successfully. We evaluate our proposed scheme via simulations under different network topologies and parameters in terms of network lifetime and run-time efficiency and observe approximately 50% improvement in the number of obtained active node sets when compared with different active node set selection mechanisms.
Open Access
Algorithms for sink mobility in wireless sensor networks to improve network lifetime
(2008) Koç, Metin
A wireless sensor network (WSN) consists of hundreds or thousands of sensor nodes organized in an ad-hoc manner to achieve a predefined goal. Although WSNs have limitations in terms of memory and processor, the main constraint that makes WSNs different from traditional networks is the battery problem. Since sensor nodes are generally deployed to areas with harsh environmental conditions, replacing the exhausted batteries become practically impossible. This requires to use the energy very carefully in both node and network level. Different approaches are proposed in the literature for improving network lifetime, including data aggregation, energy efficient routing schemes and MAC protocols, etc. Main motivation for these approaches is to prolong the network lifetime without sacrificing service quality. Sink (data collection node) mobility is also one of the effective solutions in the literature for network lifetime improvement. In this thesis, we focus on the controlled sink mobility and present a set of algorithms for different parts of the problem, like sink sites determination, and movement decision parameters. Moreover, a load balanced topology construction algorithm is given as another component of network lifetime improvement. Experiment results are presented which compare the performance of different components of the mobility scheme with other approaches in the literature, and the whole sink mobility scheme with random movement and static sink cases. As a result, it is observed that our algorithms perform better than random movement and static cases for different scenarios.
Open Access
Constructing energy efficient bluetooth scatternets for wireless sensor networks
(2004) Saginbekov, Sain
The improvements in the area of wireless communication and micro-sensor technology have made the deployment of thousands, even millions, of low cost and low power sensor nodes in a region of interest a reality. After deploying sensor nodes in a target region of interest, which can be inaccessible by people, people can collect useful data from the region remotely. The sensor nodes use wireless communication and can collaborate with each other. However, sensor nodes are battery powered and therefore they have limited energy and lifetime. This makes energy as the main resource problem in sensor networks. The design process for sensor networks has to consider energy constraints as the main factor to extend the lifetime of the network. The wireless technology used for communication among sensor nodes can affect the lifetime of the network, since different technologies have different energy consumption parameters. Bluetooth, being low power and low cost, is a good candidate for being the underlying wireless connectivity technology for sensor networks tailored for various applications. But in order to build a large network of Bluetooth-enabled sensor nodes, we have to first form a Bluetooth scatternet. The topology of the Bluetooth scatternet affects the routing scheme to be used over that topology to collect and route informaton from sensor nodes to a base station. And routing scheme, in turn, affects how much energy is consumed during transport of information. Therefore, it is important to build a Bluetooth scatternet wisely to reduce and balance the energy consumption, hence extend the lifetime of a sensor network. In this thesis work, we propose a new Bluetooth scatternet formation algorithm to be used in Bluetooth-based sensor networks. Our algorithm is based on first computing a shortest path tree from the base station to all sensor nodes and then solving the degree constraint problem so that the degree of each node in the network is not greater than seven (a Bluetooth constraint). We also propose a balancing algorithm over the degree constrained tree to balance the energy consumption of the nodes that are closer to the base station. The closer nodes are the nodes that will consume more energy in the network since all traffic has to be forwarded over these nodes. Our simulation results show that our proposed algorithm improves the lifetime of the network by trying to reduce the energy consumed during data transfer and also by balancing the load among the nodes.
Open Access
Fog supported wireless sensor networks for forest fire detection
(2018-09) Amira, Fouad
Fog computing is a new paradigm that aims to extend the concept of cloud computing to the edge of the network, providing the end users network with extra storage and processing power. One big contribution of Fog computing is in the context of Wireless Sensor Networks (WSNs). WSNs consist of cheap, battery powered and simple processing devices that make it fall short in handling relatively complex processes.Therefore, applying fog computing to WSNs will fill the gap between the cloud and the network and by that, it will enable computationally extensive operations which were earlier possible only at the cloud side. In our work, we exploit the processing power provided by the Fog to minimize the power consumption of WSNs for forest fire detection through the use of data mining techniques. The Fog layer uses the data generated by the network such as temperature, humidity, rain, etc., to train a model that predicts the probability of forest fires. Next, the Fog layer uses this model to predict the mode of operation of the network based on the current condition of the environment. While a high predicted probability of forest fire results in an increased activity of the WSN, a low fire probability results in a reduced network activity. As a result, our proposed model optimizes the energy consumption within the WSN and improves the detection time of forest fires.
Open Access
An inquiry into the metrics for evaluation of localization algorithms in wireless ad hoc and sensor networks
(2008) Aksu, Hidayet
In ad-hoc and sensor networks, the location of a sensor node making an observation is a vital piece of information to allow accurate data analysis. GPS is an established technology to enable precise position information. Yet, resource constraints and size issues prohibit its use in small sensor nodes that are designed to be cost efficient. Instead, most positions are estimated by a number of algorithms. Such estimates, inevitably introduce errors in the information collected from the field, and it is very important to determine the error in cases where they lead to inaccurate data analysis. After all, many components of the application rely on the reported locations including decision making processes. It is, therefore, vital to understand the impact of errors from the applications’ point of view. To date, the focus on location estimation was on individual accuracy of each sensor’s position in isolation to the complete network. In this thesis, we point out the problems with such an approach that does not consider the complete network topology and the relative positions of nodes in comparison to each other. We then describe the existing metrics, which are used in the literature, and also propose some novel metrics that can be used in this area of research. Furthermore, we run simulations to understand the behavior of the existing and proposed metrics. After having discussed the simulation results, we suggest a metric selection methodology that can be used for wireless sensor network applications.
Open Access
Location based multicast routing algorithms for wireless sensor networks
(2007) Bağcı, Hakkı
Multicast routing protocols in wireless sensor networks are required for sending the same message to multiple different destination nodes. Since most of the time it is not convenient to identify the sensors in a network by a unique id, using the location information to identify the nodes and sending messages to the target locations seems to be a better approach. In this thesis we propose two different distributed algorithms for multicast routing in wireless sensor networks which make use of location information of sensor nodes. Our first algorithm groups the destination nodes according to their angular positions and sends a message toward each group in order to reduce the number of total branches in multicast tree which also reduces the number of messages transmitted. Our second algorithm calculates an Euclidean minimum spanning tree at the source node by using the positions of the target nodes. According to the calculated MST, multicast message is forwarded to destination nodes. This helps reducing the total energy consumed for delivering the message to all target nodes since it tries to minimize the number of transmissions. We compare these two algorithms with each other and also against another location based multicast routing protocol called PBM according to success ratio in delivery, number of total transmissions, traffic overhead and average end to end delay metrics. The results show that algorithms we propose are more scalable and energy efficient, so they are good candidates to be used for multicasting in wireless sensor networks.
Open Access
Power efficient data gathering and aggregation in wireless sensor networks
(Association for Computing Machinery, 2003) Tan, H. Ö.; Körpeoǧlu, İ.
Recent developments in processor, memory and radio technology have enabled wireless sensor networks which are deployed to collect useful information from an area of interest The sensed data must be gathered and transmitted to a base station where it is further processed for end-user queries. Since the network consists of low-cost nodes with limited battery power, power efficient methods must be employed for data gathering and aggregation in order to achieve long network lifetimes. In an environment where in a round of communication each of the sensor nodes has data to send to a base station, it is important to minimize the total energy consumed by the system in a round so that the system lifetime is maximized. With the use of data fusion and aggregation techniques, while minimizing the total energy per round, if power consumption per node can be balanced as well, a near optimal data gathering and routing scheme can be achieved in terms of network lifetime. So far, besides the conventional protocol of direct transmission, two elegant protocols called LEACH and PEGASIS have been proposed to maximize the lifetime of a sensor network. In this paper, we propose two new algorithms under name PEDAP (Power Efficient Data gathering and Aggregation Protocol), which are near optimal minimum spanning tree based routing schemes, where one of them is the power-aware version of the other. Our simulation results show that our algorithms perform well both in systems where base station is far away from and where it is in the center of the field. PEDAP achieves between 4x to 20x improvement in network lifetime compared with LEACH, and about three times improvement compared with PEGASIS.
Open Access
Real-time routing with priority scheduling and power adjustment in wireless sensor networks
(2008) Çelikkaya, Emine Büşra
Many wireless sensor network applications require real-time communication, and real-time applications require packets to reach destination on time. However, applications may send packets with different priorities and hence delay bounds for packets may vary significantly. Therefore packet differentiation in the network is essential for meeting the deadline requirements. We propose a routing protocol that supports real-time communication by utilizing transmit power adjustment in order to meet the deadline of urgent packets and use energy efficiently. Our protocol also provides packet scheduling and gives precedence to urgent packets. We have conducted experiments on our sensor network testbed to observe the effects of transmit power on end-to-end delay. As expected, increasing transmit power increases the range and link quality, and reduces the number of hops to reach destination. Therefore adjusting transmit power has a great effect on delivery time and can reduce the end-to-end delay. Our protocol, Real-time Routing with Priority Scheduling and Power Adjustment, uses different levels of transmit power for packets with different priorities. It sends urgent packets with maximum power to minimize end-to-end delay and lower priority packets with reduced power to save energy and balance the load on nodes. Simulation results show that our routing protocol increases the deadline meet ratio of packets and reduces the transmit energy spent per packet when compared to routing protocols that use fixed transmit power. Additionally, results indicate that our approach lessens the interference on sensor nodes that are caused by other transmissions and helps balancing the load on the nodes.
Open Access
Sleep scheduling for energy conservation in wireless sensor networks with partial coverage
(2006) Yardibi, Tarık
Wireless sensor networks, which consist of many sensor devices communicating with each other in order to sense the environment, is an emerging field in the area of wireless networking. The primary objective in these wireless networks is the efficiency of energy consumption. Since these networks consist of a large number of sensors, allowing some of the nodes to sleep intermittently can greatly increase the network lifetime. Furthermore, some applications do not require 100% coverage of the network field and allowing the coverage to drop below 100%, i.e., partial coverage, can further increase the network lifetime. A sleep scheduling algorithm must be distributed, simple, scalable and energy efficient. In this thesis, the problem of designing such an algorithm which extends network lifetime while maintaining a target level of partial coverage is investigated. An algorithm called Distributed Adaptive Sleep Scheduling Algorithm (DASSA) which does not require location information is proposed. The performance of DASSA is compared with an integer linear programming (ILP) based optimum sleep scheduling algorithm, an oblivious algorithm and with an existing algorithm in the literature. DASSA attains network lifetimes up to 89% of the optimum solution, and it achieves significantly longer lifetimes compared with the other two algorithms. Furthermore, the minimum number of sensors that should be deployed in order to satisfy a given partial coverage target with a certain probability while maintaining connectivity is computed and an ILP formulation is presented for finding the minimum number of sensors that should be activated within the set of deployed sensors.