An Efficient Distributed Data Extraction Method for Mining Sensor NetworkNetwork’’’’ssss Data Azhar Mahmood 1, Ke Shi 1 and Shaheen Khatoon 1 1 School of Computer and Applied Technology Huazhong University of Science & Technology (HUST) Wuhan, China Abstract applied to sensor network. Development of algorithms that A wide range of Sensor Networks (SNs) are deployed in real consider the characteristics of sensor networks, such as world applications which generate large amount of raw sensory energy and computation constraints, network dynamics, data. Data mining technique to extract useful knowledge from faults, constitute an active area of current research. these applications is an emerging research area due to its crucial Several techniques have been proposed in the literature for importance but still it’s a challenge to discover knowledge knowledge extraction from sensor data e.g. association efficiently from the sensor network data. In this paper we proposed a Distributed Data Extraction (DDE) method to extract rules [12-14] frequent patterns mining, knowledge data from sensor networks by applying rules based clustering and discovery over data streams[15, 16], and clustering [17] to association rule mining techniques. A significant amount of enhance the performance of SNs. In these applications sensor readings sent from the sensors to the data processing large numbers of sensors are distributed in the physical point(s) may be lost or corrupted. DDE is also estimating these world and generate streams of data that need to be missing values from available sensor reading instead of combined, monitored, and analyzed on central side. requesting the sensor node to resend lost reading. DDE also However, collecting all data in a central computing node apply data reduction which is able to reduce the data size while with a high computational power does not optimize the use transmitting to sink. Results show our proposed approach of energy-costly transmissions. Indeed in most cases all exhibits the maximum data accuracy and efficient data extraction in term of the entire network’s energy consumption. raw data are not needed, we are only interested in an estimate of a small number of parameters. Instead of Keywords: Sensor Network, Data Mining, Data Extraction, computing such parameters on the sink node, a better Association Rules, Clustering, Frequent Pattern, Data Reduction. approach suggests that each node contributes to the computation. Since accessing the data, processing data, and transmitting data are all tasks that consume energy 1. Introduction which is a limited resource in sensor node. So, what should be the solution for theoretical and applicative Advances in wireless communication and microelectronic research in SNs for efficient data extraction? This question devices led to the development of low power sensors and motivates us to develop a distributed data extraction (DDE) the deployment of large scale sensor networks. With the method which pre-processes the raw data directly at sensor capabilities of pervasive surveillance sensor networks has node. Hence, instead of sending the raw data to the central attracted significant attention in many applications site, sensor nodes use their processing abilities to locally domains, such as habitat monitoring [1, 2], object tracking carry out simple computations and transmit only the [3, 4], environment monitoring [5-7], military [8, 9], required and pre-processed data. The processing performs disaster management [10], just to mention a few at each sensor node is helpful for taking real time decision example[11]. These applications yield huge volume of as well as can serve as prerequisite for development of dynamic, geographically distributed and heterogeneous scalable data mining technique on central side. In DDE data. The raw data if analyzed in an appropriate way might method the major contributions are following: help to automatically and intelligently solve a variety of 1. Rule based clustering technique for efficiently tasks thus making the human life more safe and extracting data from sensors nodes to optimize comfortable. Recently, extracting knowledge from sensor network lifetime in term of energy and data size. data has been received a great deal of attention by the data These rules are identified by applying association mining community. However, the extremely constrained rule mining on cluster head (CH) node. nature of sensors and the potentially dynamic behavior of 2. A significant amount of sensor readings sent from SNs hinder the use of traditional mining approaches the sensors to the data processing point(s) may be commonly applied on other domains. Traditional lost or corrupted. In DDE this problem is approaches are meant for multi-step methodologies and addressed by estimating missing values from multi-scan algorithms, which cannot be straightforwardly available sensor reading instead of requesting the sensor node to resend lost reading. The key consideration the distributed nature of wireless sensor advantage of our missing value estimation is that networks to discover frequent patterns of events with it is done directly at sensor node and can be used certain spatial and temporal properties. Whereas, Chong et to identify the behavior of the sensor nodes. Data al. finds strong rules from sensor readings and use these Reduction is applied which is able to reduce the learnt rules as a triggers to control sensor network data size received from sensor nodes. The operations or supplement sensor operations. For example, extracted data is more compact than raw sensor triggers activated from the rules could be used to sleep data and can therefore be more efficiently sensors or reduce data transmissions to conserve sensor transmitted to sink from the sensor network. energy. Our proposed in-network technique is different The rest of this paper is organized as follow: after from Romer’s and Chong et al. approach in a way that introducing basic concept of SNs data mining in Section 1; extracted rules are used to cluster the sensor node and we provided an overview of related work of data estimating missing sensor’s values. extraction methods either centralized or distributed in For missing values identification Halatchev and Section 2. Proposed method, algorithms and its details are Gruenwald [22] proposed a centralized methodology presented in section 3; Simulation results are presented in called Data Stream Association Rule Mining (DSARM) to section 4 and finally sections 5 concludes the paper and identify the missing sensor’s readings. It uses Association suggest directions for the future work. Rule Mining algorithm to identify sensors that report the same data for a number of times in a sliding window called related sensors and then estimates the missing data from a 2. Related Work sensor by using the data reported by its related sensors. For the clustering issues in sensor networks, several Several techniques have been proposed in the literature to methods have been proposed. Clustering protocol for node enhance the performance of SNs, such as frequent pattern clustering such as LEACH [23], ACE [24], HEED [25], mining, clustering, classification, prediction, just to DEEH [26] and Energy Aware Protocol (EAP) [27] are mention a few examples. In this section we review past proposed to solve energy consumption problems in SNs. studies in term of three categories related to this research: These protocols probabilistically selects several nodes as Association Rule Mining, Missing value identification and cluster heads according to their residual energy, and then Clustering methods. remainder nodes are joined into clusters to minimize the Tanbeer et al. [18] and Boukerche and Samarah [12] communication cost between them and corresponding proposed centralized data mining models to find cluster heads. Yoon and Shahabi [28], Beyens et al. [29], association among the sensors nodes. They proposed tree- Yeo et al. [30] proposed data correlation clustering based data structure that used FP-growth approach to architecture for WSNs in which cluster-heads obtain the frequency of all events detecting sensor. spatiotemporally correlate. In Beyens et al. approach Tanbeer et al. used Sensor Pattern Tree (SP-Tree) to cluster head maintains a local prediction model that is used construct a prefix-tree and reorganize the tree in a to select a suitable node of the cluster to be activated. The frequency descending order. Through the reorganization idea is to put a sensor node to sleep when there are no the SP-tree can maintain the frequently event-detecting objects in its sensing region. In Yoon and Shahabi sensors’ nodes at the upper part of the tree, which provides approach nodes are groups based on similar values and high compactness in the tree structure. Once the SP-tree is only one reading per group is transmitted. Whereas, in Yeo constructed FP-growth mining technique is applied to find et al. approach the size of data size is reduced at each the frequent event-detecting sensor sets. Boukerche, and S. cluster head by applying data suppression technique. Samarah [19] used Positional Lexicographic Tree (PLT) All the above techniques have focused on extracting data structure for mining association rules in which the event- regarding the phenomenon monitored by the sensor nodes, detecting sensors are the main objects of the rules in which the mining techniques are applied to the sensed regardless of their values. The mining begins with the data received from the sensor nodes and accumulated at a sensor having the maximum rank by generating the central database. In our work, we have proposed an in- frequent patterns from its PLT in a recursive way. The network data extraction approach to extract the pre- computation required at each recursion to update the PLT processed sensor data required for mining by applying rule involved in the prefix part of a pattern. Therefore, the two based clustering to save energy and in-network missing database scans requirement and the additional PLT update value estimation to increase the accuracy of extracted data. operations during mining limit the efficient use of this Furthermore a data reduction method is used to reduce the approach in handling SNs data.