On-demand information retrieval enables users to query and collect up-to-date sensing information from sensor nodes. Since high energy efficiency is required in a sensor network, it is desirable to disseminate query messages with small traffic overhead and to collect sensing data with low energy consumption. However, on-demand query messages are generally forwarded to sensor nodes in network-wide broadcasts, which create large traffic overhead. In addition, since on-demand information retrieval may introduce intermittent and spatial data collections, the construction and maintenance of conventional aggregation structures such as clusters and chains will be at high cost. In this paper, we propose an on-demand information retrieval approach that exploits the name resolution of data queries according to the attribute and location of each sensor node. The proposed approach localises each query dissemination and enable localised data collection with maximised aggregation. To illustrate the effectiveness of the proposed approach, an analytical model that describes the criteria of sink proxy selection is provided. The evaluation results reveal that the proposed scheme significantly reduces energy consumption and improves the balance of energy consumption among sensor nodes by alleviating heavy traffic near the sink.
Wireless sensor networks are envisioned to support autonomous and spontaneous networking for a wide range of applications. Node addresses are essential to enable successful communication in sensor networks. This paper presents a novel address autoconfiguration scheme to automatically configure network-layer and MAC-layer addresses for sensor nodes with energy efficiency and fault tolerance. Computer simulation is conducted to study performance of address configuration, and the simulation result shows that the proposed address configuration scheme has low address collision rate and configuration overhead, even in case that netwiork size is large and address space is small.
I. INTRODUTCTIONWith the advances in wireless technology and embedded computing, small wireless sensing devsices will be capable of organizing inito networks [11. Networks of such devices present significant new opportunities for the ubiquitous commun:ity. To ensure adequate coverage an:d fault tolerance, researchers envision that these sensor networks will be comprised of a very large number of nodes, ranging from hundreds to several tlousands [2]. A large network size not only prohibits manual setup of the network, necessitating autonomous operation, but also eliminates the option of battery replacement, leading to that power conservation becomes critically important [3],[4].Node addresses are essential to enable successful communication in sensor networks. A network-layer address is essential fur sensor nodes to successfully counnmunicate with each other [5]. It can be used to distinguish various nodes for packet routing and the reconstruction of packet fragkments; and can be used as the ID of an ACK message. Due to energy constraints and the small data size in sensor netWorks, long globally unique addresses will have a high energy cost in a sensor network. Although random addressing is a simple way for each node to obtain an address, the uniqeness of the address can not be guaranteed and the incidence of address collisions will be high when the address is short.In a sensor network,, data collection, data packet delivery anld data process are generally operated iniside the sensor network [6]. Therefore, it is possible fbr a sensor node to use addresses that are locally unique in a network as its networklayer address. In other words, eaach node in a distributed system can have a network-layer address that is unique with respect to the connectivity of the network. For consvenience, the network-wide locally unique address w ill be termed as "NLU" address in the following description. A NLU address has the potential short address size, and will reduce packet size for sensor networks.
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