Energy-efficient link assessment in wireless sensor networks

Abstract

Abstrncf-For energyeonstrained stationary wireless networks of sensom, selection of links with high quality rate helps to ensure reliable long-term operation. During the implementation of a protocol targeting industrial applications of such systems, it was found that it is advantageous to acquire accurate information about the availability and quality of the RF communication links prior to the network topology formation. "Link assessment" as part of the initialization process, accomplishes this task by assessing a sufficient number of packets exchanged between neighburing nodes. This paper introduces and analyzes two different approaches to link assessment: The first approach is a random nondeterministic scheme that allows for a probabilistic guarantee of collision-free packet exchange. An alternative method is described which employs 'ronstant-weight codes' and provides a determinklic guarantee 01 success. In particular, a speciul class of constant-weight codes, known as optical orthogonal codes, are considered. Since, these codes are cyclically permutable, they make the link assessment process simpler, and therefore they are preferred over other codes. We evaluate the performance of these methods based on their energy consumption, time duration, and implementation complexity.transceivers, communication takes place via multi-hop through neighboring nodes. The information flow may be from the sensor nodes to a network access point e.g., the base station, or from the network access point to sensor nodes. or among sensors themselves. In order to fully utilize the benefits of a multi-hop RF network, the system should also be selfconfiguring and able to adapt to environmental changes by reconfiguration.The nodes are typically small and battery operated and are expected to live for at least couple of years. Therefore. energyeficiency is a crucial factor for all tasks performed throughout the lifetime of the system. Energy can he saved by communicating over reliable links and by avoiding collision of packets, which eliminates the necessity of re-transmission.Wireless sensor networks are still in the development stage with some industrial interest. e.g.. Ember, Intel_ ABB, Sensicast, Parc, Bosch. Most industrial applications for wireless sensor networks are low cost and deal with stationary scenarios. In spite of the low cost of these wireless sensor nodes (typically less than $5) it is still not low enough to allow the use of redundant sensors as proposed in current academic research. This implies that there is still a need to gather information from every availahle sensor, requiring a reliable path to every sensor in the network. During the implementation of a protocol targeting industrial applications of stationary wireless sensor networks, it was found that it is advantageous to acquire accurate information about the availability and quality of the RF communication links prior to the network topology formation. This task is accomplished by the "link assessment process".The link assessment process includes discovery ...

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