Due to hierarchical sensor networks is capable to elimination extra sensing information and reduce extra communication load, it is remarkably important to increase scalability of network and prolong lifetime of network. In the paper, we focus on relay nodes of two-layered heterogeneous sensor networks. When relay nodes transmit data without scheduling, the collision probability must increase. It will cost too much for energy to re-transmission data and listening channel. To avoid extra energy consumption, we build a grid network according to RSS, and naming IP for every relay node on the grid network. Then, all leaf nodes join a certain cluster and naming IP according to RSS. Through the exclusive IP it schedule mission for TDMA. Only when relay node comes in specific slot, it wakes up to transmit or receive data, the remaining time to sleep and save power consumption. Besides, in order to balance energy consumption of backbone or non-backbone relay nodes and prolong lifetime of network, we proposal three routing protocol (DTS¡BREARBS¡BVIPOS). According to simulation results, VIPOS is the longest lifetime above them.

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Τα ασύρματα δίκτυα αισθητήρων (WSNs) είναι πολύ αναγνωρισμένα στις μέρες μας και γύρω από αυτά έχουν αναπτυχθεί χιλιάδες εφαρμογές που με χρήση άλλης τεχνολογίας ήταν σχεδόν ακατόρθωτες. Ένα WSN αποτελείται από κόμβους οι οποίοι είναι προγραμματισμένοι να επικοινωνούν και να συλλέγουν πληροφορίες μέσω των αισθητήρων που είναι αναρτημένοι πάνω τους. Οι πληροφορίες ή σύνολο των πληροφοριών καταλήγουν τελικά στους κόμβους που είναι προγραμματισμένοι ως τερματικοί κόμβοι ή βάσεις. Οι βάσεις είναι συνήθως συνδεδεμένες με ένα υπολογιστή και μεταφέρουν τα δεδομένα του δικτύου σε αυτόν. Τα κύρια χαρακτηριστικά των ασύρματων δικτύων αισθητήρων είναι η χαμηλή κατανάλωση ενεργείας των συσκευών-κόμβων (motes), η σταθερότητα και η απλότητα του κώδικα καθώς και η μεγάλη αξιοπιστία. Μερικές εφαρμογές των WSNs είναι για παράδειγμα η μέτρηση της υγρασίας στον τάπητα ενός γηπέδου γκολφ, η παρακολούθηση των κρίσιμων μεγεθών σε μεγάλες κατασκευές (π.χ. οι τάσεις των νημάτων μιας κρεμμαστης γέφυρας ή η παρακολούθηση της καταπόνησης των δοκών ενός ουρανοξύστη). Στα πλαίσια της διπλωματικής εργασίας αυτής παρουσιάζουμε ένα ασύρματο δίκτυο αισθητήρων όπου οι αισθητήρες είναι έξυπνες κάμερες! Παρουσιάζει μεγάλο ενδιαφέρον η μελέτη ενός τέτοιου δικτύου καθώς και η ανάπτυξη εφαρμογών γύρω από αυτό. / Wireless Sensor Networks (WSNs) are very much recognized these days, and thousands of applications have been developed in relation to them, which, would have been impossible if other technologies were used. A WSN is made up of nodes programmed to collect information through sensors attached to them and transmit them. The information ends up finally to the nodes which are programmed as terminal nodes or base-stations. These base-stations are usually connected to a computer and transfer the data that have been retrieved from the network to it. The main features of a WSN is the low energy consumption by the node equipment (motes), the stability and simplicity of the code as well as their great reliability. Some applications of the WSNs are, for example, the measurement of humidity in a golf course, the monitoring of the crucial sizes in great constructions (e.g. the tensions of the fibers in a suspension bridge, the monitoring of the strains of girders in a skyscraper) Within the context of this thesis, we present a WSN where the sensors are smart cameras! The study of such a network presents great interest as well as the development of applications based on it.

Design trade-offs between estimation performance, processing delay and communication cost for a sensor scheduling problem is discussed. We consider a heterogeneous sensor network with two types of sensors: the first type has low-quality measurements, small processing delay and a light communication cost, while the second type is of high quality, but imposes a large processing delay and a high communication cost. Such a heterogeneous sensor network is common in applications, where for instance in a localization system the poor sensor can be an ultrasound sensor while the more powerful sensor can be a camera. Using a time-periodic Kalman filter, we show how one can find an optimal schedule of the sensor communication. One can significantly improve estimation quality by only using the expensive sensor rarely. We also demonstrate how simple sensor switching rules based on the Riccati equation drives the filter into a stable time-periodic Kalman filter. ￜ 2008 IEEE. / <p>QC 20110224</p>