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Réseaux urbains de capteurs sans-fil : Applications, caractérisation et protocoles

Présentée Devant 1 Quentin Lampin 2, 1
2 URBANET - Réseaux capillaires urbains
Inria Grenoble - Rhône-Alpes, CITI - CITI Centre of Innovation in Telecommunications and Integration of services
Abstract : Wireless Sensors are small electronic devices made for measuring physical properties of their environment and communicating them wirelessly to an information system. In this thesis, we study existing network architectures (long-range vs multihop) and protocols (MAC and routing protocols) to devise the best-suited configuration for typical urban wireless Sensor Network use-cases, i.e. applications, QoS/energy constraints and network topology.To that effect, we provide comprehensive analytical models to compare the different families of MAC protocols in terms of Delivery Rate and Energy Consumption, e.g. syn- chronous vs asynchronous, contention-based vs direct access etc. Headlines results include a near-optimal synchronization scheme with regards to the overall energy consumption in a data collection use-case, a mathematical framework to devise the least energy-cost contention algorithm for a given Delivery Rate and closed-form expressions of the Energy Consumption and Delivery Rate for popular access control protocols.These results are then synthesised in a comparison study of the two prevailing urban sensors network architectures, i.e. long-range and multihop. We show that long-range sen- sor networks are best-suited for low-traffic and sparser network topologies, i.e. less than 4 frames per node per day with less than 5000 nodes sharing the same collection gateway, or sink. Indeed, in our model setup, i.e. 100 bit/s to 2400bits/s radio chips, such networks perform better in terms of energy efficiency versus Delivery Rate than our reference mul- tihop architecture. Higher traffic loads and denser network topologies, however, demand switching to a multihop network operating a synchronous MAC protocol on higher bitrate radios. In our modelisation setup, i.e. a commercial 19.2Kbits radio chip, multihop net- works are shown to cope with up to 4 times more trafic and 2 times more nodes in the topology than long-range networks.Based on the analysis of the architectures best suited for each use-case scenario, i.e.low traffic loads/sparse network and high traffic loads/dense network, we identify suitable optimisations to improve the QoS performance and energy efficiency of said architectures. Those optimisations are threefold. First, we improve on the energy efficiency of the arbi- tration of the medium access by defining a cascading tournament contention algorithm. This protocol, named Cascading Tournament MAC Protocol (CT-MAC), resolve multiple timeslots allocation in a single, energy efficient contention tournament. Compared to prior existing works, where each medium access is solved independently, CT-MAC decreases the energy expenditure of the medium arbitration by up to 12%. This gain is achieved by reducing the medium polling, i.e. carrier sense, frequency by up to the number of simul- taneous access that are resolved in a single tournament. Second, we propose an adaptive relaying scheme for the long-range network architecture named The Self-Adapting Receiver Initiated MAC protocol (SARI-MAC). This scheme is an attempt to cope with coverage holes that occurs when using long-range in a dense urban habitat by letting sensor nodes relay communications of nodes whose link budgets are incompatible with the QoS requi- rements of the network. To that effect, we propose a receiver-initiated MAC protocol that self-adapts to the traffic condition so that the duty-cycle of relayers is kept as low as possible with respect to the load of frames to relay. SARI-MAC shows a decrease of the energy-consumption of up to 50% when compared to the existing state-of-the-art protocol RI-MAC. Unlike RI-MAC, SARI-MAC also proves to self-adapt to the traffic condition of all the setups of our study, without the need of calibrating its parameters.Finally, we proposed an opportunistic relaying scheme named QOR, The QoS orien- ted Opportunistic Routing Protocol. QOR is a routing protocol that exploits long-range, opportunistic radio links to provide faster and more reliable transmissions. To that effect, QOR proposes a joint routing structure and addressing scheme that allows identifying a limited set of nodes than can become opportunistic relayers between a source sensor and the sink. Those nodes then follow an original cascaded acknowledgement mechanism that brings reliable acknowledgment and ensures a replication-free forwarding of the data frames. QOR shows a significant decrease of the delivery delay with up to 40% shorter delays in our simulation setups. QOR also improves on the reliability of the transmissions (up to 15% more deliveries) and on the energy consumption (5% less energy consumption).
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Submitted on : Tuesday, December 16, 2014 - 11:30:28 AM
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Présentée Devant, Quentin Lampin. Réseaux urbains de capteurs sans-fil : Applications, caractérisation et protocoles. Réseaux et télécommunications [cs.NI]. INSA de Lyon, 2014. Français. ⟨tel-01095797⟩

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