Energy efficient data transmission in wireless sensor networks

Abstract

Despite the good perspectives of wireless sensor networks (WSNs), there are still lots of design challenges, as sensor nodes are usually low-power devices with short transmission ranges. Specifically, to increase the network lifetime, it is a critical issue to make efficient use of battery power. Since data transmission almost spends the most part of the energy at sensors, designing energy efficient data transmission schemes is clearly one of the most important issues. The transmission modes in WSNs usually can be classified into three categories, e.g., transmissions within the sensor nodes, transmissions from the sink node to the sensor nodes and transmissions from the sensor nodes to the sink(s). In this thesis, we will investigate the design of these three kinds of data transmissions with efficient energy consumption. Particularly, we identify three problems as our research targets: 1) design of routing algorithm to collaborate sensors so as to complete queries with service composition, 2) design of network coding based data dissemination from the sink to all the sensor nodes in the network so as to decrease the total number of transmissions, 3) design of a novel geographic K-ancast routing protocol to route the data from sensors to any K out of all the sinks. For our first research target, we design an efficient service composition routing to complete the collaboration between sensors. In WSNs, a query task may require a set of services, which are provided by sensor nodes, and may be carried out repetitively with a given frequency during its lifetime. A service composition routing shall be provided for each execution of such a persistent query task. However, due to the sleep scheduling designed at sensor nodes, a service composition routing may not always be valid during the lifetime of a persistent query. When a query task needs to be conducted over a new service composition routing, a routing update procedure is involved which consumes energy. In this thesis, we study service composition routing design which minimizes the number of service composition routings during the lifetime of a persistent query. We also aim to minimize the total service composition cost when the minimum number of required service composition routings is derived. The optimality of proposed algorithms provides the service composition for a persistent query with minimum energy consumption. For our second research targets, we design an efficient data dissemination scheme to complete the transmission from the sink node to the sensors. In WSNs, it is often necessary to update the software running on sensors, which requires reliable dissemination of large data objects to each sensor with energy efficiency. However, due to sleep scheduling designed for energy efficiency, some sensors may not receive some packets at some time slots. In addition, due to the unreliability of wireless communication, a sensor may not successfully receive a packet even when it is in active mode. Thus, retransmission of such packets to those sensors is necessary, which consumes more energy and increases the delay of data dissemination cycle. In this thesis, we propose a network coding based approach in data dissemination such that data dissemination can be accomplished at the earliest time. Thus, less energy is consumed. The impact of packet loss probability and the sleep probability of sensors on network coding gain is analyzed. Simulation results demonstrate the effectiveness and scalability of the proposed work. Finally, we propose a novel distributed geographic K-anycast routing protocol (GKAR) to complete the transmissions from sensors to sinks. To efficiently archive and query data in WSNs, multi-sink schemes and distributed storage systems have been proposed recently. However, such distributed access cannot be fully supported and exploited by existing routing protocols in a large-scale WSN. In this thesis, we will address this challenging issue and propose GKAR protocol for WSNs, which can efficiently route data from a source sensor to any K destinations (e.g., sinks or storage nodes). To guarantee K-delivery, an iterative approach is adopted in GKAR where in each iteration, GKAR will determine not only the next hops at each node, but also a set of potential destinations for every next hop node to reach. Efficient algorithms are designed to determine the selection of next hops and destination set division at each intermediate node. We analyze the complexity of GKAR in each round and we also theoretically analyze the expected number of rounds required to guarantee K-delivery. Simulation results demonstrate the superiority of the GKAP scheme in reducing the total duration and transmission overhead for finding K destinations.