Coding Based Energy-efficient Reliable Data Delivering Scheme For Wireless Sensor Networks

Wireless Sensor Network(WSN) usually adopts the low-power and low-rate IEEE 802.15.4 standard in its Medium Access Control(MAC) and Physical(PHY) layers. In the WSN, the nodes are powered by batteries with quite limited energy, and it is difficult to replace or recharge the batteries after the WSN is deployed. Hence, low power components are usually adopted in the nodes to reduce energy consumption. As a result, radio signals are transmitted with extreamly low power in the nodes such that they are sensitive to noise, which could not bring with a higher packet delivery reliability. Therefore, it is extremely significant to develop an energy-efficient reliable data delivery scheme for WSNs.The main work of this dissertation contains two aspects, which are described as follows:First, the basic principles of erasure coding and network coding are introducted. For the WSNs applying tree to gather data, Reed-Solomon(RS) code is used to improve reliability. A Simple RS(S-RS) code is designed, based on which the S-RS data gathering scheme is presented. In addition, the Overall Energy Consumption(OEC), the Data Gathering Ratio(DGR), and the data gathering delay(DGD) under the S-RS scheme are derived and used to build the Optimization Problem(OP) that minimizes the OEC with the constraints of DGR and DGD. Through solving the OP, the nodes are able to find the optimal values of the parameters for packet encoding and packet retransmissions such that energy consumption in the S-RS scheme is minimized while the constrains in both DGR and DGD are met. In other words, with the S-RS scheme, the nodes are able to fragment and encode the data to be delivered adopting the intra-segment coding or the inter-segment coding. The minimum OEC with the constrains of DGR and DGD is achieved by optimizating the three parameters: the number of the sensed data contained in each segment, the coding redundancy, and the maximum number of transmission retries defined in the MAC layer. Moreover, the S-RS data gathering scheme is realized in TelosW motes on the Ubuntu 12 and TinyOS operating systems, in which the application programs are developed in NesC programming language. The result of the experiment on the TelosW motes and those of simulations and numeric analysis show that the S-RS scheme achieves a higher DGR with a lower energy consumption.Second, based on the idea of opportunistic routing, an Energy-efficient Reliable Opportunistic Routing(EROR) is presented. The EROR uses the forwarding cost, which takes into account node’s residual energy and the total energy consumption expended by the nodes over a wireless link; chooses the forwarding set consisting of forwarding nodes(FNs), the main FN, and the assistant FNs efficiently; and allows a node to change its transmission power to transmit the encoded packets generated by randomly linear network coding to the forwarding set such that the data are delivered to the destination in a multi-hop, reliable, and energy-efficient way. Simulation results indicate that the EROR outperforms the existing CodePower routing in terms of network lifetime and energy consumption.The proposed S-RS data gathering scheme and the EROR routing protocol can be applied in WSNs and the outcomes presented in this dissertation are significant in theory and in practice.