J. Xu’s scientific contributions

The nodes in Wireless Sensor Networks (WSNs) are usually powered by battery. It is extremely important to let the nodes deliver data to the destination in an energy-efficient manner such that the WSNs have longer runtime. In this paper, the 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; and allows a node to change its transmission power to transmit the encoded packets, which are 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.

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 battery with very limited energy and wireless links are prone to losing packet. Moreover, in some WSN applications, it is required that the collected data are delivered to the sink node within a given time. Hence, it is extremely significant to develop an energy-efficient, low-delay, and reliable data gathering scheme for WSN applications. In this paper, Reed-Solomon (RS) code is applied to improve the reliability of packet delivery. It aims to form an Optimization Problem (OP) that integrates with energy consumption, Data Gathering Ratio (DGR), data gathering delay, and coding schemes. The set that contains the Simple Reed-Solomon (S-RS) codes is presented, and it is proved that any n members of the set are linearly independent. The data gathering scheme, called the S-RS data gathering scheme, which applies the S-RS codes, intra-segment coding, and inter-segment coding, is described in detail. In addition, based on probability theory, the Overall Energy Consumption (OEC), the DGR, and the data gathering delay under the S-RS scheme are derived, which are used to build the OP that minimizes the OEC with the constraints of DGR and data gathering delay. The number of the feasible solutions of the OP is small such that it can be easily solved using enumeration method. 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 constraints of DGR and data gathering ratio are met. Numeric analysis and simulation results show that the S-RS scheme achieves a higher DGR and a lower delay with lower energy consumption. Moreover, the derived OEC, DGR, and data gathering delay can be used in optimizing the parameters by using the S-RS scheme so as to maximize the DGR, minimize the data gathering delay, or optimize two or three of the OEC, DGR, and data gathering delay.