Research On The Model And Protocols Of Data Gathering In Wireless Sensor Networks Based On Network Coding

In recent years, research on wireless sensor networks (WSNs) has attracted more and more considerable attention. Besides, data gathering, as one of the main applications of WSNs, has also been studied more and more extensively and deeply. In the process of data gathering, sensor nodes are deployed in some area, sense their environment, produce information and transmit them collaboratively to the sink (also called base station) by multi-hop transmit manner. Since sensor nodes are energy constrained and computing resource constrained, how to transmit data securely, accurately and quickly, while saving energy as much as possible became the main objective of research on the data gathering model and protocols. Recently, a new communication technology, i.e. network coding, has been proposed and starts to be used in WSNs. Comparing with the data gathering protocols based on traditional store-and-forward routings, those protocols based on network coding obtain a variety of performance gains, including the improvement of throughput, the enhancement of robustness and the reduction of energy consumption and time delay, etc. However, after the rise of the Internet of Things, as one of the key technologies, WSNs obtain several new features, which put forward several new requirements on data gathering protocols. Specifically, first of all, WSNs used in the Internet of Things are usually large-scale networks, so they have to save more energy consumption and reduce more time delay. Secondly, needs on data gathering are richer. Sometimes, the sink needs to gather data of all the nodes periodically, and sometimes it only needs to gather the data of a certain node. Thirdly, types of data to be gathered are diversified. Sometimes it needs all the raw data, and sometimes it only needs an aggregated result of all the raw data. Finally, sensor nodes no longer belong to the same administration authority. Therefore, they are selfish and independent. Thus, in the process of data gathering, it not only requires providing security, but also requires maintaining the interest of sensor nodes in cooperation. In summary, this paper established a data gathering model used in WSNs with the above new features. In addition, it studied the data gathering protocols used in this model based on network coding, and made them suitable for being used in the environment with selfish and independent nodes. The main work and innovation of this paper are as follows:(1) It established a comprehensive model of data gathering in WSNs (CM-DG-WSN) which owns the above new features. First of all, generally, it works under the time-driven data gathering mode, i.e., all the sensor nodes transmit their data periodically to the sink. Once a node detects that a data exceeds its threshold, it will work under the event-driven mode. In this situation, only this node will transmit its data to the sink. Secondly, this model considers two types of data to be gathered, which are raw data and aggregated data. Thirdly, this model considered the selfishness and independence of sensor nodes. As a result, it not only requires providing security in the process of data gathering, but also requires maintaining the interest of nodes in cooperation.(2) It proposed a time-driven data gathering protocol, called flat-based network coding data gathering (FNCDG) protocol, which takes the intra-session network coding and opportunistic routing as its main technologies. This paper compared FNCDG with a traditional store-and-forward routing both by theoretical methods and by simulations. Their results are consistent with each other, which both demonstrate the fact that FNCDG could offer significant benefits in terms of both energy consumption and time delay in time-driven data gathering.(3) It studied how to further save energy in the process of aggregated-data gathering, where the sink only wants an aggregated result of all the data rather than the raw data themselves sensed from an area. The aggregation is hard to be performed on encoded data when using a flat-based network coding protocol. Thus, flat-based ones may waste much energy on transmitting a great deal of encoded data for decoding at the sink on the contrary. As a result, this paper proposed a cluster-based network coding data gathering (CNCDG) protocol. It reduces the encoded data to be transmitted than the flat-based network coding protocol (FNCDG) by permitting cluster heads to perform some aggregation in the transmission process, so as to saves more energy.(4) It studied the data-privacy-preserving problem in an event-driven data gathering scenario, i.e., preventing private source data from being acquired by non-intended internal nodes which use the encoded data that flowed by them to perform derivation. Unlike those existing research results, this paper considered not only attacks from any single internal node, but also those from multiple nodes that are in cahoots with each other. This paper proposed a data-privacy-preserving network coding (DPPNC) protocol by making use of the vulnerability of network coding to pollution and data obfuscation. This protocol requires low overhead on computation and communication. Then, to further improve the security of this protocol, this paper proposed two extended protocols, called HDPPNC-1and HDPPNC-2respectively.(5) It proposed a formalized model, called secure network coding-based data gathering (SNCDG) model. This model can not only preserve private source data, but also prevent external pollution attacks. In addition, this paper designed a data-privacy preserving and pollution preventing (DPP&PP) protocol, used in this model by using data obfuscation. This protocol not only can prevent both internal attacks and external attacks, but also requires low overhead on computation and communication.