Research On Technologies Of Data Transmission For Delay Tolerant Mobile Sensor Network

Recognized as one of the most important technologies in the21st century, wireless sensor network(WSN) has been attacked a lot of attentions in academia, and it could work well in many challenging special environments where traditional networks are difficult to be applied, such as remote areas, emergency communications fields and areas with harsh natural conditions. With the continuous expansion of its application requirements, sensor nodes are often deployed in a large monitoring area, and need to be placed on moving objects. In this network, the stable end-to-end communication connect can not be provided as traditional networks, because sensor nodes have the characteristics of the random movements, sparsity and the limited communication range. In order to efficiently transmit data packets in these environments, the concept of delay tolerant mobile sensor network(DTMSN) is proposed to face these challenges.DTMSN is a kind of network which is characterized by node random mobility and intermittent connectivity between nodes. As a non-connection oriented network, DTMSN is suitable for many applications, such as environmental data acquisition, virus spreading informantion monitoring, battlefield information gathering, et al, and has drawn wide attentions. At present, most of exsiting DTMSN research still foucs on improving data delivery routing mechanism, and many research achievements in this field has been obtained. Its main goal is to achieve a higher data delivery radio with the lower delivery delay and energy consumption. Based on the in-depth analysis and systematical summary of relevant works, we do a comprehensive and detailed research on DTMSN data delivery technology based on the characteristics of this network. The main studies foucs on the following issues:(1) How to efficiently discover neighbor nodes with a lower probing energy consumption in an asynchronous case;(2) How to efficiently delivery data to improve the delivery radio, decrease the delivery delay and energy consumptions;(3) How to efficient achieve the secure data delivery with a lower computational cost. The innovative research achievements are shown as following:1. To solve the issue of neighbor discovery, an Efficient Asynchronous Probing Scheme(EAPS) for DTMSN is proposed. EAPS divides the status of sensor nodes into two categories:wakeup and sleeping, and designes a slotted-wakeup schedule based oncoprime cycle pairs to improve the probing accuracy and decrease the discovery delay under the low energy consumption. Additionally, EAPS gives a reasonable regional plan based on the study of stochastic properties of Random Way-Point(RWP) mobility model, and optimal coprime cycle pairs are selected in these different regions to further improve the discovery radio and reduce energy consumption.2. To solve the issue of data delivery routing, a Motive State-Aware data Delivery scheme(MSAD) for DTMSN is proposed. MSAD adopts two communication frequencies f1, f2to obtain motive state of sensor nodes and forward data. On the frequency of f1, MSAD uses a new positioning method based on time different of arrival(TDOA) which has a lower cost than GPS, sensor nodes obtain their own motive state by cyclical positioning and calculate their delivery probability by predicting their position in the next moment. On the frequency of f2, data delivey routing between sensor nodes will be determined by comparing the delivery probability. Additionally, to efficiently manage the message queue, MSAD employs the principle of selfish(SF) and the survival time(ST) to avoid the issue of imbalance number of message copies caused by only adopting ST and the issue of the large delivery delay caused by only adopting SF 3. To solve the issue of secure data delivery, we analyze the applicability of identity-based cryptography in DTMSN, and an Identity-based Signature scheme with Batch Authentication(ISBA) is proposed to reduce the computational cost for DTMSN. ISBA is composed of online/offline signature, batch authentication and message forwarding algorithm improve-ment based on MSAD. Specially, online/offline signature has a very light computational cost at the online signature phase; Batch authentication could reduce the computation cost by validating multiple signatures simultaneously instead of verifying them one by one; Additionally, the minimum remaining space(MRS) is introduced to improve MSAD that new connections can’t be established until the remaining space of the receiver isn’t less than MRS, therefore, average message number in each batch authentication increases and the computational cost reduces. Simulation results show that the improved mechanism of MSAD does not induce negative impact on the delivery performance.