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

As one of the most important science and technologies in the beginning of twenty-first century, wireless sensor network, to be a bridge between the physical world, the information world and human society, is widely used in industrial production and our lives because of its idea of "ubiquitous". However, with the expansion of the application requirements and application fields, sensor nodes often need to be attached to the moving objects, or deployed in the moving medium, for example underwater circumstance. In addition, the movements of sensor nodes and the practical application environment often make the communication links between sensor nodes have the feature of intermittent connectivity. The wireless sensor network with characteristics of node mobility and intermittent connectivity is referred as Delay Tolerant Mobile Sensor Network(DTMSN).As a non-connection oriented network, DTMSN can be wildly used in the field of intelligent transportation, information access,underwater information collection et al., and has drawn wide attention.As a basic function of network, data transmission is the basis and premise of the operation of the network. In DTMSN, data is difficult to be transmitted to the destination timely and reliably because of the mobility and intermittent connectivity of sensor nodes. Hence, the DMTSN has the drawbacks of high communication overhead, high latency, low reliability and poor security, which has become the bottleneck of the practical application of the DTMSN. Therefore, the most important issue that to be resolved is to design efficient and reasonable data transmission mechanism to transmit data fast and reliably, and achieve the balance of delivery rate, communication cost and transmission delay.To solve the problems in the data transmission of DTMSN, we make a comprehensive analysis and summary on the hot points and state-of-the-art of data transmission of DTMSN, and do a deeply research on the key technologies of data transmission based on the characteristics of network and its applications. The main contents and results of the paper are as follows:1. An Adaptive Contact Probing Scheme (ACPS) of DTMSN is proposed, which is based on the study of stochastic properties of Random Way-Point (RWP) mobility model. The main idea of ACPS is to adjust adaptively the time and the number of contact probing according to the arrival rate of contact arrival process, which can effectively deduce the probing energy cost and contact discovery delay by improving the probe efficiency and accuracy. Based on the user’s computing ability, we customized two schemes, ACPS-EIP and ACPS-EPP, to determine the probing time and the number of probes. Compare with the Fixed-cycle Probing Scheme (FPS), ACPS has higher discovery ratio and lower discovery delay with lower energy cost, and is helpful to improve the performance of the data transmission of DTMSN.2. Proposed a Motion State-based Delivery scheme (MSD) for DTMSN. MSD is composed of message delivery and message management. During the process of messages forwarding, sensor nodes divide themselves into multiple states based on the motion trends to the base station and using two communication frequencies:f1and f2. By using the broadcasting signal of base station (BS) on the frequency of f1, sensor nodes can compute their own motion states and delivery probabilities which provide the basis for messages transmitting between nodes on the frequency of f2In order to improve network performance, MSD employs the message survival time and prior forwarding mechanism of own messages to manage the message queue. MSD is mainly used for network-aware data upload. Simulation results show that the proposed MSD data delivery scheme has a higher message delivery ratio with lower transmission cost and less data delivery delay than other DTMSN data delivering approaches.3. In order to reduce the latency of broadcasting, a Netcoding-based Broadcast Transmission scheme (NBT) is proposed for DTMSN. In NBT, the data are batched transmitted by BS, and each batch contains finite number of original packets. BS encodes the original packets of one batch with uncorrelated vectors and unicasts them to the different sensor nodes in its coverage, and the sensor nodes exchange encoded packets with each other by flooding mechanism. Because of the packets are encoded, the probability that sensor nodes have the same packets is low and the correlation of data between sensor nodes is reduced too. To improve the cost of broadcasting in NBT, a Netcoding-based Efficient Broadcast Transmission scheme (NEBT) is proposed. NEBT optimize the strategy for data exchange between nodes, and try to broadcast messages when the nodes have multiple contacts, which can decrease the communication overhead. Simulation results show that the proposed NBT and NEBT schemes can effectively reduce the broadcasting delay, and NEBT has lower communication overhead.4. Traditional mutual authentication mechanisms for DTMSN cannot resist the cloning attack. In order to improve the security of data transmission, this paper proposes a Mutual Authentication scheme based on Physical unclonable function (MAP). We take advantages of the physical characteristics of chip with Physical Unclonable Function (PUF) to implement the mutual authentication of sensor nodes by using the stored "Challenge-Response Pairs"(CRPs) in each other. The MAP scheme gets rid of the dependence on the CRPs database and has the advantages of high speed, safe and anti-cloning attack. Based on the MAP scheme, this paper presents a hierarchical Key Management scheme based on PUF (KMP). The KMP mechanism has the advantages of simple, safe and efficient, and can effectively protect the communication security of DTMSN.In summary, in order to resolve the problems of data transmission and improve its performance for DTMSN, we make a deeply research on the key technologies of data transmission of DTMSN based on the application requirements and network characteristics by using the technologies of statistical analysis, netcoding and PUF et al. And we proposed specific solutions for contact probing, information collection, data broadcasting and communication security, which are proved correct and feasible by simulations and analysis. The results of our research can improve the performance of data transmission and promote the practical application of DTMSN.