Delay Tolerant Sensor Networks Research Articles

A Novel Hybrid MAC Protocol for Sustainable Delay-Tolerant Wireless Sensor Networks

Efficient MAC protocols are fundamental to conserve energy and enable sustainable delay-tolerant sensor networks (DTSNs). They can be explored to reduce energy consumption, deal with relaxed latency requirements, support mobility and address diverse traffic loads. In this paper, we theoretically analyze the performance of reservation-based and contention-based MAC protocols in DTSNs regarding throughput and energy consumption, respectively. According to the derived theoretical results, we propose a TRaffic-adaptive energy-efficient MAC protocol (TREEM) to achieve better data transmissions as well as energy efficiency, in order to satisfy DTSN requirements. More precisely, our protocol can dynamically switch its working mode between contention and reservation to adapt to the varying data traffic. In addition, to further improve the energy efficiency of DTSN, our algorithm can also calculate the more suitable duty/active period length. The simulation results of TREEM demonstrate better performance in terms of energy efficiency and traffic adaptability than the schedule-based MAC protocol TDMA, the contention-based protocol CSMA, and the traffic-adaptive protocol TRAMA under mobile DTSN environments.

A data sample algorithm applied to wireless sensor network with disruptive connections

This paper presents a data sample algorithm applied to wireless sensor network applications with disruptive connections. Additionally, it defines a model for delay-tolerant sensor network where drop strategies are applied to improve the phenomenon coverage in an application that monitors the forest temperature incidence for wildlife observation. The environmental application model comprises: i) Phenomenon generation based on a Gaussian random field along with the Matern covariance model; ii) Sensing nodes deployment based on simple sequential inhibition process with a mobile sink node following a random walk process; iii) Data collection and processing based on a data-aware drop strategy; and iv) Phenomenon reconstruction based on simple kriging interpolation. This research employed the data-aware drop strategy and compared it with the others, reported in the literature. Besides the satisfactory application of this model, the results show that the performance of data-aware drop strategy is twice better than conventional ones in all evaluated scenarios.

On Applicability of Network Coding Technique for 6LoWPAN-based Sensor Networks.

In this paper, the applicability of the network coding technique in 6LoWPAN-based sensor multihop networks is examined. The 6LoWPAN is one of the standards proposed for the Internet of Things architecture. Thus, we can expect the significant growth of traffic in such networks, which can lead to overload and decrease in the sensor network lifetime. The authors propose the inter-session network coding mechanism that can be implemented in resource-limited sensor motes. The solution reduces the overall traffic in the network, and in consequence, the energy consumption is decreased. Used procedures take into account deep header compressions of the native 6LoWPAN packets and the hop-by-hop changes of the header structure. Applied simplifications reduce signaling traffic that is typically occurring in network coding deployments, keeping the solution usefulness for the wireless sensor networks with limited resources. The authors validate the proposed procedures in terms of end-to-end packet delay, packet loss ratio, traffic in the air, total energy consumption, and network lifetime. The solution has been tested in a real wireless sensor network. The results confirm the efficiency of the proposed technique, mostly in delay-tolerant sensor networks.

Robot Delay-Tolerant Sensor Network for Overhead Transmission Line Monitoring

The rapid development of the smart grid has led to higher maintenance cost and greater scalability of transmission lines. An effective and secure monitoring system for power lines has become a bottleneck restricting the intellectualization of power grids. To address this problem, a novel method is proposed for the intelligent monitoring of power grids (Robot Delay-Tolerant Sensor Network, RDTSN) based on an inspection robot, Wireless Sensor Network (WSN) and Delay-Tolerant Sensor Network (DTSN) to achieve low-cost, energy-efficient, elastic and remote monitoring of power grids. With RDTSN, a smart grid can detect the fault of transmission lines and evaluate the operational state of power grids. To build an effective monitoring system for a smart grid, this research focuses on designing a methodology that achieves efficient and secure delivery of the data inspected on transmission lines. Multiple RDTSN scenarios are performed, in which different routing algorithms are explored to determine the optimal parameters, with a balance in network performance and financial cost. Furthermore, a data delivery strategy is introduced to ensure communication security.

A new model of vehicular ad hoc networks based on artificial immune theory

Vehicular ad hoc networks (VANETs) are highly mobile and wireless networks intended to aid vehicular safety and traffic monitoring. To achieve these goals, we propose a VANET model based on immune network theory. Our model outperforms the delay tolerant mobility sensor network (DTMSN) model over a range of node numbers in terms of data packet arrival delay, arrival ratio, and throughput. These findings held true for the on-demand distance vector and connection-based restricted forwarding routing protocols. The model performed satisfactorily on a real road network.

MAC transmission protocols for delay-tolerant sensor networks

Wireless data transmissions often experience long delays in sensor networks due to harsh environments and limited resources. Many sensor applications allow transmission latency and require improved performance in energy conservation, throughput, reliability and mobility. The MAC layer is suitable for detecting unstable wireless channels and improve transmission performance in Delay-Tolerant Sensor Networks (DTSN). This paper builds on various strategies on MAC designs in DTSN, and presents a comprehensive study on MAC protocols in DTSNs. We study MAC protocols, which trade long, unpredictable delays in data transmissions for energy conservation, mobility, throughput and/or reliability. We also present MAC protocols in DTSN which adapt their access control and transmission processes to the predictable delays. From the aspect of delay tolerance, the paper examines these MAC protocols through the trade-off between delay and other performance metrics, and shows the effectiveness and limitations of these MAC designs. Next, we review and analyze current MAC protocols that are suitable for DTSNs, and then discuss future research trends towards the design of new MAC protocols for DTSNs.

A MAC transmission strategy in sparse Vehicular Delay-Tolerant Sensor Networks

In wireless sensor networks that lack telecommunication infrastructure, vehicular sensors may experience the following severe connectivity issues: sparse and intermittent connectivity, long and variable delays, high latency, high error rates, highly asymmetric data rates, and lack of end-to-end connectivity. The MAC layer can make use of this connectivity problem and play an important role in solving data throughput efficiency, energy conservation and different service issues in sparse Vehicular Delay-Tolerant Sensor Networks (VDTSN). In this paper we propose an efficient transmission strategy in the MAC layer which coordinates the working procedure of vehicular sinks and ordinary sensors. We also designed three transmission algorithms for different quality requirements of data, with energy conservation considerations in one contact interval. Transmission power consumption and data throughput are the main measurements used to evaluate transmission efficiency performance. We compare and analyse our scheme with two other important MAC protocols in wireless sensor networks and vehicular ad-hoc networks in throughput, delay, energy consumption etc. The simulation results show that the strategy performs the transmission of different types of data more effectively in an energy-saving and data-throughput-balanced way than other MAC approaches in sparse VDTSN.

SAFM: An Adaptive Socially Aware Feedback Mechanism in Delay Tolerant Sensor Networks

In Delay Tolerant Sensor Networks (DTSN), it is a challenge to ensure the delivery reliability, due to the lack of end-to-end path, intermittent connection, and high latency. In addition, the resource utilization is decreased because of the limited resources and a large number of redundant copies. To this end, this paper proposes an adaptive Socially Aware Feedback Mechanism (SAFM). In this mechanism, the historical information of the encountered nodes is utilized to construct social links which indicates the level of social relationship between nodes. In the feedback process, acknowledgements are forwarded to the nodes whose social link (SL) is higher than a given thresholdα. After getting the acknowledgements, nodes will delete the copies of messages which have been received by the destination nodes, so as to reduce the redundancy. This mechanism is to reach a tradeoff between overhead and delivery efficiency. In simulation, the thresholdαis obtained to reach the best performance of SAFM. Compared with active and passive receipt approaches in an acceptable range of delay, SAFM improves the delivery probability, decreases the buffer occupancy, and reduces the overhead.

A routing algorithm on delay-tolerant of wireless sensor network based on the node selfishness

According to the problem of the intermittent connectivity of the nodes in the delay-tolerant sensor network, considering that the nodes in the network are of social selfishness, we study how to reduce transmission delay and communication overhead on the basis of ensuring the message delivery success rate of the entire network. We present a delay-tolerant routing algorithm based on the node selfishness (DTSNS). Firstly, we divide the activity area into grids. Secondly, we predict the next mobile location of the nodes based on the Markov process and estimate the credibility of the nodes based on the node selfishness in order to reduce the network communication overhead and improve message delivery success rate. Then, we put forward the delay-tolerant algorithm based on delay constraints. Lastly, the simulation results show that the DTSNS has better performance which has higher level of data delivery rate and lower level of message delay and resource, compared with Spray and Focus, Spray and Wait, and Epidemic.

Generic prediction assisted single-copy routing in underwater delay tolerant sensor networks

One challenge in delay tolerant networks (DTNs) is efficient routing, as the lack of contemporaneous end-to-end paths makes conventional routing schemes inapplicable. Although many DTN routing protocols have been proposed, they often have two limitations: many protocols are not mobility cognizant, so they only suit specific mobility models and become inefficient when the environment changes; some protocols employ multi-copy replication to accommodate mobility diversity for increased delivery probability or reduced delay, but they usually do not perform well in resource constrained networks. Due to the unique characteristics of underwater sensor networks (UWSNs), efficient DTN routing becomes even more challenging. In this paper, we propose a generic prediction assisted single-copy routing (PASR) scheme that can be instantiated for different mobility models. PASR first collects a short-duration trace with network connectivity information and employs an effective off-line greedy algorithm to characterize the underlying network mobility patterns, depict the features of best routing paths and provide guidance on how to use historical information. Then it instantiates prediction assisted single-copy online routing protocols based on the guidance. As a result, the instantiated protocols are energy efficient and cognizant of the underlying mobility patterns. We demonstrate the advantages of PASR in underwater sensor networks with various mobility models.

Design and Analysis of Delay-Tolerant Sensor Networks for Monitoring and Tracking Free-Roaming Animals

This paper is concerned with the design and analysis of delay-tolerant networks (DTNs) deployed for free-roaming animal monitoring, wherein information is either transmitted or carried to static access-points by the animals whose movement is assumed to be random. Specifically, in such mobility-aided applications where routing is performed in a store-carry-and-drop manner, limited buffer capacity of a carrier node plays a critical role, and data loss due to buffer overflow heavily depends on access-point density. Driven by this fact, our focus in this paper is on providing sufficient conditions on access-point density that limit the likelihood of buffer overflow. We first derive sufficient access-point density conditions that ensure that the data loss rates are statistically guaranteed to be below a given threshold. Then, we evaluate and validate the derived theoretical results through comparison with both synthetic and real-world data.

A Group-based Data transmission algorithm in delay tolerant sensor networks

A Group-based Data transmission algorithm in delay tolerant sensor networks

Connectivity restoration in delay-tolerant sensor networks using game theory

Due to limited resources and harsh environments, partitioning can be inevitable in wireless sensor networks (WSNs). To re–establish network connectivity, healthy mobile sensor nodes can be repositioned in an on–demand basis. However, the nodes are equipped with limited batteries and their movement requires excessive energy consumption. In this paper, we address the problem of minimising the movement cost when re–establishing network connectivity in delay tolerant WSNs by presenting a distributed heuristic approach based on Game Theory. Compared to centralised heuristics which assume complete knowledge of the network and failures, this approach is self–healing that can work with uncertain network/failure information. Under limited knowledge on partitions and failure locations, Game Theory is used to facilitate decision making on the selection of the nodes to be moved and their movement directions. Extensive simulations have revealed the efficiency of the proposed approach in terms of movement distance and network coverage.

Event Delivery in Publish/Subscribe System for Delay Tolerant Sensor Networks

This paper proposes CET,a community based event transmitting protocol in publish/subscribe system for Delay Tolerant Sensor Networks(DTSN).The core idea of CET is that event transmitting is based on communities which are formed by sensors in the network according to their connectivity.CET consists of two key components data transmission and queue management.In data transmitting,not only events are transmitted to mobile subscribers as best as possible,some events in subscribers are also retransmitted to sensors in community,for enhancing the data delivery ratio.The queue management employs both the event survival time and the successful delivery time to decide whether the event should be transmitted or dropped for minimizing the transmission overhead.Simulation results have shown that the proposed CET achieves a higher event delivery ratio with the lower transmission overhead and event delivery delay than DG(direct gathering protocol).

Temporal privacy in wireless sensor networks

Although the content of sensor messages describing “events of interest” may be encrypted to provide confidentiality, the context surrounding these events may also be sensitive and therefore should be protected from eavesdroppers. An adversary armed with knowledge of the network deployment, routing algorithms, and the base-station (data sink) location can infer the temporal patterns of interesting events by merely monitoring the arrival of packets at the sink, thereby allowing the adversary to remotely track the spatio-temporal evolution of a sensed event. In this paper we introduce the problem of temporal privacy for delay-tolerant sensor networks, and propose adaptive buffering at intermediate nodes on the source-sink routing path to obfuscate temporal information from the adversary. We first present the effect of buffering on temporal privacy using an information-theoretic formulation, and then examine the effect that delaying packets has on buffer occupancy. We observe that temporal privacy and efficient buffer utilization are contrary objectives, and then present an adaptive buffering strategy that effectively manages these tradeoffs. Finally, we evaluate our privacy enhancement strategies using simulations, where privacy is quantified in terms of the adversary's mean square error.

A Community-Based Event Delivery Protocol in Publish/Subscribe Systems for Delay Tolerant Sensor Networks

The basic operation of a Delay Tolerant Sensor Network (DTSN) is to finish pervasive data gathering in networks with intermittent connectivity, while the publish/subscribe (Pub/Sub for short) paradigm is used to deliver events from a source to interested clients in an asynchronous way. Recently, extension of Pub/Sub systems in DTSNs has become a promising research topic. However, due to the unique frequent partitioning characteristic of DTSNs, extension of a Pub/Sub system in a DTSN is a considerably difficult and challenging problem, and there are no good solutions to this problem in published works. To ad apt Pub/Sub systems to DTSNs, we propose CED, a community-based event delivery protocol. In our design, event delivery is based on several unchanged communities, which are formed by sensor nodes in the network according to their connectivity. CED consists of two components: event delivery and queue management. In event delivery, events in a community are delivered to mobile subscribers once a subscriber comes into the community, for improving the data delivery ratio. The queue management employs both the event successful delivery time and the event survival time to decide whether an event should be delivered or dropped for minimizing the transmission overhead. The effectiveness of CED is demonstrated through comprehensive simulation studies.

Node localization using mobile robots in delay-tolerant sensor networks

We present a novel scheme for node localization in a delay-tolerant sensor network (DTN). In a DTN, sensor devices are often organized in network clusters that may be mutually disconnected. Some mobile robots may be used to collect data from the network clusters. The key idea in our scheme is to use this robot to perform location estimation for the sensor nodes it passes based on the signal strength of the radio messages received from them. Thus, we eliminate the processing constraints of static sensor nodes and the need for static reference beacons. Our mathematical contribution is the use of a robust extended Kalman filter (REKF)-based state estimator to solve the localization. Compared to the standard extended Kalman filter, REKF is computationally efficient and also more robust. Finally, we have implemented our localization scheme on a hybrid sensor network test bed and show that it can achieve node localization accuracy within 1 m in a large indoor setting.