Duty-cycled Wireless Sensor Networks Research Articles

SDORP: SDN Based Opportunistic Routing for Asynchronous Wireless Sensor Networks

In wireless sensor networks (WSNs), it is inappropriate to use conventional unicast routing due to the broadcast storm problem and spatial diversity of communication-links. Opportunistic-Routing (OR) benefits the low duty-cycled WSNs by prioritizing the multiple candidates for each node instead of selecting one node as in conventional unicast-routing. OR reduces the sender waiting time, but it also suffers from the duplicate packets problem due to multiple candidates waking up simultaneously. The number of candidates should be restricted to counterbalance between the sender waiting time and duplicate packets. In this paper, software-defined networking (SDN) is adapted for the flexible management of WSNs by allowing decoupling of the control plane from the sensor nodes. This study presents SDN-based load-balanced opportunistic-routing for duty-cycled WSNs that addresses two parts. First, the candidates are computed and controlled in the control plane. Second, the metric used to prioritize the candidates considers the average of three distributions, transmission distance distribution, expected number of hops distribution and residual energy distribution so that more traffic is guided through the nodes with higher priority. Simulation results show that our proposed protocol significantly improve network lifetime, routing efficiency, energy consumption, sender waiting time, and duplicate packets as compared with the benchmarks.

A Dynamic Opportunistic Routing Protocol for Asynchronous Duty-Cycled WSNs

Opportunistic routing (OR) is widely adopted in Wireless Sensor Networks (WSNs) running asynchronous duty-cycled MAC protocols. In conventional routing, where packets are forwarded along predetermined routes, the sender may wait for the receiver to wake up for a long time. To reduce the sender waiting time, the OR protocols allow nodes to select multiple neighbors as the forwarders so that the packets could be forwarded by multi-path. Thus, the forwarders selection algorithm affects network performance seriously. However, an excessive number of forwarders increases the probability that more than one forwarders wake up simultaneously. This will consume more energy since each of them will receive the packet. To address the two issues, a Dynamic Opportunistic Routing protocol using Analytical Hierarchy Process (AHP) and Fuzzy Inference System (FIS) called DORAF is proposed in this paper. DORAF is implemented in three steps. First, multiple criteria (i.e., residual energy, distance, and angle) at the network layer are defined to evaluate the nodes where the importance of these criteria is determined by AHP. Second, the pairwise comparison matrices in AHP are generated by using mathematical functions (i.e., Boltzmann function and Logistic function) and FIS. Third, each node uses AHP and FIS to prioritize its neighbors based on the criteria and selects appropriate ones as the forwarders dynamically in a distributed manner. The experimental results demonstrate that our protocol performs better than other state-of-the-art in terms of network lifetime, energy consumption, and average redundant transmissions.

TORAS: Trustworthy Load-Balanced Opportunistic Routing for Asynchronous Duty-Cycled WSNs

As opportunistic routing (OR) becomes more popular in low-duty wireless sensor networks (WSNs), there is a greater demand for reliable and consistent data transmission. Only efficient and secure network protocols can guarantee reliable data transmission. Existing cryptographic algorithms for WSNs are inadequate due to their excessive energy usage. Data transmission reliability, security, and consistency will be provided via trust-based OR, while utilizing less energy and limited resources. OR uses opportunistic criteria to obtain a list of potential candidates for each sender node. This study proposes a trustworthy load-balanced opportunistic routing for asynchronous duty-cycled WSNs that consist of three parts. First, four probability distributions with their average term in <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OR Metric</i> are considered for balancing the load among the nodes: distance from the node to the sink, expected number of hops, node degree, and residual energy. Second, two probability distributions with their average term in <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Trust Metric</i> are considered for measuring the trust factor: direct trust and recommended trust. Finally, in order to guide more data through the prioritized nodes, the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Trusted OR Metric</i> is determined by multiplying the average probability distributions of the two metrics. When compared to benchmarks, the simulation results show that the proposed protocol improves network performance in terms of energy consumption, average end-to-end delay, average throughput, packet delivery ratio, network lifetime, and detection rate.

Distributed Optimization Framework for Mobile Data Collection With Energy Harvesting in Duty-Cycle WSNs

The increased dynamics and complexity of wireless sensor networks (WSNs) raises higher requirements on the flexibility and applicability of data collection algorithms. Therefore, a novel distributed optimization framework for data collection with energy harvesting in duty-cycle (DC) WSNs is developed in this article, which employs the mobile collector (called SenCar) to collect data from the selected sensors (called anchors) to circumvent the bottlenecks caused by the variations of energy distribution. In order to guarantee the optimality of mobile data collection, it is divided into two steps: Firstly, a method for calculating the optimal number of anchors is developed and then an adaptive anchor selection algorithm is proposed to determine those anchors. Secondly, the mobile data collection problem of DC WSNs is formulated as a delay optimization problem constrained by flow conversation, congestion control and energy balance. Then, we focus on designing the distributed algorithm to resolve that optimization problem, in which each sensor node only needs to communicate with its neighbors to make decisions without any global information and can locally adjust the information weight of its neighbors. Besides, the accelerated distributed algorithm with the uncoordinated step size is also proposed to improve the convergence rate. Furthermore, the explicit convergence analysis of the proposed algorithm is provided in this paper. Finally, the numerical results show that our algorithm can quickly converge to the optimal solution and has obvious superiority in adjusting link flow, storing energy, and extending network lifetime.

Distributed Data Collection Algorithm With Unknown Objective Function in Adaptive Duty-Cycle WSNs

With the rapid development of wireless sensor networks (WSNs), higher requirements are raised for the flexibility and applicability of data collection algorithms. Therefore, a novel distributed algorithm for data collection in adaptive duty-cycle WSNs is proposed in this article. On the one hand, the priority in data transmission is considered, in which the queues are used to realize the data storage and data transmission with different priorities and then a scheme for selecting the optimal transmission path for the sensor nodes is developed to ensure that high-priority data can be transmitted more efficiently. Next, a method that can adaptively adjust the duty cycle of the sensor nodes is designed to reduce the transmission delay, where each sensor can update its own duty cycle according to the amount of data with different priorities. On the other hand, the relation between the objective function and the variables in the data collection problem may be difficult to establish accurately or even unknown due to the complexity of WSNs, while the most existing data collection algorithms require the objective function to be explicitly expressed, making them inapplicable to the above scenarios. Hence, the data collection problem with unknown objective function in adaptive duty-cycle WSNs is also investigated in this article. Since the objective function cannot be established, a distributed optimization algorithm with randomized gradient-free is developed to solve that problem. In particular, the proposed algorithm solely relies on the row-stochastic weight matrix, where each sensor needs to communicate only with its neighbors to make decision and locally allocates the information weight of its neighbors, making the algorithm easier to implement. Under some reasonable assumptions, the explicit analysis for the convergence of the proposed algorithm is provided. Finally, the convergence and effectiveness of the proposed algorithm are substantiated through numerical simulations.

Structure-Free Broadcast Scheduling for Duty-Cycled Multihop Wireless Sensor Networks

Broadcasting is an essential operation in wireless networks for disseminating the message from the source node to all other nodes. Unfortunately, the problem of Minimum Latency Broadcast Scheduling (MLBS) in duty-cycled wireless sensor networks is not well studied. In existing works, the construction of broadcast tree and the scheduling of transmissions are conducted separately, where a tree-based structure is used as the input of the scheduling algorithm. Relying on a pre-determined tree may result in a much large latency even using the optimal scheduling method. Thus, the MLBS problem in duty-cycled WSNs without the above limitation is investigated in this paper. First, to avoid relying on a pre-determined structure, a two-step scheduling algorithm is proposed to construct the broadcast tree and compute a collision-free schedule simultaneously. To the best of our knowledge, this is the first work that can integrate these two kinds of operations together. Second, a novel transmission mode, i.e., concurrent broadcasting, is first introduced for wireless networks and several techniques are designed to further improve the broadcast latency. Third, the multiple messages broadcasting and all-to-all broadcasting algorithms, which can generate a series of broadcast schedules independently without a pre-determined tree, are also proposed by taking care of the collisions in both the current and the previous broadcast schedules. Finally, the theoretical analysis and experimental results demonstrate the efficiency of the proposed algorithms in terms of latency.

Low-Delay Opportunistic Routing with Reducing Overhead in Asynchronous Duty-Cycled Wireless Sensor Networks

The Internet of Things (IoT) and cloud computing are well developed and applied in different services. Among these services, some of them take latency and overhead as the metrics to evaluate the quality of services. This paper introduces how an opportunistic routing (OR) protocol reduces latency and overhead when it is applied in wireless sensor network (WSN) application among lightweight devices. OR mitigates the delay problem and balances the energy consumption and delay of the nodes in WSNs. However, OR, with the nature of broadcasting, can easily cause heavy overhead such as redundant data and control packets in the forwarding process. In the current solution, the number of candidates (potential forwarders) is not limited by the dynamics of forwarding process. Also, the overhead of establishing the candidate sets is high due to global information calculation. Therefore, a low-delay OR protocol with reducing overhead which designs the dynamic candidate area (DCA) to establish candidate sets is first proposed in this paper. The main work is as follows. (a) The duty cycle of a node is adjusted according to the distance between the node and sink node in the initialized network. (b) A method to establish dynamic candidate sets is proposed based on the adaptive duty cycle. Before and during the forwarding process, the dynamic candidate area is adjusted in time. (c) According to the feature of the candidate area, the corresponding routing metric is proposed to complete the cooperative communication among candidates. Through further theoretical analysis and simulations, the results indicate that this protocol achieves better performance in terms of transmission delay, data and control overhead, and network lifetime compared to the state-of-the-art solutions.

Effective neighbor node discovery using improved Bayesian clock synchronization‐gossip routing protocol in mobile low duty cycle wireless sensor network

AbstractIn wireless application, mobile low duty cycle wireless sensor network (MLDC‐WSN) gained more attention among the researchers, because it includes advantages like growing node life, saving node power, and network reliability. However, the sleeping features and mobility of MLDC‐WSN results in topology change that restricts the speed of neighbor node discovery. To highlight this concern, a novel routing protocol named as improved Bayesian clock synchronization‐gossip routing protocol is proposed for an effective neighbor node discovery in MLDC‐WSN. The proposed routing protocol reduces end‐to‐end delay, and clock drifts problems. Also, the proposed routing protocol improves the clock synchronization and captures the neighbor discovery nodes by identifying the next neighbor set in the next moment, due to the prediction of the distance and movement speed of neighbors. Simulation and analytical results showed that the proposed routing protocol superiorly decreases the end‐to‐end delay and energy consumption compared to the existing algorithms.

Delay-aware data fusion in duty-cycled wireless sensor networks: A Q-learning approach

In wireless sensor networks (WSNs), the sensor nodes (SNs) are deployed to acquire the data from the area of interest and transmit it to the sink via multi-hop communications. Due to computation, buffer, and energy constraints, the SNs need efficient routing to forward the data in time to sink with limited energy drain, and it is a challenging task. It is more difficult in duty-cycled WSNs because the SNs are active for a limited time and inactive in the remaining time to minimize the energy drain. In this context, we propose a delay-aware data fusion (DADF) approach to the trade-off between the delay and energy while performs the data fusion. Initially, the DADF performing the data fusion operation to avoid duplicating and inconsistent data at each SNs using a simple statistical approach during its active state. Afterward, the sink uses reinforcement learning to identify the best forwarding node of each SN for data communications with minimum delay and energy in duty-cycled WSNs. Each forwarding node operates the data fusion once if it acquires the data from its child nodes. The proposed method using various performance metrics such as network lifetime, throughput, energy consumption, buffer utilization, and end-to-end delay are compared with recent and relevant existing techniques, and our methods outperform them in varying dynamic conditions.

Cross-layer multipath approach for critical traffic in duty-cycled wireless sensor networks

Ensuring that an active path is provided at all times in a Wireless Sensor Network (WSN) is fundamental for securing the timely delivery of critical data and maintaining the quality of service required to effectively support delay-sensitive applications. In duty cycling mode, ensuring such a path becomes a real challenge as the activity scheduling of different nodes should be regulated and adjusted to provide a pipe-lined node activity from source to sink. Furthermore, some transmission delays may be incurred in waiting for a next-hop node to be awakened. The data transfer time is mainly influenced by the performance of both MAC and routing protocols; an inter-layer design allowing efficient coordination between the MAC and routing is then necessary to make the appropriate decisions relating to the selection of the next hop and the adjustment of the duty cycle. In this article, we provide a cross-layer multi-path routing approach designed to support the transfer of critical data over duty-cycled WSN networks. This approach establishes multi-node disjoint paths with complementary duty-cycling schedules to ensure the availability of an active path capable of transmitting critical data at all times. It relies on a tight cooperation between the routing and MAC layers in order to appropriately adjust and regulate the wake-up schedules of involved nodes in the forwarding phase. We analytically proved the correctness of the proposed scheduling adjustment rules. We conducted extensive simulations to show the ability of the CL-NDRECT to provide a viable trade-off between energy conservation and real time responsiveness. Simulation results show that CL-NDRECT provides around 65% cumulative energy saving during route establishment and data transfer compared to the always-on multipath approach at the cost of around 10% increase in response time.

FLORA: Fuzzy Based Load-Balanced Opportunistic Routing for Asynchronous Duty-Cycled WSNs

Many opportunistic routing (OR) schemes treat network nodes equally, neglecting the fact that the nodes close to the sink undertake more duties than the rest of the network nodes. Therefore, the nodes located at different positions should play different roles during the routing process. Moreover, considering various Quality-of-Service (QoS) requirements, the routing decision in OR is affected by multiple network attributes. The majority of these OR schemes fail to contemplate multiple network attributes while making routing decisions. To address the aforesaid issues, this paper presents a novel protocol that runs in three steps. First, each node defines a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Routing Zone (RZ)</i> to route packets toward the sink. Second, the nodes within RZ are prioritized based on the competency value obtained through a novel model that employs Modified Analytic Hierarchy Process (MAHP) and Fuzzy Logic techniques. Finally, one of the forwarders is selected as the final relay node after forwarders coordination. Through extensive experimental simulations, it is confirmed that FLORA achieves better performance compared to its counterparts in terms of energy consumption, overhead packets, waiting times, packet delivery ratio, and network lifetime.

WITHDRAWN: A survey on continuous neighbor discovery for mobile low duty cycle wireless sensor network

Abstract In the network implementation point, neighbourhood exploration is a very significant phenomenon. However, due to the complex existence of WSN and the probability of adding new nodes and withdrawing nodes from the network, continuous exploration of neighbours is required. It does suggest that the identification of neighbours is not a one-time operation. There are also benefits of WSN for the identification of neighbours. In addition to saving node power and growing node life, network reliability is increased. The analysis of the literature in this paper gives valuable insights into the latest state of the art in continuous exploration of neighbours in WSN. In specific, it reflects on the WSNs of the low duty mobile cycle. The analysis holes found in the literature are also given.

在占空比无线传感器网络中寻找多约束路径的算法

在占空比无线传感器网络中寻找多约束路径的算法

Bi-adjusting duty cycle for green communications in wireless sensor networks

Green communications is a challenging issue for communications and networking. In order to save energy, nodes of the wireless sensor networks (WSNs) usually adopt the low duty cycle mode which brings a large delay to the event detection and data transmission to the sink and deteriorates the network’s timely processing of the event. In this paper, bi-adjusting duty cycle schedule (BADCS) scheme is proposed to reduce event detection latency as well as data routing delay for low duty cycle wireless sensor networks. BADCS scheme consists mainly of two duty cycle adjustment algorithms: (a) active slot asynchronous adjustment algorithm for nodes in the same sensing area; (b) the continuous adjustment algorithm for two adjacent nodes on the routing path with one active slot interval. Specifically, the operations are 2-fold. First, perform asynchronous operations on the active slots of the nodes in the same sensing area, so that the active slots of the nodes in the same sensing area are distributed as evenly as possible without overlapping. In this way, it is possible to reduce the latency by the time the event is perceived after its occurrence. Secondly, active slots of the nodes on the routing path are adjusted to be with pipeline style, so that when the nodes receive the data packet, they can route through the continuous active slots, thus greatly reducing the delay of data routing. Two adjustment algorithms of active slot are given in detail in this paper. The performance of BADCS mode is discussed in detail, and its performance is better than the previous strategy. Comprehensive experiments are conducted, and the results demonstrate that the proposed BADCS scheme significantly improves event detection performance in terms of detection latency, detection probability, and routing delay. Detection delay and routing delay are reduced as high as 3.91% and 56.22% respectively.

Shortest-Latency Opportunistic Routing in Asynchronous Wireless Sensor Networks with Independent Duty-Cycling

For opportunistic routing in independent duty-cycled wireless sensor networks (WSNs), a sender dynamically determines a relay candidate set depending on the real-time network conditions. Due to independent and varying duty cycle length, the sender may handle different waking-up orders of the potential forwarders when it tries to forward data packets at different time instants. Conventional opportunistic routing protocols overlook the time-varying property of the waking-up order of the candidate nodes. In this paper, we theoretically analyze how to obtain an optimal candidate set for each node in order to minimize the end-to-end latency. Then, considering the realistic scenarios, we propose an opportunistic routing which jointly considers global and localized optimizations. Based on the relatively stable topology and duty-cycle length information, an original candidate set is constructed. Then, by considering the real-time link and duty cycle information in the local context, a further optimization for the original candidate set can be achieved. Simulation results show that our proposed schemes can significantly improve the end-to-end latency compared with the benchmarks.

Energy-efficient routing under delay constraint in duty-cycle wireless sensor networks

In this paper, we investigate the problem of energy-efficient routing design from a sensor node to a sink node under a given delay constraint. The network topologies in duty-cycle wireless sensor networks (WSNs) are changed from one time-slot to another due to each sensor node's active/dormant schedule. A series of network topologies over a period of time are modelled as a virtual time-expanded graph. Then, the problem of routing design on the time-expanded graph is defined, whose aim is to find a space-time path from a sensor node to the sink node with the minimum energy consumption under a delay constraint. Next, an energy-efficient routing algorithm in time-expanded graph (ERTG) is proposed to find the optimal space-time path. Simulation results validate the effectiveness of the proposed algorithm in energy savings.

Energy-efficient routing under delay constraint in duty-cycle wireless sensor networks

Energy-efficient routing under delay constraint in duty-cycle wireless sensor networks

PAX-MAC: A Low Latency Anycast Protocol with Advanced Preamble.

Wireless sensor networks employ duty-cycles to save energy, with the cost of enlargement of end-to-end latency. Cross-layer protocols that use anycast medium access control achieve latency reduction in asynchronous duty-cycled wireless sensor networks (WSNs). A series of strobed preambles is sent in order to achieve rendezvous with the next relay, selected from a forwarding candidate set (FCS). This paper proposes PAX-MAC: Pramble Ahead Cross-layer Medium Access Control. It is a novel anycast protocol for low latency packet propagation in duty-cycled WSNs. In PAX-MAC, preambles propagate ahead of data packet, prospecting the route towards sink node, while the message is sent some hops later. Simultaneous propagation of preambles and data packets provides latency reduction. The cardinality of FCS determines the average preamble propagation speed, which is lower bounded by data packet propagation speed. Differently from other approaches, our protocol takes the data packet size into account in order to maintain an optimal distance between preamble and data to minimize latency. For determining this distance, a detailed mathematical model is introduced. The performance of several state-of-the-art asynchronous protocols was appraised and compared with PAX-MAC. Our protocol outperforms in latency all other protocols for the simulated scenarios. Its energy expenditure was compatible with the best result among the other protocols. In the worst case, PAX-MAC spent more energy than the best one for a gain of in latency.

ENERGY COMPETENCY FOR GEOGRAPHICAL ROUTING SCHEME USING DUTY CYCLED WIRELESS SENSOR NETWORK

Wireless sensor networks have wide range of applications. The major constraint in such application lies in the limitation of energy resource. The sensors are often equipped with tiny and irreplaceable batteries. It arise the need of energy efficient routing algorithms to prolong the network lifetime. This project mainly focuses on sleep scheduling for geographic routing in duty-cycled WSNs with mobile sensors by using geographic-distance-based connected-k neighborhood (GCKN) sleep scheduling algorithms. It ensures that coverage rotates such every purpose within the surroundings is perceived at intervals some default interval of your time, referred to as the detection delay. The structure is optimized for rare event detection and permits favorable compromises to be achieved between event detection delays and eventual coverage for every purpose. The cluster activation protocol makes sure that the foremost potential clusters activated to perform target pursuit, reducing consumed energy throughout the hand-off operation. The experimental results show that when there are mobile sensors, geographic routing can achieve much shorter average lengths for all paths using GCKN sleep scheduling compared with those in WSNs employing CKN and GSS sleep scheduling.

Oppo-Flood: An Energy-Efficient Data Dissemination Protocol for Asynchronous Duty-Cycled Wireless Sensor Networks

In this paper, we propose a data dissemination protocol for asynchronous duty-cycling wireless sensor networks. In an asynchronous duty-cycling network, each node independently selects its wake-up time. In this environment, data dissemination becomes energy consuming, because broadcasting a packet does reach all neighbors but only the neighbors that are awake at the time. A node can forward its packet to all neighbors by continuously transmitting the packet for a whole wake-up interval, but it leads to high energy consumption and high dissemination delay. The idea proposed in this paper is to use opportunistic forwarding, where each node forwards the packet to a neighbor that wakes up early and receives the packet. Each node forwards the packet, as long as there is a neighboring node that has not received the packet yet. The main benefit of this opportunistic forwarding-based dissemination is that every time a packet is disseminated, it may take a different path to reach the nodes. At the beginning of dissemination, a sender needs to transmit for a very short duration of time because there are plenty of neighboring nodes to receive the packet. As more nodes receive the packet, the transmit duration of the sender becomes longer, thus consuming more energy. Since the order of dissemination is different every time, energy consumption is naturally balanced among the nodes, without explicit measures. Through extensive simulations, we show that the proposed protocol achieves longer network lifetime and shorter dissemination delay compared to other dissemination protocols in various network environments.