Cluster-tree Wireless Sensor Networks Research Articles

Dynamic Reconfiguration of Cluster-Tree Wireless Sensor Networks to Handle Communication Overloads in Disaster-Related Situations.

The development of flexible and efficient communication mechanisms is of paramount importance within the context of the Internet of Things (IoT) paradigm. IoT has been used for industrial, commercial, and residential applications, and the IEEE 802.15.4/ZigBee standard is one of the most suitable protocols for this purpose. This protocol is now frequently used to implement large-scale Wireless Sensor Networks (WSNs). In industrial settings, it is becoming increasingly common to deploy cluster-tree WSNs, a complex IEEE 802.15.4/ZigBee-based peer-to-peer network topology, to monitor and control critical processes such as those related to oil or gas, mining, or certain specific chemicals. The remote monitoring of critical events for hazards or disaster detection in large areas is a challenging issue, since the occurrence of events in the monitored environment may severely stress the regular operation of the network. This paper proposes the Dynamic REconfiguration mechanism of cluster-Tree WSNs (DyRET), which is able to dynamically reconfigure large-scale IEEE 802.15.4 cluster-tree WSNs, and to assign communication resources to the overloaded branches of the tree based on the accumulated network load generated by each of the sensor nodes. A complete simulation assessment demonstrates the proposed mechanism’s efficiency, and the results show that it can guarantee the required quality of service level for the dynamic reconfiguration of cluster-tree networks.

An Energy-efficient Distributed TDMA Scheduling Algorithm for ZigBee-like Cluster-tree WSNs

The design of Medium Access Control (MAC) protocol for Wireless Sensor Networks (WSNs) with both limited energy consumption and data delivery time is crucial for industrial and control applications. Since Time Division Multiple Access (TDMA) MAC eliminates the collision occurrence and seeks the minimization of the number of time-slots assigned to each node, the energy consumption of the nodes is reduced. Furthermore, with the proper allocation of the time-slots to the nodes, the transmission delay can be significantly reduced. In this article, we propose TDMA scheduling algorithm for Cluster-tree topology WSNs that meets the timeliness and the energy demands. The algorithm adopts an elegant approach that expresses the timing constraints of the data transmissions as an integer multiple of the length of the schedule period. Moreover, since the distributed algorithm is well-suited to the scarce resources of the WSNs, we focus on the distributed methods that allow each cluster to come up with its allocated time-slots. The algorithm is based on graph theory, such as distributed shortest path, distributed topological ordering, and distributed graph coloring algorithms. The efficiency of the algorithm, regarding the elapsed time to construct the schedule and the energy consumption, is evaluated over benchmark instances up to several thousands of nodes.

An Energy Efficient Schedule for IEEE 802.15.4/ZigBee Cluster Tree WSN with Multiple Collision Domains and Period Crossing Constraint

Cluster scheduling respecting collision avoidance is a complex problem in cluster-tree wireless sensor networks (WSNs). The difficulty of the problem also increases significantly when the traffic is organized as time-constrained data flows with opposite directions. Thus, in this paper, we seek a collision-free cluster schedule that meets all the data flow deadlines as given in time units. In this context, we have found an elegant approach that expresses the deadline of each flow as an integer number of the length of the schedule period (i.e., period crossing constraints). Consequently, the data flow timeliness requirements become easier to be tackled. Due to the scarce resources of the WSNs, the minimization of the energy consumption of the nodes is a problem of paramount importance. Therefore, the objective is to maximize the lifetime of the network by maximizing the time when the nodes stay in low-power mode. In this paper, we present a novel heuristic scheduling algorithm to obtain the desired schedule. The algorithm is based on very interesting formulations of graph theory problems. Thus, it is efficient in both computational time (instances with thousands of devices are solved in a short time) and solution quality (evaluated over smaller size instances while comparing it with optimal solutions obtained by integer linear programming).

클러스트-트리 무선센서네트워크에서 비콘 프레임 충돌 회피를 위한 멀티채널 시분할 스케줄링

클러스트-트리 무선센서네트워크에서 비콘 프레임 충돌 회피를 위한 멀티채널 시분할 스케줄링

CT-SIM: A simulation model for wide-scale cluster-tree networks based on the IEEE 802.15.4 and ZigBee standards

The IEEE 802.15.4/ZigBee set of standards is one of the most used wireless sensor network technologies. This set of standards supports cluster-tree networks, which are suitable topologies for wide-scale deployments. The design of wide-scale wireless sensor networks is a challenging task because it is difficult to test, analyse and validate new designs in real scenarios. Thus, simulation becomes a convenient and feasible method for its assessment before deployment. Within this context, we provide a set of simulation models for IEEE 802.15.4/ZigBee-based networks, which are able to deal with wide-scale cluster-tree wireless sensor networks and to address their major challenges. The provided simulation models implement important mechanisms for the assessment of wide-scale cluster-tree networks and associated data communication mechanisms, enabling an easier design and test of wide-scale wireless sensor network implementations.

Superframe Duration Allocation Schemes to Improve the Throughput of Cluster-Tree Wireless Sensor Networks.

The use of Wireless Sensor Network (WSN) technologies is an attractive option to support wide-scale monitoring applications, such as the ones that can be found in precision agriculture, environmental monitoring and industrial automation. The IEEE 802.15.4/ZigBee cluster-tree topology is a suitable topology to build wide-scale WSNs. Despite some of its known advantages, including timing synchronisation and duty-cycle operation, cluster-tree networks may suffer from severe network congestion problems due to the convergecast pattern of its communication traffic. Therefore, the careful adjustment of transmission opportunities (superframe durations) allocated to the cluster-heads is an important research issue. This paper proposes a set of proportional Superframe Duration Allocation (SDA) schemes, based on well-defined protocol and timing models, and on the message load imposed by child nodes (Load-SDA scheme), or by number of descendant nodes (Nodes-SDA scheme) of each cluster-head. The underlying reasoning is to adequately allocate transmission opportunities (superframe durations) and parametrize buffer sizes, in order to improve the network throughput and avoid typical problems, such as: network congestion, high end-to-end communication delays and discarded messages due to buffer overflows. Simulation assessments show how proposed allocation schemes may clearly improve the operation of wide-scale cluster-tree networks.

A Reliable IEEE 802.15.4 Model for Cyber Physical Power Grid Monitoring Systems

Cyber physical systems (CPSs) can significantly improve the resiliency of the smart grid. In CPSs, real time and reliable monitoring require an accurate and stable model of the wireless sensor network (WSN)-based monitoring system. Furthermore, WSNs require strict quality of service (QoS) provisioning as the data generated by the monitored equipment is generally delay and reliability-sensitive. QoS provisioning in WSNs has been widely studied in the literature where most of the work addresses the issue by QoS-aware protocol design. However, analytical models that consider delay, throughput, and power consumption have not matured for CPSs. In this paper, we propose a Markov-based model for cluster-tree WSN topologies that enhances the stability of the WSNs. Cluster-tree deployments are particularly of interest to cyber-physical power grid monitoring systems since they are suitable for large-scale deployments. We perform an exhaustive performance evaluation using different traffic and network conditions in star and cluster-tree WSN topologies. Furthermore, we test the accuracy of our model by performing simulations in environments that are consistent with the analytical model.

Sequential Beacon Scheduling Mechanism for Cluster-Tree WSNs

To solve the beacon collision problem in IEEE 802.15.4/ZigBee cluster-tree Wireless Sensor Networks, we proposed a Sequential Beacon Scheduling (SBS) mechanism. In this mechanism, the Cluster Headers (CHs) choose the beacon transmission time in a certain order. The CH which finishes the sequence chosen sends out control frame to inform other CHs in its interference range. The simulation results indicate that SBS general has better delivery ratio, latency, and throughput than three other beacon scheduling mechanisms.

The Influence Factor Analysis on Stability of Communication Links Based on Cluster-Tree WSN Using ZigBee

Zigbee technology which targets low data rate, low power consumption and low cost application is suitable for Wireless Sensor Network (WSN) as its wireless communication technology. In the construction of WSN using Zigbee, the factors which could affect the stability of communication links should be considered. In this work, we discuss the construction environment of WSN. Then, in order to access the performance of Cluster-Tree network, we develop an NS2 simulator for Cluster-Tree WSN, and analysis the influence to stability of communication links caused by sending packet ratio and communication range. The simulation results show that it is not useful to improve the stability of communication links by increasing sending packet ratio and communication range simply. Both of them should be in a relatively balanced state.

Dimensioning and worst-case analysis of cluster-tree sensor networks

Modeling the fundamental performance limits of Wireless Sensor Networks (WSNs) is of paramount importance to understand their behavior under the worst-case conditions and to make the appropriate design choices. This is particular relevant for time-sensitive WSN applications, where the timing behavior of the network protocols (message transmission must respect deadlines) impacts on the correct operation of these applications. In that direction this article contributes with a methodology based on Network Calculus, which enables quick and efficient worst-case dimensioning of static or even dynamically changing cluster-tree WSNs where the data sink can either be static or mobile. We propose closed-form recurrent expressions for computing the worst-case end-to-end delays, buffering and bandwidth requirements across any source-destination path in a cluster-tree WSN. We show how to apply our methodology to the case of IEEE 802.15.4/ZigBee cluster-tree WSNs. Finally, we demonstrate the validity and analyze the accuracy of our methodology through a comprehensive experimental study using commercially available technology, namely TelosB motes running TinyOS.

Energy Efficient Scheduling for Cluster-Tree Wireless Sensor Networks With Time-Bounded Data Flows: Application to IEEE 802.15.4/ZigBee

Cluster scheduling and collision avoidance are crucial issues in large-scale cluster-tree Wireless Sensor Networks (WSNs). This paper presents a methodology that provides a Time-Division Cluster Scheduling (TDCS) mechanism based on the cyclic extension of Resource Constrained Project Scheduling with Temporal Constraints (RCPS/TC) problem for a cluster-tree WSN, assuming bounded communication errors. The objective is to meet all end-to-end deadlines of a predefined set of time-bounded data flows while minimizing the energy consumption of the nodes by setting the TDCS period as long as possible. Since each cluster is active only once during the period, the end-to-end delay of a given flow may span over several periods when there are the flows with opposite direction. The scheduling tool enables system designers to efficiently configure all required parameters of the IEEE 802.15.4/ZigBee beacon-enabled cluster-tree WSNs in the network design time. The performance evaluation of the scheduling tool shows that the problems with dozens of nodes can be solved while using optimal solvers.

TDBS: a time division beacon scheduling mechanism for ZigBee cluster-tree wireless sensor networks

Synchronization is a challenging and important issue for time-sensitive Wireless Sensor Networks (WSN) since it requires a mutual spatiotemporal coordination between the nodes. In that concern, the IEEE 802.15.4/ZigBee protocols embody promising technologies for WSNs, but are still ambiguous on how to efficiently build synchronized multiple-cluster networks, specifically for the case of cluster-tree topologies. In fact, the current IEEE 802.15.4/ZigBee specifications restrict the synchronization to beacon-enabled (by the generation of periodic beacon frames) star networks, while they support multi-hop networking in mesh topologies, but with no synchronization. Even though both specifications mention the possible use of cluster-tree topologies, which combine multi-hop and synchronization features, the description on how to effectively construct such a network topology is missing. This paper tackles this issue by unveiling the ambiguities regarding the use of the cluster-tree topology and proposing a synchronization mechanism based on Time Division Beacon Scheduling (TDBS) to build cluster-tree WSNs. In addition, we propose a methodology for efficiently managing duty-cycles in every cluster, ensuring the fairest use of bandwidth resources. The feasibility of the TDBS mechanism is clearly demonstrated through an experimental test-bed based on our open-source implementation of the IEEE 802.15.4/ZigBee protocols.