Timing-sync Protocol For Sensor Networks Research Articles

Adaptive Fractional-Order Operator Clock Synchronization Algorithm Based on Grey Prediction

As a result of the influence of clock drift and uncertainty delay in synchronous message transmission, the clock synchronization model based on statistical distribution cannot accurately describe clock deviation. This model also requires a large number of timestamp samples that cause a storage occupation issue for wireless sensor nodes with limited resources. The modeling method based on grey prediction has advantages of low sample demand and simple modeling process. However, the accuracy of the existing clock synchronization models needs to be improved. Based on the grey prediction theory, this paper proposes an adaptive fractional-order operator clock synchronization algorithm considering uncertainty delay. First, based on the clock model and clock offset model, the frequency offset between nodes is optimized by taking the mean on the clock frequencies. Second, a grey prediction algorithm based on a fractional-order operator is proposed by estimating the uncertainty delay in message transmission to obtain the clock offset. Finally, the order of the fractional-order accumulation is adjusted adaptively in the grey prediction model according to the collected timestamp sample values so that the estimation of the uncertainty delay is more accurate, thereby improving the accuracy of the clock offset. Compared with the first-order accumulative grey prediction clock synchronization algorithms and timing-sync protocol for sensor networks, the proposed scheme improved the synchronization accuracy by 29.18% and 44.01%, respectively, and reduced the variance of the clock offset by 48.66% and 64.89%. Thus, the proposed algorithm is characterized by improved stability.

Maximum Probable Clock Offset Estimation (MPCOE) to Reduce Time Synchronization Problems in Wireless Sensor Networks

Time synchronization is an essential characteristic for the faithful functioning of wireless sensor networks. Hypothetically, it is stated that the two clocks are considered to be synchronized with each other if their clock offset and frequency components within the oscillator are running at the same rate. But, practically, there is some degree of inaccuracy in the manufacturing of these clocks; as a result, their frequency sources have slight variations. This paper proposes a unique mathematical model which is based on maximum probable theory maximum probable clock offset estimation, along with the propagation delay factor for finding the best probable estimate for clock offset. In addition, a novel two-way message passing scheme-based network communication model is presented here. Based on results, it has been predicted that estimating the clock offset will help in improving the efficiency of the existing time-synchronization protocols i.e. time-sync protocol for sensor networks (TPSNs). It was observed that the standard error deviation of modified TPSN with MPCEO was reduced from 2.324 to 0.064 ms. This will make the modified TPSN model more accurate, efficient, and reliable.

An inland Wireless Sensor Network system for monitoring seismic activity

Efficient early-warning systems for earthquakes should be able to provide accurate information on the seismic event allowing ample time for precautionary measures. In this paper, an assessment of the feasibility of using a Wireless Sensor Networks (WSNs) for monitoring seismic activity on the island of Mauritius using primary waves (P-waves) is carried out. Mauritius is one of the countries which are highly at risk to natural calamities. A simulation platform is designed and implemented to test the efficiency of a WSN in monitoring seismic activity. The system estimates the location of the hypocenter and the local velocity using time delays in P-wave arrival at each sensing node. Deviations between the estimated and actual quantities are used to study the efficiency of the system. Cross-correlation analysis of the recorded P-wave signals allowed accurate propagation delay estimation up to signal-to-noise ratios (SNRs) as low as -15dB. Time synchronization between the sensing nodes using timing-sync protocol for sensor networks improved the performance of the relocation algorithm by reducing the nodes’ clock offsets to within 0.50ms. The proposed system was tested through numerical simulations with various SNRs, sampling frequencies and number of sensing nodes.

A Novel Synchronization Scheme Based on a Dynamic Superframe for an Industrial Internet of Things in Underground Mining.

The Industrial Internet of Things (IIoT) has a wide range of applications, such as intelligent manufacturing, production process optimization, production equipment monitoring, etc. Due to the complex circumstance in underground mining, the performance of WSNs faces enormous challenges, such as data transmission delay, packet loss rate, and so on. The MAC (Media Access Control) protocol based on TDMA (Time Division Multiple Access) is an effective solution, but it needs to ensure the clock synchronization between the transmission nodes. As the key technology of IIoT, synchronization needs to consider the factors of tunnel structure, energy consumption, etc. Traditional synchronization methods, such as TPSN (Timing-sync Protocol for Sensor Networks), RBS (Reference Broadcast Synchronization), mainly focus on improving synchronization accuracy, ignoring the impact of the actual environment, cannot be directly applied to the IIoT in underground mining. In underground mining, there are two kinds of nodes: base-station node and sensor node, which have different topologies, so they constitute a hybrid topology. In this paper, according to hybrid topology of unground mining, a clock synchronization scheme based on a dynamic superframe is designed. In this scheme, the base-station and sensor have different synchronization methods, improving the TPSN and RBS algorithm, respectively, and adjusts the period of the superframe dynamically by estimating the clock offset. The synchronization scheme presented in this paper can reduce the network communication overhead and energy consumption, ensuring the synchronization accuracy. Based on theCC2530 (Asystem-on-chip solution for IEEE 802.15.4, Zigbee and RF4CE applications), the experiments are compared and analyzed, including synchronization accuracy, energy consumption, and robustness tests. Experimental results show that the synchronization accuracy of the proposed method is at least 11% higher than that of the existing methods, and the energy consumption can be reduced by approximately 13%. At the same time, the proposed method has better robustness.

Performance Analysis of Time Synchronization Protocols on Different Commercial Mote Platforms

Wireless sensor networks (WSNs) have astounding advantages for monitoring environmental properties and object movement. The small size of sensors in a WSN is used very craftily and is ideal for obscured observations. However, for these observations, the sensor clocks should be synchronized within a few microseconds of each other to accurately determine the point of origin. This paper shows the performance analysis of different time synchronization protocols over different mote platforms. Time synchronization protocols like Reference Broadcast Synchronization (RBS), Timing-Sync Protocol for Sensor Networks (TPSN), Hybrid Energy-Aware protocol and Minimum Distance Clustering Hybrid Synchronization (MDCHS) protocol are simulated over different mote platforms viz., MICA2Dot433, MICA2Dot916, MICAz and TelosB. Different performance metrics like Energy Usage and Synchronization Time are used to analyse the performance of these protocols. The model is simulated using MATLAB. The effects of changes in network topology and node density are also studied.

A Revised Timing-sync Protocol for Sensor Networks by a Polling Method

TPSN(Timing-sync Protocol for Sensor Networks), the representative of time synchronization protocol for WSN(wireless sensor networks), was developed to provide higher synchronization accuracy and energy efficiency. So, TPSN’s approach has been referenced by so many other WSN synchronization schemes till now. However, TPSN has a collision problem due to simultaneous transmission among competing nodes, which causes more network convergence delay for a network-wide synchronization. A Polling-based scheme for TPSN is proposed in this paper. The proposed scheme not only shortens network-wide synchronization time of TPSN, but also reduce collision traffic which lead to needless power consumption. The proposed scheme’s performance has been evaluated and compared with an original scheme by simulation. The results are shown to be better than the original algorithm used in TPSN.

RPATS – Reliable power aware time synchronization protocol

Many applications of Wireless Sensor Networks (WSNs) need the local clocks of the individual sensor nodes (SN) to be synchronized. Almost any form of sensor data fusion or coordinated actuation requires synchronized physical time for reasoning about events in the physical world. However, while the clock accuracy and precision requirements are often stricter in WSN than in traditional distributed systems, energy and channel constraints limit the resources available to meet these goals. In this paper, we present a power aware time synchronization protocol, of type sender–receiver, suitable for implementation in duty-cycled WSN. By using this proposal most of the non-deterministic time delays during packet transfer (media access, waiting packets in queues, propagation delay) as dominant ones (order of several hundred milliseconds), in respect to data processing (interrupt handling, testing status registers in program loop) as minor (up to hundred microseconds), are bypassed. In addition reliable and unreliable data transfer between SNs is considered. With aim to compensate SN’s oscillator instability, i.e. error in time synchronization, we propose duty cycle time extension. Apart from that, in order to evaluate the low-power capability of the proposed protocol we have involved quantitative performance metric called lifetime efficiency and compared it with equivalent (same) metric of the well known Reference-Broadcast Synchronization, RBS, and Timing-sync Protocol for Sensor Networks, TPSN, protocols, for different error prone environment and different period of time synchronization.

Low Power, Accurate Time Synchronization MAC Protocol for Real-Time Wireless Data Acquisition

The issues of real-time wireless data acquisition, how to design and manage thousands of sensor nodes located over a vast geographical area, have received more and more attention during the last years. This paper proposes a real-time wireless data acquisition MAC protocol meeting the requirements of high throughput, low end-to-end latency, low energy consumption and accurate time synchronization. A hybrid approach, combining the advantages of Time Division Multiple Access (TDMA) and Frequency Hopping Spread Spectrum (FHSS), is adopted for anti-jamming and collision prevention. The packets of commands and data are delivered in a “bucket brigade”-like manner for optimum bandwidth utilization and low end-to-end latency. Experiments show that the bandwidth utilization exceeds 25%, and the mean latency per hop is kept to 8 to 9 milliseconds. Correspondingly, we propose a novel time synchronization approach which tightly coupled with TDMA scheme. As the non-determinism of time-stamp is removed from the transmission path, the frequency difference between local clock and parent's clock is estimated by periodically receiving beacons. The average per-hop synchronization error is in the 0.6µs range, which is markedly better than those of widely used algorithms, such as Reference-Broadcast Synchronization (RBS) and Timing-sync Protocol for Sensor Networks (TPSN).

Modeling and Evaluation of Wireless Sensor Network Protocols by Stochastic Timed Automata

Wireless Sensor Networks (WSNs) are widely used in different kinds of environments. They may encounter lots of stochastic uncertainties and disturbances like message loss and node dynamics. Thus, it is critical to ensure the correctness of low level protocols in WSNs and evaluate their performance under different circumstances. In this paper, we propose a new method to analyze and evaluate WSN protocols based on stochastic timed automata and statistical model checking.For modeling, the work flow of a WSN protocol can be modeled with classical timed automata. Then, to model the uncertainties such as message loss and node dynamics, which are common in realistic circumstances, the timed automata can be extended by stochastic transitions, resulting in the stochastic timed automata. For analysis, the correctness of the protocol can be answered by classical model checking on the timed automata, while the performance of the protocol under realistic environments can be evaluated by statistical model checking on the stochastic model. To illustrate the feasibility and scalability of the modeling and verification method presented in this paper, Timing-sync Protocol for Sensor Networks (TPSN) will be studied completely throughout the paper.

Time synchronization algorithm based on hierarchical structure in wireless sensor network

Time synchronization is one of the key technologies for wireless sensor networks,and it plays an irreplaceable role for the work and development of the entire wireless sensor network.This paper proposed an improved Timing-sync Protocol for Sensor Networks(TPSN) algorithm based on hierarchy.This algorithm took level-broadcast in phase of level establishment,and a combined active and inactive two-way synchronization algorithm was used in phase of time synchronization,obtaining a relatively small cost of packet and system maintenance.This improved algorithm carried out time-frequency offset correction,and ensured the accuracy of the node.The improved TPSN algorithm not only enhances the accuracy of synchronization,but also saves the energy consumption for the network.

基于随机时间自动机和统计模型检验技术的无线传感网络协议建模与分析

Recently, sensor technology has seen significant achievement. Meanwhile, Wireless Sensor Network (WSN) technique has attracted lots of attention because of its open and dynamic behaviors, and has become a very important component of the Internet-based computing. The behavior of WSN system is very complex and may encounter lots of stochastic uncertainties and disturbances like message loss and node dynamics. Furthermore, WSN system is difficult to change and maintain once it is deployed. Thus, it is critical to ensure the quality of the low level protocols of WSN system in design phase. Designers should ensure the logical correctness of a protocol, as well as evaluate the performance of the protocol under certain target environments. To handle these issues, in this paper, we propose a framework to analyze and evaluate WSN protocols based on stochastic timed automata and statistical model checking. We propose to address the modeling of the uncertainties in the realistic behaviors by weighted stochastic transitions in the timed automata model of the protocol. Furthermore, we propose that the performance of the protocol under realistic environments should be evaluated by statistical model checking which is much cheaper and more scalable. To illustrate the feasibility and detail of the modeling and verification approach presented in this paper, two well-known WSN protocols, Timing-sync Protocol for Sensor Networks (TPSN) and Flooding Time Synchronization Protocol (FTSP), are studied thoroughly throughout the paper.

단일 플러딩 라우팅 알고리즘을 활용한 센서 네트워크의 시간 동기화 기법

Usually time synchronization is performed after routing tree is constructed. This thesis proposes a time synchronization algorithm combined with single-flooding routing tree construction algorithm in a single path. TSRA (Time Synchronization Routing Algorithm) uses routing packets to construct a routing tree. Two types of time information are added to the routing packet: one is the packet receiving time, and the other is the packet sending time. Time offset and transmission time-delay between parent node and child node could be retrieved from the added time information using LTS (Lightweight Time Synchronization) algorithm. Then parent node sends the time offset and transmission time to children nodes and children nodes can synchronize their time to the parent node time along the routing tree. The performance of proposed algorithm is compared to the TPSN (Timing-sync Protocol for Sensor Networks) which is known to have high accuracy using NS2 simulation tool. The simulation result shows that the accuracy of time synchronization is comparable to TPSN, the synchronization time of all sensor nodes is faster than TPSN, and the energy consumption is less than TPSN.

Time Synchronization in Wireless Sensor Networks: A Survey

Time synchronization is a critical piece of infrastructure for any distributed system. Wireless sensor networks have emerged as an important and promising research area in the recent years. Time synchronization is important for many sensor network applications that require very precise mapping of gathered sensor data with the time of the events, for example, in tracking and vehicular surveillance. It also plays an important role in energy conservation in MAC layer protocols. The paper studies different existing methods, protocols, significant time parameters (clock drift, clock speed, synchronization errors, and topologies) to achieve accurate synchronization in a sensor network. The studied Synchronization protocols include conventional time sync protocols (RBS, Timing-sync Protocol for Sensor Networks -TPSN, FTSP), and other application specific approaches such as all node-based approach, a diffusion-based method and group sync approaches aiming at providing network-wide time. The goal for writing this paper is to study most common existing time synchronization approaches and stress the need of a new class of secure-time synchronization protocol that is scalable, topology independent, fast convergent, energy efficient, less latent and less application dependent in a heterogeneous hostile environment. Our survey provides a valuable framework by which protocol designers can compare new and existing synchronization protocols from various metric discussed in the paper. So, we are hopeful that this paper will serve a complete one-stop investigation to study the characteristics of existing time synchronization protocols and its implementation mechanism in a Sensor network environment.