Statistical Inference – methods by which generalizations are made about a population Two Major Areas of Statistical Inference 1. Estimation – a parameter is established based on the sampling distribution of a proportion, establishing a certain degree of accuracy from the estimate 2. Test of Hypothesis – a decision is arrived at about a prestated hypothesis, thereby accepting or rejecting the hypothesis.

http://ieeexplore.ieee.org/iel5/9/24158/01101399.pdf

Estimation theory

In practical wireless sensor networks, time synchronization functions are usually integrated in existing network transmissions to minimize total energy consumption. In this letter, a hybrid synchronization scheme using one-way message dissemination and emerging timestamp-free synchronization is developed for wireless sensor networks without additional communication overhead, which not only estimates the fixed delay efficiently but also provides improved clock offset estimation. Under Gaussian delay model, the maximum likelihood estimator for the joint estimation of clock offset, skew and fixed delay is derived, as well as corresponding Cramer-Rao lower bounds. Simulation results demonstrate significant performance enhancement of the hybrid approach.

Clock Offset and Skew Estimation Using Hybrid One-Way Message Dissemination and Two-Way Timestamp Free Synchronization in Wireless Sensor Networks

Clock synchronization is crucial for applications in wireless sensor networks, such as event scheduling and data fusion. In practical wireless networks, environmental changes cause the oscillator to be imperfect. Thus, it is necessary to track the nonlinear varying clock dynamically. In this paper, we propose a timestamp-free clock skew (frequency difference) and offset (time difference) joint tracking algorithm based on extended Kalman filter (EKF), which can be embedded into the general network data flow to achieve long-term synchronization without additional communication overhead. To further improve energy efficiency of clock synchronization, this paper develops an EKF clock skew tracking algorithm for silent nodes in receiver-only synchronization. For the situation that silent node overhears synchronization information from multiple active nodes, we present multi-information timestamp-free synchronization and multi-observation clock skew fusion scheme for silent nodes. Simulation results show the effectiveness of the proposed tracking algorithms.

Timestamp-Free Clock Parameters Tracking Using Extended Kalman Filtering in Wireless Sensor Networks

With the widespread application of the Industrial Internet of Things (IIoT), the requirements for sensing equipment to collect data and information continue to increase, and industrial wireless sensor networks (IWSNs) with industrial information perception capabilities have emerged as the times require. The data stream transmission of important value information requires the network to provide safe and reliable service quality assurance. Therefore, it is imperative to meet the requirements of end-to-end delay and reliable service between nodes and solve the problems of high energy consumption and poor security of the existing Quality-of-Service (QoS) routing protocols. To this end, considering the QoS constraints of end-to-end delay, security, and energy consumption, a multiobjective secure routing model based on trust awareness is designed. Subsequently, using the advantages of the proposed model, a novel QoS-secure routing algorithm based on multiobjective chaotic elite adaptive ant colony optimization (ACO) (i.e., MCEAACO-QSRP) is proposed. Specifically, a chaotic optimization strategy is designed to initialize the population, which increases the diversity of the population and enhances the ability of the algorithm to jump out of the local optimal. In addition, the adaptive optimization strategy is designed to dynamically adjust the algorithm trend, which effectively improves the algorithm convergence speed. The performance of the proposed algorithm is evaluated in different scale scenarios. The simulation results show that compared with other state-of-the-art QoS routing solutions, the proposed MCEAACO-QSRP has obvious advantages, which can effectively improve routing security, reduce network energy consumption, and satisfy multi-QoS constrains for the end-to-end delay and reliable service. 

MCEAACO-QSRP: A Novel QoS-Secure Routing Protocol for Industrial Internet of Things

With the widespread application of the Industrial Internet of Things (IIoT), the requirements for sensing equipment to collect data and information continue to increase, and industrial wireless sensor networks (IWSNs) with industrial information perception capabilities have emerged as the times require. The data stream transmission of important value information requires the network to provide safe and reliable service quality assurance. Therefore, it is imperative to meet the requirements of end-to-end delay and reliable service between nodes and solve the problems of high energy consumption and poor security of the existing Quality-of-Service (QoS) routing protocols. To this end, considering the QoS constraints of end-to-end delay, security, and energy consumption, a multiobjective secure routing model based on trust awareness is designed. Subsequently, using the advantages of the proposed model, a novel QoS-secure routing algorithm based on multiobjective chaotic elite adaptive ant colony optimization (ACO) (i.e., MCEAACO-QSRP) is proposed. Specifically, a chaotic optimization strategy is designed to initialize the population, which increases the diversity of the population and enhances the ability of the algorithm to jump out of the local optimal. In addition, the adaptive optimization strategy is designed to dynamically adjust the algorithm trend, which effectively improves the algorithm convergence speed. The performance of the proposed algorithm is evaluated in different scale scenarios. The simulation results show that compared with other state-of-the-art QoS routing solutions, the proposed MCEAACO-QSRP has obvious advantages, which can effectively improve routing security, reduce network energy consumption, and satisfy multi-QoS constrains for the end-to-end delay and reliable service.

Existing packet-based synchronization approaches take extensive energy for industrial wireless sensor networks due to substantial timing message exchanges. Combined with acknowledgement (ACK), this article proposes an energy-efficient synchronization protocol without exchanging timestamps. Also, a mapping rule of ACK response time is presented for the joint estimation of skew and fixed delay without requiring a following response in each cycle, so that estimation can be implemented in parallel to data transmission. Then, the timestamp-free synchronization technique is extended to the receiver-only synchronization scenario to further reduce communication overhead. Assuming Gaussian variable delays, the maximum likelihood estimators and corresponding lower bounds for slave node and silent node are developed, as well as a low-complexity estimator for silent node. In addition, considering the dynamics of clock, a timestamp-free clock skew tracking algorithm using Kalman filtering is developed. Simulation results validate the efficiency of the proposed estimators.

Fei Yu

Papers

Clock Skew Estimation for Timestamp-Free Synchronization in Industrial Wireless Sensor Networks

Clock Offset and Skew Estimation Using Hybrid One-Way Message Dissemination and Two-Way Timestamp Free Synchronization in Wireless Sensor Networks