On Clock Synchronization Algorithms for Wireless Sensor Networks Under Unknown Delay

Abstract

In this paper, three clock-synchronization algorithms for wireless sensor networks (WSNs) under unknown delay are derived. They include the maximum-likelihood estimator (MLE), a generalization of the estimator of Noh et al., and a novel lowcomplexity estimator. Their corresponding performance bounds are derived and compared, and complexities are also analyzed. It is found that the MLE achieves the best performance with the price of high complexity. For the generalized version of the estimator of Noh et al., although it has low complexity, its performance is degraded with respect to the MLE. On the other hand, the newly proposed estimator achieves the same performance as the MLE, and the complexity is at the same level as that of the generalized version of the estimator of Noh et al.

Maximum-Likelihood Estimator of Clock Offset between Nanomachines in Bionanosensor Networks

“…Figure 5 compares the MSEs of the estimated clock offsets by using the proposed MLE algorithm, the direct synchronization, and the estimator proposed in [42]. In the direct synchronization algorithm, the receiver ignores the propagation delay, and considers that the difference between its recorded receiving time stamp and the received transmitting time stamp from the transmitter is the clock offset.…”

“…In the direct synchronization algorithm, the receiver ignores the propagation delay, and considers that the difference between its recorded receiving time stamp and the received transmitting time stamp from the transmitter is the clock offset. The algorithm in [42] is similar to the algorithm proposed in this paper but considers both the clock offset and the clock skew estimation. For fair comparison, all the three algorithms use the same input data in the simulations.…”

“…The model is simplified compared to the other two algorithms, while in a real scenario, the molecular communication incurs a propagation delay, which affects the estimation significantly. The reason that the proposed algorithm outperforms the estimator described in [42] is because the estimation in [42] is a joint estimation for the clock offset and the clock skew. The result is obtained when both of the two estimators achieve their maximum likelihood.…”

“…Comparison among the proposed algorithm, direct synchronization, and estimator proposed in [42]; ${\beta }_0$ = 100 μs, μ = 5 μs and λ = 1.…”

Clock synchronization protocol for wireless sensor networks with bounded communication delays

“…In Chaudhari, Serpedin, and Qaraqe (2008), the joint Maximum-Likelihood Estimation (MLE) of the clock offset and skew is introduced assuming an exponential delay model. In Leng and Wu (2010), the authors derive three clock-synchronization algorithms for WSNs under unknown delays. In Kim, Lee, Serpedin, and Qaraqe (2011), a clock synchronization algorithm, called the Iterative Gaussian mixture Kalman particle filter (IGMKPF) is introduced.…”