Effect of information delay on string stability of platoon of automated vehicles under typical information frameworks

The effect of the information delay, which was caused by thc naturc of the distance sensors and wireless communication systems, on the string stability of platoon of automated vehicles was studied. The longitudinal vehicle dynamics model was built by taking the information delay into consideration, and three typical information frameworks, i.e., leader-predecessor framework （LPF）, multiple-predecessors framework （MPF） and predecessor-successor framework （PSF）, were defined and their related spacing error dynamics models in frequency domain were proposed. The string stability of platoon of automated vehicles was analyzed for the LPF, MPF and PSF, respectively. Meanwhile, the related sufficient string stable conditions were also obtained. The results demonstrate that the string stability can be guaranteed tbr the LPF and PSF with considering the information delay, but the ranges of the control gains of the control laws are smaller than those without considering the information delay. For the MPF, the ＂weak＂ string stability, which can be guaranteed without considering the information delay, cannot be obtained with considering the information delay. The comparative simulations further demonstrate that the LPF shows better string stability, but the PSF shows better string scalable performance.

Effects of information transmission delay and channel blocking on synchronization in scale-free Hodgkin-Huxley neuronal networks

In this paper,we investigate the evolution of spatiotemporal patterns and synchronization transitions in dependence on the information transmission delay and ion channel blocking in scale-free neuronal networks.As the underlying model of neuronal dynamics,we use the Hodgkin-Huxley equations incorporating channel blocking and intrinsic noise.It is shown that delays play a significant yet subtle role in shaping the dynamics of neuronal networks.In particular,regions of irregular and regular propagating excitatory fronts related to the synchronization transitions appear intermittently as the delay increases.Moreover,the fraction of working sodium and potassium ion channels can also have a significant impact on the spatiotemporal dynamics of neuronal networks.As the fraction of blocked sodium channels increases,the frequency of excitatory events decreases,which in turn manifests as an increase in the neuronal synchrony that,however,is dysfunctional due to the virtual absence of large-amplitude excitations.Expectedly,we also show that larger coupling strengths improve synchronization irrespective of the information transmission delay and channel blocking.The presented results are also robust against the variation of the network size,thus providing insights that could facilitate understanding of the joint impact of ion channel blocking and information transmission delay on the spatiotemporal dynamics of neuronal networks.

Taming desynchronized bursting with delays in the Macaque cortical network

Inhibitory coupled bursting Hindmarsh-Rose neurons are considered as constitutive units of the Macaque corti- cal network. In the absence of information transmission delay the bursting activity is desynchronized, giving rise to spatiotemporally disordered dynamics. This paper shows that the introduction of finite delays can lead to the synchro- nization of bursting and thus to the emergence of coherent propagating fronts of excitation in the space-time domain. Moreover, it shows that the type of synchronous bursting is uniquely determined by the delay length, with the transi- tions from one type to the other occurring in a step-like manner depending on the delay. Interestingly, as the delay is tuned close to the transition points, the synchronization deteriorates, which implies the coexistence of different bursting attractors. These phenomena can be observed by different but fixed coupling strengths, thus indicating a new role for information transmission delays in realistic neuronal networks.

The effect of propagation delay on the dynamic evolution of the Bitcoin blockchain

This paper analyzes the selfish-mine strategy in the Bitcoin blockchain introduced in 2013 by I.Eyal and E.G.Sirer.This strategy could be used by a colluding pool of miners to earn more than their fair share of the mining revenue and in consequence to force other honest miners to join them to decrease the variance of their revenues and make their monthly revenues more predictable.It is a very dangerous dynamic that could allow the rogue pool of miners to go toward a majority by accumulating powers of news adherents and control the entire network.Considering that the propagation delay of information between any two miners in the network,which is not negligible and follows a normal distribution with mean proportional to the physical distance between the two miners,and a constant variance independent of others'delays,we prove that no guarantee can be given about the success or failure of the selfish-mine attack because of the variability of information propagation in the network.

Investigating GNSS PPP-RTK with external ionospheric constraints

Real-Time Kinematic Precise Point Positioning(PPP–RTK)is inextricably linked to external ionospheric information.The PPP-RTK performances vary much with the accuracy of ionospheric information,which is derived from diferent network scales,given diferent prior variances,and obtained under diferent disturbed ionospheric conditions.This study investigates the relationships between the PPP–RTK performances,in terms of precision and convergence time,and the accuracy of external ionospheric information.The statistical results show that The Time to First Fix(TTFF)for the PPP-RTK constrained by Global Ionosphere Map(PPP-RTK-GIM)is about 8–10 min,improved by 20%–50%as compared with that for PPP Ambiguity Resolution(PPP-AR)whose TTFF is about 13–16 min.Additionally,the TTFF of PPP-RTK is 4.4 min,5.2 min,and 6.8 min,respectively,when constrained by the external ionospheric information derived from diferent network scales,e.g.small-,medium-,and large-scale networks,respectively.To analyze the infuences of the optimal prior variances of external ionospheric delay on the PPP–RTK results,the errors of 0.5 Total Electron Content Unit(TECU),1 TECU,3 TECU,and 5 TECU are added to the initial ionospheric delays,respectively.The corresponding convergence time of PPP–RTK is less than 1 min,about 3,5,and 6 min,respectively.After adding the errors,the ionospheric information with a small variance leads to a long convergence time and that with a larger variance leads to the same convergence time as that of PPP-AR.Only when an optimal prior variance is determined for the ionospheric delay in PPP-RTK model,the convergence time for PPP-RTK can be shorten greatly.The impact of Travelling Ionospheric Disturbance(TID)on the PPP-RTK performances is further studied with simulation.It is found that the TIDs increase the errors of ionospheric corrections,thus afecting the convergence time,positioning accuracy,and reliability of PPP-RTK.

Security and performance evaluation of master node protocol based reputation blockchain in the bitcoin network

Bitcoin is a digital currency based on a peer-to-peer network to propagate and verify transactions.Bitcoin is gaining wider adoption than any previous crypto-currency.However,the mechanism of peers randomly choosing logical neighbours without any knowledge about the underlying physical topology can cause a delay overhead in information propagation which makes the system vulnerable to double spend attacks.Aiming at alleviating the propagation delay problem,this paper introduces a proximity-aware extension to the current Bitcoin protocol,named Master Node Based Clustering(MNBC).The ultimate purpose of the proposed protocol,which is based on how clusters are formulated and how nodes can define their membership,is to improve the information propagation delay in the Bitcoin network.In the MNBC protocol,physical internet connectivity increases as well as the number of hops between nodes decreases through assigning nodes to be responsible for maintaining clusters based on physical Internet proximity.Furthermore,a reputation-based blockchain protocol is integrated with MNBC protocol in order to securely assign a master node for every cluster.We validate our proposed methods through a set of simulation experiments and the findings show how the proposed methods run and their impact in optimising the transaction propagation delay.