Research On Timeliness Based Data Collection Scheme In Internet Of Things

With the development of cyber-physical system(CPS),the integration between information network and physical world are getting deeper and more critical.In CPS,decision making(such as real-time monitoring and accurate control)is prone to timeliness of information,which is neglected in delay and throughput oriented network.Age of information(Aol)is proposed as a new performance metric to quantify the timeliness in recent years.In single-hop network,age-oriented problems are widely investigated to schedule multiple devices to access the shared wireless medium.Considering the limited power at each sensor,the sampled data may be forwarded to central controller for further processing via multiple hops.On one hand,AoI of each information flow is affected by multiple factors such as inter node interference and transmission path selection.To improve the end-to-end timeliness of multi-flow in the network,data sampling,routing and link scheduling strategies need to be considered comprehensively.On the other hand,great energy consumption brings challenge to battery powered end devices.In order to solve the aforementioned problems,the main contribution of this thesis is given as follows:(1)As for the timeliness concern in multi-flow network,a joint data sampling and transmission strategy is proposed for obtaining fresh information.Considering data sampling at sources nodes,routing along the paths,scheduling among communication links,age based optimization problem was formulated and falls in the category of Integer Non-Linear Program(INLP).To solve the long-term age minimization problem efficiently,we derived an age reduction reward function for each time slot,and employed Lyapunov optimization techniques to characterize the tradeoff between age reward and system stability.Then a distributed scheme consisting of sampling strategy at source node,as well as routing and link activation strategy at each hop is proposed.Simulation results show that our proposed scheme outperforms delay-based schemes in delivering information in a timely manner.(2)As for the energy consumption concern in energy-constrained network,an information freshness optimization strategy in Simultaneous Wireless Information and Power Transfer(SWIPT)enabled scenario is proposed.Considering data packet arrival process,channel model and other system settings,closed-form expressions of long term expected Aol and lifetime of relay node are obtained.An age-based relay strategy jointly optimizing information freshness and energy status of relay nodes can be obtained based on energy evolution at relay node.Simulation results show that our proposed scheme indicates a great performance improvement in terms of information freshness and energy efficiency.