任务卸载是雾计算的主要技术之一，即计算能力不足的节点将任务卸载给具有富余资源的节点帮助计算。以优化任务平均卸载时延和提升卸载服务成功率为目标，利用多臂老虎机理论为动态雾计算网络提出一种基于在线学习的任务卸载算法，可实时做出最优卸载决策。将该算法扩展到非稳定网络状态，使之可以动态追踪网络中节点的资源与环境变化，实时调整卸载决策。详细分析所提出算法的性能、复杂度和存储占用情况。仿真结果表明，这两种算法可达到的长期平均任务卸载时延均十分接近理想算法下的最优时延，卸载服务成功率也得到显著提升。此外，所提算法在非稳定的网络状态下能够追踪到计算资源与环境的变化。
Task offloading is one of the main techniques of the fog computing, and it means that the computation-limited nodes offload the tasks to the capable nodes for help. Firstly, we propose TOD (online learning-based task offloading algorithm for the dynamic fog networks under stationary status) using the MAB (multi-armed bandit) theory, which aims at minimizing the long term offloading delay and improving the task offloading success ratio. Then, we propose TOD-N (online learning-based task offloading algorithm for the dynamic fog networks under non-stationary status) to efficiently track the changes of the sharing computing resources and the channel environment. Moreover, we analyze the performances of the two algorithms on the optimality, the computational complexity, and the memory usage. Simulation results show that the long term average offloading delays achieved by the two algorithms are almost as good as the one achieved by the Oracle algorithm, and the offloading success ratios are also efficiently promoted. Moreover, TOD-N tracks the optimal resources efficiently under non-stationary network status.
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