Mobile edge computing and fog computing are promising techniques providing computation service closer to users to achieve lower latency. In this work, we study the optimal offloading strategy in the three-tier federated computation offloading system. We first present queueing models and closed-form solutions for computing the service delay distribution and the probability of the delay of a task exceeding a given threshold. We then propose an optimal offloading probability algorithm based on the sub-gradient method. Our numerical results show that our simulation results match very well with that of our closed-form solutions, and our sub-gradient-based search algorithm can find the optimal offloading probabilities. Specifically, for the given system parameters, our algorithm yields the optimal QoS violating probability of 0.188 with offloading probabilities of 0.675 and 0.37 from Fog to edge and from edge to cloud, respectively.
翻译:移动边缘计算和雾计算是提供更接近用户的计算服务的有希望的技术,以达到较低的延迟度。在这项工作中,我们研究了三层联合计算卸载系统中的最佳卸载策略。我们首先提出了用于计算服务延迟分布和任务超过某一阈值的延迟可能性的排队模型和封闭式解决方案。然后我们根据亚梯度方法提出了一个最佳卸载概率算法。我们的数字结果显示,我们的模拟结果与我们封闭式解决方案非常匹配,而我们次梯级搜索算法可以找到最佳卸载概率。具体地说,对于特定系统参数,我们的算法得出了最佳QOS违反0.188概率的概率,从浮点到边缘和从边缘到云点的概率分别为0.675和0.37。