标题： 感知可用性的MEC启用的5G网络中的VNF放置和请求路由 显示英文标题

标题： Availability-Aware VNF Placement and Request Routing in MEC-Enabled 5G Networks

摘要： 在本文中，我们研究了在移动边缘计算（MEC）启用的5G网络中的虚拟网络功能（VNF）放置问题，以满足uRLLC应用严格的可靠性和延迟要求。我们将它建模为一个约束优化问题，这是NP难的，旨在通过服务uRLLC服务请求来最大化网络服务提供商的总奖励。我们提出了一种近似的随机舍入方法，在多项式时间内解决NP难的优化问题。我们证明了所提出的随机方法在有限违反资源约束的情况下实现了性能保证。此外，我们提出了一种贪心启发式方法来处理资源约束的违反。仿真结果表明，所提出的随机舍入和贪心方法分别能达到最优解的95%和90%的总奖励。此外，我们将所提出的贪心方法与不考虑可用性要求的现有方案进行了比较。我们观察到，现有方案在总奖励方面表现较差，因为对可用性要求的忽视会负面影响成功服务请求数量。这些发现突显了在延迟敏感的uRLLC应用中可用性与资源效率之间的权衡。我们还使用开源软件平台实现了5G网络的软件原型，并采用了VNF的冗余放置。从原型实现中获得的包传递率和延迟结果在具有不同故障概率的冗余VNF中也得到了改善。 显示英文摘要

摘要： In this paper, we study the virtual network function (VNF) placement problem in mobile edge computing (MEC)-enabled 5G networks to meet the stringent reliability and latency requirements of uRLLC applications. We pose it as a constrained optimization problem, which is NP-hard, to maximize the total reward obtained by a network service provider by serving uRLLC service requests. We propose an approximated randomized rounding approach to solve the NP-hard optimization problem in polynomial time. We prove that the proposed randomized approach achieves performance guarantees while violating the resource constraints boundedly. Furthermore, we present a greedy-heuristic approach to tackle the violations of resource constraints. Simulation results show that the proposed randomized rounding and greedy approaches achieve a total reward which is within 5% and 10% of the optimal solution, respectively. Furthermore, we compare the proposed greedy approach with the existing schemes that do not consider the availability requirements. We observe that the existing schemes perform poorly in terms of total reward, as negligence to the availability requirements negatively impacts the number of successfully served requests. These findings highlight the trade-off between availability and resource efficiency in latency-sensitive uRLLC applications. We also implement a software prototype of a 5G network using open-source software platforms with redundant placement of VNFs. The results on packet delivery ratio and latency obtained from the prototype implementation are also improved in the redundant VNFs with different failure probabilities.