A single-player Monte Carlo tree search method combined with node importance for virtual network embedding

© 2020, Institut Mines-Télécom and Springer Nature Switzerland AG. As a critical technology in network virtualization, virtual network embedding (VNE) focuses on how to allocate physical resources to virtual network requests efficiently. Because the VNE problem is NP-hard, most of the existing approaches are heuristic-based algorithms that tend to converge to a local optimal solution and have a low performance. In this paper, we propose an algorithm that combines the basic Monte Carlo tree search (MCTS) method with node importance to apply domain-specific knowledge. For a virtual network request, we first model the embedding process as a finite Markov decision process (MDP), where each virtual node is embedded in one state in the order of node importance that we design. The shortest-path algorithm is then applied to embed links in the terminal state and return the cost as a part of the reward. Due to the reward delay mechanism of the MDP, the result of link mapping can affect the action selected in the previous node mapping stage, coordinating the two embedding stages. With node importance, domain-specific knowledge can be used in the Expansion and Simulation stages of MCTS to speed up the search and estimate the simulation value more accurately. The experimental results show that, compared with the existing classic algorithms, our proposed algorithm can improve the performance of VNE in terms of the average physical node utilization ratio, acceptance ratio, and long-term revenue to cost ratio

Modeling Guaranteed Delay of Virtualized Wireless Networks Using Network Calculus

Wireless network virtualization is an emerging technology that logically divides a wireless network element, such as a base station (BS), into multiple slices with each slice serving as a standalone virtual BS. In such a way, one physical mobile wireless network can be partitioned into multiple virtual networks each operating as an independent wireless network. Wireless virtual networks, as composed of these virtual BSs, need to provide quality of service (QoS) to mobile end user services. One such key QoS parameter is network delay, in particular upper bound delay. This paper presents a delay model for such a wireless virtual network. This delay model considers resources (in particular queues) of both physical nodes and virtual nodes and provides a realistic modelling of the delay behaviours of wireless virtual networks. Network calculus, which usually provides finer insight into a system, is utilized to fulfil the modelling task. The numerical results have shown the effectiveness of the proposed model. The model is useful for both off-line network planning and online network admission control