Satellite edge computing has become a promising way to provide computing services for Internet of Things (IoT) devices in remote areas, which are out of the coverage of terrestrial networks, nevertheless, it is not suitable for largescale IoT devices due to the resource limitation of satellites. Cloud computing can provide sufficient available resources for IoT devices but it does not meet the service requirements of delay sensitive users as high network latency. Collaborative edge and cloud computing is to facilitate flexible service provisioning for numerous IoT devices by incorporating the advantages of edge and cloud computing. In this paper, we investigate the virtual network function (VNF) placement problem in collaborative satellite edge and cloud computing to minimize the satellite network bandwidth usage and the service end-to-end delay. We formulate the VNF placement problem as an integer non-linear programming problem and propose a distributed VNF placement (D-VNFP) algorithm to address it, as the VNF placement problem is NP-hard. The experiments are conducted to evaluate the effectiveness of the proposed D-VNFP algorithm. The results show that the proposed D-VNFP algorithm outperforms the existing baseline algorithms of Greedy and Viterbi for solving the VNF placement problem in satellite edge and cloud computing.Index Terms-Satellite edge and cloud computing, virtual network function (VNF) placement, network bandwidth cost, end-to-end delay, distributed algorithm.
I. INTRODUCTIONT HE Internet of Things (IoT) has been widely applied in various fields, e.g., disaster monitoring, ocean transportation, target recognition and tracking, etc [1]. Large amount of computation tasks produced by IoT devices need to be offloaded by terrestrial networks to remote servers for execution as IoT devices have the low computing capacity and battery power. However, terrestrial networks have not been set up in some remote areas due to high capital expenditures and harsh environments. Fortunately, low earth orbit (LEO) satellite networks, which have low communication delay and global coverage, can provide data collection, computing, and communication services for remote IoT devices without the coverage of terrestrial networks [2]. In general, there are two computation offloading approaches in satellite-based IoT environment, where one is that computation tasks should be offloaded to ground cloud data centers by satellite networks for further processing [3]-[5], the other is that edge servers deployed on satellites can directly provide computing services for computation tasks [6]- [8].