Controller Placement and TDMA Link Scheduling in Software Defined Wireless Multihop Networks
Yiannis Papageorgiou, Merkourios Karaliopoulos, Iordanis Koutsopoulos · 2023
In this paper, we iterate on Software Defined wireless Multihop Networks (SDWMNs) and TDMA-scheduled links, where data and SDN control traffic compete for the same resources. Two control functions are key in ensuring adequate Quality of Service (QoS) for data flows and high responsiveness (low latencies) for the SDN control-plane messages exchanged between the network nodes: the SDN Controller placement, which determines the paths of SDN control messages across the network and their overlap with the data traffic paths; and the TDMA scheduling, which distributes time slots between these two types of traffic, prioritizing them in different ways. Our take, in this paper, is that by coordinating these two control functions, rather than executing them independently, we can deal more efficiently with the data QoS-SDN responsiveness trade-off. We, thus, pursue the joint optimization of controller placement and link scheduling, formulating the respective optimization problem and proposing a novel heuristic algorithm for it. Its main idea is to, first, determine maximal sets of simultaneously transmitting non-interfering links to serve the data traffic requirements and, then, seek a Controller placement that takes best advantage of the spare link transmission opportunities in those sets. We compare our algorithm with benchmark solutions that carry out the two control functions independently and find that it trades far better the rate that can be allocated to data traffic with the communication delays at the SDN control plane.