A Software-Defined Approach to Enabling Network Controllers for Smart Environment Digital Twins

The rapid deployment of Internet-of-Things (IoT) devices in smart environments such as smart campuses and cities necessitates robust Quality-of-Service (QoS) management across heterogeneous networks. In this paper, we extend the concept of Network Digital Twin (NDT) to networked IoT devices, presenting the Network Digital Twin Controller (NDTC) that enhances the functionality and performance of smart environments. Our NDTC addresses key challenges by creating Digital Twins (DTs) of Physical Twins (PTs), synchronizing their states, and performing QoS-related what-if analyses. Specifically, we built a DT-enabled IoT-instrumented smart environment using an open-source Software-Defined Network (SDN) controller. We formulated and solved the state synchronization problem using our proposed Optimal Update (OU) and Gradient-driven Update (GU) algorithms, carefully adjusting the update frequency and data granularity to minimize DT/PT state deviation within given network bandwidth budgets. We also formulated and addressed the what-if analysis problem by selecting optimal what-if analyzers using our Optimal Selection (OS) algorithm for the most accurate QoS predictions under a given computing time budget. Our extensive experiments on a real testbed demonstrated the merits of our proposed solution: (i) our developed NDTC and algorithms meet the functional requirements, (ii) our OU and GU algorithms significantly reduce the state deviation between PTs and DTs, and (iii) our OS algorithm largely reduces the prediction errors of what-if analyses.