Unlicensed Spectrum for Ultra-Reliable Low-Latency Communication in Multi-tenant Environment

We study in this paper the transport of Ultra-Reliable Low-Latency Communications (URLLC) in the presence of multiple tenants in a system composed of unlicensed and licensed spectrum, the former being shared by the tenants. Due to the stringent reliability and latency constraints of URLLC, the more expensive 5G licensed spectrum is used to serve the traffic that is not served by the unlicensed spectrum within a certain time budget. In a competitive scenario, where each tenant tries egoistically to minimize its share of the licensed spectrum, this may result in the tragedy of the commons like situation. We formulate the problem using a game-theoretic approach to model the non-cooperative multi-tenant scenario. We model the medium access of the combined unlicensed and licensed system to quantify the performance of the system, in terms of the overall probability of failure, and validate the model against simulations. We then derive the strategies that minimize individual cost functions. Our work gives insights about the existence of Nash equilibria and identify them numerically. Finally, we quantify the so-called price of anarchy, i.e., ratio of the utility yielded by the competitive setting to the outcome of a cooperative scenario.