Reliability and QoS Assurance in RIS-Assisted Indoor Networks

Future smart factories are expected to deploy reliable applications over high-performance indoor wireless channels in the millimeter-wave (mmWave) bands. Since these bands are known to be susceptible to high path losses and Line-of-Sight (LoS) blockages, low-cost Reconfigurable Intelligent Surfaces (RISs) are used to enhance the reliability of wireless links. In this paper, we formulate a combinatorial optimization problem, solved with Integer Linear Programming (ILP) to optimally maintain reliable connectivity by solving the problem of allocating RIS to robots in an indoor wireless network. Our model exploits a new feature of the so-called nulling interference from RISs by tuning reflection coefficients. We further consider the system reliability by defining Quality-of-Service (QoS) at receivers in terms of Signal-to-Interference-plus-Noise Ratio (SINR) and connection outages due to insufficient transmission quality. Numerical results for the optimal solution and heuristics show the benefits of optimally deploying RISs by providing continuous connectivity through SINR. We also show that our method can significantly reduce outages due to link quality, while meeting the requirements on system and service reliability.