Custom Design and Experimental Evaluation of Passive Reflectors for mmWave Private Networks

Future 6G private networks rely on millimeter-wave (mmWave) cells for ultra-high local connectivity, but non-line-of-sight (NLOS) scenarios demand costly dense deployments. Instead, a new approach gaining much attention in research introduces intelligent reflecting surfaces (IRSs) to increase coverage with fewer full-blown active antennas. In an earlier work, we introduced and validated a new passive IRS architecture leveraging additive manufacturing to provide reflections tailored exactly to the needs of a specific scenario. The design goal for so-called HELIOS reflectors is to procure a geometry realizing high power gains for mobile devices in a well-defined service area. This contribution introduces a design process coupling electromagnetic (EM) simulations with differential evolution-based optimization to custom-tailor the reflector shape. Our indoor measurements confirm the specified reflection characteristics and find that up to, on average, 41.2 % higher gain in receive power is attained over a broad angular range compared with a narrow-reflecting IRS. By increasing the IRS size, the peak gain of 20 dB can be matched. Moreover, it is found that the designed HELIOS reflectors support the entire mmWave spectrum. An additional benefit is given by the fact that the sub-6 GHz anchor link attains power gains of up to 12 dB from the same reflectors.