Passive Intelligent Reflecting Surfaces for Efficient 6G mmWave Networks: Design, Validation, and Field Trials

6G millimeter-wave (mmWave) communication systems aim to provide high-capacity networks that span larger areas than before. Particularly, obstacle-induced blockages leading to underconnected non-line-of-sight (NLOS) regions shall be mitigated with cost- and energy-efficient intelligent reflecting surfaces (IRSs) mounted at strategic positions. Static IRSs are particularly promising because they may be realized entirely passively, scaled more easily, incur less implementation loss, and integrated without control signaling. However, they must be deployed with scenario-tailored reflection characteristics. Against this background, this article first presents a holistic beam shaping approach forHELIOS IRSgeometries, allowing for directed reflection patterns with pre-determined beamwidths and in-beam gains. The analytic model-driven investigation reveals that the changes of module tilt parameters, surface dimensions, and module arrangement successfully deliver quality of service (QoS)-compliant IRSs with little loss against the theoretical performance bound. We then conduct a cross-validation through laboratory measurements and electromagnetic (EM) simulations, which confirm the targeted far-field (FF) performance. The findings also attest good signal integrity and specular suppression characteristics that are better than that of external IRSs. An urban outdoor trial with commercial mmWave devices shows that NLOS user equipment (UE) connectivity stabilizes, with more than 10 dB improvements in both received and transmit power levels as beam management adopts the introduced reflection path. Consequently, throughput enhances by up to 275 Mbit/s.