UC San Diego prototypes nearly double indoor millimeter-wave rates

At UC San Diego, electrical engineering Ph.D. student Wuqiong Zhao holds a six-inch-by-six-inch tile that looks more like a small panel than a piece of network equipment. Inside it are thousands of elements smaller than millimeter waves, arranged to redirect signals around the walls, furniture and people that normally stop them. The team led by professor Xinyu Zhang has demonstrated the FlowForm system, and reports nearly doubled average indoor link data rates.

The problem is physical. Unlike Wi-Fi or cellular signals, millimeter-wave channels cannot pass through walls, furniture or other objects. FlowForm replaces powered equipment with coordinated reflective tiles: engineers map an indoor space, locate the hardware sending and receiving the signals, then design tiles that steer the waves through the available paths. Some tiles focus long relay chains around obstacles; others spread the signal into areas where users need coverage.

The tiles are made from 3D-printed plastic filament with a conductive paint layer. They cost roughly $2 each, need no power, control or runtime coordination, and do not require firmware changes or modifications to standard network protocols. Mounted on walls or ceilings, they work with standard millimeter-wave radios. The team mapped five different indoor environments, designing a separate arrangement for each one.

According to the UC San Diego engineers, FlowForm doubled the wireless coverage area in challenging indoor environments. Its gains matched those available from active reconfigurable intelligent surfaces, or RIS—a leading 6G research approach that actively changes how signals are redirected—while using less complexity and cost. The researchers presented the work at ACM SIGCOMM 2026.

In practical terms, the tiles could make high-capacity millimeter-wave links usable in more corners of an indoor space without adding powered relay hardware or asking existing radios to recognize a new network layer. Their fixed surfaces can also serve mobile users: as people move, access points scan steerable beams and can use whichever subset of surfaces offers the strongest route. But this remains a demonstrated prototype. The reported figures come from the UC San Diego team, and each environment requires mapping and a site-specific set of tiles.