Radio‐Frequency Front‐End‐Free Hybrid Code‐Division and Space‐Division Wireless Multiplexing Using Space‐Time‐Coding Metasurface

Code‐division multiplexing (CDM) is essential for supporting massive connectivity in wireless networks, but its implementation typically requires complex and costly radio‐frequency (RF) chains. This work presents a simplified wireless CDM system based on a space‐time‐coding metasurface (STCM). By modulating distinct spatial partitions of the metasurface with data streams prespread via orthogonal pseudo‐random codes, the STCM functions as a distributed parallel modulator. This architecture enables the metasurface to perform simultaneous upconversion while directing modulated reflections from multiple spatial partitions toward either shared or distinct directions. Although these data‐carrying waves may physically overlap in the far‐field, the inherent orthogonality of the spread codes ensures that the receiver can successfully decorrelate and recover each multiplexed stream. Experimental validation demonstrates three core scenarios: multistream to a single direction, distinct single‐stream to distinct directions, and multistream to multiple directions (each direction gets multiple streams), all achieved without conventional RF chains. The proposed STCM‐based hybrid CDM and space‐division multiplexing (SDM) architecture enables simultaneous multiuser communication with a radically simplified RF front‐end, paving the way for simplified, high‐capacity wireless systems for future wireless networks.