A Millimeter-Wave Antenna Subset Modulation Transmitter Array for Low-Overhead Physical-Layer Security Against Wireless Eavesdropping Attacks

This article presents the design and evaluation of a millimeter-wave (mm-Wave) antenna subset modulation (ASM) transmitter (TX) array. The array consists of an application-specific integrated circuit (ASIC) packaged with on-board antennas, operating in the 28-GHz 5G NR band. For each transmission symbol, the ASM array dynamically selects a subset of antennas for radiation, leading to scrambled I/Q symbols outside the intended direction and thereby enabling resilience against eavesdropping attacks. Compared with prior efforts in this space, which suffer from compromised radio performance and insufficient confidentiality against intelligent eavesdroppers, our system incorporates three key ASIC and antenna innovations, achieving a high level of security protection with minimal performance overhead and development overhead. Specifically, we integrate an on-chip high-speed true random number generator (TRNG), achieving I/Q symbol scrambling in a truly random fashion at the symbol rate. As a result, it is almost impossible for eavesdroppers to predict any future antenna subset (AS) selections, even with the knowledge of all transmitted symbols in the past. In over-the-air (OTA) measurements, the ASM TX array is able to support 1.2-Gb/s 64-QAM communication with a sharp information beamwidth (IB) of ±2°, while achieving competitive radio performance on par with state-of-the-art 28-GHz CMOS phased-array transceivers. To the best of our knowledge, this is the first demonstration of incorporating ASM into the existing mm-Wave communication frameworks. Our results highlight the great potential and practicality of integrating ASM technology into future mm-Wave radios.