Energy-efficient Mechanical Beam Scanning for mmWave Systems with Over-the-Air Modulation

Recently, an over-the-air modulation (OTAM) technique has been proposed, which utilizes differences in channel attenuation to achieve signal modulation, rather than viewing attenuation merely as a detrimental effect. OTAM-based systems eliminate the requirement for radio frequency chains and modulation components, enabling a low-cost, low-power millimeter-wave (mmWave) communication approach. However, OTAM-based systems suffer from the low energy efficiency of wide beams, potential misalignment of fixed-directional beams, and inadequate support for multiple nodes. To address these fundamental challenges, this paper proposes a mechanical-beamscanning OTAM mmWave (MOM) system, which is an extension of the conventional OTAM framework. Firstly, we redesign the antenna pattern to obtain high-gain narrow beams. Secondly, we enable nodes to steer beam direction by mechanical devices. Thirdly, we develop a multi-node access mechanism that adapts the access strategy to support joint beam scanning and alignment between nodes and the access point. As a result, the MOM system exhibits superior transmission performance and access efficiency compared to the OTAM system, as validated through extensive experiments. Furthermore, we built and tested a hardware prototype of the MOM system, which achieved higher cost and energy efficiency than other mmWave systems.