DoA Estimation for Grating Lobes Caused by Antenna Spacing in COTS Communication Devices

With the proposal and development of integrated sensing and communication (ISAC), utilizing existing communications devices to realize the function of sensing is the current hot research. In existing research, the system is usually implemented based on path parameters, i.e., parameters such as direction of arrival (DoA). Obtaining accurate angle information requires the assumption that antennas are equally spaced and at a standard half wavelength. However, the antenna spacing of commercial-off-the-shelf (COTS) communication devices is often arranged in communication in a manner that is wider than half-wavelength, which may produce grating lobes that result in incorrect angle estimates. Therefore, to resolve this challenge, this paper first deeply analyzes the problem of incorrect angle estimates due to grating lobes. Then, we propose a phase projection-based ambiguity eliminate model and a power-based parameter estimate algorithm. Finally, simulation experiments are conducted to verify the proposed algorithm performance, and a system prototype is built for field trial. The experimental results show that using a 4 -antenna array, the proposed algorithm achieved median errors of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$6.12^{\circ}, 4.18^{\circ}$</tex>, and 2.53° for antenna spacing of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.6,0.8$</tex>, and 1 times the wavelength, respectively. In addition, we use localization as a case study to demonstrate the promising work done in this paper for ISAC.