Bluetooth Channel Sounding employs two methods for distance estimation: Phase-Based Ranging (PBR) and Round-Trip Time (RTT). Among them, PBR utilizes the phase rotation characteristics of RF signals—a signal traveling a distance D will generate a phase offset, and the relative distance between devices is calculated by measuring the phase difference between signals of different frequencies. This process essentially depends on precise perception of wireless channel transmission characteristics.

Under a single-antenna configuration, the device can only acquire the amplitude and phase information (i.e., IQ data) of the channel from a fixed spatial sampling point. However, real-world wireless channels are not ideal models—factors such as relative orientation changes between devices, human body obstruction, environmental obstacles, and multipath effects will all cause distortion in the phase information of the received signal, thereby introducing errors into the distance estimation algorithm.

The fundamental advantage of multi-antenna configurations lies in the introduction of spatial diversity. By deploying multiple antennas at different spatial locations, the device can sample the same channel from multiple angles, obtaining multiple sets of independent or weakly correlated IQ data. This provides redundant information for subsequent signal processing—such as suppressing environmental interference through multipath identification and optimal path selection—thereby enhancing the reliability and accuracy of ranging. A detailed analysis of this will be unfolded below.