Reducing Ground Reflection Multipath Errors for Bluetooth Angle-of-Arrival Estimation by Combining Independent Antenna Arrays

Abstract

For outdoor navigation using Bluetooth direction finding, elevation angle estimate errors due to ground reflection multipath interference is a significant challenge at low elevation angles. One of the ways to reduce this issue is to increase the vertical dimension of the array. We consider the synchronization of measurements from two independent arrays stacked vertically to achieve the same effect without needing to construct a larger array, allowing hardware modularity using low-cost equipment. The measurement synchronization is itself affected by the multipath, and a method to handle this effect is proposed. Using measurements from a 15 cm × 15 cm array in field experiments, we demonstrate a reduction in elevation error of up to 10∘ at elevation angles in the 7∘ – 15∘ range, where the error was largest when using a single array.