Experimental Evaluation of Multicarrier Phase Difference Localization in Bluetooth Low Energy

Historically, the first indoor localization method using Bluetooth low energy (BLE) relied on received signal strength indicator (RSSI) measurements. This simple and cost-effective method suffers from limited accuracy due to its high susceptibility to environmental factors. The introduction of angle-of-arrival (AoA) functionality in BLE v5.1 significantly improved accuracy by enabling signal phase measurements. AoA exploits the phase difference of the received signal across spatially distributed antennas to estimate the direction of arrival and then pinpoint the location using triangulation. In contrast, the multicarrier phase difference (MCPD) leverages the phase difference of the signal at a single antenna but across different frequencies. The phase difference is used to estimate the distance, which allows the location to be determined using multilateration. MCPD is a recent addition to the BLE standard known as channel sounding, but unfortunately, real-world evaluations of this method are scarce. This article addresses this gap by experimentally analyzing the performance of MCPD in an indoor environment. We conduct comprehensive experiments in a 100 m2 office space, comparing the accuracy of MCPD with RSSI and AoA-based approaches in the same area. The results show that the MCPD technique yields similar localization accuracy to the AoA method, with a mean localization error of 0.98 and 1.26 m, respectively, while avoiding the need for complex antenna arrays. In addition, MCPD significantly outperforms RSSI-based methods, which have a mean localization error of 3.83 m.