BLE beacons are broadly used for indoor localization as those devices are cheap, energy efficient and are omnipresent. Typical BLE-based localization systems employ signal strength measurements to estimate the distance between two devices although this approach suffers from poor accuracy. A recent alternative uses Multi-Carrier Phase Difference (MCPD) of Arrival and its current evaluation results are very promising. No method nor evaluation has been demonstrated so far for MCPD taking advantage of the multiple antennas capabilities of BLE 5.1. Your job is to design such a method, implement on real devices and evaluate it.