Ambiguity resolution in ZigBee phase shift measurements using MAFA method

Abstract

This paper presents ZigBee module that is used for ranging in indoor positioning. The system is using the phase shift measurements to determine the distances between user and anchors. The nature of phase shift measurements is causing the results to be in the range of a single wave length. Thus, as in GNSS measurements, appears the problem with ambiguity resolution. In satellite positioning this issue is well described but in range-based ZigBee positioning this problem needs to be solved. The standard procedure to find the correct values of ambiguities is to search for a combination of observation equations with smallest RMS. The authors propose a different solution – the Modified Ambiguity Function Approach (MAFA). It is a method of GNSS carrier phase data processing. In this method, the integer nature of ambiguities is taken into account in the functional model of the adjustment.