An efficient ranging method for wireless sensor networks

The Radio Interferometric Positioning System (RIPS) provides a localization method with high accuracy and simple hardware configuration for sensor networks by means of measuring the phase difference of the interference signal. However, due to the periodicity of phase, it is hard to determine the actual distance difference only from a single phase measurement. To solve the problem, RIPS makes multiple measurements at different frequencies so as to convert phase difference to distance difference, which is a computationally intensive searching process and not suitable for the energy-constrained wireless sensor nodes. In this paper, we propose an efficient ranging method based on Chinese Remainder Theorem (CRT). Meanwhile, we utilize some properties of the coefficients in the CRT algorithm to avoid the over-sensitivity of the traditional CRT, which increases the robustness of the algorithm. We apply this robust CRT algorithm to the ranging process which calculates the distance difference directly in a closed form equation and therefore reduces the response time and energy consumption of the ranging procedure.