High-resolution range estimation technique using shift invariant TOA estimation algorithm for indoor localization of chirp spread spectrum system

We proposed a subspace-based two-way ranging system for high resolution indoor ranging that is robust to frequency offset. The problem of sampling frequency offset (SFO) is resolved by adopting SDS-TWR protocol, which is developed against SFO. Although there are many papers about subspace-based TOA estimations, they do not consider the effect of carrier frequency offset (CFO). We consider and resolve the effect of CFO through the proposed algorithm with chirp spread spectrum (CSS) signals. Experimental results are obtained through the prototype ranging system composed of a FPGA development board and a RF kit. Results show that the ranging error of the proposed ranging system averages less than 1 meter in an indoor environment.

1 Introduction

With recent advances in sensor networks, there is increasing demand for smaller, less expensive, less complicated sensor nodes. Sensor networks are used in surveillance-type tasks, such as asset tracking, finding people on the move, and mobile tracking in emergency situations. These location-based applications have gained increasing interest in recent decades, especially those for the user sensor network (USN). Several localization techniques have been investigated, including the received signal strength (RSS) indicator [1], time of arrival (TOA) [2], time difference of arrival (TDOA) [3], and angle of arrival (AOA). We focus on the asynchronous TOA-based ranging approach known as two-way ranging (TWR).