Closed-Form Algorithm for 3-D Near-Field OFDM Signal Localization under Uniform Circular Array.

Xiaolong Su,Xin Chen,Zhen Liu,Xizhang Wei

doi:10.3390/s18010226

Abstract

Due to its widespread application in communications, radar, etc., the orthogonal frequency division multiplexing (OFDM) signal has become increasingly urgent in the field of localization. Under uniform circular array (UCA) and near-field conditions, this paper presents a closed-form algorithm based on phase difference for estimating the three-dimensional (3-D) location (azimuth angle, elevation angle, and range) of the OFDM signal. In the algorithm, considering that it is difficult to distinguish the frequency of the OFDM signal’s subcarriers and the phase-based method is always affected by errors of the frequency estimation, this paper employs sparse representation (SR) to obtain the super-resolution frequencies and the corresponding phases of subcarriers. Further, as the phase differences of the adjacent sensors including azimuth angle, elevation angle and range parameters can be expressed as indefinite equations, the near-field OFDM signal’s 3-D location is obtained by employing the least square method, where the phase differences are based on the average of the estimated subcarriers. Finally, the performance of the proposed algorithm is demonstrated by several simulations.

Highlights

The orthogonal frequency division multiplexing (OFDM) signal has superior performance due to the practical applications in wireless local area networks (WLAN), 4G mobile communications, digital audio broadcasting (DAB) systems, radar, etc., which have received considerable attention in the field of source localization [1,2,3]
The results show that the proposed algorithm can accurately estimate the frequenciesand and thecorresponding correspondingphases phasesof ofthe theOFDM
In order to verify that sparse representation can decouple the subcarriers of the OFDM signal in the frequency domain and obtain the corresponding phases, we consider a simulation that the OFDM signal has 8 subcarriers and the carrier frequency f c = 100 MHz

Summary

Introduction

The orthogonal frequency division multiplexing (OFDM) signal has superior performance due to the practical applications in wireless local area networks (WLAN), 4G mobile communications, digital audio broadcasting (DAB) systems, radar, etc., which have received considerable attention in the field of source localization [1,2,3]. In [9], by using a fixed rotary UCA with a center sensor, Chen et al considered the condition of multiple mono-frequency sources and the ambiguity in the phase-based algorithm, the phase difference before and after rotation is utilized to obtain the 3-D localization and resolve ambiguity. It is limited by the specific condition that the frequency spacing should be more than 8 times frequency resolution, which cannot be extended to the localization for the wideband signal

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Methods

Results

Conclusion