# Orthogonal Chirp Division Multiplexing for Power Line Sensing via Time-Domain Reflectometry

## TL;DR

This paper introduces an OCDM-based TDR system for power line sensing, utilizing a modified DFnT for distributed measurements, offering comparable range resolution and increased measurement capacity over existing schemes.

## Contribution

The study proposes a novel OCDM-based multiple access scheme for power line sensing that exploits the Fresnel domain for orthogonality, enhancing measurement capacity compared to traditional HS-OFDM methods.

## Key findings

- Achieves the same range resolution as existing schemes.
- Provides the highest number of measurements over time.
- Offers fair SINR performance, slightly below some HS-OFDM schemes.

## Abstract

In this study, a time-domain reflectometry (TDR) system based on a baseband version of the orthogonal chirp-division multiplexing (OCDM) scheme, which is relies on a modified discrete Fresnel transform (DFnT), is proposed for power line sensing. After a detailed description of the system model, a multiple access scheme that exploits the contolution theorem of the modified DFnT for enabling distributed reflectometric and transferometric sensing of the monitored power line. Considering typical European underground low-voltage and US overhead medium-voltage (MV) power distribution networks, range resolution and maximum unambiguous range for the measurements are assessed for the proposed scheme. Next, a comparison with multiple access schemes based on the Hermitian symmetric orthogonal frequency-division multiplexing (HS-OFDM) discussed in a previous work is performed considering a Brazilian MV overhead scenario, being the number of measurements obtained over time, as well as signal-to-interference-plus-noise ratio (SINR) used as performance metrics. The attained results show that the proposed multiple access scheme results in the same range resolution as the others. Also, the highest number of measurements over time is obtained by the proposed scheme, which produces orthogonality among signals transmitted by different power line modems (PLMs) neither and time nor frequency domains, but rather in the Fresnel domain. Meanwhile, although its yielded SINR values are fair among the PLMs consisting the distributed sensing system, the proposed scheme is slightly outperformed by the HS-OFDM based on code-division multiple access and by the HS-OFDM based on frequency-division multiple access at some PLMs.