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

Abstract

In this study, a time-domain reflectometry (TDR) system based on a baseband version of the orthogonal chirpdivision 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-plusnoise 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 frequencydivision multiple access at some PLMs.Index Terms-Time-domain reflectometry, orthogonal chirpdivision multiplexing, multiple access, power line communication.

Discrete-Fresnel Domain Channel Estimation in OCDM-based Radar Systems

“…) . The results from ( 23) and (24) indicate that the convolution with the CIR followed by a frequency shift f ∆ during the propagation of the transmit OCDM signal through a channel results in a circular shift by k ∆ = f ∆ /B samples on top of the circular shifts caused by the convolution with the…”

“…For this purpose, the discrete-Fresnel domain pilot design strategy introduced in [21] for coherent optical OFDM systems, which was also investigated for reflectometric sensing of power lines in baseband OCDM systems as reported in [24] and further improved in [22], is considered. The original pilot design from [21] performs unbiased channel estimation under the assumption that no frequency shifts take place.…”

“…. , P − 1} are to operate simultaneously in a MU or MIMO scenario, then the elements of the matrix Ẋp ∈ C N ×M that represents the discrete-Fresnel domain transmit frame of the pth transmitter are given by This equation indicates that the FrDM scheme [12], which was originally proposed in [24] for distributed reflectometric sensing of power lines, is adopted to enable orthogonal transmission of signals associated with each of the P transmitters as depicted in Fig. 2.…”

“…In the face of limitations of typical radar processing schemes for OCDM-based systems, a potential alternative is the use of discrete-Fresnel domain channel estimation, which has been introduced in [21] for coherent optical OFDM systems and further investigated in [22] and [23]. The aforementioned channel estimation strategy has also been used in the context of sensing, namely for enabling reflectometric sensing of power lines [24] with a baseband OCDM system [25]. The simplest discrete-Fresnel domain channel estimation strategy consists of transmitting a pilot OCDM symbol where only the first subchirp is active.…”

Power Line Communication and Sensing Using Time Series Forecasting

“…Several cable diagnostic solutions have been historically proposed that use high-frequency probing or testing signals, for example, using time-frequency reflectometry [ 31 , 32 , 33 , 34 , 35 , 36 ]. Such techniques have been shown to be efficient at detecting abrupt cable anomalies, e.g., a cable fault introduced due to neighboring infrastructure upgrade, such as a neighboring line drilling.…”