  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.
