Cramér-Rao Lower Bound for Power Line Integrated Communication and Sensing

Power line communication (PLC) modems are transmitting high-frequency signals through the electric grid infrastructure. These signals can also be interpreted as probing or sensing signals. PLC is thus a natural candidate for integrated sensing and communication (ISAC). The implementation of grid sensing or monitoring with PLC has already been studied in previous work. In this paper, we ask the question what accuracy for (fault) parameter estimation can be achieved through power line ISAC. Since this is the first study of this kind, we are mainly concerned with introducing methodology. We adopt the Cramér-Rao lower bound (CRLB) as a performance criterion that is universally applicable regardless of the specific ISAC implementation. We show how to connect measurement variables and unknown parameters typically experienced in grid monitoring to obtain expressions for the CRLB. Using transmission-line modeling for PLC signal propagation, we identify automatic differentiation as a suitable tool to evaluate those expressions. The effectiveness of power line ISAC is illustrated through numerical results for a fault location estimation use case.