Trade-off in Waveform Sensitivity to Environment in Integrated Sensing and Communications: An Electromagnetic Field Analysis

Integrated Sensing and Communications (ISAC) are expected to be one of the six pillars of 6G wireless networks. It integrates both functions in the same waveform, thus substantially improving the system efficiency of bandwidth and power. A significant trade-off exists between communications and sensing in ISAC, in terms of the sensitivity of waveform to the environment (or equivalently, of electromagnetic (EM) field to scatterers): on the one hand, if the EM field is sensitive to the scatterers, the field measurement at the sensing receiver will be more distinct with respect to different scenarios of scatterers, thus benefiting the purpose of sensing; on the other hand, more sensitivity to the environment brings the transmit waveforms (as communication codewords) more confusions, thus impairing the performance of communications. In this paper, the sensitivities of EM field to scatterers and transmit waveforms are analyzed for communications and sensing, respectively. The corresponding performance trade-off is quantified for evaluating the performance of ISAC.