Interference Mitigation in Joint Communications and Sensing-Part I: Correlation and Collision

The technology of joint communications and sensing (JCS), in which both functions share the same waveform and thus the same spectrum band and power, is expected to be deployed in various cyber physical systems (CPSs) such as vehicular ad hoc networks (VANETs) and advanced air mobility (AAM). In the context of densely deployed JCS networks, such as in VANETs, the interference from multiple JCS transceivers may significantly impair the performances of communications and sensing. Due to the large bandwidth required for radar sensing, it is difficult to assure orthogonal channel access in JCS. Therefore, spectrum spreading is a promising solution to the interference mitigation, similarly to code division multiple access (CDMA), modulated by communication symbols. Then, the design of waveform is to optimize the ambiguity function (AF) and cross AF (CAF), such that the sensing performance is improved while the interference is mitigated. The key difference from traditional sensing waveform synthesis is the randomness incurred by the communication modulation. Therefore, the variances of AF and CAF are taken into account of waveform synthesis, whose performances are demonstrated by numerical simulations.