Dual-Function Multiplexing for Waveform Design in OFDM-Based Joint Communications and Sensing: An Edgeworth Box Framework

In joint communications and sensing (JCS), which is a potential technology for the 6G wireless communication networks, the multiplexing of communication and sensing functions is of critical importance. In the signaling framework of orthogonal frequency division multiplexing (OFDM), if all subcarriers are used for communications (which can also be used for sensing as a byproduct), the randomness of data will add significant uncertainty to the sensing results; meanwhile, if deterministic signals are used for all subcarriers, in order to optimize the sensing performance, the function of communications is invalidated due to the loss of randomness. Therefore, it is proposed to multiplex the communication and sensing functions in different OFDM subcarriers. The mutual benefits of communication and sensing subcarriers are analyzed, in which communication subcarriers provide extra bandwidth and power for sensing, while sensing subcarriers with deterministic sensing signals are used as pilots for communication channel estimation. The allocation of power and subcarriers for communications and sensing is solved using the Edgeworth Box in economics. Numerical simulations are used to demonstrate the proposed multiplexing scheme in JCS.