Mutual Information-Driven Power Allocation in OFDM Dual-Function Radar-Communication Systems

Abstract

This paper studies the orthogonal frequency-division multiplexing (OFDM) waveform design for dual-function radar-communication (DFRC) systems in an information-theoretic framework. Mutual information (MI) is used as the performance metrics for both functions. MI defines the information rate in communications and has attracted interest in extended target estimation. A cognitive framework assumes knowledge of the communication channel state and the second-order statistics of the stochastic extended target. Compared to state-of-the-art designs, the transmitted waveform is regarded as a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">random</i> variable to derive not only the communication MI <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">but also</i> the radar MI. The so-called <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">conditional</i> MI (CMI) is thus considered between the stochastic target’s impulse response and the received signal while averaging over the distribution of all waveform realizations. Accordingly, a power allocation problem is formulated to maximize the weighted sum of radar and communication MIs with a power constraint. Jensen’s and Hadamard’s inequalities are successively applied to the radar CMI to formulate two suboptimal yet tractable problems. The two proposed waveforms are studied in various scenarios, demonstrating their ability to trade off MIs between radar and communication functions.