This paper considers a multiple-input multiple- output (MIMO) joint radar-communication (JRC) transmission with hybrid precoding and low resolution digital to analog converters (DACs). An energy efficient radio frequency (RF) chain and DAC bit selection approach is presented for a sub- arrayed hybrid MIMO JRC system. W e introduce a weighting formulation to represent the combined radar-communications information rate. The presented selection mechanism is incorpo- rated with fractional programming to solve an energy efficiency maximization problem for JRC which selects the optimal number of RF chains and DAC bit resolution. Subsequently, a weighted minimization problem to compute the precoding matrices is formulated, which is solved using an alternating minimization approach. The numerical results show the effectiveness of the proposed method in terms of high energy efficiency whilst main- taining good rate and desirable radar beampattern performance. Index T erms—Joint radar-communications, energy efficient, RF chain optimization, low resolution DACs, hybrid precoder . I.
The proposed hybrid precoding approach with low-resolution DACs achieves significantly higher energy efficiency (EE) compared to the fully digital baseline, particularly at lower SNR levels, while maintaining comparable communication rates.
The proposed method achieves a highly directive radar beampattern with minimal sidelobes, comparable to conventional fully-digital systems, even with low-resolution DACs, ensuring effective radar functionality.
The proposed approach exhibits a clear energy-rate trade-off, allowing operators to balance communication throughput and energy consumption by adjusting the radar-communication traffic ratio (ρ), demonstrating its flexibility in practical deployments.