Joint radar-communications (JRC) benefits from multi-functionality of radar and communication operations using same hardware and radio frequency (RF) spectrum resources. Thus, JRC systems possess very high potential to be employed into the sixth generation (6G) standards. Besides, intelligent re- flecting surfaces have attracted wide attention in communication systems, due to low complexity of implementation. This paper designs a dynamic beamformer for reconfigurable intelligent surfaces (RIS) which maximizes spectral efficiency (SE). We jointly express the mutual information rate for communication and radar entities including a weighting factor which depicts the dominance of one operation over the other. The joint-SE based proposed method optimally selects the RIS subset. Furthermore, when the communication operation takes place the proposed method takes into account the interference occurring from the radar operation and vice-versa. Fractional programming based selection procedure is used for solving the problem of subset selection. Simulation results are presented and compared with different baselines to show effectiveness of the proposed method.
The proposed algorithm consistently outperforms baseline methods across all SNR regimes, achieving higher detection probability and communication rate.
The algorithm exhibits rapid convergence even for large subset sizes, validating its computational efficiency.
Increasing the reflection coefficient magnitude improves both radar detection probability and communication rate, with diminishing returns beyond a certain threshold.
System performance improves with more reflecting elements, but the rate of improvement diminishes, indicating an optimal configuration size for the given setup.