RSMA Design for DMA under Frequency-Selective Wideband Lorentzian-Constrained Model

Dynamic metasurface antennas (DMAs) have emerged as a promising solution for reducing cost and power consumption in next-generation wireless systems employing large antenna arrays. Existing studies on DMA-based architectures typically adopt a frequency-flat approximation to model the frequency response of individual elements, in which only the phase of each element is adjustable, while the amplitude tuning remains uninvolved. Additionally, this approximation is valid only for narrowband signaling and becomes increasingly inaccurate in wideband and ultra-wideband scenarios. In contrast, by adopting the accurate non-linear frequency-selective Lorentzianconstrained model and jointly optimizing the resonance frequency and quality factor of each element, both the phase and magnitude responses are directly incorporated in the resource management process, thereby providing a more faithful representation of the frequency-dependent behavior of DMA elements in wideband and ultra-wideband systems. Motivated by this, we propose a rate-splitting multiple access (RSMA) design for DMA-based architectures using the frequency-selective Lorentzian model in wideband transmissions, aiming to maximize the minimum achievable sum-rate across all subcarriers. To this end, we jointly optimize the transmit beamforming vectors across all subcarriers as well as the resonance frequency and the quality factor of all DMA elements. Simulation results indicate that the nonlinear frequency-selective Lorentzian model achieves an approximately 40% performance gain over the frequency-flat approximation in DMA architectures with RSMA for wideband transmissions.