Robust DWMMSE Framework for Energy-Efficient Relay-Assisted Carrier Aggregation (RACA) in Power-Constrained XR Systems

Extended Reality (XR) applications demanding high data rates pose significant challenges for uplink transmissions from user equipment (UE) with limited power and antenna resources. Recently, relay-assisted carrier aggregation (RACA) systems have been proposed to enhance data rates by transmitting data across two frequency bands. This paper addresses the practical issues of power-constrained XR devices and imperfect channel state information (CSI) in RACA systems. We propose a robust Dinkelbach's-transformed weighted minimum mean square error (DWMMSE) framework to maximize energy efficiency (EE) and minimize mean square error (MSE) under Gaussian CSI errors. The framework adapts to content-intensive, powerconstrained, and reliability-critical XR scenarios through specific alternating optimization settings. Simulation results demonstrate that DWMMSE achieves superior EE with a 92% reduction in complexity compared to baseline methods. Moreover, it delivers lower MSE and bit error rate (BER) than non-robust schemes.