Joint Spectral and Power Efficiency Optimization in Uplink Radio Stripes

The radio stripe (RS) concept has been emerging as a practical implementation of the cell-free (CF) massive multiple-input-multiple-output (MMIMO) network where all access points (APs) that perform the signal processing required to serve the users' equipment (UEs) share a common stripe. In such a system, an uplink (UL) power optimization must be performed to increase the system's spectral and power efficiencies (SE and PE). In this work, we develop a set of multi-objective UL power optimization models and algorithms based on the differential evolution (DE) meta-heuristic (MH) considering the optimal sequential linear processing (OSLP) and maximum ratio combining (MRC) detection schemes. The bi-objective approaches aim at deriving nondominated solutions in models to: 1) maximize the max-min fairness (MMF) and max-sum rate (MSR) metrics; 2) maximize the MMF and minimize transmission power (MTP); 3) maximize the MSR and minimize the MTP. A tri-objective approach is also developed to maximize the MMF and MSR and minimize the MTP. Solutions displaying interesting trade-offs are obtained with the proposed models and algorithmic approaches, compared with the case where the UEs employ full power in the UL. Results show that improved SE and PE can be attained with the proposed bi-objective and tri-objective optimization approaches.