In this work, a resource allocation problem is investigated for a relay-based multiuser cooperative orthogonal frequency division multiple access (OFDMA) uplink system, considering a very large antenna array at the base station and nonlinear power amplifiers (PAs) in both user and relay nodes. Firstly, a theoretical characterization of the considered scenario is performed. Then, some analytical expressions for the nonlinear distortion (NLD) variance and the PA constant of a third-order polynomial PA are derived, as well as the instantaneous signal-to-noise ratio (SNR) of the considered system is calculated. Then, a low-complexity suboptimal relay selection and subcarrier allocation technique is proposed for the considered scenario based on the developed expressions. Numerical simulation results are presented to validate the derived expressions and to evaluate the performance of the proposed technique.

This paper presents two new per-subcarrier relay selection techniques for cooperative orthogonal frequency division multiplexing (OFDM) communication systems with nonlinear power amplifiers (PAs) and considering the amplify-and-forward (AF) protocol. The proposed techniques are based on a developed theoretical expression for the instantaneous signal-to-noise ratio (SNR) of an AF cooperative OFDM system taking into account the nonlinear distortions introduced by the relays' PAs. Our results show that both the proposed techniques can significantly improve the system capacity when compared to a classical relay selection method. Numerical simulation results are presented to validate the performance of the proposed techniques.

This work proposes the formulation of a data rate maximization problem in an orthogonal frequency division multiplexing (OFDM) system taking into account the distortions inserted by a third-order (3rd) polynomial nonlinear power amplifier (PA). Based on this formulation, two suboptimal heuristic algorithms are proposed for power allocation in the considered scenario. The two heuristics, named HH-MI (Hughes-Hartogs - Modified 1) and HH-M2 (Hughes-Hartogs - Modified 2), are based on the HH algorithm. These methods try to maximize the system capacity, but taking into account the distortions inserted by a nonlinear PA. One of the advantages of such techniques is that energy gains can be obtained, as the power is only allocated if the distortions do not affect system. Finally, we present a performance analysis in which the gains of the proposed heuristics are demonstrated with respect to the conventional HH.