On the Multiband Carrier Aggregated Nonlinear LTE-A System

This paper analyzes the impact of nonlinear high power amplifiers (HPAs) on the multiband carrier aggregated (CA) long-term evolution-advanced (LTE-A) system. It is assumed that the LTE-A system consists of a multi-input-multioutput (MIMO) orthogonal frequency-division multiplexing (OFDM)-based downlink physical-layer architecture. It has been shown that the nonlinear distortion caused by HPAs can be represented in terms of a complex attenuation factor and additive zero mean Gaussian “nonlinear" noise. The closed-form generalized expressions of complex attenuation factor and variance of additive Gaussian nonlinear noise are derived that are applicable to any number of aggregated bands with any nonlinearity order and memory depth. From these expressions, the overall performance of a multiband CA-MIMOOFDM system in terms of symbol error rate and error vector magnitude for M-ary quadrature amplitude modulation (M-QAM) has been evaluated. We also investigate the combined effect of a number of aggregated bands, input-back off, and diversity gain on the performance of a CA-MIMO-OFDM system. It is observed that diversity gain can improve the performance of CA-MIMO-OFDM in low signal-to-noise ratio (SNR) region. However, in the high SNR region, there is no substantial effect of increasing diversity on the performance. A good agreement between the analytical and simulation results in the multipath Rayleigh fading channel validates the theoretical results obtained in this paper.