Improved FBMC/OQAM uplink performance using an antenna array in a highly frequency selective fading channel

Abstract

Filter bank multicarrier with offset quadrature amplitude modulation (FBMC/OQAM) is an attractive alternative to orthogonal frequency division multiplexing, as it yields a higher spectral efficiency and robustness to frequency dispersion; however, FBMC/OQAM suffers from multipath interference owing to the absence of the cyclic prefix, especially in the signal environments of widely spread multipaths. Although conventional techniques such as multiple‐input multiple‐output along with equalization can combat multipath fading, these techniques do not effectively resolve the multipath interference unless each subcarrier channel can be assumed to be of a flat fading. This article presents a systematic procedure of applying a receive antenna array to FBMC/OQAM systems that removes the multipath interferences using a nicely‐shaped beam pattern for each of the multipaths associated with a severe frequency selectivity. The performance of the proposed array system has been demonstrated in terms of its bit error rate in the adverse multipath‐spread environment of the Extended Typical Urban model of the 3rd Generation Partnership Project, in which each subcarrier channel suffers from a severe frequency‐selective fading. Using various computer simulations, we found that the proposed array system can completely resolve multipath interferences with an array of N = 10, 16, and 22 when Δθ = 15°, 10°, and 5°, respectively, where N and Δθ denote the number of antennas in each subarray and the interpath direction of arrival difference, respectively. In addition, the proposed array system also provides a signal‐to‐noise ratio gain that is proportional to N, once the multipath interferences are successfully resolved.