Improved Fbmc/Oqam Uplink Performance Using An Antenna Array In A Highly Frequency Selective Fading Channel

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 Delta theta = 15 degrees, 10 degrees, and 5 degrees, respectively, where N and Delta theta 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.