Finer SVD-Based Beamforming for FBMC/OQAM Systems

Abstract

The combination of singular value decomposition (SVD)-based beamforming and filter bank multicarrier with offset quadrature amplitude modulation (FBMC/OQAM) has not been successful to date. The difficulty of this combination is that, the beamformers may change dramatically between adjacent subchannels, therefore destroy the orthogonality of FBMC/OQAM real-valued symbols, under frequency selective channels. In this paper, we address this problem from two aspects: 1) an SVD-FBMC/OQAM architecture is proposed to support beamforming with finer granularity in frequency domain based on the frequency spreading FBMC (FS- FBMC) structure; 2) a method is proposed to smooth the beamformers from tone to tone (FS-FBMC tone). The proposed finer beamforming and smoothing greatly improve the smoothness of beamformers, therefore effectively suppress the leaked ICI/ISI from adjacent subchannels. Simulations are conducted under the scenario of IEEE 802.11n wireless LAN. Results show that the proposed SVD- FBMC/OQAM system shares very close BER performance with its orthogonal frequency division multiplexing (OFDM) counterpart under the frequency selective channels. The proposed finer beamforming architecture may also serve as a paradigm for the combinations of other multiple- antenna (MIMO) techniques and FBMC/OQAM.