Research On Precoding Based On SVD In MIMO-OQAM/FBMC Communication Systems

Filter bank multicarrier with offset quadrature amplitude modulation(OQAM/FBMC)adopts good time-frequency shaping prototype filter on each subcarrier.Thus,the high sidelobes and bandwidth leakage are greatly reduced.Users no longer need strict orthogonality and synchronization,which,on one hand,create conditions for the transmission with low delay,and on the other hand,makes it possible for providing flexible parameters configuration for diverse communications.Meanwhile,cyclic prefix(CP)is not needed in OQAM/FBMC system,which increases the frequency efficiency.Therefore,OQAM/FBMC has become a hot research of the next generation wireless communication system.Differently from orthogonal frequency division multiplexing(OFDM)technology,the orthogonality of OQAM/FBMC is only hold in the real domain,interference exists in the form of imaginary.The integration of multiple-input multiple-output(MIMO)techniques with OQAM/FBMC,in general,is more complicated than with OFDM.Thanks to the adding of CP,a subchannel(subcarrier band)is exact flat and independent from other subchannels in OFDM systems.Thus,MIMO precoding and equalization independently,without leading to any inter-carrier interference(ICI)or inter-symbol interference(ISI).However,without CP,the MIMO precoding and equalization of QOAM/FBMC systems are more complicated and could lead to considerable ICI/ISI under frequency selective channels.SVD is a very efficient precoding method,which can transform a MIMO channel to a diagonal matrix.According to the above problems,this paper propose an SVD-OQAM/FBMC architecture to support beamforming with finer granularity in frequency domain,based on the frequency spreading FBMC(FS-FBMC)structure.In addition,two methods are proposed to smooth the beamformers from tone to tone.That are phase factor optimization and orthogonal iteration.Results show that the proposed SVD-OQAM/FBMC system shares close bit error rate(BER)performance with its OFDM counterpart under frequency selective channels.