On the ergodic achievable rate of FBMC system without subband orthogonality

A new multi-carrier multiple access scheme based on filter bank multi-carrier (FBMC) without sub-band orthogonality, referred to as imperfect reconstructed filter bank multiple access (iPR-FBMA), has been recently proposed. While it entitles substantial performance improvement on the peak-to-average power ratio and bit error rate compared to the conventional orthogonal frequency division multiplexing (OFDM) scheme, its achievable information rate, the ultimate performance limit of this non-orthogonal scheme, has not been fully unveiled. As a consequence, whether the introduction of non-orthogonality to FBMA is really worthy from information perspective remains an open issue. In this paper, we present a comparative study on the ergodic achievable rate and region of iPR-FBMA with that of two orthogonal multiple access schemes based on OFDM and OFDM with offset QAM (OFDM/OQAM), respectively, in uplink multiple access with flat fading channels. We prove that the achievable rate of iPR-FBMA is largely determined by the number of non-zero singular values of its transmission matrix, which is directly related to the means of subbands allocation, the oversampling factor and the numerical precision. Numerical results show that iPR-FBMA with critical sampling has even lower sum rate compared to OFDM and OFDM/OQAM although it is non-orthogonal. However, with oversampling, iPR-FBMA could get much larger rate region than the orthogonal schemes, especially for imbalanced power constraints and interleaved subband allocation, and it could achieve the entire channel capacity region if the numerical precision could be fully guaranteed.