Intrinsic interference reduction in a filter bank-based multicarrier using QAM modulation

The offset QAM-based filter-bank multicarrier (FBMC/OQAM) has recently attracted a lot of research interest thanks to its high spectral efficiency. The data in the FBMC/OQAM are carried by real-valued symbols transmitted at each half period (T/2). At the receiver side, the received symbols are corrupted by pure imaginary intrinsic interference terms which prevent the application of some well-known schemes such as Alamouti coding and maximum likelihood (ML) detection in spatial multiplexing (SM) systems. Receiver schemes with interference cancellation are not always effective, due to error propagation. Interference cancellation can be effective when the signal-to-interference ratio is beyond a certain threshold. In this paper, we propose reducing the intrinsic interference power by modifying the conventional FBMC/OQAM system by transmitting QAM data symbols instead of OQAM ones. Consequently, the real orthogonality condition is no longer satisfied. On the other hand, we can show that, by using receivers based on iterative interference cancellation, we can successfully remove the intrinsic interference. We test the proposed FBMC/QAM in both schemes: 2x1 Alamouti coding scheme and 2x2 SM with ML detection. The bit-error rate performance is assessed and illustrated by Monte Carlo simulations. (c) 2013 Elsevier B.V. All rights reserved.