Reducing Pilot Overhead: Channel Estimation With Symbol Repetition in MIMO-FBMC Systems

In this article, we aim to reduce the pilot overhead of channel estimation in multiple input multiple output (MIMO) systems employing filter bank multicarrier (FBMC). The key idea is the employment of the concept of symbol repetition in frame structure. Firstly, we propose an MIMO-FBMC system based on block repetition, in which complex-valued symbols are transmitted instead of only real-valued symbols in classic MIMO-FBMC systems without block repetition. Then, we present two low-overhead channel estimation approaches in the block-repetition based MIMO-FBMC system and only two columns of symbols are required as the pilot overhead. However, the existence of the block repetition results in the increased sensitively to the channel coherence time. Then, the two channel estimation approaches are extended into classic MIMO-FBMC systems without block repetition. It is proved that, the proposed methods exhibit significant advantage in terms of pilot overhead, compared with the conventional interference approximation method (IAM) and frequency-division multiplexing (FDM) methods. To evaluate the performances of the proposed approaches, we also derive the Cramer-Rao Bound (CRB) bound, and carry out numerical summations with respects to both mean square error and bit error ratio metrics.