Equalization of OFDM for doubly very selective channels

The performance reduction caused by inter-carrier interference (ICI) on orthogonal frequency division multiplexing (OFDM) systems over time-varying channels is relevant especially when large OFDM symbols are employed in order to achieve an higher throughput. In this paper we propose a design method of an equalization scheme using several full-length FFTs operating on non-overlapping windows of the received OFDM symbol. In particular the FFTs outputs are combined minimizing the mean square error (MSE) at the detection point. Subsequently we recall another technique to mitigate ICI, which still operates on sub-blocks, but using smaller FFTs of size equal to the length of each sub-block. A comparison between these two schemes is performed in terms of computational complexity, which is an important issue in OFDM systems employing long symbols, and bit error rate, considering a possible extension of the new digital video broadcasting standard DVB-T2 to an hand-held version (DVB-NGH).