On throughput optimization for coded OFDM with variable cyclic prefix length

Orthogonal frequency-division multiplexing (OFDM) generally gains its resistance against channel delay spread by insertion of cyclic prefix (CP). In principle, the intersymbol interference (ISI) as well as inter-carrier interference (ICI) can be avoided provided that the CP length is longer than the effective channel delay spread. However, the delay spread is not known a priori in general, and increasing CP length also leads to reduction of spectral efficiency, especially when the number of subcarriers in the OFDM system is small. In this work, under the framework of BICM-OFDM where capacity approaching channel codes are employed, we first attempt to mitigate the degradation caused by the excessive channel delay spread by appropriately adjusting the decoder metric that takes into account the resulting signal-to-interference-plus-noise ratio (SINR). Furthermore, based on the trade-off between the achievable SINR and spectral efficiency, we attempt to optimize the CP length such that the throughput is maximized.