Energy efficiency of OFDM systems using shorten-and-forward in outdoor-to-indoor relaying scenarios with short guard intervals

In outdoor to indoor relaying scenarios, the radio signals go through different propagation channels and the compounded channel may result in large delay spreads. In cases where spectral efficiency is important, shorter guard intervals would be favoured, but a combination of large delay spreads and shorter guard interval will result in drastic degradation of system performance. In this paper, we propose the use of a channel shortener at the relay node and show that this will dramatically improve system performance in cases of both shorter guard interval and large delay spreads.