Fischer, Robert F. H. (Lehrstuhl für Informationsübertragung, Friedrich-Alexander-Universiät Erlangen-Nürnberg, Cauerstrasse 7/LIT, 91058 Erlangen, Germany)
The capacity of OFDM with 4-QAM modulation per carrier over channels with clipping at the transmitter side is studied. For this, the individual capacities of the OFDM frames are considered. It is shown that capacity is linearly related to the energy of the OFDM frame after clipping. Based on the insight that the power leakage is the main source of the loss, via geometrical considerations a very tight upper bound on the capacity of clipped OFDM is derived. Clipped OFDM performs the same as unclipped OFDM with accordingly reduced signal-to- noise ratio.