Peak-to-average power ratio performance of interleaved spread spectrum OFDM signals

In this paper we propose an interleaved spread spectrum orthogonal frequency division multiplexing (ISS-OFDM) transmission scheme and demonstrate its reduced peak-to-average power ratio (PAR). The proposed ISS-OFDM signal is realized by two steps. The first step is to modulate the data symbol by complex exponential spreading and the second is to use an interleaving technique to spread the signal spectrum as well as reduce the signal peak-to-average power ratio. The distinctive features of the proposed method are that in the frequency domain the same data information is carried by a number of subbands to effectively spread the signal spectrum and in the time domain the spread signal components are not constructively added together so that signal peaks in the transmitted waveform are avoided. This principle of PAR reduction is unique compared with other techniques such as selected mapping (SLM), partial transmit sequences (PTS), and clipping. With the increase of the number of signal subbands, the PAR performance is improved significantly.