On the Behaviour of Non-linearly Distorted OFDM Signals

In recent years, the wireless industry has shown great interest in OFDM systems. Indeed, such systems have been adopted in a variety of wireless applications such as digital audio broadcasting (DAB) and digital video broadcasting (DVB). Moreover, OFDM has also been proposed for indoor wireless networks and fixed wireless broadband access [1,2]. This growing interest was due to the realisation that OFDM is an efficient scheme to convey information in a frequency selective fading channel without requiring complex equalisers [3]. Moreover, OFDM uses the available bandwidth efficiently and can be efficiently generated and detected using the IFFT and the FFT, respectively [4]. The main drawback of OFDM is its high peak-to-average power ratio (PAPR) and consequently its vulnerability to non-linear distortion [5-10]. Note that high PAPR imply large amplitude fluctuations that will occasionally hit the non-linear region of elements in the OFDM communication system. In the open literature, it has always been assumed that the higher the number of OFDM sub-channels and hence the higher the PAPR the larger the error probability of non-linearly distorted OFDM signals [5-10]. In this paper, we show however that the error probability performance of such signals can in fact decrease as the number of OFDM sub-channels is increased.