Performance Analysis of OFDM Based UWB Systems Enhanced with Frequency-Domain Spreading

In this paper, a performance analysis of orthogonal frequency-division multiplexing (OFDM) based ultra-wideband (UWB) systems with frequency-domain spreading is presented. A continuum of schemes from a plain nonspread OFDM scheme to a maximally spread multicode scheme via medium-spread combinations of the variable spreading factor (VSF) and multi- code transmissions is considered. The channel is assumed to be Rayleigh fading with exponentially decaying delay power profile. Furthermore, the analysis takes into account the intersymbol interference (ISI) caused by the multipath delay components exceeding the guard interval. Numerical results demonstrate that frequency-domain spreading can improve the performance remarkably when sufficient spreading factors and a suitable combining method is used.