Adaptive Space-Time Multiband-OFDM UWB Scheme with OFDM-Based Channel Models

In this paper, we propose an adaptive space-time (ST) multiband (MB) orthogonal frequency division multiplexing (OFDM) scheme for the ultra-wideband (UWB) systems to exploit both the spatial and spectral diversity of the rich multipath indoor fading channels. First, due to the quasi-static characteristics of the UWB indoor fading channels and the specific band-hopping patterns designed for supporting multiple simultaneously operated piconets (SOPs), the adaptive ST scheme needs to be designed with the band-hopping patterns when the channel state information (CSI) is available to the OFDM transmitter. In addition, for the UWB indoor fading channels with rich multipath information, an equivalent OFDM-based channel model is obtained through an iterative channel modeling method. Based on this OFDM-based channel models, we can find that the UWB indoor line-of-sight (LOS) scenario is quite different from an outdoor narrowband (NB) LOS scenario which is usually referred to as the Ricean fading.This channel model may also reduce the CSI feedback compared with the channel frequency response (CFR)-based method. Numerical results show that our adaptive ST MB-OFDM scheme can yield appreciable power gain over the non-adaptive (Alamouti) scheme.