Range improvement of UWB systems using adaptive multicarrier spread-spectrum and MIMO techniques
Résumé
In this paper, we investigate the use of multiple-input multiple-output (MIMO) techniques with a linear precoded orthogonal frequency division multiplexing (LP-OFDM) waveform, known as spread-spectrum multicarrier multiple-access (SS-MC-MA), for high data rate ultra-wideband (UWB) systems. This scheme is an evolution of the well-known multiband OFDM (MB-OFDM) solution supported by the WiMedia Alliance. The aim of this paper is to improve the UWB system range while not significantly increasing the system complexity compared to the WiMedia solution. Firstly, an analytical study of the single-input single-output (SISO) LP-OFDM waveform allows to find how to efficiently precode an OFDM signal in order to improve the system range. To go further and exploit the available spatial diversity, a MIMO component is added and a new geometric statistic MIMO channel model is considered. Secondly, a global MIMO LP-OFDM system study is led to highlight the benefits of combining MIMO and LP techniques for UWB applications. The analytical and simulation results show that the joint use of MIMO and LP-OFDM leads to a significant range improvement compared to the WiMedia solution.