Performance evaluation of UWB-IR and DS-UWB with MMSE-Frequency Domain Equalization (FDE)

Ultra Wideband (UWB) has recently attracted much attention as an indoor short range high-speed wireless communication [1]. Of all UWB systems, ultra wideband-impulse radio (UWB-IR) [2] and direct sequence-ultra wideband (DS-UWB) [3] - [5] use extreme short pulses and have the advantage of the extremely high path resolutions. The RAKE receiver is known as a technique that can effectively combine paths with different delays, obtain the path diversity gain, and improve the transmission characteristics [7], [8]. However, multipath is spread over dozens of symbols in the case of ultra high-speed communications of several hundreds Mbps, which causes the strong frequency selective channel. As a result, the transmission performance degrades. Meanwhile, the single-carrier (SC) transmission with frequency domain equalization (FDE) has also recently attracted much attention [9]. It is reported that the SC with FDE has few problems of peak to average power ratio (PAPR) and also obtains an excellent performance as well as orthogonal frequency division multiplexing (OFDM) even in the strong frequency selective channel where multipath is spread over dozens of symbols. In this paper, we propose UWB-IR and DS-UWB with minimum mean square error (MMSE)-FDE. We evaluate the bit error rate (BER) of UWB-IR and DS-UWB with MMSE-FDE and compare it to that of UWB-IR and DS-UWB with maximal ratio combining (MRC-RAKE and MMSE-RAKE. In consequences, we show that UWB-IR with MMSE-FDE can achieve the better BER than UWB-IR with MRC-RAKE and MMSE-RAKE. We also show that DS-UWB with MMSE-FDE has the better BER than DS-UWB with MRC-RAKE and MMSE-RAKE, particularly when M is large.