Random Sign Repetition Time-Hopping UWB with Multiuser Detection
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Random Sign Repetition Time-Hopping UWB with Multiuser Detection Jinho Choi School of Electrical Engineering and Telecommunications, Faculty of Engineering, The University of New South Wales, (UNSW), Sydney, NSW 2052, Australia Email: [email protected] Received 6 September 2004; Revised 2 May 2005; Recommended for Publication by Tho Le-Ngoc A modified time-hopping (TH) ultra-wideband (UWB), called the random sign repetition TH-UWB, is considered to improve the performance of the minimum mean square error (MMSE) multiuser detector. We show that the increase of dimension or the number of repetitions is important to improve the performance of the MMSE detector in the random sign repetition TH-UWB for either coded or uncoded signals. Keywords and phrases: ultra-wideband, multiuser detection, performance analysis.
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INTRODUCTION
Recently, ultra-wideband (UWB) technology, which uses a very short pulse for wireless digital communications, has been extensively investigated due to its significance that enables to transmit data sequences at a very high rate. Although the propagation range of UWB signals is short (about ten meters [1]), its impact on wireless home networks can be quite significant. Apart from the support of a high data rate, UWB can also provide multiple access so that multiple transmitters can be active simultaneously [2] and construct wireless networks [3]. A conventional UWB uses time-hopping (TH) sequences for multiple access and pulse-position modulation (PPM) for signaling [2]. There are other variations of UWB. In [4], an UWB based on direct sequence spreading has been considered and compared to the conventional TH-UWB. Due to the cochannel interference from other UWB transmitters, the performance is generally limited by the cochannel interference. In [5, 6], a characterization of the cochannel interference and performance analysis for the conventional TH-UWB are discussed. Since UWB systems suffer from the cochannel interference as code-division multiple-access (CDMA) systems, it would be possible to apply some interference suppression methods in CDMA to UWB. In [7], the multiuser detection for UWB that employs CDMA signaling is discussed. In [8], the multiuser detection for the conventional TH-UWB is investigated. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
In this paper, we consider the multiuser detection in UWB. Using the multiuser formulation, we are able to characterize UWB signals in a multiuser environment. From this, a modification of TH-PPM signaling has been made for improving the performance of multiuser detection. The modified TH-PPM signaling is called the random sign repetition TH-PPM signaling. Through some analysis and simulation results, we can observe that the random sign repetition THUWB can provide better performance than the conventional TH-UWB. In addition, we find the increase of the number of repetitions i
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