Study On Multiple Access Technology Employing Generalized Orthogonal Sequences In DS-UWB Systems

In the short-distance wireless communication systems, the Ultra Wide-Band (UWB) technique, which is based on the radar and remote sensing techniques, is developed quickly and become one of the most active areas of military and business applications. As a kind of physical layer technique in WPAN (Wireless Personal Area Network), UWB technique has been discussed in the workgroup of IEEE 802.15.3a. Because of its strong anti-multipath ability, high data rate, low probability of interception and detection, low power consumption and so on, UWB technique is being accepted by more and more people in the short-distance high data rates wireless communication system.In the UWB wireless communication system, the multiple access technique acts as a key technique. To ensure more users and devices can share the limited frequency spectrum effectively and improve the system capacity, multiple access technique should be utilized to coordinate the access requirement of users and devices.The thesis aims at the researches on multiple access technique used in single-cell DS-UWB system based on Impulse Radio (IR) technique. First of all, background information of UWB system, including the history, concepts and features, is introduced; together with the research status of UWB system and its multiple access technique are described. Meanwhile, the property and spectral characteristic of several UWB pulsees including Gaussian pulse are provided. After that, several multiple-access techniques are analyzed and their performances are compared. The construction methods and the correlation properties of GO sequence, which exhibits better performance in quasi-synchronization system, are introduced. Thereafter, the multi-user asynchronous uplink UWB system model in AWGN channel is discussed in this thesis, based on which, the BER expressions are obtained, together with the analysis of the influence exerted on the system performance and capacity by different pulse waveforms. In addition, the model of the multi-user asynchronous uplink UWB system in the multipath channel recommended by the workgroup of IEEE 802.15.3a is dicussed in this thesis. The BER expressions based on MRC combining in RAKE receiver in channel CM1, CM2, CM3 and CM4 respectively, are derived and both the numerical and simulation results are obtained. In the end, it is concluded that the UWB system based on GO sequences exhibits better system performance and higher system capacity both in AWGN channel and multipath fading channels.