The Study On Timing Acquisition And Multi-user Detection Technology Of Ultra-wideband Communication Systems

For the advantage of simple device, lower transmission power, low probability of detection and interception, higher gain and data rate and fine multipath resolution capability, the research on Ultra-wideband(UWB) communication technology shows more significant in recent years. Accordingly, it is highly necessary to research all the key technologies of UWB. It is well known that the timing acquisition is a very imporant technology to affect the quality and efficiency in the wireless communication. Because of the very short pulses characteristic and the effect of multipath channel, it is very important to realize precise timing acquisition. Moreover, the multi-user detection is another most popular approach of UWB system, multiple access communication is the important aspect both in Ad-Hoc networks and Wireless Personal Area Network(WPAN). However, at the same time, catastrophic collisions between users are unavoidable as user numbers increase. Therefore, how to eliminate multiple access interference (MAI) so as to improve system performance is also an important task. So, the research on timing acquisition and multi-user detection technology of impulse radio UWB system is our main content.This paper firstly introduces the development, technologic characteristics, status of UWB at present and the researching purpose of this paper. Following impulse models, multi-access modulation and propagation channel are analyzed. And several realizing methods of receiver in multipath are discussed and compared. The main innovation of this paper can be listed as below:1) It proposes an acquisition scheme for UWB signals based on maximum-likelihood (ML) criterion, achieveing timing acquisition and channel estimation at the same time, well resolving the acquisition problem of UWB signals in the dense multipath channel, and also enhancing the performance and reducing the complexity of receiver. Finally, through the results of simulation , showing the correctness and advantage of this scheme.2) Then we discuss the multi-user detector of TH-PAM and TH-PPM UWB systems, and present a multi-user detector which combines time diversity theory and parallel interference cancellation algorithm. This novel detector eliminates multiple access interference efficiently and improving the performance of whole system, moreover, that can be implemented easily. Finally, the results of simulation also demonstrate the superiority of the multi-user detector proposed in this paper.