Code Acquisition Using Adaptive Threshold with MAI Estimation for Hybrid TH/DS UWB System

• Main Authors: Hong-Bin Su, 蘇宏斌
• Other Authors: Jyh-Horng Wen
• Format: Others
• Language: en_US
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/23919262994499731923

碩士 === 國立暨南國際大學 === 通訊工程研究所 === 94 === Ultra-wideband (UWB) communication techniques have attracted a great interest in both academia and industry in the past few years for applications in short-range wireless mobile systems. This is due to the potential advantages of UWB transmissions such as low power, high rate, immunity to multi-path propagation, less complex transceiver hardware, and low interference. However, tremendous research and development efforts are required to face various technical challenges in developing UWB wireless systems. One of the crucial challenges is the achieving fast timing acquisition and synchronization to minimize preamble overhead. This thesis presents a two-stage signal acquisition scheme for UWB systems employing a hybrid signaling format involving direct sequence (DS) spreading and time hopping (TH), which significantly reduces the search space. The resulting acquisition system consists of two stages. The first stage is for the acquisition of the TH sequences while the second stage is for the acquisition of DS sequences. The final synchronization is achieved in the second stage. In order to determine whether a cell corresponds to the synchronous position or not, the received signal is correlated with the locally generated delay-controllable version of the same code. The correlative value is compared to a threshold to make a decision about that cell. How to set the threshold value effectively is a critical issue. So, we propose a sub-optimal adaptive threshold algorithm to improve the mean acquisition time. Finally, the influence of MAI on our proposed scheme over multi-path and AWGN channel is also simulated in this thesis.