Space-Time Processing for Mobile Communications with Multipath Fast Fading and Co-Channel Interference

• Main Authors: King-Tai Yang, 楊金泰
• Other Authors: Jeng-Kuang Hwang
• Format: Others
• Language: en_US
• Online Access: http://ndltd.ncl.edu.tw/handle/18094540167776680110

碩士 === 元智大學 === 電資與資訊工程研究所 === 86 === In this thesis, we consider the problems of wireless mobile communication system under the difficult situation like combined realistic fast Rayleigh fading, frequency selective channel and the presence of co-channel interference (CCI) by using smart antenna technique to improve both the performance and capacity. In contrary to the conventional digital beam- forming technique which adjusts the array weighting to specify the beam pattern, our approach follows the concept of spatial diversity combination and extends it to space-time processing (STP) for dealing with such difficult cases. The proposed method uses the adaptive spatial and temporal combining antenna array to combat frequency selective fast fading and suppress CCI. A short known training sequence is used for determining the space-time processor weights periodically by a RLS algorithm and decision-directed mode is used to keep track of channel variation during data transmission. The STP structure used is a sum of T/2-spaced tapped delay line filters following after the antennas, then connected with an optional T-spaced decision-feedback filter. As expected, this structure behaves better than T-spaced STP and is also insensitive to the timing phase error. Furthermore, we also formulate the multi-user detection problem where multiple signals of interest are transmitted on the same frequency band and to be detected at the same time. In such a case, we present a STP technique, which incorporates a CCI cancellation method to predict the CCI and cancel it.