Performance Improvement of the Uplink WCDMA Scrambling Code Identification Using Multiple Antennas Combining

Abstract

In this thesis, I develop an eavesdropping method for uplink wideband code division multiple access (WCDMA) system. In order to achieve effective eavesdropping of uplink WCDMA message, one of the most demanding systematic characteristics is the scrambling code information. While the previous works of identifying the scrambling code use only one antenna and cannot operate well in practical environments having low signal to noise power ratio (SNR), I propose an improved method for robust identification performance in more practical scenarios by using multiple antennas. The proposed method exploits not only multiple antennas but also non-coherent combining (NCC) which enables combining the received signals of each antenna without any channel state information (CSI). Through numerical simulation, I demonstrate that the proposed method is effective for both slow and fast fading environments and evaluate the performance using various system parameters. In the second Chapter, I explain the conventional scrambling code identification method. This method consists of chip-level processing, min-sum algorithm, and scrambling code identification. Chip-level processing makes the received signal to the shifted m-sequence from upper shift register sequence (SRS) of the scrambling code generator. Min-sum algorithm is used to reliably detect the shifted m-sequence in the presence of interference. Finally, scrambling code identification determine the uplink scrambling code by using shifted m-sequence and transition matrices. In the third Chapter, I described the proposed NCC in order to obtain better performance, discuss how the proposed method differs from the conventional method, and analyze how the performance gain in performance is achieved. ⓒ 2017 DGIST