Some Designs for communication systems on channels with intersymbol interference

• Main Author: 林佳賢
• Other Authors: 林茂昭
• Format: Others
• Language: zh-TW
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/38002403205663571316

碩士 === 國立臺灣大學 === 電信工程學研究所 === 90 === Abstract In this thesis, two systems which integrate the design of equali- zation and channel coding are investigated. The first system employs Tomlinson-Harashima precoding. Generalized Low Density (GLD) codes and Turbo codes are used in this system. GLD codes can be considered as the generalization of Low Density Parity Check (LDPC) codes. The performance of GLD codes is comparable to that of Turbo codes. Similar to Turbo codes, iterative algorithms (BCJR, SOVA) are used in the decoding of GLD codes. In the precoding system, the received data is a periodic extension of the transmitted data constellation, plus the white noise. Thus the decoding algorithms used in the AWGN channel can not be directly applied to this system. To compensate for this problem, we make a little modification on the original BCJR algorithm. In addition, an approach for reducing the average transmitted power in Tomlinson -Harashima precoding is proposed. Through simulation, we find that the bit error rate (BER) of the power-reduced system can achieve a gain about 0.2~0.5dB. A complexity-reduced approach for power reduction is also considered. The complexity can be greatly reduced with little loss in performance. The second system is Turbo Equalization that uses GLD codes as its coding scheme. Both conventional and low-complexity approaches for joint Turbo Equalization and GLD codes are considered.