Complexity Reduction and Ambiguity Resolution of Blind Data Detector in SFBC-OFDM Systems

• Main Authors: Tang-wen Cheng, 鄭唐文
• Other Authors: Chih-Peng Li
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/d98xd7

碩士 === 國立中山大學 === 通訊工程研究所 === 102 === In this research, a low-complexity blind data detector scheme for orthogonal frequency division multiplexing (OFDM) system is proposed, where the generalized likelihood ratio test (GLRT) approach is adopted. The traditional GLRT data detector (GDD) suffers from prohibitively high computational complexity since all the subcarriers are jointly considered. Therefore, previous studies proposed a sub-group GDD (SGDD) by progressively dealing with a subgroup of subcarriers at one time. It is shown that, the unique solution of SGDD is guaranteed if the size of sub-group is larger than the order of channel impulse response (CIR). In this study, we proved that the size of SGDD can be even smaller than the channel order if the partition meets some requirements. Furthermore, the proposed partition method is extended to SFBC-based MIMO-OFDM systems. It is worth noting that, most of the SFBC, including Alamouti-SFBC, are rotatable, which leads to a code ambiguity. In this research, we introduce an asymmetric modulation to solve this problem. Simulation results show that the computational complexity is significantly reduced by adopting this novel sub-carrier partition scheme. In addition, the code ambiguity and sign ambiguity, which require extra pilot symbols in existing literatures, can be simultaneously solved by our proposed asymmetric modulation without sacrificing any bandwidth efficiency.