Frequency domain signal processing for multi-carrier modulation systems

• Main Author: Yan, Yanxin
• Other Authors: Ma Maode
• Format: Theses and Dissertations
• Language: English
• Published: 2015
• Subjects: DRNTU::Engineering::Electrical and electronic engineering::Wireless communication systems
• Online Access: https://hdl.handle.net/10356/64261
• Institution: Nanyang Technological University

Cognitive Radio (CR) was introduced to exploit the unused spectrum and coexist with other wireless services. With multi-carriers modulation (MCM) transmission and the use of discrete Fourier transform (DFT), Orthogonal Frequency Division Multiplexing (OFDM) and multi-carrier code-division multiple access (MC-CDMA) are the nature choice for CR systems. Firstly this thesis focuses on MCM systems such as OFDM and MC-CDMA systems, and proposes the frequency domain oversampling (FDO) technique together with minimum mean square error (MMSE) equalizer to improve the bit error rate (BER) performance for zero padding (ZP) and cyclic prefx (CP) MCM systems in multiple interferences environment. The FDO diagonal MMSE, FDO noise fixed diagonal MMSE and FDO zero-forcing equalizers are derived to reduce the complexity of implementation. Secondly, the thesis analyzes the effect of DFT size on detecting narrow band signals in OFDM systems, and suggests using the large DFT size to improve the probability of detection in frequency domain. In case that the DFT size cannot be chaged, the thesis further proposes a novel energy detection algorithm with noise smoothing method to improve the probability of detection with fixed DFT size and without increasing the number of DFTs.