Abstract
Orthogonal frequency-division multiplexing (OFDM) is an efficient transmission scheme for multicarrier systems, but its output signals may exhibit high peak-to-average power ratios. To deal with the high PAPR problem, many PAPR reduction methods have been proposed. Selected mapping (SLM) and partial transmit sequences (PTS) are two important techniques for PAPR reduction, but they need to transmit side information at the transmitter side. Guided scrambling (GS) SLM and GS-PTS techniques augment the binary data sequence with several bits in the first data bit position. The augmenting bits set the scrambler’s initial condition in the GS-SLM and GS-PTS methods. Thus with different patterns of the augmenting bits, the candidate signals to be selected for transmission can be generated by passing different augmented data sequences through the scrambler, the constellation mapping block, and the IFFT block. At the receiver in the GS-SLM and GS-PTS methods, the received sequence is unscrambled and the augmenting bits are removed directly. GS-SLM and GS-PTS do not require the transmission of side information, but they still need a bank of IFFT’s, i.e., involving high computational complexity. In this thesis, we focus on reducing the high computational complexity of the GS-SLM and GS-PTS methods. We separate the operations of the augmented data sequence into the operations of the augmenting bits and the operations of original data sequence. Different augmenting bits are processed in advance and the results are saved into a ROM. After the operations of the data sequence are performed, the result is added by previous computed signals in ROM to generate a set of candidate signals. One candidate signal with the lowest PAPR will be selected for transmission. The proposed methods only need one IFFT, few adders, and a ROM and thus significantly reduce the computational complexity of the original GS-SLM and GS-PTS methods. The simulation results also show that the proposed GS-SLM and GS-PTS methods have almost the same PAPR performance as the original ones.