A Computational Complexity Reduction Scheme Using Walsh Hadamard Sequence in SLM Method

SLM (selective mapping) method is one of the efficient techniques to reduce PAPR (peak to average power ratio) in OFDM (orthogonal frequency division multiplexing) system. So, in many papers, it has been proposed. However, SLM method has a serious disadvantage. Because the SLM uses many copy branches and IFFT blocks, it requires much system complexity and computational burden. In this paper, we proposed a new SLM method which rotates the phase of input data after IFFT by using Walsh Hadamard code to solve this problem. Walsh Hadamard code can be generated by multiplying several cyclic sequences constituted by a certain short sub-sequence. By using the DFT characteristics of these cyclic sequences, we can rotate the phase of input data after IFFT and make many copy branches which have a small computational burden. From the simulation results, we can find that the proposed SLM method has 0.5 dB lower PAPR reduce effect than common SLM in same number of copy branch U. However, it can reduce a computational burden more than about 50%. In this paper, we consider about plusmn1 phase rotation. If also plusmnj is used for phase rotation with plusmn1, our proposed method can reduce a computational burden more largely