The drawbacks of the conventional selective mapping (SLM) method for peak to average power ratio (PAPR) reduction in an orthogonal frequency division multiplexing (OFDM) system are the loss in data rate transmission caused by transmitting side information and the high computational complexity. This paper proposes an improved SLM method without side information

which has the advantages of high bandwidth efficiency and low complexity. In the method

quaternary data is mapped onto ring circles first

and then finishes the serial-to-parallel conversion

sub-blocks division and phase factor rotation

when an original constellation point is mapped to multiple points with no coincidence on the ring circle. After inverse fast Fourier transform (IFFT) operations

one sub-block is cyclically shifted and recombined with another one

so more candidate signals are generated. The lowest PAPR signal can be selected for transmission finally. Thus

the method can further reduce the appearing probability of high PAPR. Computer simulation results show that the proposed scheme achieves excellent performance in terms of reduction both in PAPR and symbol error rate at the power line communication channel.