The use of interleaving to reduce the peak-to-average power ratio of an OFDM signal

Abstract

An interleaver based technique for improving the peak-to-average power ratio (PAP) of an orthogonal frequency division multiplexing (OFDM) signal is presented. For this technique, K-1 random interleavers are used to produce K-1 permuted sequences from the same information sequence. PAPs of the permuted sequences and the original information sequence are then computed using K oversampled FFTs (OFFTs). The sequence with the lowest PAP is chosen for transmission. The complementary cumulative density function (CCDF), of PAP of an interleaved OFDM signal is observed. Results show that for 256 subcarriers and QPSK data symbols, even with K=2, the 0.1% CCDF is reduced by 1.3 dB and with K=4, is reduced by 2 dB. The 0.1% CCDF can be reduced by 3 dB and 0.01% CCDF by 4 dB at a cost of 16 OFFTs and a data rate loss of less than 0.8% with K-16. Further statistical improvement for the PAP is obtained by combining this approach and the partial transmit sequence (PTS) approach. This paper also proposes an adaptive approach to reduce the complexity of the interleaving technique.