Alternative Symbol Representations with Radial Symmetry for PAPR Reduction in OFDM Systems

Abstract

This paper proposes a new method for peak to average power ratio (PAPR) reduction in orthogonal frequency division multiplexing (OFDM) systems using two alternative signalling points to represent one symbol. In this redundant signal representation with no need for side information, the expanded constellation of signalling points used on each OFDM subcarrier is comprised of a conventional modulation scheme such as PSK or QAM and an external circle of alternative signalling points. The design of the expanded constellation maintains the minimum distance between signalling points and its advantage stems from the location of the alternative signalling point being radially symmetric to the original signalling point in the conventional constellation. Significant PAPR reduction is achieved by choosing for transmission signalling points which result in lower PAPRs. Specifically, the complementary cumulative distribution function (CCDF) of the modified OFDM signal shows about a five (5) dB improvement in PAPR at clipping probability of 10 4 over the original OFDM signal. This performance is comparable to that in similar PAPR reduction schemes; however it is achieved at a significantly lower computational overhead.