A Novel Constellation Shaping Method to Reduce PAPR for Rate Compatible Modulation

Abstract

Although rate compatible modulation (RCM) achieves continuous and efficient spectrum efficiency, it has high peak to average power ratio (PAPR) because that its modulation constellation is a dense rectangular. To reduce PAPR of RCM, this paper proposes a novel constellation shaping method, namely transform from rectangular to circle (TR2C), which different to the traditional constellation shaping methods. The TR2C approach compress the points, that with higher amplitude and lower probability, into a circle, such that it can reduce the PAPR of shaping constellation. Furthermore, to deal with the problem of AWGN noise amplification in inverse transform of TR2C, we give out the geometrical method of estimating noise variance. Simulations show that, comparing with original constellation, TR2C scheme can achieve 1 dB performance gain at BER = $10^{-5}$ by improving the transmission power with 1.8 dB. And TR2C achieves the capacity performance close to original constellation when SRN from 5 dB to 30 dB.