Modified [formula omitted]-law Root Companding for PAPR reduction in GFDM signals

Abstract

Generalized Frequency Division Multiplexing (GFDM) is a multicarrier modulation technique and able to meet the requirements of next generation wireless systems. But it exhibits high peak to average power ratio (PAPR), which degrades the efficiency of the power amplifier (PA). In this work, modified Root Companding and modified μ-law Root Companding are proposed to reduce PAPR in GFDM signals. The existing methods alter the average power due to expansion of small signals, whereas the proposed method keeps the average power as constant by adjusting both small and large signals. Therefore, the adjustment of dynamic gain in PA is not required. Transform gain and achievable PAPR reduction of the proposed methods are compared by varying companding metrics such as companding root R and companding parameter μ. Also, bit error rate (BER) performance is analysed over AWGN channel and the value of R, μ is chosen such that companding distortion is small. The theoretical PAPR distribution of the proposed methods are derived and validated with Monte-Carlo simulations. The BER performance over multipath fading channel is also analysed. Further, the BER, PAPR and power spectral density performance of the proposed methods are compared with conventional OFDM, GFDM and existing PAPR reduction methods. The computational complexity is also analysed.