Polynomial-based compressing and iterative expanding for PAPR reduction in GFDM GFDM (generalized frequency division multiplexing) is a non-orthogonal waveform that is being discussed as a candidate for the fifth generation of wireless communication systems (5G). GFDM is a multicarrier technique with circular pulse shaping that is designed in a way to address emerging applications in 5G networks such as Internet of Things (IoT) and machine-to-machine communications(M2M). The same as other multicarrier systems, GFDM suffers from a high peak to average power ratio (PAPR). To attack PAPR problem, in this paper, we propose a polynomial based companding method with iterative expansion that is called polynomial-based companding technique (PCT). Based on our simulation results, a great amount of PAPR reduction can be achieved through utilization of our proposed technique. Through simulations, we have also investigated the bit error rate (BER) performance of the system while adopting our PCT method. Our simulations reveal that there is a tradeoff between PAPR reduction and BER performance.