All-Pass Filters as a Low-Complexity PAPR Reduction Scheme for SC-FDMA System

This paper presents a low-complexity peak-to-average power ratio (PAPR) reduction scheme for single-carrier frequency division multiple access (SC-FDMA) system that is based on all-pass filters (APFs). The basic idea of the APF scheme is that it allows a flat magnitude response with a non-linear phase response. This means that this type of filters passes all frequency content of the input signal, while the phase is severely or intentionally degraded. This idea is well-exploited in this paper for generating random phase sequences that can be treated as multiple versions of an input sequence for the SC-FDMA system. The heart of traditional PAPR reduction techniques such as the conventional selective mapping and blind selective mapping schemes is the generation of multiple random phase sequences for the proper selection of the sequence that achieves the minimum PAPR. This can be accomplished through multiple inverse fast Fourier transform (IFFT) operations, which add more complexity to the system performance. In contrary, with the proposed APF scheme, we generate the signals with different phases through passing the original signal through multiple APFs with different phase responses, which reduces the system complexity.