PAPR Reduction in GFDM Systems Using an SLM Technique

Abstract

In the fifth generation (5G) cellular network system, user capacity should be improved com- pare with the current 4G network system. To this end, higher resource efficiency is an essential. Orthogonal frequency division multiplexing (OFDM) and orthogonal frequency division mul- tiple access (OFDMA), which has high spectral efficiency resorting to orthogoanlity between subcarriers, is the most commonly used modulation technique in the current 4G network sys- tem. To maintain orthogonality, several types of frame structures are used for synchronized signal transmission and reception in Long Term Evolution (LTE). However, these fixed frame structures result in a fundamental limit for reducing latency. Thus an asynchronous commu- nication scheme has been emerged as one of the solutions to reduce latency. On the contrary, without synchronization, OFDM signals generate interference to each other. Recently, general- ized frequency division multiplexing (GFDM) has been proposed for the asynchronous multiple access. Many studies have evaluated that GFDM has higher sum-rate than OFDM for the asyn- chronous systems owing to the higher spectral efficiency and lower out-of-band emission (OOB). Despite the many advantages, GFDM also has disadvantages such as a high peak-to-average power ratio (PAPR). If the numbers of GFDM and OFDM subcarriers are equal, GFDM will get higher PAPR than OFDM due to multiple subsymbols. To reduce the PAPR, various PAPR reduction techniques have been studied on OFDM such as clipping, selective mapping (SLM), partial transmit sequence (PTS), Tone reservation (TR), and single-carrier frequency division multiple access (SC-FDMA) for LTE uplink. In GFDM, precoded GFDM and generalized fre- quency division multiple access (GFDMA) have been proposed as PAPR reduction techniques. Among PAPR reduction techniques, SLM is one of applicable techniques to the GFDM without signal distortions. In this paper, GFDM SLM is proposed as a PAPR reduction technique. In addtion, the performance analysis is compared in terms of the PAPR, OOB, and spectral efficiency among SC-FDMA, OFDMA, GFDMA, precoded GFDM, and GFDM SLM.