Unused Beam Reservation for PAPR Reduction in Massive MIMO System

Abstract

In this paper a new unused beam reservation (UBR) algorithm is proposed to reduce peak-to-average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) signal in the downlink channel of Massive Multiple Input Multiple Output (MIMO) system. The main challenge with PAPR reduction in coming 5G system is the selection of a method, which has an ultra-low latency and ability to reduce PAPR without performance degradation of high order modulation users (QAM256, QAM1024). This paper reviews some conventional PAPR reduction techniques with respect to selective tone reservation algorithm (STR, [1]) and finally we propose the UBR algorithm, which provides an extra gain in multi-user (MU) MIMO application scenarios. UBR is a non-iterative algorithm compared with a well-known tones reservation, constellation extension and clipping & filtering methods. It is based on a non-iterative modulation of unused beams amplitudes in the downlink channel of MU-MIMO so that target users are not degraded while PAPR is reduced on each TX antenna. Also UBR is fully consistent with 5G standard requirements and has a low latency. Advantages and disadvantages of this technique are discussed in details, simulation results are presented for 64 antennas of virtual Massive MIMO cell.