A reduced peak-to-average power ratio algorithm based on PMI mode in NR

Orthogonal frequency division multiplexing technology, as a key technology of NR air interface transmission, has the advantages of resisting frequency selective fading and narrowband interference, but the problem of high peak-to-average power ratio (PAPR) is easy to cause semiconductor devices to work in the nonlinear region. There are serious problems with intermodulation component, in-band interference, and out-band spectrum regeneration. Especially in NR 3GPP R15 protocol, the PAPR of the demodulation reference signal symbol is further increased when the three or four-layer beamforming is carried out based on the precoding matrix indicator (PMI) mode. The paper analyzes the cause of this problem, theoretically. And in order to solve the above problem, a rotation factor algorithm based on step gradient is proposed. The simulation results show that the algorithm can effectively reduce the PAPR of DMRS symbol in PMI mode without affecting the demodulation performance of data symbols and is easy to implement in engineering with low computational complexity.