Research On Peak-to-average Power Ratio Schemes For ADMA-based Massive MIMO Systems

Massive multiple-input multiple-output(MIMO)based on angle division multiple access(ADMA)is a promising technology for the 5th generation(5G)mobile communication sys-tems.It combines the advantages of massive MIMO and ADMA technology,able to explore spatial degree of freedom fully and improve spatial resolution highly.However,ADMA-based massive MIMO systems may cause high peak-to-average power ratio(PAPR),which poses a big challenge to radio frequency components,degrades power efficiency considerably and in-crease hardware cost greatly.To deploy low-cost ADMA-based massive MIMO systems,a well-designed PAPR reduction scheme has become a necessity.In this thesis,we mainly focus on PAPR reduction schemes in ADMA-based massive MIMO systems,including beam domain PAPR reduction and PAPR-aware precoding,with the knowledge of multiple access technology in massive MIMO systems and PAPR reduction methods in massive MIMO-OFDM systems.Firstly,we study characteristics of ADMA-based massive MIMO systems and then de-scribe the PAPR problem in ADMA-based massive MIMO systems.Through researching on the transmission model and channel model of ADMA-based massive MIMO systems,we study the multiuser transmission strategy,including angle pattern estimation,channel estimation and data transmission.After that,we introduce the PAPR problem in ADMA-based massive MIMO systems and analyze statistical models of transmit signal and transmit signal PAPR briefly.Secondly,we study beam domain PAPR reduction schemes.Through researching down-link transmission model of ADMA-based massive MIMO systems and ADMA-based massive MIMO-OFDM systems,we analyze statistic characteristics of transmit signal PAPR.Consider-ing the structure of ADMA systems,we propose a novel PAPR reduction scheme named idle beam exploitation(IBE)for ADMA-based massive MIMO systems and we also put forward extended idle beam exploitation(E-IBE)scheme for ADMA-based massive MIMO-OFDM systems to reduce PAPR of the transmit signal.Simulation results demonstrate that both IBE scheme and E-IBE scheme can achieve prominent PAPR reduction performance with negligible symbol error ratio(SER)performance loss.Finally,we study PAPR-aware precoding schemes.Through analyzing the system model of ADMA-based massive MIMO systems and ADMA-based massive MIMO-OFDM systems,we present an optimization problem for the design of PAPR-aware joint precoding schemes.To solve this problem,the corresponding algorithm implementation is studied emphatically.Start-ing from the alternating direction method of multipliers,Iterative Discrete Estimation(IDE)and low-complexity version of IDE,called IDE2,are introduced.Then,a simplified version of IDE,called Iterative Discrete Estimation Lite(IDEL),is further proposed.Simulation re-sults demonstrate that both IDE2 and IDEL precoding scheme can achieve outstanding PAPR reduction performance while maintaining good SER performance.