Research On Low PAPR Sequences And Precoding In MM-Wave MIMO System

With the rapid development of mobile Internet, the increasing demand of high data rate promotes the revolution of mobile communicaition. As a key technology of next generation mobile communication, millimeter-wave (mm-WAVE) wireless system has been widely concerned. The hybrid analog and digital (hybrid A/D) mm-WAVE system which is the combination of mm-WAVE and massive MIMO becomes a highlight of these technologys. The mm-WAVE system will adopt OFDM technology. As high attrition, borad band and ultra-high frequency of mm-WAVE makes it is sensitive to the high PAPR. At the same time, the splitted hybrid A/D mm-WAVE architecture has captured intensive attention. The study of splitted hybrid A/D architecture is not yet sufficient. The analog precoding of mm-WAVE SU-MIMO system as well as the hybrid precoding of mm-WAVE MU-MIMO is still an open problem. This paper researched the key technology of mm-WAVE systems focusing on the IEEE 802.11 mm-WAVE scenario. Facing the challenge above, the research and innovations in this paper are as follow:First of all, an overview of mm-WAVE communication was presented including reseach on the characteristics, advantages and challegens of mm-WAVE MIMO systems.as the first step. For instance of mm-WAVE wlan, we exhibited the problem of mm-WAVE such as the high PAPR, the analog precoding of mm-WAVE SU-MIMO system and the hybrid precoding of mm-WAVE MU-MIMO. As we set the IEEE 802.11aj as our main research scenario, we explained the PHY specfications of it detailly. Considering the IEEE 802.11ad/ay/ax protocol, we made some prospective study on the key technologies.In this paper a near-optimal design scheme of low PAPR training sequence in mm-WAVE was presented. We proposed a CEO-based low PAPR sequence design algorithm which has thress advantages. First, it can obtain a low PAPR binary sequence which is well-implemented. Second, there is no limit to the length of the sequence. Third, it can achieve good performance satisfying the different spectrum constrains in practiacal system. Numerical simulation had verified the proposed algorithm.At the same time, a study on the low complexity analoge precoding of hybrid A/D mm-WAVE SU-MIMO system was presented. We proposed a UCT-based beam vector alignment algorithm which is another expression of analoge precoding. The algorithm is available for hybrid A/D architecture. Compared with the existing algorithms, the proposed algorithm significantly reduces the number of training times by resulting in little performance loss. The simulation verified that the proposed algorithm can achieve good performance in different kinds of configuration.Finally, a research on hybrid precoding scheme of splitted hybrid A/D mm-WAVE MU-MIMO system was exhibited. Two algrorithm was proposed. One is codebook-based multi-user hybrid precoding algrorithm which advantages in low complexity. The other is UCT-ZF-based iterative hybrid precoding algrorithm which enhances the performance. Two algrorithm can collaborate in practical system. The numerical results proved that the algrorithms are available in practical system.