Research And Implementation On Algorithm For Precoding In Mmwave Massive MIMO Systems

Since the wireless communication technology became commercially available,the increasing demand for wireless high-speed data communication requires the future communication systems a 10x even 100 x advance compared with 4G systems.Meanwhile,the wireless communication systems have to face many challenges,such as limited spectrum resources,the shortage of spec-trum efficiency,etc.Thus,many researchers have already invested a lot of time and energy into the research in the mmWave range,where exists vast amounts of relatively idle spectrum.Because of strong pathloss,atmospheric and rain absorption and other factors,the propagation qualities of mmWave are rather hostile.Despite of these disadvantages,the decrease in wavelength enables packing a large number of antenna elements into small form factors.Therefore,millimeter wave massive MIMO technology has been one of the most popular topics in 5G systems.In order to pre-vent the pilot pollution and improve the system capacity,precoding technology is quite important.Considering the expensive cost of power and money in massive MIMO systems,the traditional full-digit precoding algorithms,where a RF chain is allocated for each antenna element,will be no longer suitable,and thus many researchers have paid their attention to the research of hybrid precoding.In this paper,we focus on the research of the precoding algorithms in mmWave massive MI-MO systems.We propose a low-complexity and high energy-efficient hybrid precoding algorithm.Furthermore,we finish the design and implementation of the precoder based on zero-forcing algo-rithm.The contributions mainly include the following aspects:1)We introduce the rationale of mmWave massive MIMO systems,including several methods of channel modeling and the analysis of system capacity for two different systems(point-to-point system and multi-cell multi-user system).Then,we introduce several popular full-digit precod-ing algorithms and one classical hybrid precoding algorithm respectively.Finally,three common schemes of the feedback of CSI is briefly introduced.2)We consider the downlink communication in the multi-user mmWave massive MIMO sys-tem and propose an energy-efficient hybrid precoding algorithm.This algorithm designs the digital part and analogous part separately.Firstly,in order to decrease the complexity of implementation in the baseband station,we apply an adaptive connection network to the analogous precoder instead of the complex joint architecture.Then,the digital part of precoder and combiner are iteratively updated by WMMSE algorithm to maxmize the system rate.Simulation results verify that the proposed algorithm improves the energy efficiency at the cost of a little loss of the sum-rate per-formance.Furthermore,we analyse the performance of the antenna selection algorithm based on shift network in the combiner,the results show that this algorithm is not suitable for low SNR environment.3)Considering the system hardware platform,we design and implement the zero-forcing pre-coder based on FPGA.We use the module design method and divide the full precoder into five modules.The architecture and key steps of each module are introduced.Meanwhile,We analyse the computation complexity and the occupancy of resources.Finally,the correctness of the design is verified by the functional simulation and the board test.