Research On Massive MIMO Channel Based On Measurement

In order to meet the future development of mobile communication systems in the data traffic business needs, the fifth generation mobile communication (5G) system ready to come out. IMT-2020 (5G)promotion group in May last year, officially released the "5G wireless technology architecture white paper." In the past year, a number of research units around the world have carried out on large-scale antenna-related measurement activities, including Huawei, CITIC,Datang and so on. In addition, the intelligent terminal's vigorous development and extensive application make the channel modeling of outdoor to indoor (O2I) scene has important research significance. In this paper, channel measurement is carried out based on outdoor to indoor typical urban skyscrapers. The temporal and spatial characteristics of the wideband Massive MIMO channel are analyzed statistically. At the same time, the performance of the transmission channel is evaluated. The work of this research project includes the following four aspects:First, broadband large-scale antenna channel measurement system design and implementation. The main contents of this paper are large-scale antenna channel, which is characterized by large transmission bandwidth, large number of antenna elements, large antenna size,complex floor environment, and so on for future communication system outdoor to indoor O2I high-rise scene. Therefore, we use a professional measurement platform Propsound measurements. At the beginning of the project, there were no large-scale antennas on the market. Most of the research on large-scale antenna channels remained in the simulation, and some of them were stitching in single antenna array. In this paper, the base station side by translating a 32-element array of planar array 8,stitching formed a 256-element virtual large-scale antenna. Such a base station antenna not only considers the horizontal propagation characteristics but also studies the pitch angle of the channel. The number of antenna array elements is the largest among all the published studies at this stage.Second, the time-domain characteristics of large-scale antenna. The conventional conventional MIMO time delay is based on the log-normal fitting of all subchannel delay spreads. As the antenna size becomes larger and the number of subchannels becomes larger, it is necessary to verify the reasonableness of this method. In this paper, the channel impulse response (CIR) of the real channel is obtained by measuring the received signal, and the time domain characteristic parameters are calculated. In this paper, a comparative study of the array antenna element delay spreads at different positions for large-scale antenna size is presented. The results show that the large bandwidth has a certain effect on the fading of the multipath fading channel. The 7-layer propagation environment is more serious, the mean and variance of the delay spread Are larger than the results of four layers.Thirdly, using the Space Alternating Generalized Expectation Maximization (SAGE) to estimate the polarization gain, the multipath propagation delay, the Doppler shift, the horizontal angle of arrival of the channel impulse response, And the horizontal departure angle and the pitch arrival angle and the pitch departure angle. Based on the estimated angle and gain parameters, the angular power spectrum is analyzed under the actual scene. It is found that the angle of departure is relatively concentrated in the measurement scene, and the angle dispersion is serious and the time domain characteristic is consistent. The calculated results of the cyclic angle extension further confirm the above conclusion,and the parameter results can provide data for more in-depth modeling work.Fourth, the transmission performance of multi - antenna Massive MIMO channel is studied. Combining the results of channel impulse response, the performance of the channel capacity in a certain signal to noise ratio is calculated. Under the bandwidth of 100MHz, considering the number of antennas in the base station, the number of antennas is chosen as the main factor. The results show that the number of antenna elements increases, but when the receiving antenna element is fixed, the bottleneck is no longer the number of antenna elements at the base station.The number of 128 elements is an appropriate choice in this thesis.Considering the difference of the seven-layer scattering environment and the four layers, and the influence of the bandwidth on the dispersion,assuming that there is no channel capacity of frequency selective fading,the results show that the seven layers have better performance, which is the performance of indoor hotspots. Some reference opinions.This thesis provides valuable data for the development and planning of large-scale antenna technology in the future mobile communication system through actual measurement, and has a certain reference value.