| With the increasing demand of global mobile data traffic,the fifth generation(5G)mobile communication system needs to support a peak rate of up to 20 Gbps.Multiple input multiple output(MIMO)technology has become one of the key technologies of 5G because it can make full use of the degree of freedom(DOF)in the channel and effectively improve the spectral efficiency and system capacity.On the other hand,antenna multi-polarized technology can improve the compactness of mobile devices,reduce the size of devices,and improve the spectral efficiency.Therefore,multi-polarized MIMO technology can provide support for the realization of 5G vision and requirements.Channel characteristics determine the upper limit of wireless communication system performance,which is the basis of system technology evaluation and optimization.In view of this,based on the actual channel measurements in the real communication environment,this paper takes the multi-polarized MIMO channel characteristics as the research object,focuses on the tri-polarized MIMO channel characteristics in typical indoor scenarios and Urban Microcell(UMi)scenario,and explores whether the tri-polarized MIMO technology can effectively improve the system capacity in the actual channel environment.It provides a basic theoretical reference for the application of tri-polarized MIMO technology in 5G wireless mobile communication.Based on two typical application scenarios of UMi and indoor,the measurements of tri-polarized MIMO channels with center frequencies of 3.5 GHz and 4.9 GHz were conducted.The cross-polar discrimination(XPD),correlation coefficient(CC),eigenvalue of channel matrix,condition number,the channel capacity and capacity gain(CG)of tri-polarized MIMO channel are analyzed and studied.The specific research work of this paper is organized as follows:(1)Tri-polarized MIMO channel measurement platform is built.In this paper,the existing single input single output(SISO)measurement platform is used to simulate the transmission and reception of signals in different polarization directions by rotating the receiving and transmitting antenna,while keeping the center of the antenna in the same physical position during the rotation process.Based on the channel impulse responses collected in different polarization directions,a tri-polarized MIMO channel matrix is constructed.(2)Research on the characteristics of tri-polarized MIMO channel in typical indoor scenarios.In this paper,the tri-polarized MIMO channel matrix is constructed by rotation,and the actual channel measurement was carried out in two typical indoor scenarios,office and corridor.The channel capacity of the two scenarios is compared and analyzed.Secondly,the influence of antenna height and antenna alignment on the capacity of tri-polarized MIMO channel are studied.(3)Research on the characteristics of tri-polarized MIMO channel in UMi scenario.At present,the research on tri-polarized MIMO channel mainly focuses on the simulation of multi-polarized channel and a small amount of indoor scenario measurement,lacking of tri-polarized MIMO channel measurement in outdoor scenario.Therefore,in this paper,we carry out the measurement of tri-polarized MIMO channel in the typical UMi scenario,and study the influence of line of sight(LOS)and non-line of sight(NLOS)subchannel correlation,cross-polar discrimination on channel capacity,and the robustness of tri-polarized MIMO channel.To sum up,in order to meet the needs of 5G multi polarization MIMO technology development,this paper studies the influence of antenna height and antenna alignment state on channel capacity by measuring the tri-polarized MIMO channel in typical UMi and typical indoor scenarios(office,corridor),and verifies that the tri-polarized MIMO system has higher channel capacity and stronger robustness in the actual communication scenario.The research results of this paper provide theoretical support for the evaluation and optimization of 5G tri-polarized MIMO technology. |
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