| Wireless mobile communication systems are moving toward the fifth generation.In the era of mobile Internet,data explosively grows.In order to meet the challenge,5G must make breakthroughs in key technologies.Among them,wireless transmission technology is the focus,and the popular technology that attracts attention in wireless transmission technology is Multiple Input Multiple Output(MIMO).The main extension direction of MIMO technology is the dimension and number of antennas.If the dimension is extended to the vertical dimension,it becomes 3D MIMO.If the number of transceiver antennas is increased a lot,it becomes Massive MIMO.The existing traditional band spectrum resources available for wireless communication are already very tight compared to the demand,and many studies have been carried out in high frequency bands such as the millimeter band.Although many researchers have turned their attention to other frequency bands,this does not mean that the traditional working frequency band of wireless communication no longer needs further research.The scale and dimensions of MIMO technology in 5G have been greatly expanded.In the popular traditional frequency bands such as 3.5 GHz,it is a very effective way to carry out the field channel measurement of these bands in order to gain an in-depth understanding of the practical MIMO channel state.For channel measurement,the measurement scenarios are also a key part to consider.5G defines the main typical deployment scenarios for the future.Among them,for the indoor propagation environment focuses are mainly on indoor hotspot(InH)and indoor office scenarios.For the outdoor propagation environment focuses are mainly on urban micro cell(UMi),urban macro cell(UMa)and some other scenarios,in addition to the outdoor to indoor(O2I)scenario,the future indoor service demand will be the main growth segment,accounting for over 50%of the total service demand.Based on the measured channel data of InH and UMi,UMa,021 scenarios,the propagation characteristics of 3D MIMO and Massive MIMO channels are studied,and the influencing factors of system performance are studied.Specific research points include:(1)Study the autocorrelation and cross-correlation properties of 3D MIMO channel parameters in InH scenarios.First,the channel measurement platform is built and the 3D MIMO channel measurement of the InH scenario is conducted.The center frequency of the measurement platform is set to 3.5 GHz,the bandwidth is 200 MHz,the transmit antenna adopts an omnidirectional antenna array of 32 array elements is used at the transmitting end,and an omnidirectional antenna array of 56 array elements is used at the receiving end.Then based on the measurement data we complete the parameter extraction,calculate the autocorrelation of the parameters and the cross-correlation between the parameters,the autocorrelation distance of the parameters can be obtained and compared with the modeling method proposed by 3 GPP.(2)Study the propagation characteristics and performance of Massive MIMO channel in different scenarios.Set up a channel measurement platform to conduct the Massive MIMO measurements in UMi,UMa,and 021 scenarios.The channel parameters are extracted and analyzed.The angle spread of the Massive MIMO channel,the channel matrix singular value distribution and the channel capacity are mainly studied.Both the angle spread and the singular value distribution can reflect the Massive MIMO subchannel correlation,and the subchannel correlation affects the Massive MIMO channel capacity.In the analysis of the measurement data,we focus on the analysis of the channel capacity,and the effects of propagation environment,bandwidth,antenna number and structure are studied by comparing the results under different conditions.(3)Verify the condition for favorable propagation of Massive MIMO under different scenarios.As an important feature of the Massive MIMO system,the favorable propagation condition(FPC)mainly refers to the mutual orthogonality of the subchannel vectors.In this paper,the condition for the favorable propagation of Massive MIMO in the specific scenarios are verified by using the angle spread values obtained under these scenarios. |
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