Research On Characteristics And Modeling Approaches Of Spatial-Temporal Non-Stationary Wireless Channels

Looking ahead to the year 2020 and beyond,the explosive growth of mobile data traffic,massive number of interconnected devices,and emergence of new services and application scenarios for the vertical industry are expected.The 5th generation mobile communication(5G)will emerge to address the challenges beyond the differentiated per-formance indicators in a variety of scenarios.The enhanced mobile broadband scenario in 5G is expected to meet the requirements of wide-area coverage and the needs of ultra-high data rate in hotspot areas for cellular networks.The ultra-reliable and low latency communication scenario is mainly expected to realize in the scenarios where the low la-tency is of highest importance,such as the intelligent transportation system(ITS).The development of these two new scenarios in 5G relies on massive multiple-input-multiple-output(MIMO)and vehicle-to-vehicle(V2V)wireless communication systems.The transmission rate and transmission quality in wireless communication system-s are directly affected by radio propagation characteristics in wireless channels,which are therefore regarded as the basis for the design of wireless communication systems.Thus,the accurate knowledge of massive MIMO and V2V channel characteristics is the prerequisite condition to design these two communication systems.Even though numer-ous research has been conducted on massive MIMO and V2V channel characteristics and modeling approaches,however,there are still the following limitations:In terms of the scenarios under research,the current research on massive MIMO and V2V wire-less channels cannot provide complete channel model base in various scenarios for the network planning and design of communication systems.In terms of the insight into propagation characteristics,the existing understandings of the non-stationary character-istics in massive MIMO and V2V channels are not investigated throughly.In terms of the channel modeling theory and methodology,the current research on massive MIMO and V2V channel modeling cannot meet the requirements of the complexity and universality of channel models for the upper layer design of wireless communication systems.In order to solve above problems,this thesis investigates the radio propagation char-acteristics and modeling approaches of spatial-temporal non-stationary wireless channels for massive MIMO and V2V communications.The main works are as follows:1)For the lack of research on spatial non-stationary characteristics for massive MIMO channels,the massive MIMO channel measurements based on the virtual antenna ar-ray at different frequencies are conducted in indoor hall scenario.The improvement scheme of the extraction algorithm for massive MIMO channel parameters is pro-posed to improve the accuracy of such an algorithm.Based on the collinearity matrix theory,the estimation method of spatial quasi-stationarity regions in massive MI-MO channels is proposed,and the characterization method of spatial non-stationary characteristics is also studied based on the clustering method of radio propagation multipath components and their power contributions.Therefore,the fundament of spatial non-stationary characteristics in massive MIMO channels is fully revealed.2)For the lack of research on spatial non-stationary modeling for massive MIMO chan-nels,the massive MIMO channel measurements for different distances between trans-mitter and receiver are conducted in subway station scenario,and the spatial non-stationary characteristics of broadband channel parameters are modeled through the statistical approach.Based on the ray-tracing simulation and the massive MIMO channel measurements,the statistical characteristics of different channel parameters versus transmitter-receiver distance in point-to-point and massive MIMO communi-cation systems are revealed,and.a distance-dependent spatial non-stationary model is developed for massive MIMO channels.3)For the lack of research on vehicular obstruction scenarios in V2V channels,the chan-nel measurement scheme in urban and highway scenarios is proposed.The influences on vehicular shadowing attenuation and delay dispersion are investigated for different scenarios,different obstructed vehicles,and different relative driving positions of ve-hicles.The characterization method of temporal non-stationary characteristics as well as the estimation method of stationarity distance for V2V channels is proposed,and the relationship between stationarity distance and vehicular shadowing attenuation(or delay dispersion)is established.4)For the lack of research on temporal non-stationary channel modeling for V2V com-munications,the V2V channel measurements based on multiple antennas are con-ducted in suburban scenario.A framework of automatic clustering and tracking for time-variant multipath components is proposed to describe the dynamic evolution of multipath clusters in V2V channels,and the accuracy of the framework is verified by the ray-tracing simulator and the existing channel model.Finally,a cluster-based temporal non-stationary channel model for V2V communications is developed,which helps to enrich the theory of dynamic channel modeling.To sum up,this thesis investigates the wireless channels for massive MIMO and V2V communications,compensates the deficiency of channel characteristic analysis and modeling in representative scenarios,reveals the fundaments of spatial non-stationary massive MIMO channels and temporal non-stationary V2V channels,and supports a the-oretical method with reference value for the research on wireless channel modeling in different 5G scenarios.