Research On Location Method For 5G Ultra Dense Networks

In recent years,with the rapid growth of the market for location services,location information has been widely used in additional location-based services such as social networks.High-precision,high universality,low complexity,and low-cost positioning methods have become research hotspots in related fields.The ubiquitous cellular base station has the potential to meet this requirement,but it is currently limited by the loose distribution of base stations and the non-line-of-sight propagation of signals in traditional cellular networks.Various positioning methods that use cellular networks do not enable the positioning accuracy which people are satisfied with.With the advent of the 5G era,compared with traditional cellular network structures,ultra-dense networks structures and full-featured small cells equipped with array antennas have brought new opportunities and challenges to cellular positioning.The main content of this thesis is based on the positioning method research of 5G ultra dense networks based on the distribution and functional characteristics of base stations in the ultra dense networks.The main work and research results of the thesis are summarized into the following parts according to the division of horizontal positioning and vertical positioning:In terms of horizontal positioning,considering the diversity of users'requirements for location service coverage and positioning accuracy:1.Aiming at the distribution characteristics of base stations in 5G ultra dense networks,a non-ranging geometric positioning method based on the distance order between base stations and users is proposed,and several factors affecting the positioning accuracy of this method are studied and analyzed.Experimental results show that under the cell number selection scheme in this thesis,this method only needs a small amount of information to achieve a positioning accuracy of 20 meters or even higher.In 5G ultra dense networks,this method can provide the most extensive positioning service support and is used as an initial scene with low accuracy requirements such as positioning have high stability and universality.2.For scenes that require higher accuracy,a positioning method based on ranging is necessary.This thesis studies and analyzes the relationship between the positioning base station selection scheme in 5G ultra-dense network scenarios and the accuracy of TOA and other geometric positioning methods based on ranging.First,using the TOA-based position estimation model to derive and quantify the relationship between the base station selection scheme and the Cramero lower bound of horizontal positioning accuracy.Secondly,using stochastic geometry to model the distribution of base stations in 5G ultra dense networks scenarios.And on this basis,according to the above-mentioned quantization relationship formula,the positioning performance of the selection scheme of the number of fixed base stations often used in traditional positioning is simulated and analyzed.The experimental results show that the positioning performance under this scheme will not benefit from 5G Densification of ultra-dense networks.Thirdly,in view of the problem that the selection scheme of the fixed base station number cannot fully exert the advantages of 5G ultra-dense networks densification,this thesis proposes a dynamic base station selection scheme.Experimental results show that in the 5G ultra-dense networks scenario,for the geometric positioning methods based on ranging such as TOA,the positioning performance of the base station selection scheme proposed in this thesis is significantly better than that of the fixed base station number selection scheme,and it is different from the traditional scheme.Its positioning performance will also increase with the further densification of the network.For vertical positioning:The current indoor vertical positioning mainly relies on barometric altimetry,aiming at the problems that the method is susceptible to the environment,the overall accuracy is not high,and additional equipment is difficult to promote in practical applications.This article uses the densely distributed full-featured base stations in 5G ultra-dense networks,combined with the existing barometric altimetry principle,to design a smart phone as the carrier for the future 5G ultra-dense network vertical positioning system.The experimental results show that the vertical positioning system can stably reach sub-meter positioning accuracy in the scenario of 5G ultra-dense network and does not require additional equipment.It has high universality and is easy to popularize.