Optimization Of Ultra-wideband Indoor Positioning Base Station Configuration Based On Multi-parameter Fusion

With the increasing demand of location based service in daily production and life,indoor positioning has become one of the research hotspots.Ultra-wideband(UWB)positioning has become the representative technology for indoor positioning because of its centimeter level positioning accuracy.However,the problems such as NLOS propagation,multipath effect and base station(BS)configuration still need to be solved,especially the BS configuration directly affects the line of sight(LOS)and non-line of sight(NLOS),the measurement accuracy of signal arrival time and so on,and then affect the ranging accuracy and positioning accuracy.Therefore,the optimization of UWB BS configuration plays an important role in improving the positioning accuracy.Aiming at the optimization of BS configuration,this paper first analyzes the adaptability of DOP in UWB indoor positioning BS configuration optimization,and then proposes three evaluation indexes of BS configuration:Cramer Rao bound(CRB),position dilution of precision(PDOP)and time difference of arrival(TDOA)measurement error.Taking these three evaluation indexes as optimization objectives,the mathematical model of base station configuration optimization is established,and the global approximate optimal base station configuration is solved by genetic algorithm and firefly algorithm respectively.The research contains the following steps:(1)Analysis of the applicability of DOP in the BS configuration optimization.It is necessary to analyze the applicability of DOP in indoor positioning BS configuration optimization because the distribution of PDOP error is far from the actual error.From the principle of DOP,the relationship between DOP and BS,application scenarios and other aspects,this paper analyzes and demonstrates that although DOP has reference value in objectively evaluating the impact on positioning results,it has certain limitations in indoor positioning due to its not comprehensive consideration.The TDOA measurement error model is then deduced from the UWB ranging error,which is used as an evaluation index of base station configuration,and the optimized BS configuration with TDOA measurement error as the optimization target is obtained.Finally,the experiments are conducted in 8m×8m×3m small-scale scene and 100m×30m×10m large-scale scene respectively to compare the positioning accuracy of the three BS configurations under different receiving signal-to-interference ratio(SIR).At the same time,the experiment is conducted in outdoor standard football field to compare the influence of multipath on the positioning accuracy of the three BS configurations under the conditions of two SIR.The experimental results show that the optimized BS configuration with PDOP as the optimized target proposed in reference[79]is not the best BS configuration,and the positioning accuracy is not as good as the commonly used cuboid 8-BS configuration in low SIR environment.It proves that DOP cannot be used as a decisive metric for the BS configuration optimization of UWB indoor positioning,but can be used as a reference index.(2)Optimization method of UWB BS configuration.The purpose of BS configuration optimization is to improve the positioning accuracy and stability.Firstly,this paper proposes a multi-objective joint optimization framework based on these two objectives.Then,three evaluation indexes of BS configuration are put forward,which are CRB,PDOP and TDOA time-difference measurement error.The mathematical model of BS configuration optimization is established with these three evaluation indexes.The global approximate optimal BS configuration can be obtained by using intelligent algorithms such as genetic algorithm and firefly algorithm.Theoretical derivation and simulation test show that the optimized BS configuration has better mean error and variance than the traditional cuboid 8-BS configuration.The experimental results in 14.5m×7.6m×3m exhibition hall show that the positioning accuracy of the optimized BS configuration is improved by0.7132cm,and the variance is reduced by 50.6496cm~2,which has high stability.