| Modern communication technology is developing rapidly,and people are desire better positioning services.Although the outdoor positioning method(GPS)is mature,there is still a long way to utilize the indoor positioning service.The outdoor positioning scheme doesn't work in the indoor environment.Firstly,the signal intercepts by buildings,signals like GPS cannot enter the indoor environment.Secondly,even if the signal is included in the room,the outdoor positioning method will be affected by the multipath or unable to meet the accuracy requirements of indoor positioning.Therefore,a high-precision positioning method for indoor environment is required.The fingerprint localization method is generally regarded as suitable for indoor environments,and has become a hot spot for indoor positioning in recent years.The fingerprint method utilizes multipath effects by using the channel feature as a fingerprint in indoor positioning to achieve channel independence.However,the accuracy is limited by the coherence distance of the channel so that the accuracy of indoor positioning is also being limited.The purpose of this thsis is to explor a high-precision indoor positioning solution.This thsis proposes a rich-scattering environment,constructing a multipath environment by artificially,the scattering distribution near the receiver can be changed.The rich-scattering environment extends the angular spread of the near field and reduces the correlation between channels,which overcome the limitation of coherence distance.This thsis proposes a rich scattering antenna.The antenna is surrounded by random micro-structure scatterers,so a rich-scattering environment is constructed in the near field.In this thsis,the fingerprint location system platform based on channel impulse response is built firstly,and then an indoor positioning scheme based on rich-scattering environment is designed using the effect of the rich scattering antenna.By utilizing the uniqueness of the multipath distribution,the system uses the channel impulse response as fingerprint to achieve a high-resolution effect.In this thsis,the performance of the rich-scatterring antenna and the classic antenna in the same environment is tested,and the effect of the rich-scatterring antenna is proved.At the same time,the rich-scatterring scheme has higher positioning accuracy,and the system completes the positioning accuracy of 5-cm in the indoor environment.Finally,this thsis proposes a time-reversal optimization scheme for the rich-scattering location system.Because the time-reversal algorithm focus the power of the transmitted signal in both time and space domains,the positioning accuracy and stability of the system can be enhanced.The effects of time inversion algorithm and cross-correlation algorithm are compared in this thsis,and the stability of time-reversal algorithm is verified.Moreover,the effects of three positioning schemes on the coherence distance are compared.The test results show that the rich-scattering environment effectively reduces the coherence distance of the channel,and the time-reversal algorithm also has a certain effect on the reduction of the coherence distance.At the same time,the positioning effect of three indoor positioning systems was tested.The optimized system system finally achieved the positioning accuracy of 5cm in the indoor environment with 100%accuracy,and the positioning accuracy is better than the traditional fingerprint positioning scheme. |
