Application Research And Implementation Of Indoor Localization Based On LoRa And Bluetooth RSSI

The emergence of technologies such as wireless communication and Internet of Things has promoted the development of location services.People's demand for positioning is no longer limited to outdoor,and the demand for indoors is also growing,and related technologies have gradually become a research hotspot.The emergence and popularity of Bluetooth Low Energy(BLE)brings new life to indoor positioning.The beacon in Bluetooth positioning system is based on BLE technology.The positioning systems using BLE technology have the advantages like low power consumption,low cost,and small size.The communication distance of Bluetooth is relatively short,and the positioning range is limited.In the positioning system in which the Bluetooth gateway participates,a large number of data lines are often required to establish a data link,which is easy to cause damage to the on-site environment,and the deployment period is long,and the workload is large in a relatively large area.LoRa(Long Range,LoRa)has the characteristics of long-distance communication.Therefore,LoRa is used to reduce the cable deployment based on Bluetooth positioning.The positioning method can be divided into two types: based on ranging and non-ranging.Among them,based on the Receive Signal Strength Indication(RSSI)path loss ranging positioning does not require complex hardware devices.RSSI can be obtained in the Bluetooth data link,and the positioning accuracy can also meet user needs.Therefore,a positioning algorithm based on RSSI ranging is adopted.Although RSSI is easy to obtain,it is also susceptible to environmental interference and the variance is increased,so filtering is required.The specific work is as follows:(1)We combine LoRa on Bluetooth positioning technology,and make use of its long-distance transmission characteristics to simplify the data transmission networks.The main design includes: the collected beacon data is reported to the LoRa gateway by the location tags that integrated the LoRa and Bluetooth,and finally the data flows into the positioning server to estimate the target coordinates which will display on the host computer.The interaction between the location tags and the LoRa gateway includes: the location tags reports the beacon data to the LoRa gateway in a TDMA scheme,and 10 time slots are divided on each channel,and the reporting period of location data is 2s.These time slots are not fixedly associated with the location tags.That means the location tags have to apply for slots to the LoRa gateway before entering the positioning state,and the slots occupied will be released when exiting the positioning state.In the process of time slots allocation,the data collision between the location tags is reduced by the combining slotted ALOHA anti-collision.In addition,the uplink and downlink data interaction format is defined,which is responsible for location data interaction between the location tags and the LoRa gateway.(2)RSSI path loss model is more dependent on the environment,and we tested the effects of different factors on the ranging model and used linear regression to estimate the parameters of the RSSI ranging model at different locations to determine the ranging model.Secondly,the RSSI is susceptible to environmental interference,resulting in a large variance,especially a large outlier,which has an impact on the late coordinate estimation.Therefore,the median weighted filtering of the RSSI is performed to reduce the variance of the RSSI.Finally,a weighted centroid algorithm based on the trilateral positioning is used to estimate the coordinates of the target.(3)Based on the above work,the positioning system based on LoRa and Bluetooth is completed,including the design of the positioning label software and hardware,the hardware and software design of the LoRa gateway,the software design of the computer.After that,the positioning effect and the positioning data link combined with LoRa was tested.It is feasible to report the positioning data in combination with LoRa.The target can be located by selecting the idle time slot access and reporting the positioning data in TDMA polling.The average positioning accuracy is 2.37 m after the RSSI processing and the deployment is more convenient with the help of LoRa's long-distance transmission feature.