The Analysis Of DRIPS And UDRIPS Indoor Positioning Methods And The Study Of Asynchronous Positioning Algorithm Based On Dual-tone Radio Technology

With the rapid development of internet and IOT(Internet Of Things),there is a fast growth in data and multimedia services,and the smart devices like smart phone,tablet computer and wearable devices are quite common in our lives,all these lead to a strong demand for LBS(Location-Based Services).Location-aware services are quite important for most WSN applications.There are a lot of range-based localization systems that have been proposed.Global Positioning System(GPS)is well used in outdoor environments,and it can achieve a positioning accuracy of 5 m.However,its performance for indoor environments is inferior because it is difficult for satellite radio signals to penetrate buildings.Moreover,the ultra-wideband(UWB)localization systems have high accuracy,but the high cost discourages their popularity.The radio interferometric positioning system(RIPS)proposed in 2005 utilizes two transmitters to create the interferometric signal directly.The frequencies of the two transmitters are close.Thus,the interferometric signal has a low-frequency envelope,which can be measured by cheap hardware readily available on a WSN node.Recently the DRIPS and uDRIPS are proposed,they use the dual-tone signal for indoor radio interferometric positioning.These methods have low complexity and are robust to flat-fading channels.This thesis mainly focus on the indoor positioning technologies in WSN.As radio signal is the most common signal in WSN,we use the radio signal in our methods.The study in this thesis can be divided into two parts: the first part we use the PXI platform to implement the dual-tone radio interferometric ranging experiments,and evaluate the performance of DRIPS and uDRIPS.The second part we propose a new method which is an asynchronous TDOA positioning system using dual-tone radio signal,in this method all the nodes can be asynchronous,and this reduces the cost of nodes in the system.The following contributions are made by this thesis.(1)DRIPS is a dual-tone radio interferometric positioning system,the two tones of the dual-tone signal are close and the frequency difference is small than the coherence bandwidth,therefore the two tones of the dual-tone signal experience the same channel fading effect.However,it employs the squaring operation to produce a low-frequency differential signal,which results in a high noise power.The uDRIPS is a DRIPS with undersampling techniques which avoid noise amplification by directly sampling the received dual-tone signal.The uDRIPS is robust to flat-fading channels as well.We employ NI PXI(National Instruments' PCI eXtensions for Instrumentation)to implement and evaluate the ranging methods proposed in DRIPS and uDRIPS,respectively.In the experiments,we use only a single transmitter-receiver pair.We can obtain lots of data by the experiments,and then we evaluate these two methods through the analysis of the data.(2)Synchronization is a quite common issue in many indoor localization technologies,it will increase the cost and complexity of the system.Especially when it comes to the indoor localization with radio signals,which have a velocity of light,and this brings a real challenge for the localization systems.Therefore,we propose an Asynchronous TDOA Positioning System using the dual-tone radio signal,named ATPS.By adding one reference anchor node(node with known position)as transmitter in ATPS,all the nodes can be asynchronous,which simplifies the system and reduces hardware costs.An ESPRIT algorithm is adopted to estimate the basic frequency and the frequency difference of the dual-tone signal for the subsequent phase estimation.We extract TDOA information from the phases of the received dual-tone signal in the ATPS,then we use Chan's hyperbolic position algorithm to locate the blind node(node with unknown position).Furthermore,we evaluate and discuss the performance of the method by simulation experiments.In summary,this thesis mainly studies the dual-tone radio interferometric indoor positioning technologies.First,we use the PXI to implement and evaluate two methods,which use the dual-tone radio for indoor positioning.And second,we propose a new method which is an asynchronous TDOA positioning system using dual-tone radio signal,the main contribution of this method is that we do not need synchronization in positioning system.This thesis is helpful for indoor positioning technologies' development and applications.