Research On BeiDou Navigation Receiver Signal Acquisition And Integrity Monitoring

The BeiDou navigation satellite system(BDS)is developing quickly in applications of different fields,which results in higher service performance requirements for BDS receiver.The BDS receiver applied to China-made civil aircraft and flight tested successfully for the first time expedited the demand of BDS to safety-of-life applications like civil aircraft terminal approach.The integrity of satellite navigation need to meet more stringent requirements.The aim of this paper is to enhance the performance of BDS navigation receiver.Signal acquisition and receiver autonomous integrity monitoring are the two main research technologies.The researches supply important references for the development of BDS and multi-constellation navigation receiver and the applications of BDS in more fields.Satellite signal acquisition is the first step of receiver baseband signal processing.The secondary encoding makes it more complex.This paper studies the BDS signal acquisition modulated with NH code.Firstly,a NH code evasion method based on a novel input signal sequence is proposed.The method can evade the impact of NH code transition to the BeiDou signal acquisition.Furthermore,a NH code stripping method based on Pre-NH modulated code is proposed.The NH code can be stripped synchronously with the sub-frame synchronization in tracking.Finally,the above NH code coping scheme are tested on a BeiDou software-defined receiver in a real BDS B1 I signal environment.The proposed evasion method has a good acquisition generality with BDS GEO satellite,and GPS and GLONASS signals which modulated with NH code.Signal attenuation is a situation that receivers often face.It is a key technology for the receiver to acquire the true satellite signal in weak signal environment without any aids.Furthermore,this paper has studies the BDS weak signal acquisition.A method based on improved double block zero padding is proposed.The NH code phase searching scheme is simplified.Then,the processing of block-level operation and coherent integration is improved.All above researches can reduce the calculation complexity and computational burden.Finally,the tests on software-defined receiver with the input of weak signals generated from the simulator verified the acquisition sensitivity and running time.The safety-of-life applications like civil aircraft approach ask higher requirements for the integrity of satellite navigation.It is also a chance for satellite navigation to extend its application.The advanced receiver autonomous integrity monitoring(ARAIM)is a new technology proposed to meet the above application.ARAIM cannot work normally only if all the harsh availability criteria can be met synchronously.It should be robust and keep the availability in circumstance like one satellite outage.The researches about the impact of one satellite outage to ARAIM and the endurance capacity of different constellations are not mature.This paper has studies the availability of BDS/GPS ARAIM.A position estimator based on constellation weighted is proposed.The impact of constellation performance difference to the ARAIM availability is compensated and the availability is dramatically improved.The important conclusions also include that the geometric configuration difference caused by the one satellite outage is the main cause of availability loss.The balance of constellation is more important than more satellites in orbit.Determining the fault modes with the help of integrity support message(ISM),is one of the futures that the ARAIM is different from traditional RAIM.Based on the research and improvement of ARAIM availability,this paper has further studied the fault mode determination of ARAIM.Firstly,the promote space related to the redundant probability of not monitored risk,the number of fault modes and the continuity risk are discussed.Then,a fault modes determination method based on feedback structure with probability accumulation(FSPA)is proposed.The integrity threshold is the core criteria and the fault modes are accumulated in descending order of fault probability.The characteristic of the feedback structure is that all the judgment of the integrity risk threshold,the judgment of observability and the judgment of continuity are formed as a feedback loop.Finally,the effectiveness of FSPA method is verified.The important conclusions also include that it is not better to monitor more fault modes.More fault modes will probably enlarge the protection level and EMT,then cause ARAIM availability loss.The ultimate aim of ARAIM is the application in civil aircraft terminal approach.The actual signal test for ARAIM key technologies are executed and studied in this paper.Firstly,a simplified statistical method for user range error of signal in space is implemented.The precise ephemeris and broadcast ephemeris are used to count the error in space.The performance of the different types of BDS satellites and different blocks of GPS satellites are analyzed.This method is applied to the parameters involved in ISM and has a reference for the generation and monitor of Offline ISM.Then,the ARAIM user algorithms are tested based on observed data published by observation stations in Asian-Pacific region.Finally,an ARAIM test platform based on multi-rotor unmanned aerial vehicle is established.The effectiveness of above improved ARAIM algorithms are tested using the flight data.The Beidou navigation satellite system is still in the key stage of vigorous development.By improving the service performance of Beidou receiver,the BDS can serve all fields better and gives more help to the continuous development of the economic,society and human civilization.