【作者】 张光华；

【导师】 孟维晓；

【作者基本信息】 哈尔滨工业大学 ， 信息与通信工程， 2013， 博士

【摘要】 随着移动通信技术的发展和移动增值业务的全面展开，以辅助全球定位系统（Assisted Global Positioning System，A-GPS）为代表的辅助全球导航卫星系统（Assisted Global Navigation Satellite System，A-GNSS）移动定位业务逐渐得到越来越多的应用，在现有的用户终端（User Equipment，UE）中，大多都有具有A-GNSS移动定位功能。辅助数据的应用不仅大大降低了UE的首次定位时间（Time To First Fix，TTFF），而且还提高了系统的灵敏度，使得UE能在更弱的信号下仍然可以进行定位。虽然辅助数据的应用给人们带来了很大的好处，但是仍然无法摆脱至少需要四个观测条件才能进行定位的限制。而在实际的应用环境中，人们并不是时刻处在天空完全通视的环境中，当无法获得这些基本定位条件的时候，UE就无法获得自己的位置，造成定位失效。因此，当UE定位条件无法满足时如何通过其他途径来实现定位，满足用户对位置信息的需求，成为GNSS辅助与增强定位技术研究的关键。本文也将围绕这个问题，对辅助定位系统中参考接收机的服务范围、卫星捕获时辅助数据的作用、开阔条件下的定位增强以及非开阔条件下增强定位等问题，展开相关的研究。论文首先在对GNSS和A-GNSS相关理论深入研究的基础上，提出了一种A-GNSS中参考接收机服务范围的评估方法。该方法通过软件仿真的方式，模拟建立卫星空间模型和参考接收机与UE的应用场景，给出了参考接收机与UE相距不同距离时两者对相同可见星观测时长的变化情况，从而评估出参考接收机的服务范围，为辅助定位的应用奠定了基础，同时也为A-GNSS的工作开展提供了方法参考。其次论文在对全球导航卫星系统（Global Navigation Satellite System，GNSS）信号捕获原理和捕获算法研究的基础上，深入研究了辅助数据的应用对于捕获的影响。并从多普勒频率辅助的角度推导了接收机与卫星相对运动引起的多普勒频移的范围以及辅助信息对接收机多普勒频移的预测，分析了辅助信息对多普勒搜索范围的影响，并给出了多普勒频移的预测和实测结果对比；同时通过仿真的方式定量的研究了辅助的应用对相干累积时间以及弱信号捕获算法中捕获时间的影响。再次，论文以伪距定位为研究对象，以A-GNSS为系统架构，对开阔条件下A-GNSS定位增强进行了深入的研究。在深入分析了伪距测量误差的影响因素基础上给出了一种加权最小二乘（Weighted Least-square，WLS）算法下复合权重系数的选取方法，并进行了WLS验证；在此基础上，根据WLS和扩展卡尔曼滤波（Extended Kalman Filter，EKF）的优势互补，提出一种WLS-EKF联合的改进定位算法，该方法通过定位结果触发WLS提供迭代初值，然后将EKF预测下的伪距残差与WLS的伪距残差进行优化选择，再进行EKF滤波，从而得到最优的位置及钟差偏差估计，取得了较好的定位效果，实现了A-GNSS定位性能的增强。最后对非开阔条件下A-GNSS的增强定位进行深入研究。论文在对高度辅助定位误差分析的基础上，提出了几种UE传统GNSS定位无法实现时利用辅助实现定位的方法。当可见星为三颗时，有基站位置与高程差联合辅助实现定位法，距离补偿辅助定位法，多普勒测量辅助定位法、三星复观测定位法以及基站辅助的三星复观测定位法；当可见星为两颗时，有基站位置与多普勒测量联合辅助定位法，两星复观测定位法以及基站辅助的两星复观测定位法。通过前面的定位解算算法对这些定位方法进行了实际应用及仿真分析，均获得了优于蜂窝网络定位误差的定位性能。在UE观测到的可见星个数不满足传统定位方式的条件下，这些辅助方法的应用，可以帮助用户解决对位置信息的需求，扩大了A-GNSS的应用环境，增强了A-GNSS的定位性能。更多还原

【Abstract】 With the development of mobile communication technology and mobilevalue-added services in full swing, the mobile positioning service based on theAssisted Global Navigation Satellite System (A-GNSS) has gotten more and moreapplications, which takes the Assisted Global Positioning System (A-GPS) as arepresentative. In present, the A-GNSS based mobile positioning function modulehas been included in most of the User Equipment (UE).The application of assisted information not only reduces the Time To FirstFix (TTFF), but also enhances sensitivity of the system, which enables thepositioning under weak signal. However, four sets of observation conditions arestill minimum requirements for the positioning. In fact, it is hard to keep UEalways in the environment with complete visibility, and the correspondingpositioning will fail without the basic positioning conditions. Therefore, othermethods are needed to provide additional positioning information when the basicpositioning conditions cannot be met, which is the key for the research of A-GNSSbased positioning technology. Around this problem, this thesis researches on theproblems about the service range of the reference receiver, function of the assistedinformation during satellite acquisition, enhancement of positioning in openenvironment and the realization of positioning in non-open environment.First, based on an in-depth study on GNSS and A-GNSS, an evaluationmethod for services scope of the referenced receivers in A-GNSS is proposed. Itmodels the spatial model of satellites and the application scenario of thereferenced receivers and UE. It provides the changes for observation time lengthof the referenced receiver and UE to the same visible satellite with differentdistance between them. Then the service range of the receiver can be obtainedaccording to the change of observation time, which is the foundation for theassisted positioning and provides reference method for the work about A-GNSS.Second, based on analyzing the principles of signal acquisition and thealgorithms for signal acquisition in the Global Navigation Satellite System(GNSS), this thesis offers a deep research about the influence of the assistedinformation on the signal acquisition. The range of Doppler shifts aroused by the relative motion between the receiver and satellites and the forecast for the Dopplershifts of the receiver by assisted information are also deduced. Then, the influenceof the assisted information on search range of Doppler shifts is analyzed and thecomparison between the forecasted Doppler shifts and the actual measurement isalso provided. Additionally, a quantitative analysis on the influences of theassisted information on coherent accumulation time and the acquisition time ofweak signals acquisition with the assisted information are also provided.Third, taking pseudo-range as the object of study, taking A-GNSS as thesystem architecture, this thesis offers an in-depth research on the A-GNSSpositioning enhancement in open environment. Based on the analyzing theinfluence of measuring error of pseudo-range, a method of selecting compositeweighted coefficients of Weighted Least-square (WLS) algorithm is proposed, andthe relative verification is also provided. Based on all these, according to thecomplementary advantages between WLS and the Extended Kalman Filter (EKF),a joint WLS-EKF positioning algorithm is proposed. The initial value is providedby the WLS algorithm, and then making a choice between the residual errors ofpseudo-range with EKF and WLS. After EKF filtering, the optimal position andclock bias can be obtained, and an enhanced positioning performance is achieved.Finally, the calculations for positioning in non-open environment with otherassisted information are studied. Based on the analysis of altitude-assistedpositioning errors, several methods are proposed for the situation when the numberof visible satellites misses the basic requirements of positioning. When the numberof visible satellites is three, a method assisted by the position of the based stationand the difference of elevation jointly, a method assisted by compensated range, amethod assisted by the measurement of Doppler, a method based ondouble-observation of three satellites and a double-observation based methodassisted by the base station are proposed. When the number of visible satellites istwo, a method assisted by the position of the based station and the measurement ofDoppler jointly, a method based on double-observation of two satellites and adouble-observation based method assisted by the base station are proposed.Through the application and simulated analysis of the above positioningcalculation algorithms, a better positioning performance compared with thecellular-based positioning can be observed. When the number of visible satellites does not meet the requirements of traditional positioning methods, the applicationof assisted information is able to help users to obtain their positions, whichextends the application of satellites positioning technology and also enhances theperformance of A-GNSS.更多还原