## 1 Introduction  
The global navigation satellite system (GNSS) has been widely applied in outdoor positioning. Nevertheless, it is difficult to obtain reliable GNSS signals in sheltered environments or indoors [1], where a pseudolite system can make up for the shortage of GNSS [2,3]. Relative to the GNSS, indoor pseudolite observations have no tropospheric and ionospheric errors. The PL/receiver clock and antenna phase error can also be eliminated by DD observations which greatly reduce the difficulty in processing error sources in indoor PL positioning [4]. However, the multipath effect, noise, and fixed satellite constellations are still the problems indoors. What is worse, the indoor pseudolite system has a great nonlinear effect due to the close distance between the receivers and pseudolites. If initial position estimation has poor accuracy, the nonlinear error caused by linearization will be severe. Therefore, large code measurement errors caused bythe above factors may result in low accuracy and reliability of positioning results. At present, the research on the indoor pseudolite system mainly focuses on the design of pseudolite constellation or high-precision positioning based on the carrier phase, but few on the reliability of positioning. According to quality control methods of GNSS carrier phase positioning, they can be divided into two categories: priori and posteriori quality control methods. As to priori methods, there are some classical methods, such as cycle slip detection, DD method. Cycle slip detection can effectively eliminate such faults as cycle slip or signal interruption. The double differenced method will eliminate clock difference and weaken troposphere and ionosphere delays. In general, the posteriori quality control method does not distinguish which kind of error sources, such as RAIM, IGG III, and variance component estimation. These methods can effectively improve the positioning accuracy. However, the existing legacy approaches cannot eliminate all faults, such as multipath effect, noise and so on, which is also the current problem. In an indoor environment, the influence of multipath and noise is greater than outdoors. A holistic approach to guarantee the reliability of positioning for indoor pseudolite based on carrier phase is proposed and the feasibility of the method is verified by some experiments. The proposed method creatively considers the fault of indoor positioning source (pseudolite) and other error sources, including complete fault detection, exclusion procedure, andformula derivation of pseudolite protection level. Faults on reference pseudolite are also considered. Although we cannot deal with any specific error source, the data with poor quality can be effectively identified no matter which error source. By excluding the corresponding epochs, the positioning accuracy and reliability will be guaranteed. The research on indoor pseudolite high-precision positioning algorithms has become a hotspot in recent years and the key is to use carrier phase observations and ambiguity resolution [4, 5, 6].Reference [4] has successfully introduced AFM (Ambiguity Function Method) into PL-AR (Pseudolite-Ambiguity Resolution). However, due to the multi-peak characteristic of AFM, the reliability of the solutions is sometimes difficult to be guaranteed compared with the LAMBDA method. In addition, the way to ensure the reliability of positioning has not been discussed. References [5,6] proposed a new OTF-AR method for ground-based positioning systems which solely relies on carrier phase measurements and applies to cases where no sufficiently accurate measurements were provided in advance; however, the gross error must be given careful consideration in practical applications and the experiments in the references were conducted under relatively good conditions. Actually, it is the poor conditions that lead to unreliable positioning results. Some research institutes used KPI when LAMBDA and ratio tests are applied to obtain the integer ambiguity resolution [7].