Combination of Asynchronous Array Pseudolites and GNSS for Outdoor Localization

Global navigation satellite systems (GNSS) are usually unable to provide location-based service (LBS) in urban canyons, thus the pseudolite positioning system has become an important way to enhance the availability and the accuracy of GNSS in such environments. However, the challenge of the traditional pseudolite positioning system is time synchronization, which requires complex hardware and visibility between pseudolites and reference receiver. Thus, the positioning in the urban environment becomes very difficult and complex. To solve this problem, a new asynchronous array pseudolites system is proposed in this paper. Multi-channel transmitters in array pseudolites system have an identical clock source and are based on an identical 1 pulse per second (1PPS) as well. The clock deviation of pseudolites' pseudorange can be eliminated by making the difference between array channels. The minimum positioning system consisting of one array pseudolite and three navigation satellites is used for positioning experiment in this paper. The results of the simulation verify the effectiveness of the minimum positioning system based on combined positioning. Compared with four navigation satellites, the horizontal positioning accuracy is improved slightly by exploiting the minimum positioning system.