Читать книгу Position, Navigation, and Timing Technologies in the 21st Century - Группа авторов - Страница 73

To establish and maintain a connection between cellular CDMA BTSs and the UE, each BTS broadcasts comprehensive timing and identification information. Such information could be utilized for PNT. The sequences transmitted on the forward link channel, that is, from BTS to UE, are known. Therefore, by correlating the received cellular CDMA signal with a locally generated sequence, the receiver can estimate the TOA and produce a pseudorange measurement. This technique is used in GPS. With enough pseudorange measurements and knowing the states of the BTSs, the receiver can localize itself within the cellular CDMA environment.

This section is organized as follows. Section 38.5.1 provides an overview of the modulation process of the forward link channel. Section 38.5.2 presents a receiver architecture for producing navigation observables from received cellular CDMA signals. Section 38.5.3 analyzes the precision of the cellular CDMA pseudorange observable. Section 38.5.4 shows experimental results for ground and aerial vehicles navigating with cellular CDMA signals.