Coding in a wide area positioning system (WAPS)

摘要

Embodiments describe determining position by selecting a set of digital pseudorandom sequences. The magnitudes of the cross-correlation between any two sequences of the chosen set are below a specified threshold. A subset of digital pseudorandom sequences are selected from the set such that the magnitudes of the autocorrelation function of each member of the subset, within a specified region adjacent to the peak of the autocorrelation function, are equal to or less than a prescribed value. Each transmitter transmits a positioning signal, and at least a portion of the positioning signal is modulated with at least one member of the subset. At least two transmitters of the plurality of transmitters modulate respective positioning signals with different members of the subset of digital pseudorandom sequences.

主权项

1. A method for transmitting position location signals from a plurality of transmitters, comprising:
identifying a set of pseudorandom sequences, wherein a maximum magnitude of a cross-correlation function between any two pseudorandom sequences of the set of pseudorandom sequences is below a specified threshold; identifying, from the set of pseudorandom sequences, a subset of at least three pseudorandom sequences, wherein all magnitudes of an autocorrelation function corresponding to the pseudorandom sequences of the subset, within a specified region adjacent to a peak of the autocorrelation function, are equal to or less than a prescribed value, and wherein two or more magnitudes of the autocorrelation function, outside of the specified region, exceed the prescribed value; transmitting a first positioning signal from a first transmitter, wherein at least a portion of the first positioning signal is modulated in accordance with a first pseudorandom sequence of the subset of pseudorandom sequences; and transmitting a second positioning signal from a second transmitter, wherein at least a portion of the second positioning signal is modulated in accordance with a second pseudorandom sequence of the subset of pseudorandom sequences.