Methods and apparatus for improving signal timing accuracy

A system for determining the time of arrival of a signal, comprising:

• a transmitter configured to generate a spread spectrum signal comprising a plurality of code sectors each including a periodic sequence of spread spectrum chips that correspond to a predetermined correlation function, wherein the periodic sequences of chips of the code sectors are shifted in time by differing amounts relative to a periodic time reference such that the plurality of code sectors respectively correspond to a plurality of time-shifted correlation functions;
• and
• a receiver configured to periodically sample the spread spectrum signal to produce the plurality of time-shifted correlation functions, such that different sampling points on the correlation function are generated from different code sectors, the receiver determining a time of arrival of the spread spectrum signal via curve fitting of the sampling points from the plurality of time-shifted correlation functions.

An apparatus for transmitting a signal, comprising:

• a processor configured to generate a digital signal to be transmitted;
• and
• a modulator configured to generate a spread spectrum signal corresponding to the digital signal, the spread spectrum signal comprising a plurality of code sectors each including a periodic sequence of spread spectrum chips that correspond to a predetermined correlation function, wherein the periodic sequences of chips of the code sectors are shifted in time by differing amounts relative to a periodic time reference such that the plurality of code sectors respectively correspond to a plurality of time-shifted correlation functions.

An apparatus for receiving a signal, comprising:

• a receiver configured to receive a spread spectrum signal comprising a plurality of code sectors each including a periodic sequence of spread spectrum chips that corresponds to a predetermined correlation function, wherein the periodic sequences of chips of the code sectors are shifted in time by differing amounts relative to a periodic time reference, and periodic sampling of the spread spectrum signal by the receiver yields different sampling points on the predetermined correlation function for different code sectors such that a plurality of time-shifted correlation functions are generated from time shifts of the code sectors;
• and
• a processor configured to determine a time of arrival of the spread spectrum signal via curve fitting of the sampling points from the plurality of time-shifted correlation functions.

A spread spectrum signal embodied in a carrier wave, comprising:

• a plurality of code sectors each comprising a periodic sequence of spread spectrum chips that corresponds to a predetermined correlation function, wherein the periodic sequences of chips of the code sectors are shifted in time by differing amounts relative to a periodic time reference such that a plurality of time-shifted correlation functions corresponding to the plurality of code sectors result from periodic sampling of the spread spectrum signal and different code sectors yield different sets of sampling points of the predetermined correlation function for determining a time of arrival of the spread spectrum signal at a receiver via curve fitting.