Methods and apparatus for detection of signal timing

A method for determining the timing of a received signal, the received signal including one or more time-delayed versions of a reference signal traveling over respective different signal paths, the method comprising:

• (a) correlating the received signal with the reference signal to produce a correlated signal;
• (b) extracting energy of the correlated signal at a chip level to emphasize the correlated signal in peak chips containing signal peaks, wherein the signal peaks correspond to potential signal paths of the received signal;
• (c) extracting energy of the correlated signal at a sample level to emphasize the correlated signal in peak samples in the peak chips;
• (d) determining whether a signal peak of the correlated signal corresponds to the direct path of the received signal, the direct path providing the timing of the received signal;
• and
• (e) iteratively repeating (a) through (d) until a signal peak is determined to correspond to the direct path of the received signal, wherein each successive iteration includes:
• regenerating the reference signal corresponding to at least a greatest signal peak in the correlated signal;
• and eliminating from the received signal contributions from each regenerated reference signal, such that the correlated signal in successive iterations excludes contributions from signals determined in previous iterations not to correspond to the direct path.

An apparatus for determining the timing of a received signal, the received signal including one or more time-delayed versions of a reference signal traveling over respective different signal paths, the apparatus comprising:

• means for iteratively correlating the received signal with the reference signal to produce a correlated signal;
• means for emphasizing the correlated signal in peak chips containing signal peaks by reducing the amplitude of the correlated signal in other chips, wherein the signal peaks correspond to potential signal paths of the received signal;
• means for emphasizing the correlated signal in peak samples in the peak chips by reducing the amplitude of other samples in the peak chips;
• means for determining whether the correlated signal includes a signal peak corresponding to a direct path of the received signal, the direct path providing the timing of the received signal, wherein correlation iterations cease once a signal peak is determined to correspond to the direct path;
• means for regenerating, in each iteration, the reference signal corresponding to at least a greatest signal peak in the correlated signal in response to no signal peak being determined to correspond to the direct path;
• and
• means for modifying, in each iteration, the received signal to be correlated to remove contributions from the regenerated reference signals, such that the correlated signal in successive iterations excludes contributions from signals determined in previous iterations not to correspond to the direct path.