Time tracking loop for diversity pilots

A method of time tracking a plurality of pilot sequences, a first pilot sequence transmitted from a first antenna, each of the remaining plurality of pilot sequences transmitted on a corresponding plurality of antennas, each remaining pilot sequence generated by multiplying each symbol of the first pilot sequence by a value from an orthogonalizing sequence of a plurality of orthogonalizing sequences, the symbols consisting of a first pre-determined number of chips, comprising:

• calculating a difference between the energy in a correlation of the first pilot sequence with an early received sequence of input samples and the energy in a correlation of the first pilot sequence with a late received sequence of input samples, the correlations for a pre-determined length, the early and late sequences referenced to a timing reference;
• updating a tracking loop with the difference to produce the timing reference;
• and
• estimating the plurality of pilot sequences in accordance with the timing reference.

An apparatus, operable with a base station configured for transmit diversity, transmitting a first pilot sequence on a first antenna, transmitting each of the remaining plurality of pilot sequences transmitted on a corresponding plurality of antennas, each remaining pilot sequence generated by multiplying each symbol of the first pilot sequence by a value from an orthogonalizing sequence of a plurality of orthogonalizing sequences, the symbols consisting of a first pre-determined number of chips, comprising:

• means for calculating a difference between the energy in a correlation of the first pilot sequence with an early received sequence of input samples and the energy in a correlation of the first pilot sequence with a late received sequence of input samples, the correlations for a pre-determined length, the early and late sequences referenced to a timing reference;
• means for updating a tracking loop with the difference to produce the timing reference;
• and
• means for estimating the plurality of pilot sequences in accordance with the timing reference.

Processor readable media operable to perform the following steps:

• calculating a difference between the energy in a correlation of a first pilot with an early received sequence of input samples and the energy in a correlation of the first pilot sequence with a late received sequence of input samples, the correlations for a pre-determined length, the early and late sequences referenced to a timing reference;
• updating a tracking loop with the difference to produce the timing reference;
• and
• estimating a plurality of pilot sequences in accordance with the timing reference, the plurality of pilot sequences including the first pilot sequence, and a plurality of pilot sequences generated by multiplying symbols of the first pilot sequence by a plurality of orthogonalizing sequences.

A mobile station, operable with a base station configured for transmit diversity, transmitting a first pilot sequence on a first antenna and a second pilot sequence on a second antenna, the second sequence generated by multiplying each symbol of the first pilot sequence by a value from an orthogonalizing sequence, the symbols consisting of a first pre-determined number of chips, comprising:

• a first timing offset for receiving input samples and for generating an early sequence of samples corresponding to a pre-determined offset before a timing reference;
• a second timing offset for receiving input samples and for generating a late sequence of samples corresponding to a pre-determined offset after a timing reference;
• a first despreader for despreading the early sequence of samples with the first pilot sequence;
• a second despreader for despreading the late sequence of samples with the first pilot sequence;
• a first accumulator for accumulating despread samples from the first despreader for a second pre-determined number of chips to produce a first accumulation;
• a second accumulator for accumulating despread samples from the second despreader for the second pre-determined number of chips to produce a second accumulation;
• a first magnitude squarer for generating a first squared magnitude from the first accumulation;
• a second magnitude squarer for generating a second squared magnitude from a second accumulation;
• a subtractor for generating the difference between the first and second squared magnitudes;
• a tracking loop for generating the timing reference in response to the difference;
• and
• a pilot decover for estimating the first and second pilots from the input samples in accordance with the timing reference.

A mobile station, operable with a base station configured for transmit diversity, transmitting a first pilot sequence on a first antenna, transmitting each of the remaining plurality of pilot sequences transmitted on a corresponding plurality of antennas, each remaining pilot sequence generated by multiplying each symbol of the first pilot sequence by a value from an orthogonalizing sequence of a plurality of orthogonalizing sequences, the symbols consisting of a first pre-determined number of chips, comprising:

• means for calculating a difference between the energy in a correlation of the first pilot sequence with an early received sequence of input samples and the energy in a correlation of the first pilot sequence with a late received sequence of input samples, the correlations for a pre-determined length, the early and late sequences referenced to a timing reference;
• means for updating a tracking loop with the difference to produce the timing reference;
• and
• means for estimating the plurality of pilot sequences in accordance with the timing reference.

A wireless communication system including a mobile station, operable with a base station configured for transmit diversity, transmitting a first pilot sequence on a first antenna, transmitting each of the remaining plurality of pilot sequences transmitted on a corresponding plurality of antennas, each remaining pilot sequence generated by multiplying each symbol of the first pilot sequence by a value from an orthogonalizing sequence of a plurality of orthogonalizing sequences, the symbols consisting of a first pre-determined number of chips, comprising:

• means for calculating a difference between the energy in a correlation of the first pilot sequence with an early received sequence of input samples and the energy in a correlation of the first pilot sequence with a late received sequence of input samples, the correlations for a pre-determined length, the early and late sequences referenced to a timing reference;
• means for updating a tracking loop with the difference to produce the timing reference;
• and
• means for estimating the plurality of pilot sequences in accordance with the timing reference.