Delay lock loops for wireless communication systems

A method for deriving sample timing for a plurality of signal instances received on a plurality of antennas at a receiver unit in a wireless communication system, comprising:

• updating a loop filter for each of the plurality of signal instances based on an error metric derived for each signal instance;
• estimating a signal quality of each of the plurality of signal instances;
• comparing the estimated signal qualities of the plurality of signal instances;
• selecting one of the plurality of signal instances based on a result of the comparing;
• loading a loop filter value for the selected signal instance onto the loop filter for each remaining one of the plurality of signal instances;
• and
• deriving the sample timing for each signal instance based on an output of the loop filter for each signal instance.

A method for deriving sample timing for a plurality of signal instances received on a plurality of antennas and corresponding to a single propagation path at a terminal in a CDMA communication system, comprising:

• deriving an error metric for each of the plurality of signal instances with an early/late discriminator and based on data samples for each signal instance;
• estimating a signal-to-noise-and-interference ratio (SINR) of each of the plurality of signal instances;
• comparing the estimated SINRs of the plurality of signal instances;
• selecting a signal instance having the highest SINR;
• updating a loop filter based on the error metric derived for the selected signal instance;
• and
• deriving the sample timing for the plurality of signal instances based on an output of the loop filter.

A method for deriving sample timing for a plurality of signal instances received on a plurality of antennas at a receiver unit in a wireless communication system, comprising:

• deriving an error metric for each of the plurality of signal instances;
• combining error metrics for the plurality of signal instances to provide a composite error metric;
• updating a loop filter based on the composite error metric;
• deriving the sample timing for the plurality of signal instances based on an output of the loop filter;
• and
• estimating a signal quality of each of the plurality of signal instances, wherein error metrics for signal instances having estimated signal qualities above a particular threshold are combined.

A method for deriving sample timing for a plurality of signal instances received on a plurality of antennas at a receiver unit in a wireless communication system, comprising:

• deriving an error metric for each of the plurality of signal instances;
• estimating a signal quality of each of the plurality of signal instances;
• selecting one of a plurality of possible loop modes for a delay lock loop based on the estimated signal qualities of the plurality of signal instances;
• updating a loop filter for the delay lock loop based on one or more error metrics for one or more selected signal instances and in accordance with the selected loop mode;
• and
• deriving the sample timing for the plurality of signal instances based on an output of the loop filter.

A method for deriving sample timing for a received signal instance at a receiver unit in a wireless communication system, comprising:

• estimating a signal quality of the signal instance for each of a plurality of different time offsets, wherein each time offset corresponds to a different sample timing for the signal instance;
• updating a loop filter based on an error metric derived for the signal instance;
• determining a nominal time offset to be used for the sample timing for the signal instance based on an output of the loop filter;
• detecting for a change between a current and a prior nominal time offset;
• if a change in the nominal time offset is detected,
• comparing the estimated signal quality for the current nominal time offset to the estimated signal quality for the prior nominal time offset, and
• retaining the current nominal time offset if the estimated signal quality for the current nominal time offset is better than the estimated signal quality for the prior nominal time offset.

A memory communicatively coupled to a digital signal processing device (DSPD) for interpreting digital information to:

• estimate a signal quality of each of a plurality of signal instances received on a plurality of antennas;
• compare the estimated signal qualities of the plurality of signal instances;
• select one of the plurality of signal instances based on a result of the comparing;
• update a loop filter based on an error metric derived for the selected signal instance;
• and
• derive the sample timing for the plurality of signal instances based on an output of the loop filter.

A method for deriving sample timing for a received signal instance at a receiver unit in a wireless communication system, comprising:

• estimating a signal quality of the signal instance;
• determining a current operating mode for a delay lock loop used to provide the sample timing for the signal instance, wherein the delay lock loop is operable in one of a plurality of operating modes at any given moment;
• and
• switching to a new operating mode for the delay lock loop if the estimated signal quality surpasses a threshold associated with the new operating mode;
• wherein the plurality of operating modes includes a normal mode and an enhanced mode;
• and
• wherein the enhanced mode comprises adjusting the sample timing for the signal instance in response to an error metric derived for the signal instance only if it would improve the signal-to-noise-and-interference ratio for the signal instance.

A method for deriving sample timing for a received signal instance at a receiver unit in a wireless communication system, comprising:

• estimating a signal quality of the signal instance;
• determining a current operating mode for a delay lock loop used to provide the sample timing for the signal instance, wherein the delay lock loop is operable in one of a plurality of operating modes at any given moment;
• and
• switching to a new operating mode for the delay lock loop if the estimated signal quality surpasses a threshold associated with the new operating mode;
• wherein the plurality of operating modes includes a normal mode and an enhanced mode, and
• wherein the normal and enhanced modes are associated with first and second thresholds, respectively, and wherein the first threshold is lower than the second threshold.

A digital signal processor comprising:

• at least one pilot processor operative to estimate a signal quality of each of a plurality of signal instances received on a plurality of antennas, and to derive an error metric indicative of error in sample timing for each signal instance;
• a controller operative to compare the estimated signal qualities of the plurality of signal instances and to select one of a plurality of signal instances based on a result of the comparison;
• and
• a loop filter operative to accumulate the error metric derived for the selected signal instance, wherein the sample timing for the plurality of signal instances is derived based on an output of the loop filter.

A digital signal processor comprising:

• at least one pilot processor operative to estimate a signal quality of a received signal instance for each of a plurality of different time offsets, wherein each time offset corresponds to a different sample timing for the signal instance, and to derive an error metric indicative of an error in the sample timing for the signal instance;
• a loop filter operative to accumulate the error metric derived for the signal instance;
• and
• a control unit operative to determine a nominal time offset to be used for the sample timing for the signal instance based on an output of the loop filter, to detect for a change between a current and a prior nominal time offset, and to retain the current nominal time offset if a change in the nominal time offset has been detected and the estimated signal quality for the current nominal time offset is better than the estimated signal quality for the prior nominal time offset.

A digital signal processor comprising:

• at least one pilot processor operative to estimate a signal quality of a received signal instance and to derive an error metric indicative of an error in a sample timing for the signal instance;
• a loop filter operative to accumulate the error metric derived for the signal instance;
• and
• a control unit operative to determine a current operating mode for a delay lock loop implemented in part by the loop filter and used to provide the sample timing for the signal instance, wherein the delay lock loop is operable in one of a plurality of operating modes at any given moment, and wherein the control unit is further operative to switch to a new operating mode for the delay lock loop if the estimated signal quality surpasses a threshold associated with the new operating mode.

A receiver unit in a wireless communication system, comprising:

• at least one pilot processor operative to estimate a signal quality of each of a plurality of signal instances received on a plurality of antennas, and to derive an error metric indicative of error in sample timing for each signal instance;
• a controller operative to compare the estimated signal qualities of the plurality of signal instances and to select one of a plurality of signal instances based on a result of the comparison;
• and
• a loop filter operative to accumulate the error metric derived for the selected signal instance, wherein the sample timing for the plurality of signal instances is derived based on an output of the loop filter.

A receiver apparatus in a wireless communication system, comprising:

• means for estimating a signal quality of each of a plurality of signal instances received on a plurality of antennas;
• means for comparing the estimated signal qualities of the plurality of signal instances;
• means for selecting one of the plurality of signal instances based on a result of the comparing;
• means for deriving an error metric indicative of error in sample timing for the selected signal instance;
• means for accumulating the error metric derived for the selected signal instance;
• and
• means for deriving the sample timing for the plurality of signal instances based on the accumulated error metric.