Pilot interpolation for a gated pilot with compensation for induced phase changes

In a CDMA communication system employing a gated pilot transmission scheme, a method for deriving interpolated pilot symbols based on pilot bursts in a received signal, comprising:

• deriving first and second recovered pilot symbols based on pilot bursts received at first and second time instances, respectively;
• estimating a phase change induced in the received signal at a third time instance between the first and second time instances;
• deriving an interpolated pilot symbol at the third time instance based on the first and second recovered pilot symbols;
• rotating the interpolated pilot symbol at the third time instance by the estimated induced phase change to derive first and second phase-rotated symbols;
• deriving interpolated pilot symbols between the first and third time instances based on the first recovered pilot symbol and the first phase-rotated symbol and using linear interpolation;
• and
• deriving interpolated pilot symbols between the third and second time instances based on the second phase-rotated symbol and the second recovered pilot symbol and using linear interpolation.

A memory communicatively coupled to a digital signal processing device capable of interpreting digital information to:

• obtain a first recovered pilot symbol for a first time instance and a second recovered pilot symbol for a second time instance derived based on pilot bursts received for a gated pilot;
• estimate a phase change induced in a received signal at a third time instance between the first and second time instances;
• derive first and second phase-rotated symbols based on the first and second recovered pilot symbols and the estimated induced phase change;
• derive interpolated pilot symbols between the first and third time instances based on the first recovered pilot symbol and the first phase-rotated symbol;
• and
• derive interpolated pilot symbols between the third and second time instances based on the second phase-rotated symbol and the second recovered pilot symbol.

A computer program product for deriving interpolated pilot symbols for a gated pilot, comprising:

• code for obtaining a first recovered pilot symbol for a first time instance and a second recovered pilot symbol for a second time instance;
• code for estimating a phase change induced in a received signal at a third time instance between the first and second time instances;
• code for deriving first and second phase-rotated symbols based on the first and second recovered pilot symbols and the estimated induced phase change;
• code for deriving interpolated pilot symbols between the first and third time instances based on the first recovered pilot symbol and the first phase-rotated symbol;
• code for deriving interpolated pilot symbols between the third and second time instances based on the second phase-rotated symbol and the second recovered pilot symbol;
• and
• a computer-usable medium for storing the codes.

A pilot processor for use in a wireless communication system, comprising:

• a first unit operative to obtain a first recovered pilot symbol for a first time instance and a second recovered pilot symbol for a second time instance, wherein the first and second recovered pilot symbols are derived based on pilot bursts received for a gated pilot;
• a symbol generator operative to derive first and second phase-rotated symbols based on the first and second recovered pilot symbols and an estimate of a phase change induced in a received signal at a third time instance between the first and second time instances;
• and
• an interpolator operative to derive interpolated pilot symbols between the first and third time instances based on the first recovered pilot symbol and the first phase-rotated symbol, and to derive interpolated pilot symbols between the third and second time instances based on the second phase-rotated symbol and the second recovered pilot symbol.

A rake receiver comprising a plurality of finger processors, each finger processor including

• a despreader operative to receive and despread data samples to provide despread samples;
• a data decoverer operative to decover the despread samples with a first channelization code to provide data symbols;
• a pilot decoverer operative to decover the despread samples with a second channelization code to provide recovered pilot symbols for pilot bursts received for a gated pilot;
• a pilot processor operative to process the recovered pilot symbols to provide a reference signal having a phase that includes phase changes induced in a received signal;
• and
• a data demodulator operative to demodulate the data symbols with the reference signal to provide demodulated symbols.

A digital signal processor comprising:

• a first unit operative to obtain a first recovered pilot symbol for a first time instance and a second recovered pilot symbol for a second time instance, wherein the first and second recovered pilot symbols are derived based on pilot bursts received for a gated pilot;
• a symbol generator operative to derive first and second phase-rotated symbols based on the first and second recovered pilot symbols and an estimate of a phase change induced in a received signal at a third time instance between the first and second time instances;
• and
• an interpolator operative to derive interpolated pilot symbols between the first and third time instances based on the first recovered pilot symbol and the first phase-rotated symbol, and to derive interpolated pilot symbols between the third and second time instances based on the second phase-rotated symbol and the second recovered pilot symbol.

A receiver unit in a wireless communication system, comprising:

• a receiver operative to process a received signal to provide data samples;
• and
• a rake receiver comprising a plurality of finger processors, each finger processor operative to process the data samples for a particular signal instance in the received signal to provide demodulated symbols for the signal instance, each finger processor including
• a despreader operative to receive and despread the data samples to provide despread samples,
• a data decoverer operative to decover the despread samples with a first channelization code to provide data symbols,
• a pilot decoverer operative to decover the despread samples with a second channelization code to provide recovered pilot symbols for pilot bursts received for a gated pilot,
• a pilot processor operative to process the recovered pilot symbols to provide a reference signal having a phase that includes phase changes induced in the received signal by circuit changes in the receiver, and
• a data demodulator operative to demodulate the data symbols with the reference signal to provide demodulated symbols.

An apparatus in a wireless communication system, comprising:

• means for obtaining a first recovered pilot symbol for a first time instance and a second recovered pilot symbol for a second time instance, wherein the first and second recovered pilot symbols are derived based on pilot bursts for a gated pilot;
• means for estimating a phase change induced in a received signal at a third time instance between the first and second time instances;
• means for deriving first and second phase-rotated symbols based on the first and second recovered pilot symbols and the estimated induced phase change;
• means for deriving interpolated pilot symbols between the first and third time instances based on the first recovered pilot symbol and the first phase-rotated symbol;
• and
• means for deriving interpolated pilot symbols between the third and second time instances based on the second phase-rotated symbol and the second recovered pilot symbol.