Interference cancellation system and method and CDMA receiver including an interference cancellation circuit

An interference cancellation circuit for cancelling interference due to particular components of a composite baseband digitized signal which contains both known and unknown information, the circuit comprising:

• known information detection and air interface characterization circuitry for detecting said known information, demodulating each said particular component and making an air interface characterization which is an estimate of an air interface channel over which the particular component was transmitted;
• estimation circuitry for making an estimate of the unknown information in each said particular component containing known information;
• combining circuitry for combining for each said particular component the known information with the estimated unknown information to make a respective combined information;
• digitized baseband component regeneration circuitry for generating an estimated component for each said combined information which is an estimate of the respective particular component of the digitized baseband composite signal by modulating said combined information taking into account said air interface characterization;
• delay circuitry for delaying the digitized baseband composite signal an amount substantially equal to the time it takes the known information detection and air interface characterization circuitry and component regeneration circuitry to create the estimated components;
• and
• subtraction circuitry for subtracting the estimated components from the delayed digitized baseband composite signal to create a corrected digitized baseband composite signal.

A CDMA receiver comprising:

• an antenna for receiving an RF composite spread spectrum signal over an air interface;
• RF down conversion and A/D conversion circuitry for converting the composite spread spectrum signal into a digitized composite baseband signal;
• an interference cancellation circuit for cancelling interference due to pilot channel components of the baseband digitized composite signal which contain both known pilot bits and unknown power control bits, the interference cancellation circuit comprising:
• a) pilot channel detection and air interface and characterization circuitry for detecting the pilot channel components present in the composite baseband digitized signal and making a respective channel estimate of an air interface over which each said pilot channel component was received;
• b) power control bit detection circuitry for estimating the power control bits in said pilot channel components;
• c) combining circuitry for combining for each pilot channel component in a respective combined information the pilot bits with the associated estimated power control bits;
• d) pilot channel reconstruction circuitry for creating a regenerated baseband digitized pilot channel component for each said combined information which is an estimate of the pilot channel component as it would have been received taking into account the respective channel estimate;
• e) delay circuitry for delaying the digitized baseband composite signal an amount substantially equal to the time it takes to make the estimates of the pilot channel components;
• and
• f) subtraction circuitry for subtracting the estimates of the pilot channel components from the delayed digitized baseband composite signal to produce a corrected composite digitized baseband signal;
• a baseband detection unit for each user connected to receive the corrected composite digitized baseband signal and the channel characterization information for that user, for producing one or more received data streams for that user.

A method of reducing interference due to components carrying known information in a composite digitized baseband signal comprising:

• detecting the known information for each said component and producing a respective estimate of an air interface over which each said component was received;
• passing the known information for each component through a model of the respective air interface which is based upon the respective estimate of the air interface to produce a respective estimated component;
• delaying the composite digitized baseband signal to produce a delayed composite digitized baseband signal an amount of time equal to how long it takes for the steps of detecting and passing;
• subtracting the estimated components from the delayed composite digitized baseband signal to produce a corrected composite digitized baseband signal.

A method of reducing interference due to particular components of a composite digitized baseband signal, each particular containing a respective known information and a respective unknown information, the method comprising the steps of:

• detecting the known information for each particular component and producing a respective estimate of an air interface over which each particular component was received;
• making an estimate of each unknown information;
• combining the estimate of the unknown information with the respective known information to create a combined information for each said particular component;
• passing each combined information through a model of the respective air interface which is based upon the respective estimate of the air interface to produce a respective estimated component;
• delaying the composite digitized baseband signal to produce a delayed composite digitized baseband signal an amount of time equal to how long it takes for the steps of detecting, making an estimate, combining and passing;
• and
• subtracting the estimated components from the delayed composite digitized baseband signal to produce a corrected composite digitized baseband signal.