Interference suppression in a CDMA receiver

A code-division multiple access (CDMA) receiver having an n-finger rake receiver producing n received traffic channel signals in response to a transmitted traffic channel signal of a CDMA transmitter and a locally generated traffic channel despreading sequence and producing n received pilot channel signals in response to a transmitted pilot channel signal of said transmitter and a locally generated pilot channel pseudonoise (pn) sequence, a method for canceling interference present in a transmitted traffic channel signal at said receiver, the method comprising the steps of:

• producing n interpolated pilot channel pn sequences, each interpolated pilot channel pn sequence corresponding to one of said fingers and produced by interpolating values of said locally generated pilot channel pn sequence between chip period values;
• producing n groups of n−1 interference signals, each group of n−1 interference signals corresponding to one of said fingers, each interference signal of a group corresponding to a finger is produced in response to said locally generated traffic channel despreading sequence corresponding to said finger and one of said n locally generated interpolated pilot channel pn sequences corresponding to another one of said fingers;
• producing n groups of n−1 correction signals, each group of n−1 correction signals corresponding to one of said fingers, each correction signal of a group corresponding to a finger is produced in response to an interference signal corresponding to said another one of said fingers and a received pilot channel signal corresponding to said another one of said fingers;
• and
• producing n corrected traffic channel signals, each corrected traffic channel signal corresponding to one of said fingers and produced by subtracting from a received traffic channel signal corresponding to said finger each of said n−1 correction signals of a group corresponding to said finger.

In a code division multiple access (CDMA) receiver having n-finger rake receiver producing n received traffic channel signals in response to a transmitted traffic channel signal of a CDMA transmitter and a locally generated traffic channel despreading sequence and producing n received pilot channel signals in response to a transmitted pilot channel signal of said transmitter and a locally generated pilot channel pseudonoise (pn) sequence, a method for canceling interference present in a transmitted pilot channel signal at said receiver, the method comprising the steps of:

• producing n locally generated interpolated pilot channel pn sequences, each locally generated interpolated pilot channel pn sentence corresponding to one of said fingers and produced by interpolating values of said locally generated pilot channel pn sequences between chip period values;
• producing n groups of n−1 interference signals, each group of n−1 interference signals corresponding to one of said fingers, each interference signal of a group corresponding to a finger is produced in response to said locally generated traffic channel despreading sequence corresponding to said finger and one of said n locally generated interpolated pilot channel pn sequences corresponding to another one of said fingers;
• producing n groups of n−1 correction signals, each group of n−1 correction signals corresponding to one of said fingers, each correction signal of a group corresponding to a finger is produced in response to an interference signal corresponding to said another one of said fingers and a received pilot channel signal corresponding to said another one of said fingers;
• and
• producing n corrected pilot channel signals, each corrected pilot channel signal corresponding to a finger and produced by subtracting from a received pilot channel signal corresponding to said finger each of said n−1 correction signals of a group corresponding to said finger.

A noise reduction circuit adapted to be coupled within a code division multiple access (CDMA) receiver including a rake receiver having at least a first finger and a second finger, the CDMA receiver for reducing noise within a received data channel signal transmitted from a transmitter, the noise reduction circuit comprising:

• a correlator adapted to correlate an interpolated pilot channel pseudonoise (pn) sequence corresponding to the second finger with despreading sequence corresponding to the second finger with a despreading sequence corresponding to the first finger to produce an interference signal;
• a multiplier adapted to multiply the interference signal with a received pilot signal corresponding to the second finger to produce a correction signal;
• and
• a subtractor adapted to subtract the correction signal from the received data channel signal to produce a corrected data channel signal.

A code division multiple access (CDMA) receiver for reducing interference in a received data channel signal transmitted from a transmitter, the receiver comprising:

• a rake receiver comprising a first finger and a second finger, wherein the first finger is adapted to receive the data channel signal;
• a noise reduction circuit coupled to the first finger and adapted to produce a correction signal based on a received pilot signal corresponding to the second finger, a pilot channel pseudonoise sequence corresponding to the second finger, and a despreading sequence associated with the first finger;
• a subtractor coupled to the first finger and the noise reduction circuit, the subtractor adapted to produce a corrected data channel signal based on the received data signal and the correction signal;
• a correlator adapted to correlate the pilot channel pseudonoise (pn) sequence corresponding to the second finger with a despreading sequence corresponding to the first finger to produce an interference signal;
• a multiplier adapted to multiply the interference signal with a received pilot signal corresponding to the second finger to produce a correction signal;
• and
• a digital interpolation filter coupled to the correlator, the digital interpolation filter having an impulse response in accordance with a function equal to the convolution of an impulse response of the input filter and an impulse response of an output filter of the transmitter, the digital interpolation filter adapted to interpolate a value of the pilot channel pn sequence between chip period values to produce an interpolated pilot channel pn sequence, the correlator adapted to produce the interference signal by correlating the interpolated pilot channel pn sequence with the despreading sequence.

In a code division multiple access (CDMA) receiver having an n-finger rake receiver producing n received traffic channel signals in response to a transmitted traffic channel signal of a CDMA transmitter and a locally generated traffic channel despreading sequence and producing n received pilot channel signals in response to a transmitted pilot channel signal of said transmitter and a locally generated pilot channel pseudonoise (pn) sequence, a system for canceling interference present in a transmitted traffic channel signal at said receiver, the system comprising:

• n cancellation circuits, each corresponding to one of said fingers and producing n−1 interference signals, each interference signal of a group corresponding to a finger produced in response to said locally generated traffic channel despreading sequence corresponding to said finger and one of said n locally generated pilot channel pn sequences corresponding to another one of said fingers;
• each cancellation circuit includes an interpolator, said interpolator producing an interpolated pilot channel pn sequence corresponding to one of said fingers and representing interpolated values of said pilot channel pn sequence between chip period values;
• each cancellation circuit producing n−1 correction signals, each correction signal of a group corresponding to a finger produced in response to an interference signal corresponding to said another one of said fingers and a received pilot channel signal corresponding to said another one of said fingers;
• and
• n correction circuits, each corresponding to a finger and subtracting from a received traffic channel signal corresponding to said finger each of said n−1 correction signals of a group corresponding to said finger.

In a code division multiple access (CDMA) receiver having an n-finger rake receiver producing n received traffic channel signals in response to a transmitted traffic channel signal of a CDMA transmitter and a locally generated traffic channel despreading sequence and producing n received pilot channel signals in response to a transmitted pilot channel signal of said transmitter and a locally generated pilot channel pseudonoise (pn) sequence, a system for canceling interference present in a transmitted pilot channel signal at said receiver, the system comprising:

• n cancellation circuits, each corresponding to one of said fingers and producing n−1 interference signals, each interference signal of a group corresponding to a finger produced in response to said locally generated pilot channel pn sequence corresponding to said finger and one of said n locally generated pilot channel pn sequences corresponding to another one of said fingers;
• each cancellation circuit includes an interpolator, said interpolator producing an interpolated pilot channel pn sequence corresponding to one of said fingers and representing interpolated values of said pilot channel pn sequence between chip period values;
• each cancellation circuit producing n−1 correction signals, each correction signal of said grouped corresponding to a finger produced in response to an interference signal corresponding to said another one of said fingers and a received pilot channel signal corresponding to said another one of said fingers;
• and
• n correction circuits, each corresponding to a finger and subtracting from a received pilot channel signal corresponding to said finger each of said n−1 correction signals of a group corresponding to said finger.