Re-orthogonalization of wideband CDMA signals

A receiver for receiving a multiplicity of overlapping spread-spectrum signals and decoding at least one of said overlapping spread-spectrum signals comprising:

• receiving means for producing I and Q quadrature baseband signals;
• high-pass filtering means for removing unwanted DC offsets from said I and Q quadrature baseband signals;
• code generator means to provide replicas of spreading codes used by said overlapping signals;
• I and Q signal despreading means for combining said quadrature baseband signals with a first of said spreading code replicas to obtain despread I and Q signals;
• and
• filtering means for removing signal energy associated with a first of said overlapping spread-spectrum signals spread with a first spreading code from said despread signals to leave first residual I and Q signals in which a total energy associated with others of said overlapping spread-spectrum signals remains substantially unaffected;
• wherein said filtering means is a high-pass filter.

A receiver for receiving a multiplicity of overlapping spread-spectrum signals and decoding at least one of said overlapping spread spectrum signals comprising:

• receiving means for producing an intermediate frequency signal;
• code generator means to provide replicas of despreading codes associated with said overlapping signals and combinations thereof;
• first despreading means for despreading said intermediate frequency signal with a first of said despreading code replicas to obtain a despread signal;
• first filtering means for removing signal energy of a first of said overlapping spread-spectrum signals spread with said first despreading code from said despread signals to leave a residual signal in which a total energy associated with other signals remains substantially unaffected;
• and
• second despreading means for despreading said residual signal using a combination of said first despreading code replica and a second despreading code replica to obtain an output signal.

A receiver for receiving a multiplicity of overlapping spread-spectrum signals and decoding at least one of said overlapping spread-spectrum signals comprising:

• receiving means for producing an intermediate frequency signal;
• code generator means for providing replicas of spreading codes used by said overlapping signals;
• despreading means for despreading said intermediate frequency signal with a first of said spreading code replicas to obtain a despread signal;
• filtering means for removing signal energy of a first of said overlapping spread-spectrum signals spread with said first spreading code from said despread signals to leave a first residual signal in which a total energy associated with others of said overlapping spread-spectrum signals remains substantially unaffected;
• respreading means for respreading said first residual signal using said first spreading code-replica to obtain a first respread signal;
• additional despreading, filtering and respreading means using other of said code replicas for removing energy associated with other signals from said first residual signal to obtain a second residual signal;
• and
• resubtraction means comprising despreading, filtering and respreading means using said first spreading code replica to remove from said second residual signal energy associated with said first signal to produce an output signal.

A receiver for receiving a multiplicity of overlapping spread-spectrum signals and decoding at least one of said overlapping spread-spectrum signals comprising:

• receiving means for producing an intermediate frequency signal;
• code generator means for providing replicas of spreading codes used by said overlapping signals and pairwise combinations thereof;
• despreading means for despreading said intermediate frequency signal with a first of said spreading code replicas to obtain a despread signal;
• filtering means for removing signal energy of a signal spread with said first despreading code from said despread signals to leave a first residual signal in which a total energy associated with other signals remains substantially unaffected;
• additional despreading and filtering means using said pairwise code combinations for removing energy associated with other signals from said first residual signal to obtain a second residual signal;
• and
• resubtraction means comprising despreading and filtering means using said pairwise code combinations including said first despreading code to remove from said second residual signal energy associated with said first signal to produce an output signal.

A receiver for receiving a multiplicity of overlapping spread-spectrum signals and decoding at least one of said signals, comprising:

• receiving means for receiving said overlapping signals and quadrature downconverting said overlapping signals to produce complex baseband I and Q signals;
• code generator means for producing replicas of spreading codes used by said overlapping signals;
• I and Q despreading means for despreading said I and Q signals using a replica of a first spreading code to produce first despread I and Q signals;
• first filtering means for removing energy from said first despread I and Q signals associated with a first signal using said first spreading code while leaving substantially unaltered energy associated with other codes to produce first residual I and Q signals;
• respreading and despreading means for respreading said first residual signals using said first spreading code replica and for despreading said first residual signals using a second code replica to produce second despread I and Q signals;
• second filtering means for removing from said second despread I and Q signals energy associated with a second signal using said second spreading code to leave second residual I and Q signals;
• signal removal means for removing from said second residual signals energy associated with signals using spreading codes other than said second spreading code to produce third residual I and Q signals;
• and
• resubtraction means for removing from said third residual signals remaining energy associated with said first signal using said first spreading code.

A receiver for receiving a multiplicity of overlapping spread-spectrum signals and decoding at least one of said signals, comprising:

• receiving means for receiving said overlapping signals and quadrature downconverting said overlapping signals to produce complex baseband I and Q signals;
• code generator means for producing replicas of the spreading codes used by said overlapping signals and time-shifted replicas of said spreading codes;
• I and Q despreading means for despreading said I and Q signals using a replica of a first spreading code to produce first despread I and Q signals;
• first filtering means for removing energy from said first despread I and Q signals associated with a first signal using said first spreading code while leaving substantially unaltered energy associated with other of said spreading codes to produce first residual I and Q signals;
• first respreading and despreading means for respreading said first residual signals using said first spreading code replica and for despreading said first residual signals using a timeshifted replica of said first spreading code to produce second despread I and Q signals;
• second filtering means for removing from said second despread I and Q signals energy associated with an echo of said first signal to produce second residual I and Q signals;
• second respreading and despreading means for respreading said second residual signals using said timeshifted replica of said first code and for despreading said second residual signals using a second code replica to produce third despread I and Q signals;
• and
• processing means for processing said third despread signals to extract desired information carried by a second signal using said second spreading code.

A receiver for receiving a multiplicity of overlapping spread-spectrum signals and decoding at least one of said signals, comprising:

• receiving means for receiving said overlapping signals and converting to an intermediate frequency signal;
• code generator means for producing replicas of spreading codes used by said overlapping signals and time-shifted replicas of said spreading codes;
• despreading means for despreading said intermediate frequency signal using a replica of a first spreading code to produce a first despread signal;
• notch filtering means for removing energy from said first despread signal associated with a first signal using said first spreading code while leaving substantially unaltered energy associated with other codes to produce a first residual signal;
• first respreading and despreading means for respreading said first residual signal using said first spreading code replica and to despread using a timeshifted replica of said first spreading code to produce a second despread signal;
• second filtering means to remove from said second despread signal energy associated with a delayed echo of said first signal to leave a second residual signal;
• second respreading and despreading means to respread said second residual signal suing said timeshifted replica of said first code and to despread using a second code replica to produce a third despread signal;
• and
• processing means to process said third despread signal to extract desired information carried by a second signal using said second spreading code.

A receiver for receiving a multiplicity of overlapping spread-spectrum signals and decoding at least one of said signals, comprising:

• receiving means for receiving said overlapping signals and quadrature downconverting said overlapping signals to produce complex baseband I and Q signals;
• code generator means for producing time-shifted replicas of the spreading codes used by said overlapping signals;
• first I and Q despreading means for despreading said I and Q signals using a first time-shifted replica of a first spreading code to produce first despread I and Q signals;
• second I and Q despreading means for despreading I and Q signals using a second time-shifted replica of said first spreading code to produce second despread I and Q signals;
• processing means to jointly process said first and second despread signals to extract desired information;
• filtering means to remove energy from said first despread I and Q signals associated with a first signal using said first spreading code while leaving substantially unaltered energy associated with other codes to produce first residual I,Q signals;
• respreading and despreading means for respreading said first residual signals using said first time-shifted replica of said first code and for despreading said first residuals using a replica of a second code to produce third despread I and Q signals;
• and
• processing means to process said third despread signals to extract desired information carried by a signal using said second spreading code.

A receiver for receiving a multiplicity of overlapping spread-spectrum signals and decoding at least one of said signals, comprising:

• receiving means for receiving said overlapping signals and converting said overlapping signals to an intermediate frequency signal;
• code generator means for producing time-shifted replicas of the spreading codes used by said overlapping signals;
• first despreading means for despreading said intermediate frequency signal using a first time-shifted replica of a first spreading code to produce a first despread signal;
• second despreading means for despreading said intermediate frequency signal using a second time-shifted replica of said first spreading code to produce a second despread signal;
• processing means to jointly process said first and second despread signal to extract desired information;
• filtering means for removing energy from said first despread signal associated with a first signal using said first spreading code while leaving substantially unaltered energy associated with other codes to produce a first residual signal;
• respreading and despreading means for respreading said first residual signal using said first time-shifted replica of said first code and for respreading using a replica of a second code to produce a third despread signal;
• and
• processing means to process said third despread signal to extract desired information carried by a signal using said second spreading code.

A receiver for receiving a multiplicity of overlapping spread-spectrum signals and decoding at least one of said signals, comprising:

• receiving means for receiving said overlapping signals and producing a downconverted signal for processing;
• code generator means for producing replicas of spreading codes used by said overlapping signals and time-shifted replicas of said spreading codes which are delayed by one or more code symbol periods;
• despreading means for despreading said downconverted signal using different time-shifted replicas of a first spreading code and producing corresponding first despread signals at least one of which forms a cascade signal output to a second despreading means;
• and
• at least one processing means connected to jointly process said first despread signals that have been despread using timeshifted replicas of the first spreading code in order to extract desired information carried by a first signal using that spreading code.