Spread spectrum CDMA interference canceler system and method

A spread-spectrum code division multiple access (CDMA) interference-canceler system for reducing interference in a spread-spectrum CDMA receiver having N channels, with each of the N channels identified by a distinct chip-code signal, comprising:

• a CDMA/DS detector for detecting and despreading a received spread-spectrum signal having a plurality of channels as a plurality of despread, spread-spectrum channels;
• a plurality of serially connected interference cancelers each for processing the plurality of despread, spread-spectrum channels and for outputting a respective plurality of estimates of the plurality of channels;
• and and
• a combiner for combining, using the outputs of the plurality of interference cancelers, a plurality of estimates of a particular channel to generate an averaged estimate.

A spread-spectrum code division multiple access (CDMA) interference-canceler system for reducing interference in a spread-spectrum CDMA receiver having N channels, with each of the N channels identified by a distinct chip-code signal, comprising:

• a CDMA/DS detector for detecting and despreading a received spread-spectrum signal having a plurality of channels as a plurality of despread, spread-spectrum channels;
• a plurality of serially connected interference cancelers each for processing the plurality of despread, spread-spectrum channels and for outputting a respective plurality of estimates of the plurality of channels;
• means for combining, using the respective plurality of estimates from said plurality of interference cancelers, a first plurality of estimates for a first channel to generate a first averaged output for channel one, a second plurality of estimates for a second channel to generate a second averaged output for channel two, and an M.sup.th plurality of estimates for an M.sup.th channel to generate an M.sup.th averaged output for channel M;
• and
• decision means for processing the first averaged output for channel one, the second averaged output for channel two, and the M.sup.th averaged output for channel M.

A method for reducing interference in a spread-spectrum code division multiple access (CDMA) receiver having N channels, with each of the N channels identified by a distinct chip-code signal, using a plurality of interference cancelers, each of said plurality of interference cancelers including a plurality of chip-code generators for generating a plurality of chip-code signals and a plurality of timed devices for generating a plurality of timed-chip-code signals, comprising the steps, within each of said plurality of interference cancelers, of:

• a. despreading, simultaneously, a plurality of spread-spectrum channels of a spread-spectrum CDMA signal as a plurality of despread signals using the plurality of chip-code signals, respectively;
• b. spread-spectrum processing, simultaneously, using the plurality of timed-chip-code-signals, the plurality of despread signals, respectively, with each of the plurality of timed-chip-code signals corresponding to a respective one of the plurality of despread signals;
• c. subtracting from the spread-spectrum CDMA signal, each of a plurality of N-1 spread-spectrum-processed-despread signals, with the plurality of N-1 spread-spectrum-processed-despread signals not including a spread-spectrum processed despread signal of an i.sup.th despread signal, thereby generating a subtracted signal;
• d. despreading the subtracted signal with an i.sup.th timed chip-code signal as an i.sup.th channel signal, producing a first set of estimates of the N channels;
• e. repeating steps a through d, using a second plurality of interference cancelers, producing a second set of estimates of the N channels;
• and
• f. repeating steps a through d, using an M.sup.th plurality of interference cancelers, producing an M.sup.th set of estimates of the N channels.

A spread-spectrum code division multiple access (CDMA) interference-canceler system for reducing interference in a spread-spectrum CDMA receiver having N channels, with each of the N channels identified by a distinct chip-code signal, comprising:

• a plurality of interference cancelers, each of said interference cancelers including,
• a plurality of chip-code-signal generators for generating, simultaneously, a plurality of chip-code signals;
• a plurality of correlators coupled to said plurality of chip-code generators through a plurality of mixers, each of said plurality of correlators responsive to a distinct chip-code signal of the plurality of chip-code-signals, for simultaneously despreading a plurality of spread-spectrum channels of a spread-spectrum CDMA signal as a plurality of despread signals, respectively;
• a plurality of delay devices coupled to said plurality of chip-code-signal generators for delaying the plurality of chip-code signals as a timed plurality of chip-code signals, respectively;
• a plurality of processing mixers coupled to said plurality of delay devices and to said plurality of correlators, responsive to the timed plurality of chip-code signals, for spread-spectrum processing, simultaneously, the plurality of despread signals, respectively, with a timed chip-code-signal corresponding to a respective despread signal, producing N spread-spectrum-processed-despread signals;
• a plurality of subtractors, each of said plurality of subtractors for subtracting from the spread-spectrum CDMA signal all but a particular one of the N spread-spectrum-processed-despread signals, with the particular one of the N spread-spectrum-processed-despread signals being different for each of said plurality of subtractors, thereby generating a plurality of subtracted signals;
• and
• a plurality of channel correlators for despreading the plurality of subtracted signals with a particular one of the plurality of timed chip-code signals, respectively, as a plurality of channel signals.

A spread-spectrum code division multiple access (CDMA) interference-canceler system for reducing interference in a spread-spectrum CDMA receiver having N channels, with each of the N channels identified by a distinct chip-code signal, comprising:

• a CDMA/DS detector for detecting and despreading a received spread-spectrum signal having a plurality of channels as a plurality of despread, spread-spectrum channels;
• a plurality of serially connected interference cancelers each for processing the plurality of despread, spread-spectrum channels and for outputting a respective plurality of estimates of the plurality of channels;
• and
• means for combining, using the respective plurality of estimates from said plurality of interference cancelers, a first plurality of estimates for a first channel to generate a first averaged output for channel one, a second plurality of estimates for a second channel to generate a second averaged output for channel two, and an M.sup.th plurality of estimates for an M.sup.th channel to generate an M.sup.th averaged output for channel M.

A spread-spectrum code division multiple access (CDMA) interference-canceler system for reducing interference in a spread-spectrum CDMA receiver having N channels, with each of the N channels identified by a distinct chip-code signal, comprising:

• a plurality of serially connected interference cancelers each for processing a plurality of despread, spread-spectrum channels and for outputting a plurality of estimates of a plurality of spread-spectrum channels corresponding to the plurality of despread, spread-spectrum channels, respectively;
• means for combining the plurality of estimates to produce a plurality of averaged estimates;
• and
• decision means for processing the plurality of averaged estimates.

A spread-spectrum code division multiple access (CDMA) interference-canceler system for reducing interference in a spread-spectrum CDMA receiver having N channels, with each of the N channels identified by a distinct chip-code signal, comprising:

• a plurality of serially connected interference cancelers each for processing a plurality of despread, spread-spectrum channels and for outputting a plurality of estimates of a plurality of spread-spectrum channels corresponding to the plurality of despread, spread-spectrum channels, respectively;
• a plurality of combiners for combining the plurality of estimates to produce a plurality of averaged estimates;
• and
• a plurality of decision devices for processing the plurality of averaged estimates.