Variable interference cancellation technology for CDMA systems
An interference canceller comprises a composite interference vector (CIV) generator configured to produce a CIV by combining soft and/or hard estimates of interference, an interference-cancelling operator configured for generating a soft-projection operator, and a soft-projection canceller configured for performing a soft projection of the received baseband signal to output an interference-cancelled signal. Weights used in the soft-projection operator are selected to maximize a post-processing SINR.
1. An apparatus configured to remove interference from a received baseband signal in a CDMA system, comprising:
a composite interference vector (CIV) generator configured to produce at least one CIV by combing estimates of interference;
an interference-cancelling operator configured for generating a soft-projection operator,
a soft-projection canceller configured for performing a soft projection operator, and
a Rake receiver.
2. The apparatus recited in claim 1 , wherein each finger of the Rake receiver is matched to at least one of a time delay and a base station spreading code.
3. The apparatus recited in claim 1 , wherein the apparatus is configured to cancel interference in a first Rake finger and the CIV generator configured to generate the at least one CIV from at least one Rake finger that does not include the first Rake finger.
4. The apparatus recited in claim 1 , wherein the CIV generator is configured to derive the estimates from at least one of a Rake receiver, an equalizer, a receiver employing receive diversity, a receiver employing transmit diversity combining, and a receiver employing space-time decoding.
5. The apparatus recited in claim 1 , wherein the interference-cancelled signal output from the soft-projection canceller is coupled to at least one of a combiner and a Rake receiver.
6. The apparatus recited in claim 5 , wherein the at least one of the combiner and the Rake receiver is configured to combine a plurality of interference-cancelled signals.
7. A method for cancelling interference from a received baseband signal in a CDMA system, comprising:
providing for generating at last one composite interference vector (CIV) by combining estimates from interfering subchannels,
providing for generating a soft-projection operator,
providing for performing a soft projection of the received baseband signal to output an interference-cancelled signal and
wherein the estimates are derived from a Rake receiver.
8. The method recited in claim 7 , wherein each finger of the Rake receiver is matched to at least one of a time delay and a base station spreading code.
9. The method recited in claim 7 , wherein the received baseband signal is coupled from a first Rake finger and providing for generating the at least one CIV is configured to generate the at least one CIV from at least one Rake finger that does not include the first Rake finger.
10. The method recited in claim 7 , wherein providing for generating the at least one CIV is configured to derive the estimates from at least one of a Rake receiver, an equalizer, a receiver employing receive diversity, a receiver employing transmit diversity combining, a receiver employing space-time decoding.
11. The method recited in claim 7 , wherein providing for performing the soft projection further comprises coupling the interference-cancelled signal to at least one of a combiner and a Rake receiver.
12. The method recited in claim 11 , wherein providing for performing the soft projection is followed by providing for combining a plurality of interference-cancelled signals.
13. A chipset configured to perform the receiving method recited in claim 7 .
14. A digital computer system programmed to perform the method recited in claim 7 .
15. A computer-readable medium storing a computer program implementing the method of claim 7 .
16. A base station configured to perform the method of claim 7 .
17. A handset configured to perform the method of claim 7 .
18. An interference-cancellation system configured for removing interference from a received baseband signal in a CDMA system, comprising:
a means for generating at least one composite interference vector (CIV) by combining estimates of interference,
a means for generating a soft-projection operator,
a means for performing a soft projection of the received baseband signal to output an interference-cancelled signal, and
a means for generating the at least one CIV is configured to obtain the estimates from a Rake receiver.
19. The system recited in claim 18 , wherein each finger of the Rake receiver is matched to at least one of a time delay and a base station spreading code.
20. The system recited in claim 18 , wherein the means for performing a soft projection is configured to couple the received baseband signal from a first Rake finger, and the means for generating the at least one CIV is configured to generate the at least one CIV from at least one Rake finger that does not include the first Rake finger.
21. The system recited in claim 18 , wherein the means for generating the at least one CIV is configured to derive the estimates from at least one of a Rake receiver, an equalizer, a receiver employing receive diversity, a receiver employing transit diversity combining, and a receiver employing space-time decoding.
22. The system recited in claim 18 , wherein the means for performing the soft projection further comprises a means for coupling the interference-cancelled signal to at least one of a combiner and a Rake receiver.
23. The system recited in claim 22 wherein the means for performing the soft projection further comprises a means for combining a plurality of interference-cancelled signals for receive diversity.
24. An apparatus configured to remove interference from a received baseband signal in a DCMA system, comprising:
a composite interference vector (CIV) generator configured to produce at least one CIV by combing estimates of interference;
an interference-cancelling operator configured for generating a soft-projection operator,
a soft-projection canceller configured for performing a soft projection operator,
a Rake receiver, and
an interference-cancelling operator configured to generate a soft-projection matrix to operate on a received data vector, the soft-projection matrix having the form F(λ)=I−λss*, where I is an identity matrix, λ is a weight, and s is a CIV.
25. The apparatus recited in claim 24 , wherein the interference-cancelling operator is configured for determining the weight λ by maximizing a post-processing SINR.
26. The apparatus recited in claim 25 , wherein the interference-cancelling operator is configured for determining the weight λ by maximizing a post-processing SINR for a handset operating in a soft-handoff mode.
27. A method for cancelling interference from a received baseband signal in a CDMA system, comprising:
providing for generating at last one composite interference vector (CIV) by combining estimates from interfering subchannels,
providing for generating a soft-projection operator,
providing for performing a soft projection of the received baseband signal to output an interference-cancelled signal, and
wherein the estimates are derived from a Rake receiver, and
wherein providing for generating the soft-projection operator is configured to generate a soft-projection matrix to operate on a received data vector, the soft-projection matrix having the form F(λ)=I−λss*, where I is an identity matrix, λ is a weight, and s is a CIV.
28. The method recited in claim 27 , wherein providing for generating the soft-projection operator is configured for determining the weight λ by maximizing a post-processing SINR.
29. The method recited in claim 28 , wherein providing for generating the soft-projection operator is configured for determining the weight λ by maximizing a post-processing SINR for a handset operating in a soft-handoff mode.
30. An interference-cancellation system configured for removing interference from a received baseband signal in a CDMA system, comprising:
a means for generating at least one composite interference vector (CIV) by combining estimates of interference,
a means for generating a soft-projection operator,
a means for performing a soft projection of the received baseband signal to output an interference-cancelled signal, and
a means for generating the at least one CIV is configured to obtain the estimates from a Rake receiver, and
a means for generating the soft-projection operator is configured to generate a soft-projection matrix to operate on a received data vector, the soft-projection matrix having the form F(λ)=I−λss*, where I is an identity matrix, λ is a weight, and s is a CIV.
31. The system recited in claim 30 , wherein the means for generating the soft projection operator is configured for determining the weight λ by maximizing a post-processing SINR.
32. The system recited in claim 31 , wherein the means for generating the soft-projection operator is configured for determining the weight λ by maximizing a post-processing SINR for a handset operating in a soft-handoff mode.