IPC분류정보
국가/구분 |
United States(US) Patent
등록
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국제특허분류(IPC7판) |
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출원번호 |
US-0900394
(2010-10-07)
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등록번호 |
US-8644264
(2014-02-04)
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발명자
/ 주소 |
- Coralli, Alessandro Vanelli
- Pfister, Henry David
- Hou, Jilei
- Smee, John Edward
- Padovani, Roberto
- Butler, Brian K.
- Levin, Jeffrey A.
- Wilborn, Thomas B.
- Bender, Paul E.
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출원인 / 주소 |
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대리인 / 주소 |
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인용정보 |
피인용 횟수 :
1 인용 특허 :
110 |
초록
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Methods and systems for estimating and canceling pilot interference in a wireless (e.g., CDMA) communication system. In one method, a received signal comprised of a number of signal instances, each including a pilot, is initially processed to provide data samples. Each signal instance's pilot interf
Methods and systems for estimating and canceling pilot interference in a wireless (e.g., CDMA) communication system. In one method, a received signal comprised of a number of signal instances, each including a pilot, is initially processed to provide data samples. Each signal instance's pilot interference may be estimated by despreading the data samples with a spreading sequence for the signal instance, channelizing the despread data to provide pilot symbols, filtering the pilot symbols to estimate the channel response of the signal instance, and multiplying the estimated channel response with the spreading sequence. The pilot interference estimates due to a plurality of interfering multipaths are accumulated to derive the total pilot interference, which is subtracted from the data samples to provide pilot-canceled data samples. These samples are then processed to derive demodulated data for each of at least one (desired) signal instance in the received signal.
대표청구항
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1. A method for canceling pilot interference in a wireless communication system comprising: oversampling a received signal, wherein the received signal comprises at least a first signal instance and a second signal instance with each of the first and second signal instances comprising data and a pil
1. A method for canceling pilot interference in a wireless communication system comprising: oversampling a received signal, wherein the received signal comprises at least a first signal instance and a second signal instance with each of the first and second signal instances comprising data and a pilot signal;determining a first channel estimate for the first signal instance;multiplying the first channel estimate by a cancellation factor α to generate a weighted channel estimate;using the weighted channel estimate to estimate a first pilot of the first signal instance;determining a second channel estimate for the second signal instance;using the second channel estimate to estimate a second pilot of the second signal instance; andsubtracting the first and second pilots from the oversampled received signal to derive a pilot-cancelled received signal. 2. The method of claim 1, further comprising: buffering the received signal in a buffer, wherein the capacity of the buffer is at least twice the length of the oversampled received signal. 3. The method of claim 2, wherein the buffer is a circular random access memory (RAM). 4. The method of claim 1, wherein using the weighted channel estimate to estimate the first pilot comprises: deriving a product of the weighted channel estimate and a convolution of a predetermined transmit pulse and a receive filter function; andfiltering a spread pilot signal associated with the first signal instance with the product of the weighted channel estimate and the convolution to estimate the first pilot. 5. The method of claim 4, wherein the filtering is performed using a polyphase finite impulse response (FIR) filter. 6. The method of claim 5, wherein a set of filter coefficients represents the convolution of the predetermined transmit pulse and the receive filter function, and wherein the set of filter coefficients corresponds to one of eight different possible phases of the received signal. 7. The method of claim 1, wherein determining the first channel estimate comprises: despreading samples of the received signal with a spreading sequence associated with the received signal to provide despread samples;de-channelizing the despread samples with a pilot channelization code to provide pilot symbols; andfiltering the pilot symbols to provide the first channel estimate. 8. The method of claim 1, further comprising: accumulating the first and second pilots with an accumulation buffer with a capacity of at least thrice the length of the oversampled received signal. 9. The method of claim 1, wherein the cancellation factor α is derived using: α=(h2/Nt)N1+(h2/Nt)Nwhere h is the first channel estimate, Nt is a noise estimate, and N is a number of samples used to estimate the first channel estimate h and the noise estimate Nt for the first signal instance. 10. The method of claim 1, wherein the cancellation factor α is based on |h|2/Nt, where h is the first channel estimate and Nt is a noise estimate, and wherein the cancellation factor α is selected from a look-up table. 11. An apparatus for canceling pilot interference in a wireless communication system comprising: a resampler for oversampling a received signal, wherein the received signal comprises at least a first signal instance and a second signal instance with each of the first and second signal instances comprising data and a pilot signal;a channel estimator for determining a first channel estimate for the first signal instance;a multiplier for multiplying the first channel estimate by a cancellation factor α to generate a weighted channel estimate;a pilot reconstruction filtering block for using the weighted channel estimate to estimate a first pilot of the first signal instance;wherein the channel estimator is further configured for determining a second channel estimate for the second signal instance, and wherein the pilot reconstruction filtering block is further configured for using the second channel estimate to estimate a second pilot of the second signal instance; andan adder for subtracting the first and second pilots from the oversampled received signal to derive a pilot-cancelled received signal. 12. The apparatus of claim 11, further comprising: a buffer for buffering the received signal, wherein the capacity of the buffer is at least twice the length of the oversampled received signal. 13. The apparatus of claim 12, wherein the buffer is a circular random access memory (RAM). 14. The apparatus of claim 11, wherein the multiplier is further configured for deriving a product of the weighted channel estimate and a convolution of a predetermined transmit pulse and a receive filter function; and wherein the pilot reconstruction filtering block is further configured for filtering a spread pilot signal associated with the first signal instance with the product of the weighted channel estimate and the convolution to estimate the first pilot. 15. The apparatus of claim 14, wherein the pilot reconstruction filtering block comprises a polyphase finite impulse response (FIR) filter. 16. The apparatus of claim 15, wherein a set of filter coefficients represents the convolution of the predetermined transmit pulse and the receive filter function, and wherein the set of filter coefficients corresponds to one of eight different possible phases of the received signal. 17. The apparatus of claim 11, wherein the channel estimator comprises: a despreader for despreading samples of the received signal with a spreading sequence associated with the received signal to provide despread samples;a pilot de-channelizer for de-channelizing the despread samples with a pilot channelization code to provide pilot symbols; anda pilot filter for filtering the pilot symbols to provide the first channel estimate. 18. The apparatus of claim 11, further comprising: a pilot interference accumulation buffer for accumulating the first and second pilots, wherein the capacity of the pilot interference accumulation buffer is at least thrice the length of the oversampled received signal. 19. The apparatus of claim 11, wherein the cancellation factor α is derived using: α=(h2/Nt)N1+(h2/Nt)Nwhere h is the first channel estimate, Nt is a noise estimate, and N is a number of samples used to estimate the first channel estimate h and the noise estimate Nt for the first signal instance. 20. The apparatus of claim 11, wherein the cancellation factor α is based on |h|2/Nt, where h is the first channel estimate and Nt is a noise estimate, and wherein the cancellation factor α is selected from a look-up table. 21. An apparatus for canceling pilot interference in a wireless communication system comprising: means for oversampling a received signal, wherein the received signal comprises at least a first signal instance and a second signal instance with each of the first and second signal instances comprising data and a pilot signal;means for determining a first channel estimate for the first signal instance;means for multiplying the first channel estimate by a cancellation factor α to generate a weighted channel estimate;means for using the weighted channel estimate to estimate a first pilot of the first signal instance;means for determining a second channel estimate for the second signal instance;means for using the second channel estimate to estimate a second pilot of the second signal instance; andmeans for subtracting the first and second pilots from the oversampled received signal to derive a pilot-cancelled received signal. 22. The apparatus of claim 21, further comprising means for buffering the received signal, wherein the means for buffering has a capacity of at least twice the length of the oversampled received signal. 23. The apparatus of claim 22, wherein the means for buffering is a circular random access memory (RAM). 24. The apparatus of claim 21, wherein the means for using the weighted channel estimate to estimate the first pilot comprises: means for deriving a product of the weighted channel estimate and a convolution of a predetermined transmit pulse and a receive filter function; andmeans for filtering a spread pilot signal associated with the first signal instance with the product of the weighted channel estimate and the convolution to estimate the first pilot. 25. The apparatus of claim 24, wherein the means for filtering comprises a polyphase finite impulse response (FIR) filter. 26. The apparatus of claim 25, wherein a set of filter coefficients represents the convolution of the predetermined transmit pulse and the receive filter function, and wherein the set of filter coefficients corresponds to one of eight different possible phases of the received signal. 27. The apparatus of claim 21, wherein the means for determining the first channel estimate comprises: means for despreading samples of the received signal with a spreading sequence associated with the received signal to provide despread samples;means for de-channelizing the despread samples with a pilot channelization code to provide pilot symbols; andmeans for filtering the pilot symbols to provide the first channel estimate. 28. The apparatus of claim 21, further comprising means for accumulating the first and second pilots, wherein the means for accumulating has a capacity of at least thrice the length of the oversampled received signal. 29. The apparatus of claim 21, wherein the cancellation factor α is derived using: α-(h2/Nt)N1+(h2/Nt)Nwhere h is the first channel estimate, Nt is a noise estimate, and N is a number of samples used to estimate the first channel estimate h and the noise estimate Nt for the first signal instance. 30. The apparatus of claim 21, wherein the cancellation factor α is based on |h|2/Nt, where h is the first channel estimate and Nt is a noise estimate, and wherein the cancellation factor α is selected from a look-up table. 31. A non-transitory computer-readable medium for canceling pilot interference in a wireless communication system, the computer-readable medium storing a computer program, wherein execution of the computer program is for performing functions comprising: oversampling a received signal, wherein the received signal comprises at least a first signal instance and a second signal instance with each of the first and second signal instances comprising data and a pilot signal;determining a first channel estimate for the first signal instance;multiplying the first channel estimate by a cancellation factor α to generate a weighted channel estimate;using the weighted channel estimate to estimate a first pilot of the first signal instance;determining a second channel estimate for the second signal instance;using the second channel estimate to estimate a second pilot of the second signal instance; andsubtracting the first and second pilots from the oversampled received signal to derive a pilot-cancelled received signal. 32. The computer-readable medium of claim 31, wherein execution of the computer program is also for buffering the received signal in a buffer, wherein the capacity of the buffer is at least twice the length of the oversampled received signal. 33. The computer-readable medium of claim 32, wherein the buffer is a circular random access memory (RAM). 34. The computer-readable medium of claim 31, wherein execution of the computer program is also for: deriving a product of the weighted channel estimate and a convolution of a predetermined transmit pulse and a receive filter function; andfiltering a spread pilot signal associated with the first signal instance with the product of the weighted channel estimate and the convolution to estimate the first pilot. 35. The computer-readable medium of claim 34, wherein the filtering is performed using a polyphase finite impulse response (FIR) filter. 36. The computer-readable medium of claim 35, wherein a set of filter coefficients represents the convolution of the predetermined transmit pulse and the receive filter function, and wherein the set of filter coefficients corresponds to one of eight different possible phases of the received signal. 37. The computer-readable medium of claim 31, wherein execution of the computer program is also for: despreading samples of the received signal with a spreading sequence associated with the received signal to provide despread samples;de-channelizing the despread samples with a pilot channelization code to provide pilot symbols; andfiltering the pilot symbols to provide the first channel estimate. 38. The computer-readable medium of claim 31, wherein execution of the computer program is also for accumulating the first and second pilots with an accumulation buffer with a capacity of at least thrice the length of the oversampled received signal. 39. The computer-readable medium of claim 31, wherein the cancellation factor α is derived using: α=(h2/Nt)N1+(h2/Nt)Nwhere h is the first channel estimate, Nt is a noise estimate, and N is a number of samples used to estimate the first channel estimate h and the noise estimate Nt for the first signal instance. 40. The computer-readable medium of claim 31, wherein the cancellation factor α is based on |h|2/Nt, where h is the first channel estimate and Nt is a noise estimate, and wherein the cancellation factor α is selected from a look-up table.
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