High data CDMA wireless communication system using variable sized channel codes
First Claim
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1. A method for demodulating a signal comprising:
- complex-multiplying a complex received signal by an in-phase pseudorandom spreading code and a quadrature-phase pseudorandom spreading code to provide an in-phase sample stream and a quadrature-phase sample stream;
filtering the in-phase sample stream to provide an in-phase pilot filter signal;
filtering the quadrature-phase sample stream to provide a quadrature-phase pilot filter signal;
multiplying the in-phase sample stream by a first short Walsh cover having a duration of fewer than sixty-four chips per orthogonal waveform period to produce an in-phase short Walsh despread symbol first channel stream;
multiplying the quadrature-phase sample stream by the first short Walsh cover to produce a quadrature-phase short Walsh despread symbol first channel stream; and
phase rotating and scaling the in-phase short Walsh despread symbol first channel stream and the quadrature-phase short Walsh despread symbol first channel stream based on the in-phase pilot filter signal and the quadrature-phase pilot filter signal to produce a soft decision first channel data stream.
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Abstract
A method and apparatus for demodulation in high rate CDMA wireless communication is described. In a described high rate CDMA wireless system, a transmitter forms a set of individually gain adjusted subscriber channels using a set of orthogonal subchannel codes having a small number of PN spreading chips per orthogonal waveform period. An illustrative high rate CDMA wireless system uses Walsh codes, each having a duration of fewer than sixty-four chips per orthogonal waveform period. A receiver demodulates each of the subscriber channels using the same orthogonal subchannel codes.
131 Citations
25 Claims
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1. A method for demodulating a signal comprising:
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complex-multiplying a complex received signal by an in-phase pseudorandom spreading code and a quadrature-phase pseudorandom spreading code to provide an in-phase sample stream and a quadrature-phase sample stream;
filtering the in-phase sample stream to provide an in-phase pilot filter signal;
filtering the quadrature-phase sample stream to provide a quadrature-phase pilot filter signal;
multiplying the in-phase sample stream by a first short Walsh cover having a duration of fewer than sixty-four chips per orthogonal waveform period to produce an in-phase short Walsh despread symbol first channel stream;
multiplying the quadrature-phase sample stream by the first short Walsh cover to produce a quadrature-phase short Walsh despread symbol first channel stream; and
phase rotating and scaling the in-phase short Walsh despread symbol first channel stream and the quadrature-phase short Walsh despread symbol first channel stream based on the in-phase pilot filter signal and the quadrature-phase pilot filter signal to produce a soft decision first channel data stream. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
summing the in-phase short Walsh despread symbol first channel stream based on the duration of the first short Walsh cover; and
summing the quadrature-phase short Walsh despread symbol first channel stream based on the duration of the first short Walsh cover.
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3. The method of claim 1 wherein the phase rotating and scaling comprises:
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multiplying the in-phase short Walsh despread symbol first channel stream by the in-phase pilot filter signal; and
multiplying the quadrature-phase short Walsh despread symbol first channel stream by the quadrature-phase pilot filter signal.
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4. The method of claim 1 wherein the first short Walsh cover has a duration of four chips.
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5. The method of claim 1 wherein the first short Walsh cover is equal to +, +,−
- ,−
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- ,−
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6. The method of claim 1 wherein the first short Walsh cover is equal to +, −
- , +, −
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- , +, −
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7. The method of claim 1 further comprising:
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multiplying the in-phase sample stream by a second short Walsh cover to produce an in-phase short Walsh despread symbol second channel stream, wherein the second short Walsh cover is orthogonal to the first short Walsh cover and has a duration of fewer than sixty-four chips per orthogonal waveform period;
multiplying the quadrature-phase sample stream by the second short Walsh cover to produce a quadrature-phase short Walsh despread symbol second channel stream; and
phase rotating and scaling the in-phase short Walsh despread symbol second channel stream and the quadrature-phase short Walsh despread symbol second channel stream to produce a soft decision second channel data stream.
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8. The method of claim 7 further comprising summing the soft decision second channel stream to produce a summed soft decision second channel stream.
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9. The method of claim 7 wherein the second short Walsh cover has a duration of four chips.
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10. The method of claim 7 wherein the duration of the first short Walsh cover is equal to the duration of the second short Walsh cover.
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11. The method of claim 7 wherein the second short Walsh cover is equal to +, +, −
- , −
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- , −
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12. The method of claim 7 wherein the second short Walsh cover is equal to +, −
- , +, −
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- , +, −
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13. A receiver apparatus comprising:
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a complex-multiplier configured to complex-multiply a complex received signal by an in-phase pseudorandom spreading code and a quadrature-phase pseudorandom spreading code to provide an in-phase sample stream and a quadrature-phase sample stream;
a first pilot filter configured to filter the in-phase sample stream to provide an in-phase pilot filter signal;
a second pilot filter configured to filter the quadrature-phase sample stream to provide a quadrature-phase pilot filter signal;
a first multiplier configured to multiply the in-phase sample stream by a first short Walsh cover having a duration of fewer than sixty-four chips per orthogonal waveform period to produce an in-phase short Walsh despread symbol first channel stream;
a second multiplier configured to multiply the quadrature-phase sample stream by the first short Walsh cover to produce a quadrature-phase short Walsh despread symbol first channel stream; and
first means for phase rotating and scaling the in-phase short Walsh despread symbol first channel stream and the quadrature-phase short Walsh despread symbol first channel stream based on the in-phase pilot filter signal and the quadrature-phase pilot filter signal to produce a soft decision first channel data stream. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
a first summer configured to sum the in-phase short Walsh despread symbol first channel stream based on the duration of the first short Walsh cover; and
a second summer configured to sum the quadrature-phase short Walsh despread symbol first channel stream based on the duration of the first short Walsh cover.
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15. The apparatus of claim 13 further comprising:
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a third multiplier configured to multiply the in-phase short Walsh despread symbol first channel stream by the in-phase pilot filter signal; and
a fourth multiplier configured to multiply the quadrature-phase short Walsh despread symbol first channel stream by the quadrature-phase pilot filter signal.
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16. The apparatus of claim 13 wherein the first short Walsh cover has a duration of four chips.
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17. The apparatus of claim 13 wherein the first short Walsh cover is equal to +, +, −
- , −
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- , −
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18. The apparatus of claim 13 wherein the first short Walsh cover is equal to +, −
- , +, −
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- , +, −
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19. The apparatus of claim 13 further comprising:
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a third multiplier configured to multiply the in-phase sample stream by a second short Walsh cover to produce an in-phase short Walsh despread symbol second channel stream, wherein the second short Walsh cover is orthogonal to the first short Walsh cover and has a duration of fewer than sixty-four chips per orthogonal waveform period;
a fourth multiplier configured to multiply the quadrature-phase sample stream by the second short Walsh cover to produce a quadrature-phase short Walsh despread symbol second channel stream; and
second means for phase rotating and scaling the in-phase short Walsh despread symbol second channel stream and the quadrature-phase short Walsh despread symbol second channel stream to produce a soft decision second channel data stream.
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20. The apparatus of claim 19 wherein the duration of the first short Walsh cover is equal to the duration of the second short Walsh cover.
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21. The apparatus of claim 19 wherein the second short Walsh cover has a duration of four chips.
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22. The apparatus of claim 19 wherein the second short Walsh cover is equal to +, +, −
- , −
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- , −
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23. The apparatus of claim 19 wherein the second short Walsh cover is equal to +, −
- , +, −
.
- , +, −
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24. The apparatus of claim 19 further comprising a summer configured to sum the soft decision second channel stream to produce a summed soft decision second channel stream.
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25. A receiver apparatus comprising:
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means for complex-multiplying a complex received signal by an in-phase pseudorandom spreading code and a quadrature-phase pseudorandom spreading code to provide an in-phase sample stream and a quadrature-phase sample stream;
means for filtering the in-phase sample stream to provide an in-phase pilot filter signal;
means for filtering the quadrature-phase sample stream to provide a quadrature-phase pilot filter signal;
means for multiplying the in-phase sample stream by a first short Walsh cover having a duration of fewer than sixty-four chips per orthogonal waveform period to produce an in-phase short Walsh despread symbol first channel stream;
means for multiplying the quadrature-phase sample stream by the first short Walsh cover to produce a quadrature-phase short Walsh despread symbol first channel stream; and
means for phase rotating and scaling the quadrature-phase short Walsh despread symbol first channel stream and the in-phase short Walsh despread symbol first channel stream based on the in-phase pilot filter signal and the quadrature-phase pilot filter signal to produce a soft decision first channel data stream.
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Specification