Spreading and precoding in OFDM
First Claim
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1. An apparatus, comprising:
- a pseudo-noise scrambler configured to encode a plurality of data bits with a pseudo-noise code;
a modulator configured to form each of a plurality of data symbols from a plurality of coded data bits;
a transform precoder operable to spread the plurality of data symbols with a plurality of spreading codes comprising complex-valued coefficients of a discrete Fourier transform (DFT) to produce a plurality of spread symbols;
a resource mapper responsive to an assignment of spectrum resources to the apparatus for selecting a plurality of orthogonal frequency division multiplexing (OFDM) subcarriers corresponding to at least one OFDM symbol interval; and
a signal generator operable to generate an OFDM signal comprising a superposition of the plurality of OFDM subcarriers modulated by the spread symbols, wherein the transform precoder generates the plurality of spreading codes to provide the superposition with a reduced peak-to-average-power ratio.
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Abstract
An OFDM transmitter spreads original data symbols with a complex-valued spreading matrix derived from a discrete Fourier transform. Spread data symbols are mapped to OFDM subcarriers. Spreading and mapping are configured to produce a transmitted spread-OFDM signal with a low peak-to-average power ratio (PAPR) and orthogonal code spaces. In MIMO systems, the complex-valued spreading matrix can comprise a MIMO precoding matrix, and the code spaces can comprise MIMO subspaces. In Cooperative-MIMO, a combination of low code-space cross correlation and low PAPR can be achieved.
297 Citations
26 Claims
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1. An apparatus, comprising:
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a pseudo-noise scrambler configured to encode a plurality of data bits with a pseudo-noise code; a modulator configured to form each of a plurality of data symbols from a plurality of coded data bits; a transform precoder operable to spread the plurality of data symbols with a plurality of spreading codes comprising complex-valued coefficients of a discrete Fourier transform (DFT) to produce a plurality of spread symbols; a resource mapper responsive to an assignment of spectrum resources to the apparatus for selecting a plurality of orthogonal frequency division multiplexing (OFDM) subcarriers corresponding to at least one OFDM symbol interval; and a signal generator operable to generate an OFDM signal comprising a superposition of the plurality of OFDM subcarriers modulated by the spread symbols, wherein the transform precoder generates the plurality of spreading codes to provide the superposition with a reduced peak-to-average-power ratio. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method for communication, performed by at least one processor, comprising:
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encoding a plurality of data bits with a pseudo-noise code to generate a plurality of coded data bits; forming a plurality of data symbols from the plurality of coded data bits; spreading the plurality of data symbols with a plurality of spreading codes comprising complex-valued coefficients of a discrete Fourier transform (DFT) to produce a plurality of spread symbols; responsive to an assignment of spectrum resources for use by a transmitter in an orthogonal frequency division multiplexing (OFDM) network, selecting a plurality of OFDM subcarriers corresponding to at least one OFDM symbol interval; and generating an OFDM signal comprising a superposition of the plurality of OFDM subcarriers, each modulated by one of the plurality of spread symbols, wherein the plurality of spreading codes are selected to provide the superposition with a reduced peak-to-average-power ratio. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A non-transitory computer-readable medium having computer executable program code stored thereon, the computer executable program code comprising:
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program code to encode a plurality of data bits with a pseudo-noise code to produce a plurality of coded data bits; program code to generate a plurality of data symbols from the plurality of coded data bits; program code to spread the plurality of data symbols with a plurality of spreading codes comprising complex-valued coefficients of a discrete Fourier transform (DFT) to produce a plurality of spread symbols; program code responsive to an assignment of spectrum resources for use by a transmitter in an orthogonal frequency division multiplexing (OFDM) network, for selecting a plurality of OFDM subcarriers corresponding to at least one OFDM symbol interval; and program code to generate an OFDM signal comprising a superposition of the plurality of OFDM subcarriers modulated by the plurality of spread symbols, wherein the plurality of spreading codes are selected to provide the superposition with a reduced peak-to-average-power ratio. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26)
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Specification