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US 9,800,448 B1Granted
Spreading and precoding in OFDM
AssigneeGenghiscomm Holdings, LLC
InventorSteve Shattil
Life of this patent
Estimating the term…
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.
Claims24
An apparatus, comprising:
- a transform precoder operable to spread a plurality of data symbols with a plurality of orthogonal spreading codes comprising complex-valued coefficients of a discrete Fourier transform (DFT) to produce a plurality of spread symbols;
- a multiple access 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 orthogonal spreading codes to provide the superposition with a reduced peak-to-average-power ratio;
- and wherein one of the plurality of spread symbols is expressed by:
- z
-
- (
- l
- ·
- M
- sc
- PUSCH
- +
- k
- )
- =
- 1
- M
- sc
- PUSCH
-
- ∑
- i
- =
- 0
- M
- sc
- PUSCH
- -
- 1
-
- d
-
- (
- l
- ·
- M
- sc
- PUSCH
- +
- i
- )
-
- e
- -
- j
-
- 2
-
- π
-
-
- ik
- M
- sc
- PUSCH
- wherein MscPUSCH is a DFT length corresponding to the plurality of orthogonal spreading codes, l is an index spanning 0 to a number of symbol intervals minus one, k is an index spanning zero to the DFT length MscPUSCH minus one, i is an index spanning zero to the DFT length MscPUSCH minus one, d(i) is an ith one of the plurality of data symbols, e is natural log, i=√{square root over (−1)}, and π is mathematical constant Pi.
55 more elements
A method for communication, performed by at least one processor, comprising:
- spreading a plurality of data symbols with a plurality of orthogonal 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 orthogonal spreading codes are selected to provide the superposition with a reduced peak-to-average-power ratio;
- wherein at least one of the plurality of spread symbols is expressed by:
- z
-
- (
- l
- ·
- M
- sc
- PUSCH
- +
- k
- )
- =
- 1
- M
- sc
- PUSCH
-
- ∑
- i
- =
- 0
- M
- sc
- PUSCH
- -
- 1
-
- d
-
- (
- l
- ·
- M
- sc
- PUSCH
- +
- i
- )
-
- e
- -
- j
-
- 2
-
- π
-
-
- ik
- M
- sc
- PUSCH
- wherein MscPUSCH is a DFT length corresponding to the plurality of orthogonal spreading codes, l is an index spanning 0 to a number of symbol intervals minus one, k is an index spanning zero to the DFT length MscPUSCH minus one, i is an index spanning zero to the DFT length MscPUSCH minus one, d(i) is an ith one of the plurality of data symbols, e is natural log, j=√{square root over (−1)}, and π is mathematical constant Pi.
55 more elements
A non-transitory computer-readable medium having computer executable program code stored thereon, the computer executable program code comprising:
- program code to spread a plurality of data symbols with a plurality of orthogonal 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 orthogonal spreading codes are selected to provide the superposition with a reduced peak-to-average-power ratio;
- wherein one of the plurality of spread symbols is expressed by:
- z
-
- (
- l
- ·
- M
- sc
- PUSCH
- +
- k
- )
- =
- 1
- M
- sc
- PUSCH
-
- ∑
- i
- =
- 0
- M
- sc
- PUSCH
- -
- 1
-
- d
-
- (
- l
- ·
- M
- sc
- PUSCH
- +
- i
- )
-
- e
- -
- j
-
- 2
-
- π
-
-
- ik
- M
- sc
- PUSCH
- wherein MscPUSCH is a DFT length corresponding to the plurality of orthogonal spreading codes, l is an index spanning 0 to a number of symbol intervals minus one, k is an index spanning zero to the DFT length MscPUSCH minus one, i is an index spanning zero to the DFT length MscPUSCH minus one, d(i) is an ith one of the plurality of data symbols, e is natural log, i=√{square root over (−1)}, and π is mathematical constant Pi.
55 more elements
Dependencies are inferred from the claim text.