Transmission signals, method and apparatus
First Claim
1. An OFDM signal transmitted from an OFDM transmitter using a plurality of transmit antennas, the OFDM signal being adapted for channel estimation for channels associated with said transmit antennas by the inclusion of orthogonal training sequence data in the signal from each said antenna, said training sequence data being derived from substantially orthogonal training sequences of length K for each said transmit antenna, said orthogonal training sequences being constructed such that a minimum required sequence length K needed to determine a channel estimate for at least one channel associated with each said transmit antenna is linearly dependent upon the number of said transmit antennas.
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Accused Products
Abstract
This invention relates to apparatus, methods, processor control code and signals for channel estimation in OFDM (Orthogonal Frequency Division Multiplexed) communication systems with a plurality of transmitter antennas, such as MIMO (Multiple-input Multiple-output) OFDM systems.
An OFDM signal is transmitted from an OFDM transmitter using a plurality of transmit antennas. The OFDM signal is adapted for channel estimation for channels associated with said transmit antennas by the inclusion of orthogonal training sequence data in the signal from each said antenna. The said training sequence data is derived from substantially orthogonal training sequences of length K for each said transmit antenna, said orthogonal training sequences being constructed such that a minimum required sequence length K needed to determine a channel estimate for at least one channel associated with each said transmit antenna is linearly dependent upon the number of said transmit antennas.
191 Citations
34 Claims
- 1. An OFDM signal transmitted from an OFDM transmitter using a plurality of transmit antennas, the OFDM signal being adapted for channel estimation for channels associated with said transmit antennas by the inclusion of orthogonal training sequence data in the signal from each said antenna, said training sequence data being derived from substantially orthogonal training sequences of length K for each said transmit antenna, said orthogonal training sequences being constructed such that a minimum required sequence length K needed to determine a channel estimate for at least one channel associated with each said transmit antenna is linearly dependent upon the number of said transmit antennas.
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8. An OFDM signal including training sequence data for channel estimation for a plurality of transmit antennas, said training sequence data being based upon training sequences of length K defined by values of exp(j2π
- kmL/K) where k indexes a value in a said sequence, m indexes a transmit antenna and L is a positive integer.
- 9. An OFDM transmitter using a plurality of transmit antennas and configured to transmit an OFDM signal, the OFDM signal being adapted for channel estimation for channels associated with said transmit antennas by the inclusion of orthogonal training sequence data in the signal from each said antenna, said training sequence data being derived from substantially orthogonal training sequences of length K for each said transmit antenna, said orthogonal training sequences being constructed such that a minimum required sequence length K needed to determine a channel estimate for at least one channel associated with each said transmit antenna is linearly dependent upon the number of said transmit antennas.
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11. An OFDM transmitter using a plurality of transmit antennas and configured to transmit an OFDM signal including training sequence data for channel estimation for said plurality of transmit antennas, said training sequence data being based upon training sequences of length K defined by values of exp(j2π
- kmL/K) where k indexes a value in a said sequence, m indexes a transmit antenna and L is a positive integer.
- View Dependent Claims (12, 23, 24)
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13. A data carrier carrying training sequence data for use with an OFDM transmitter using a plurality of transmit antennas, said training sequence data being derived from substantially orthogonal training sequences of length K for each said transmit antenna, said orthogonal training sequences being constructed such that a minimum required sequence length K needed to determine a channel estimate for at least one channel associated with each said transmit antenna is linearly dependent upon the number of said transmit antennas.
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14. A data carrier for use with an OFDM transmitter using a plurality of transmit antennas, said data carrier carrying training sequence for channel estimation for said plurality of transmit antennas, said training sequence data being based upon training sequences of length K defined by values of exp(j2π
- kmL/K) where k indexes a value in a said sequence, m indexes a transmit antenna and L is a positive integer.
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15. An OFDM transmitter having a plurality of transmit antennas, said OFDM-transmitter being configured to transmit, from each said transmit antenna, training sequence data based upon a training sequence, said training sequences upon which said training sequence data for said antennas is based being constructed such that:
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i) said training sequences are substantially mutually orthogonal;
ii) said training sequences allow a receiver to determine a channel estimate for a channel associated with each said transmit antenna; and
iii) a minimum length of each said training sequence needed to satisfy (ii) is substantially linearly dependent upon the number of transmit antennas. - View Dependent Claims (16, 17, 18)
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19. An OFDM transmitter having a plurality of transmit antennas, said OFDM transmitter being configured to transmit, from each said transmit antenna, training sequence data based upon a training sequence having values
Xmk=exp(j2π - kmL/K)
where k indexes a value in a sequence of length K, m indexes a said transmit antenna, and L is a positive integer. - View Dependent Claims (20, 21, 22)
- kmL/K)
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25. An OFDM transmitter configured to transmit an OFDM signal from a plurality of transmit antennas, the OFDM transmitter comprising:
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a data memory storing training sequence data for each of said plurality of antennas;
an instruction memory storing processor implementable instructions; and
a processor coupled to said data memory and to said instruction memory to read and process said training sequence data in accordance with said instructions, said instructions comprising instructions for controlling the processor to;
read said training sequence data for each antenna;
inverse Fourier transform said training sequence data for each antenna;
provide a cyclic extension for said Fourier transformed data to generate output data for each antenna; and
provide said output data to at least one digital-to-analogue converter for transmission; and
wherein said training sequence data for a said antenna comprises data derived from a sequence of values Xmk=exp(j2π
kmL/K)where m indexes the said antenna, k indexes values in the sequence, L is a positive integer, and wherein the sequence has a length K. - View Dependent Claims (26, 27, 28)
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29. A method of providing an OFDM signal from an OFDM transmitter having a plurality of transmit antennas with training sequence data for determining a channel estimate for each of said transmit antennas, the method comprising:
inserting training sequence data for each said transmit antenna into said OFDM signal, said training sequence data being derived from orthogonal training sequences of length K for each said antenna, said orthogonal training sequences being constructed such that a minimum required sequence length K needed to determine a channel estimate for at least one channel associated with each said transmit antenna is linearly dependent upon the number of said transmit antennas. - View Dependent Claims (30, 31, 32, 33, 34)
Specification