Adaptive time diversity and spatial diversity for OFDM
AssigneeNortel Networks Limited
InventorsShiquan Wu, Wen Tong, Leo Strawczynski
Life of this patent
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Abstract
An adaptable orthogonal frequency-division multiplexing system (OFDM) that uses a multiple input multiple output (MIMO) to having OFDM signals transmitted either in accordance with time diversity to reducing signal fading or in accordance with spatial diversity to increase the data rate. Sub-carriers are classified for spatial diversity transmission or for time diversity transmission based on the result of a comparison between threshold values and at least one of three criteria. The criteria includes a calculation of a smallest eigen value of a frequency channel response matrix and a smallest element of a diagonal of the matrix and a ratio of the largest and smallest eigen values of the matrix.
Claims20
A method of transmitting data, comprising:
- loading a first data on a sub-carrier of a first orthogonal frequency division multiplexing (OFDM) symbol associated with a first antenna;
- loading a second data on a sub-carrier of a second OFDM symbol associated with the first antenna;
- loading the first and second data on sub-carriers of OFDM symbols associated with a second antenna according to at least one conjugate mapping rule, to thereby produce a first mapped data and a second mapped data;
- transmitting the first data with the first antenna and subsequently transmitting the first mapped data with the second antenna;
- and
- transmitting the second mapped data with the second antenna and subsequently transmitting the second data with the first antenna.
An apparatus for transmitting data, comprising:
- an orthogonal frequency division multiplexing (OFDM) encoder operable:
- to load a first data on a sub-carrier of a first OFDM symbol associated with an first antenna;
- to load a second data on a sub-carrier of a second OFDM symbol associated with the first antenna;
- and
- to map the first and second data on sub-carriers of OFDM symbols associated with a second antenna according to at least one conjugate mapping rule, to thereby produce a first mapped data and a second mapped data;
- and
- and at least one transmitter operable:
- to transmit the first data with the first antenna and subsequently to transmit the first mapped data with the second antenna;
- and
- to transmit the second mapped data with the second antenna and subsequently to transmit the second data with the first antenna.
A non-transitory computer-readable medium containing instructions to configure a processor to perform operations comprising:
- load a first data on a sub-carrier of a first orthogonal frequency division multiplexing (OFDM) symbol associated with a first antenna;
- load a second data on a sub-carrier of a second OFDM symbol associated with the first antenna;
- load the first and second data on sub-carriers of OFDM symbols associated with a second antenna according to at least one conjugate mapping rule, to thereby produce a first mapped data and a second mapped data;
- cause transmission of the first data with the first antenna and subsequent transmission of the first mapped data with the second antenna;
- and
- cause transmission of the second mapped data with the second antenna and subsequent transmission of the second data with the first antenna.
Dependencies are inferred from the claim text.