Adaptive time diversity and spatial diversity for OFDM
AssigneeApple Inc.
InventorsShiquan Wu, Wen Tong, Leo Strawczynski
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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 comprising:
- receiving by a plurality of antennas of a first device a first Orthogonal Frequency-Division Multiplexing (OFDM) signal from a plurality of antennas of a second device over a wireless channel;
- transmitting information via the plurality of antennas of the first device to the second device in response to the first OFDM signal, wherein the information indicates that a second OFDM signal to be transmitted by the second device to the first device is to use one of transmitter diversity or spatial multiplexing;
- and
- receiving at the plurality of antennas of the first device the second OFDM signal from the from plurality of antennas of the second device over the wireless channel, wherein the second device uses one of transmitter diversity or spatial multiplexing to transmit the second OFDM signal based on the information.
A first device for use with multiple input multiple output (MIMO) signals, comprising:
- a plurality of antennas configured to:
- receive a first Orthogonal Frequency-Division Multiplexing (OFDM) signal from a plurality of antennas of a second device over a wireless channel;
- transmit information to the second device, wherein the information indicates that a second OFDM signal to be transmitted by the second device is to use one of transmitter diversity or spatial multiplexing;
- and
- receive the second OFDM signal from the plurality of antennas of the second device over the wireless channel, wherein the second device uses one of transmitter diversity or spatial multiplexing to transmit the second OFDM signal based on the information;
- and
- a controller configured to determine the information based on the first OFDM signal.
A first device for use with multiple input multiple output (MIMO) signals, comprising:
- a plurality of antennas configured to:
- transmit a first Orthogonal Frequency-Division Multiplexing (OFDM) signal to a second device over a wireless channel;
- receive information from the second device, wherein the information indicates that a second OFDM signal is to use one of transmitter diversity or spatial multiplexing;
- transmit the second OFDM signal to the second device using one of transmitter diversity or spatial multiplexing;
- and
- a controller configured to determine whether to transmit the second OFDM signal using transmitter diversity or spatial multiplexing based on the information.
Dependencies are inferred from the claim text.