Patent ID: 8111773

Claim:
A method comprising transmission in a multiple-input multiple-output (MIMO) system, wherein the MIMO system comprises a first device having M (>1) transmitting antennas and a second device having N (>1) receiving antennas, wherein the method comprises: determining if there is at least one MIMO transmission scheme satisfying a that consumes less energy than a single-input single-output (SISO) transmission scheme to transmit a frame at a given transmission power, wherein said at least one MIMO transmission scheme comprises at least one MIMO transmission schemes available to the first device and the second device, wherein said at least one MIMO transmission schemes is selected based on a number of activated transmitting and receiving antennas and based on a MIMO code; selecting a MIMO mode as a transmission mode if said at least one MIMO transmission scheme consumes less energy than the single-input single-output (SISO) transmission scheme and selecting a SISO mode as the transmission mode if said at least one MIMO transmission scheme consumes more energy than the single-input single-output (SISO) transmission scheme, wherein said determining comprises: calculating a minimum multiplexing gain of each of said at least one MIMO transmission scheme to transmit a frame at a given transmission power; and determining if the minimum multiplexing gain of at least one of said at least one MIMO transmission scheme has a multiplexing gain less than the minimum multiplexing gain of the SISO transmission scheme, wherein: said calculating the minimum multiplexing gain of each of said at least one MIMO transmission scheme comprises calculating a minimum multiplexing gain r min using the expression r min = min i ∈ Ψ ⁢ ( S T ⁡ ( P T + m i ⁢ P ct ) + S R ⁡ ( n i ⁢ P cr ) ) ( S T ⁡ ( P T + P ci ) + S R ⁡ ( P cr ) ) ; Ψ denotes a set comprising said at least one MIMO transmission schemes; i denotes an index of the MIMO transmission scheme; m i and n i respectively denotes the numbers of activated transmitting and receiving antennas in the i-th MIMO transmission scheme; P T denotes the given transmission power; P ct denotes power consumed for frame transmission by at least some circuits not including a power amplifier in the first device; P cr denotes power consumed for frame reception by at least some circuits in the second device; S T is equal to 1 if the first device requires power saving and otherwise is equal to 0; and SR is equal to 1 if the second device requires power saving and otherwise is equal to 0.