Patent ID: 8396157

Claim:
A method of determining a multiple-input multiple-output (MIMO) mode for a wireless communication system, the method comprising: analyzing, by a base station, input parameters affecting relative MIMO mode performance; determining, by the base station, a probability of each MIMO mode being a dominant MIMO mode, wherein MIMO modes comprise a transmit diversity mode, an open-loop spatial multiplexing mode, and a closed-loop spatial multiplexing mode, and wherein a dominant probability of the closed-loop spatial multiplexing mode is determined according to a formula parameterized by a rank of a MIMO channel, wherein: for rank=1, the dominant probability is modeled as a one-sided Gaussian distribution: P ⁡ ( SM , Rank = i , i = 1 ) = { λ ⁢ ⁢ a ⁡ ( τ , ρ ) × exp ⁡ ( - ( γ - b ⁡ ( i ) ) 2 2 ⁢ c ⁡ ( i ) 2 ) + d γ > b ⁡ ( i ) λ ⁢ ⁢ a ⁡ ( τ , ρ ) otherwise ; for rank=2, 3, . . . , n−1, the dominant probability is modeled as a two-sided Gaussian distribution: P ⁡ ( SM , Rank = i , i = 2 , 3 , … ⁢ , n - 1 ) = λ ⁢ ⁢ a ⁡ ( τ , ρ ) × exp ⁡ ( - ( γ - b ⁡ ( i ) ) 2 2 ⁢ c ⁡ ( i ) 2 ) ; and for rank=n, the dominant probability is modeled as a one-sided Gaussian distribution: P ⁡ ( SM , Rank = i , i = n ) = { λ ⁢ ⁢ a ⁡ ( τ , ρ ) × exp ⁡ ( - ( γ - b ⁡ ( i ) ) 2 2 ⁢ c ⁡ ( i ) 2 ) γ < b ⁡ ( i ) λ ⁢ ⁢ a ⁡ ( τ , ρ ) otherwise , wherein, n=min(N,M), N is a number of transmit antennas, M is a number of receive antennas, λ is a normalized factor, γ is an SNR in dB, SM denotes spatial multiplexing, a(i), b(i), c(i) and a(τ,ρ) are model parameters, d is a constant shift, ρ is a correlation between transmit antennas, τ is a normalized feedback delay, τ=f d T, where T is a report interval, f d is a Doppler frequency shift, such that f d = f c ⁢ v c , where v is a user speed, c is the speed of light, f c is a carrier frequency; comparing, by the base station, the probability of each MIMO mode to determine a highest probability; and selecting, by the base station, the MIMO mode having the highest probability of being the dominant MIMO mode.