Patent ID: 8165249

Claim:
An apparatus for estimating a time offset in a Multiple Input Multiple Output (MIMO) communication system that supports Orthogonal Frequency Division Multiplexing (OFDM) or Orthogonal Frequency Division Multiplexing Access (OFDMA), the apparatus comprising: a preamble linear phase calculator configured to calculate a preamble linear phase by employing a preamble included in a received signal frame of each of a plurality of receiving antennas; a pilot linear phase calculator configured to receive signals transmitted from a plurality of transmitting antennas using different pilot patterns through the plurality of receiving antennas, and calculate a pilot linear phase by employing the pilot patterns of the plurality of transmitting antennas, which are received from the receiving antennas, respectively; and a time offset operator configured to calculate a time offset by employing the calculated preamble linear phase and the calculated pilot linear phase, wherein the preamble linear phase calculator is configured to calculate the preamble linear phase θ TO — pre according to the following equation: θ TO_pre = { 1 3 ⁢ ⁢ a ⁢ tan - 1 ( Im ⁢ { ∑ k = 0 139 ⁢ ⁢ ∑ m = 0 1 ⁢ ⁢ p k ⁡ ( m ) · p k + a ⁡ ( m ) * · W ⁢ ⁢ 0 ⁢ ( m ) + ∑ k = 143 281 ⁢ ⁢ ∑ m = 0 1 ⁢ ⁢ p k ⁡ ( m ) · p k + a ⁡ ( m ) * · W ⁢ ⁢ 0 ⁢ ( m ) } Re ⁢ { ∑ k = 0 139 ⁢ ⁢ ∑ m = 0 1 ⁢ ⁢ p k ⁡ ( m ) · p k + a ⁡ ( m ) * · W ⁢ ⁢ 0 ⁢ ( m ) + ∑ k = 143 281 ⁢ ⁢ ∑ m = 0 1 ⁢ ⁢ p k ⁡ ( m ) · p k + a ⁡ ( m ) * · W ⁢ ⁢ 0 ⁢ ( m ) } ) ⁢ ⁢ for ⁢ ⁢ Segment ⁢ ⁢ 0 1 3 ⁢ ⁢ a ⁢ tan - 1 ( Im ⁢ { ∑ k = 0 139 ⁢ ⁢ ∑ m = 0 1 ⁢ ⁢ p k ⁡ ( m ) · p k + a ⁡ ( m ) * · W ⁢ ⁢ 0 ⁢ ( m ) + ∑ k = 142 281 ⁢ ⁢ ∑ m = 0 1 ⁢ ⁢ p k ⁡ ( m ) · p k + a ⁡ ( m ) * · W ⁢ ⁢ 0 ⁢ ( m ) } Re ⁢ { ∑ k = 0 139 ⁢ ⁢ ∑ m = 0 1 ⁢ ⁢ p k ⁡ ( m ) · p k + a ⁡ ( m ) * · W ⁢ ⁢ 0 ⁢ ( m ) + ∑ k = 142 281 ⁢ ⁢ ∑ m = 0 1 ⁢ ⁢ p k ⁡ ( m ) · p k + a ⁡ ( m ) * · W ⁢ ⁢ 0 ⁢ ( m ) } ) ⁢ ⁢ for ⁢ ⁢ otherwise , wherein, in each segment, p k represents resents a preamble, k represents a sub-carrier index, m represents a receiving antenna index, W 0 represents a predetermined preamble weight, and 3a represents a sub-carrier distance between p k and p k+a .