Abstract: A receiver and method of performing timing synchronization in an orthogonal frequency division multiplexing (OFDM) scheme. A receiver to perform timing synchronization in an OFDM scheme, the receiver including: an autocorrelation processor to calculate and accumulate an autocorrelation value with regard to samples of an OFDM symbol before an initialized starting point; and a reference value calculator to calculate the reference value of each sample index in at least one predetermined sample section, based on the accumulated autocorrelation values, wherein the reference value corresponds to a value dividing an imaginary number unit of the accumulated autocorrelation values into a real number unit, and is used to repeatedly reestablish the initialized starting point and to determine the final starting point.

Abstract: Provided are a method and apparatus for detecting a transmission symbol using a lattice-reduction matrix in a Multiple Input Multiple Output (MIMO) system. The transmission symbol detection method includes: restoring an original transmission symbol from a reception signal received through the plurality of antennas; and obtaining at least one noise component included in the reception signal from a constellation changed due to applying the lattice-reduction matrix, exchanging a position of the at least one noise component under a predetermined condition which depends on a state of the restored transmission symbol, and processing the at least one noise component whose position is changed, together with the restored transmission symbol, thereby providing a soft output. Therefore, it is possible to obtain a performance gain in channel decoding.

Abstract: A method and apparatus for performing channel estimation in an Orthogonal Frequency Division Multiplexing (OFDM) wireless communication system. The method and apparatus includes receiving a training sequence at each of a plurality of predetermined subcarriers; performing primary channel estimation on each of the training sequences by a Least Square (LS) algorithm; grouping the subcarriers into a predetermined number of subgroups, and acquiring a linear filter coefficient for each of the subgroups based on a channel estimate acquired for each of the subcarriers by the primary channel estimation; and performing secondary channel estimation on each of the subcarriers by performing a Minimum Mean-Square Error (MMSE) algorithm based on the linear filter coefficient of each subgroup.

Abstract: A method and apparatus for estimating a channel in an Orthogonal Frequency Division Multiplexing (OFDM) wireless communication system. A Least-Square (LS) channel estimator receives a training sequence, and performs LS channel estimation on each of a predetermined number of subcarriers independently. A Split Minimum-Mean-Square-Error (S-MMSE) channel estimator separates the predetermined number of subcarriers into a predetermined number of groups, calculates an S-MMSE filter for a subcarrier in each group, and estimates an S-MMSE channel by applying the S-MMSE filter to each of the groups.

Abstract: An apparatus and method for generating a reduced search set to be used to determine a data transmission rate to be allocated to each antenna in a spatial multiplexing system for simultaneously transmitting independent data streams on an antenna-by-antenna basis. Channel states are estimated with respect to multiple transmit antennas and multiple receive antennas. Data transmission rates constructing a reduced search set are computed using information regarding the estimated channel states. When the reduced search set is designated, data transmission allocation is determined which requires least energy in the reduced search set. A receiving side provides a transmitting side with index information indicating the reduced search set.

Abstract: An apparatus and method for measuring noise in a reception apparatus of a wireless communication system supporting Orthogonal Frequency Division Multiplexing (OFDM). The apparatus and method converts a preamble signal of a received OFDM frame into a frequency domain, and measures signal strength at each of subcarriers to which a null signal is allocated, from the preamble signal converted into the frequency domain. Further, the apparatus and method determines signal strength caused by noise depending on an average of signal strengths measured at the subcarriers. The preamble signal includes multiple subcarrier signals, and the subcarrier to which a null signal is allocated is a subcarrier over which no signal is transmitted by the transmission apparatus.

Abstract: Provided are a method and apparatus for detecting a transmission symbol using a lattice-reduction matrix in a Multiple Input Multiple Output (MIMO) system. The transmission symbol detection method includes: restoring an original transmission symbol from a reception signal received through the plurality of antennas; and obtaining at least one noise component included in the reception signal from a constellation changed due to applying the lattice-reduction matrix, exchanging a position of the at least one noise component under a predetermined condition which depends on a state of the restored transmission symbol, and processing the at least one noise component whose position is changed, together with the restored transmission symbol, thereby providing a soft output. Therefore, it is possible to obtain a performance gain in channel decoding.

Abstract: A receiver and method of performing timing synchronization in an orthogonal frequency division multiplexing (OFDM) scheme. A receiver to perform timing synchronization in an OFDM scheme, the receiver including: an autocorrelation processor to calculate and accumulate an autocorrelation value with regard to samples of an OFDM symbol before an initialized starting point; and a reference value calculator to calculate the reference value of each sample index in at least one predetermined sample section, based on the accumulated autocorrelation values, wherein the reference value corresponds to a value dividing an imaginary number unit of the accumulated autocorrelation values into a real number unit, and is used to repeatedly reestablish the initialized starting point and to determine the final starting point.

Abstract: A method and apparatus for estimating a channel in an Orthogonal Frequency Division Multiplexing (OFDM) wireless communication system. A Least-Square (LS) channel estimator receives a training sequence, and performs LS channel estimation on each of a predetermined number of subcarriers independently. A Split Minimum-Mean-Square-Error (S-MMSE) channel estimator separates the predetermined number of subcarriers into a predetermined number of groups, calculates an S-MMSE filter for a subcarrier in each group, and estimates an S-MMSE channel by applying the S-MMSE filter to each of the groups.

Abstract: A method and apparatus for performing channel estimation in an Orthogonal Frequency Division Multiplexing (OFDM) wireless communication system. The method and apparatus includes receiving a training sequence at each of a plurality of predetermined subcarriers; performing primary channel estimation on each of the training sequences by a Least Square (LS) algorithm; grouping the subcarriers into a predetermined number of subgroups, and acquiring a linear filter coefficient for each of the subgroups based on a channel estimate acquired for each of the subcarriers by the primary channel estimation; and performing secondary channel estimation on each of the subcarriers by performing a Minimum Mean-Square Error (MMSE) algorithm based on the linear filter coefficient of each subgroup.

Abstract: An apparatus and method for measuring noise in a reception apparatus of a wireless communication system supporting Orthogonal Frequency Division Multiplexing (OFDM). The apparatus and method converts a preamble signal of a received OFDM frame into a frequency domain, and measures signal strength at each of subcarriers to which a null signal is allocated, from the preamble signal converted into the frequency domain. Further, the apparatus and method determines signal strength caused by noise depending on an average of signal strengths measured at the subcarriers. The preamble signal includes multiple subcarrier signals, and the subcarrier to which a null signal is allocated is a subcarrier over which no signal is transmitted by the transmission apparatus.

Abstract: An apparatus and method for generating a reduced search set to be used to determine a data transmission rate to be allocated to each antenna in a spatial multiplexing system for simultaneously transmitting independent data streams on an antenna-by-antenna basis. Channel states are estimated with respect to multiple transmit antennas and multiple receive antennas. Data transmission rates constructing a reduced search set are computed using information regarding the estimated channel states. When the reduced search set is designated, data transmission allocation is determined which requires least energy in the reduced search set. A receiving side provides a transmitting side with index information indicating the reduced search set.

Abstract: A communication system including a unitary matrix filter and a processor configured with logic to adapt the unitary matrix filter at a receiver.