Abstract: A closed-loop multi-antenna system and method thereof are provided. A transmitter includes a feedback information processor and a first transmit unit. A receiver includes a channel estimator, a feedback information generator and a second transmit unit. The feedback information processor receives feedback information from the receiver, calculates each of a sum rate in a multi-user mode and a sum rate in a single-user mode using the feedback information, and selects one of the single-user mode and the multi-user mode as a transmission mode depending on a comparison result between the sum rate in the multi-user mode and the sum rate in the single-user mode. The channel estimator acquires channel quality information (CQI) for each data stream transmitted individually via each antenna group. The feedback information generator determines the CQI associated information from the CQI acquired individually for each antenna group corresponding to the transmission mode.

Abstract: Apparatuses and methods for transmission and reception in a Closed-Loop (CL)-Multiple Input Multiple Output (MIMO) system are provided. A codebook generation method includes determining weight vectors vi (i=1, . . . , 2L) for a codebook V(4, 1, L), where Nt of a codebook V(Nt, s, L) denotes a number of antennas, s denotes a number of streams, and L denotes a number of codebook index bits, determining a unitary matrix Ti using an i-th vector vi of the codebook V(4, 1, L), and determining an i-th matrix of the codebook V(4, 2, L) by selecting a first column of the unitary matrix Ti as a first column of a weight matrix and selecting a column selected from other columns excluding the first column of the unitary matrix Ti in a particular pattern, as a second column of the weight matrix.

Abstract: An apparatus and a method for selecting a transmission mode in a multi-antenna system are provided. The method includes checking a channel characteristic of a transmitting end using a signal received over at least two antennas; and determining a multi-antenna transmission mode according to the channel characteristic. Accordingly, the loss of the system capacity gain can be reduced and the capacity gain of the system can be increased.

Abstract: A method and apparatus for performing codebook-based precoding in a Multiple Input Multiple Output (MIMO) wireless communication system are provided. In a method for operating a Base Station (BS) in a MIMO wireless communication system, a reference signal including pilot signals, which are divided by a predefined number of bands and are multiplied by respective codes in a codebook, is transmitted. One or more Mobile Stations (MSs) destined for spatial multiple access are selected using an index of a band and CQI of the band corresponding to the index, which are fed back from one or more MSs. A precoding matrix is generated to process data streams of the selected one or more MSs.

Abstract: For cooperative transmission in a broadband wireless communication system, an apparatus and operating method of a Base Station (BS) in a broadband wireless communication system are provided. The method includes receiving a cooperative transmission REQuest (REQ) message which includes at least one of information designating a cooperative Mobile Station (MS), a pilot pattern of the cooperative MS, a variable determining a permutation pattern, and an orthogonal code of the cooperative MS, from a control station, allocating a resource of a predefined Coordinated MultiPoint transmit/receive (CoMP) zone occupying part of a frame, to at least one cooperative MS designated by the cooperative transmission REQ message, and communicating with the at least one cooperative MS according a cooperative transmission scheme using the resource of the CoMP zone.

Abstract: A method and apparatus for multi-cell calibration in a wireless communication system supporting cooperative Multiple Input Multiple Output (MIMO) are provided. Operations of a Base Station (BS) according to the method include transmitting a first message indicating a start of multi-cell sounding calibration to a reference Mobile Station (MS); estimating an uplink channel matrix of the reference MS using pilot symbols received from the reference MS; transmitting pilot symbols for enabling the reference MS to estimate a downlink channel matrix; when receiving downlink channel information of cooperative BSs from the reference MS, transmitting second messages comprising the downlink channel information to the cooperative BSs; and determining a multi-cell calibration matrix using the uplink channel matrix and the downlink channel information received from the reference MS.

Abstract: An apparatus and method for beamforming in a wireless communication system are provided. The base station apparatus includes a calculator, a plurality of formers, and a plurality of adders. The calculator calculates a beam coefficient considering interference to a neighbor sector to be applied to transmission signals to mobile stations. The plurality of formers performs beamforming for a transmission signal to each mobile station within a corresponding sector using the beam coefficient. The plurality of adders adds the sector-based beamformed signals each provided from the plurality of formers, on a per-transmission-antenna basis.

Abstract: An apparatus and a method for determining an optimum integer perturbation vector of a low complexity in a multiple antenna system include a transmitter that transmits data using an optimum integer perturbation vector of a low complexity in a multiple antenna system includes a module pre-processor, a shift pre-processor, and a precoder. The modulo pre-processor adds an integer perturbation vector to a transmission signal vector. The shift pre-processor phase-shifts a pseudo inverse matrix of a channel matrix using a phase angle. The precoder precodes a transmission signal vector perturbed by the integer perturbation vector using the phase-shifted pseudo inverse matrix of the channel matrix.

Abstract: A method and apparatus for allocating a feedback channel in a multiple antenna communication system are provided. In a method of operating a Base Station (BS) for allocating a feedback channel in a Multi-User Multiple-Input Multiple-Output (MU-MIMO) communication system, the method includes measuring a MIMO transmission environment, determining an amount of feedback according to the MIMO transmission environment, and allocating a feedback channel according to an amount of the feedback.

Abstract: Apparatus and method for calibration in a multi-antenna system are provided. The method includes setting at least two transmission paths connected to antennas, respectively, as reference transmission paths, when receiving compensation signals transmitted in the reference transmission paths in at least two reception paths connected to the antennas, respectively, determining a phase difference of the reception paths using the received compensation signals, and calibrating the reception paths using the phase difference of the reception paths.

Abstract: A receiving apparatus and a receiving method for interference cancellation in a wireless communication system are provided. The receiving apparatus includes a multiple-input, multiple-output (MIMO) detector for estimating a desired signal and an interference signal based on received signals in accordance with a MIMO detection scheme; a first decoder for iteratively decoding the interference signal output from the detector; a second decoder for iteratively decoding the desired signal output from the decoder; and an LLR updater for updating an interval LLR value of the second decoder using an interval LLR value of the first decoder.

Abstract: A data reception apparatus and method for generating and transmitting feedback information in a multi-antenna system using grouped antennas, and a data transmission apparatus and method for transmitting a data stream of a user according to a transmission mode selected depending on the feedback information is disclosed. The reception apparatus generates feedback information depending on maximum channel quality information, an antenna group index associated with the maximum channel quality information, rank information, and remaining channel quality information associated with the rank information, and transmits the feedback information to the transmission apparatus. The transmission apparatus selects one of a multi-user mode and a single-user mode as a transmission mode depending on the feedback information and transmits a data stream of a user via multiple antenna groups or one antenna group, according to the selected transmission mode.

Abstract: Provided are an apparatus and a method for removing an interference in a multiple antenna system. The apparatus includes a channel estimator, a covariance matrix generator, a weight calculator, and a beam forming unit. The channel estimator estimates a channel for a service cell and an interference channel for an adjacent cell using sounding signals via a plurality of antennas. The covariance matrix generator generates a covariance matrix as an average value from the interference channel. The weight calculator calculates a beam coefficient using the covariance matrix. The beam forming unit forms a beam using the beam coefficient.

Abstract: A method for allocating resource in a communication system. The resource allocation method includes dividing a data transmission region into a first region and a second region; allocating resource of the first region when a first Mobile Station (MS) among MSs is an MS located in a non-interference region; and allocating resource of the second region when a second MS among the MSs is an MS located in an interference region.

Abstract: An uplink channel sounding apparatus and method in a wireless communication system are provided, in which in an MS, a baseband MODEM generates as many channel sounding signals as the MS has antennas and outputs the channel sounding signals to an antenna switch. The antenna switch switches the channel sounding signals to the antennas in a one-to-one basis transmitting the channel sounding signals to a BS through all of the antennas of the MS.

Abstract: A data reception apparatus and method for generating and transmitting feedback information in a multi-antenna system using grouped antennas, and a data transmission apparatus and method for transmitting a data stream of a user according to a transmission mode selected depending on the feedback information is disclosed. The reception apparatus generates feedback information depending on maximum channel quality information, an antenna group index associated with the maximum channel quality information, rank information, and remaining channel quality information associated with the rank information, and transmits the feedback information to the transmission apparatus. The transmission apparatus selects one of a multi-user mode and a single-user mode as a transmission mode depending on the feedback information and transmits a data stream of a user via multiple antenna groups or one antenna group, according to the selected transmission mode.

Abstract: Provided is an apparatus and method for enhancing a demodulation performance of a receiver in a Broadband Wireless Access (BWA) system. A receiving apparatus in a broadband wireless communication system includes an estimator, a first calculator, and a second calculator. The estimator estimates a desired signal. The first calculator calculates a correlation matrix of a signal obtained by eliminating the estimated desired signal from a Received (RX) signal. The second calculator performs an interference elimination using the correlation matrix.

Abstract: A partial iterative detection and decoding apparatus in a Multiple Input Multiple Output (MIMO) system includes a detector for detecting signals received through at least one receive antenna to generate a first soft decision value, a decoder for decoding the first soft decision value to generate a second soft decision value, and a reliability determiner for determining a signal to be iteratively detected and decoded by using the second soft decision value. Accordingly, the complexity of the receiver is reduced and the number of iterations limited due to the complexity is increased, thereby improving the performance of the receiver.

Abstract: A symbol demapping method and apparatus for efficient interference cancellation in a wireless communication system. Decision signal points are generated which include decision signal points based on a modulation scheme and a virtual signal point added to a zero point. A magnitude of a complex value of an input signal is compared with a threshold based on system setting. When the magnitude of the complex value is less than the threshold, the virtual signal point of the zero point is mapped and output as a target decision signal point. When the magnitude of the complex value is greater than or equal to the threshold, one of the decision signal points based on the modulation scheme is mapped and output according to the com0plex value.

Abstract: A method and apparatus estimate a frequency offset of a receiver in a mobile communication system. A pilot signal and a signal of a control channel are received from a transmitter. Frequency offsets of the pilot signal and frequency offsets of the control channel are estimated, respectively. And the frequency offset of the pilot signal is corrected based on the frequency offset estimation of the control channel.