Abstract: The disclosure relates to techniques for beamforming in multi-user systems. The disclosure particularly relates to a base station for communication with multiple user terminals, the base station comprising: a digital precoder and an analog precoder which are configured to precode a first training signal; a radio transceiver configured to transmit the precoded first training signal and to receive a precoded second training signal upon transmission of the precoded first training signal; and a controller configured to adjust a precoding of the digital precoder based on processing of the second training signal with respect to a normalization criterion and to adjust a precoding of the analog precoder based on processing of the second training signal with respect to a multi-user beamforming criterion.

Abstract: The disclosure relates to techniques for beamforming in multi-user systems. The disclosure particularly relates to a base station for communication with multiple user terminals, the base station comprising: a digital precoder and an analog precoder which are configured to precode a first training signal; a radio transceiver configured to transmit the precoded first training signal and to receive a precoded second training signal upon transmission of the precoded first training signal; and a controller configured to adjust a precoding of the digital precoder based on processing of the second training signal with respect to a normalization criterion and to adjust a precoding of the analog precoder based on processing of the second training signal with respect to a multi-user beamforming criterion.

Abstract: A wireless device, comprising: a hybrid antenna array configured to receive a signal transmitted by another wireless device over a wireless channel; and a transceiver configured to update analog radio frequency precoders of a hierarchical codebook based on magnitudes of multipath components of the wireless channel.

Abstract: A wireless device, comprising: a hybrid antenna array configured to receive a signal transmitted by another wireless device over a wireless channel; and a transceiver configured to update analog radio frequency precoders of a hierarchical codebook based on magnitudes of multipath components of the wireless channel.

Abstract: Embodiments of the present disclosure provide an iterative procedure relying on ping-pong transmissions between two antenna arrays to determine desired beamforming weights at each device. Other embodiments may be described and claimed.

Abstract: Embodiments of the present disclosure provide an iterative procedure relying on ping-pong transmissions between two antenna arrays to determine desired beamforming weights at each device. Other embodiments may be described and claimed.

Abstract: An apparatus and method for interference cancellation in multiple-antenna communication system is disclosed. Accordingly, a receiver of a multiple-antenna communication system cancels interference by selecting either a multiple-symbol processing scheme or a single-symbol processing scheme depending on a signal type, thereby improving performance of the communication system.

Abstract: A system and method for transmitting and receiving a signal in a communication system using a relay scheme. A base station receives a first signal in a first time interval from a first mobile station which is at least one mobile station located in a third region which is a region where a first region which is a region of the base station itself overlaps with a second region which is a region of a relay station. The relay station receives a second signal in the first time interval from a second mobile station which is at least one mobile station located in a fourth region which is a region not overlapping with the first region in the second region, and receives the first signal from the first mobile station. The relay station transmits a third signal including the first signal and the second signal to the base station in a second time interval. The base station receives the third signal in the second time interval, and cancels the first signal from the third signal to detect the second signal.

Abstract: Automatic Repeat reQuest (ARQ) apparatus and method of a Multiple Input Multiple Output (MIMO system are provided. The ARQ method includes decoding, when one or more packets are received, the received packets and trying to detect the decoded packets; and storing, when error is detected from the packets, the corresponding error packet, requesting a transmitter to retransmit N-ary packets from which the error is detected and to transmit (M-N)-ary new packets when the number of the error packets N is smaller than the total number of the transmitted packets M. Accordingly, the error rate of the retransmitted data can be minimized, the number of retransmissions can be decreased, and the overall data transmission rate can be raised.

Abstract: Provided is an apparatus and method for estimating an uplink frequency offset in a wireless communication system. In a receiving apparatus of a wireless communication system using a random access channel composed of two equivalent sequences, the apparatus includes a channel receiver which extracts samples corresponding to the two sequences from an input random access channel signal; a correlator which computes first and second correlation values by correlating preceding and trailing samples among the samples output from the channel receiver with a predetermined sequence; and a frequency offset estimator which estimates a frequency offset by using a ratio of the second correlation value to the first correlation value output from the correlator.

Abstract: A method and apparatus for joint unicast using multi-user superposition coding in a wireless relay system are provided. A BS superposition-encodes first and second data messages directed to first and second MSs, respectively, scheduled at a current scheduling instant. The first and second data messages carry first and second information bit streams for the first and second MSs, respectively. The first MS has a relatively good direct link to the BS, and the second MS has a relatively bad direct link to the BS. The superposition-coded data is transmitted to the first MS and an RS connected between the BS and the first and second MSs. The RS receives the superposition-coded data from the BS, extracts the second information bit stream by decoding the superposition-coded data, and transmits a third data message carrying the second information bit stream to the first and second MSs.

Abstract: An apparatus and method for Automatic Repeat reQuest (ARQ) in a Multi Input Multi Output (MIMO) system. The method includes computing weights of erroneous packets and weights of transmitting antennas by using channel information; sorting the weights of the erroneous packets in descending order; sorting the weights of the transmitting antennas in ascending order; and assigning the transmitting antennas to the erroneous packets according to sorting results.

Abstract: A hybrid forwarding apparatus and method for cooperative relaying in an OFDM network are provided. In a hybrid forwarding apparatus in a relay terminal, a forwarding scheme selector selects a forwarding scheme for transmission. An amplify and forward (AF) block amplifies data received from the forwarding scheme selector, if an AF scheme is selected. A decode and forward (DF) block decodes and encodes data received from the forwarding scheme selector, if a DF scheme is selected. A multiplexer provides the output data of the AF block and the DF block to an OFDM modulator.

Abstract: A source node of a communication system selects one of a direct mode, a multi-hop mode, and a superposition mode as a transmission mode to be used for signal transmission from the source node to a destination node, taking into account data rates for a link between the source node and the destination node, a link between the source node and a delay node, and a link between the relay node and the destination node, thereby increasing the data rate, i.e., the throughput, of the entire communication system.

Abstract: An apparatus and method for interference cancellation in multiple-antenna communication system is disclosed. Accordingly, a receiver of a multiple-antenna communication system cancels interference by selecting either a multiple-symbol processing scheme or a single-symbol processing scheme depending on a signal type, thereby improving performance of the communication system.

Abstract: A method for an Automatic Repeat reQuest (ARQ) at a receiver in a Multiple Input Multiple Output (MIMO) system wherein when a received packet is erroneous and the erroneous packet is received from the weakest antenna in a Space Multiplexing (SM) mode, a first smallest number of retransmissions is computed to acquire a Signal to Noise Ratio (SNR) within or above an Adaptive Modulation and Coding (AMC) level. When the first number of the retransmissions is greater than a threshold, the sender is requested to retransmit the packets from the strongest antenna in the SM mode and when the first number of the retransmissions is smaller than the threshold, the sender is requested to retransmit the packets from the weakest antenna in the SM mode.

Abstract: An apparatus and method for detecting a signal in a broadband wireless communication system are provided. In a Base Station, an offset estimator estimates frequency offsets of a signal received from each of a plurality of Mobile Stations (MSs), a channel estimator estimates a channel matrix having channel coefficients of subcarriers as elements, for each MS, a modeler models the received signals using the frequency offsets of the MSs and the channel matrices of the MSs, and a detector detects signals transmitted from the MSs using the modeled received signals.

Abstract: Provided is an apparatus and method for estimating an uplink frequency offset in a wireless communication system. In a receiving apparatus of a wireless communication system using a random access channel composed of two equivalent sequences, the apparatus includes a channel receiver which extracts samples corresponding to the two sequences from an input random access channel signal; a correlator which computes first and second correlation values by correlating preceding and trailing samples among the samples output from the channel receiver with a predetermined sequence; and a frequency offset estimator which estimates a frequency offset by using a ratio of the second correlation value to the first correlation value output from the correlator.

Abstract: A method and apparatus for joint unicast using multi-user superposition coding in a wireless relay system are provided. A BS superposition-encodes first and second data messages directed to first and second MSs, respectively, scheduled at a current scheduling instant. The first and second data messages carry first and second information bit streams for the first and second MSs, respectively. The first MS has a relatively good direct link to the BS, and the second MS has a relatively bad direct link to the BS. The superposition-coded data is transmitted to the first MS and an RS connected between the BS and the first and second MSs. The RS receives the superposition-coded data from the BS, extracts the second information bit stream by decoding the superposition-coded data, and transmits a third data message carrying the second information bit stream to the first and second MSs.

Abstract: A system and method for transmitting and receiving a signal in a communication system using a relay scheme. A base station receives a first signal in a first time interval from a first mobile station which is at least one mobile station located in a third region which is a region where a first region which is a region of the base station itself overlaps with a second region which is a region of a relay station. The relay station receives a second signal in the first time interval from a second mobile station which is at least one mobile station located in a fourth region which is a region not overlapping with the first region in the second region, and receives the first signal from the first mobile station. The relay station transmits a third signal including the first signal and the second signal to the base station in a second time interval. The base station receives the third signal in the second time interval, and cancels the first signal from the third signal to detect the second signal.