Abstract: A communication apparatus includes a mobile terminal to measure a downlink channel state of a downlink between a base station and the mobile terminal, and to determine whether to transmit feedback information about the downlink channel state to the base station based on the measured downlink channel state.

Abstract: An apparatus and method to generate a preceding codebook for a Multiple-Input Multiple-Output (MIMO) system, the apparatus for generating a preceding codebook including: a clustering unit to collect a predetermined number of spatial beams into one cluster such that mutual interference is minimized, the predetermined number of spatial beams collected from among a plurality of spatial beams distributed to at least one user during a preceding process of a MIMO communication scheme; and a mapping table generator to generate a mapping table including one or more indexes generated based on information about the cluster, and a value of each element of the mapping table is generated based on interference between the clusters and/or whether overlapping of the clusters is allowed.

Abstract: An apparatus and method for transmitting and/or receiving data in a closed-loop multi-antenna system, the method of receiving data including: acquiring CQIs of data streams by channel estimation of a received signal; selecting at least one CQI from among the acquired CQIs; calculating a common CQI using the acquired CQIs; generating feedback information with the at least one CQI, the common CQI, and an index of a data stream with the at least one CQI; and transmitting the feedback information to a transmitter.

Abstract: A method for selecting an antenna in an orthogonalized spatial multiplexing system. Upon receipt of at least one symbol from a transmitter via multiple receive antennas, a receiver decodes each of the received symbols; determines a rotation angle between the received symbols, and selects an optimal subset of transmit antennas using a distance between vectors of the decoded symbols; generates feedback information including the determined rotation angle and the selected optimal subset, and transmits the generated feedback information to the transmitter. Upon receipt of the feedback information, the transmitter beam-forms an antenna corresponding to the optimal subset depending on the received feedback information, and transmits a data symbol to the receiver. The receiver detects each of data symbols received from the transmitter.

Abstract: A method of transmitting/receiving feedback information representing channel quality in a MIMO-OFDM system, in which a receiver measures channel qualities of signals transmitted on a plurality of subbands through a plurality of transmitting antennas by a transmitter, selects a predetermined number of subbands having a highest transmission performance based on the measured channel qualities and preceding information, determines at least one subband group with a maximum rate from among the selected subbands and the preceding information associated with the at least one subband group, and transmits feedback information to the transmitter, the feedback information including channel quality information about the at least one subband group and the associated preceding information.

Abstract: A data transceiver and a data reception method for reducing power consumption in a mobile communication system are provided. The data transceiver includes a transmitter which transmits a plurality of data frames during a predetermined transmission period; and a receiver which receives data frames in the predetermined transmission period, if the transmission period is allowed and monitors with minimal operation power whether data transmission is in progress or completed in the transmission period, if the transmission period is not allowed.

Abstract: An Orthogonal Spatial Multiplexing (OSM) apparatus and method in a closed-loop Multiple Input Multiple Output-Orthogonal Frequency Division Multiplexing (MIMO-OFDM) system are provided. In the OSM method, a basic signal model is set and transmission symbols are encoded. A real-valued system model corresponding to the basic signal model is obtained. To achieve orthogonality, rotations angles are calculated and are applied to the encoded transmission symbols.

Abstract: Disclosed is a method for detecting a hidden station in a specific station constituting a wireless communication network that includes receiving a frame after a lapse of an idle state interval longer than a predetermined waiting time; determining that there is a hidden station, if a size of the received frame is equal to a size of an Acknowledge (ACK) frame; and determining that there is no hidden station, if the size of the received frame is not equal to the size of the ACK frame.

Abstract: A method and apparatus for estimating available throughput of a fixed node in a mobile node of a communication network. The communication network includes fixed nodes connected to a router connected to at least one foreign network and mobile nodes connected to the fixed nodes. A second mobile node is selected from among mobile nodes connected to a fixed node whose available throughput is estimated in a first mobile node. An idle slot interval of the second mobile node connected to the fixed node is set. A transmission probability is measured in one slot interval of the second mobile node through an average of set idle slot intervals. Transmission information of the second mobile node is acquired using the measured transmission probability. The available throughput of the fixed node is estimated using the acquired transmission information.

Abstract: A power saving method of a terminal in a wireless communication system including an access point for transmitting a beacon frame and a paging frame, and a terminal for compensating for timing offset with the access point using the beacon frame and detecting a position thereof using the paging frame. The terminal supports an active mode in which data transmission/reception is actually performed and a power saving mode in which power consumption is reduced when there is no transmission/reception data. The method includes calculating a paging timing offset generated for a reception interval of the paging frame using the beacon frame, and receiving the paging frame after a lapse of a time corresponding to the paging timing offset in the power saving mode.

Abstract: Disclosed is a method for configuring a bitmap in a mobile communication system employing a block ACK scheme, which faithfully performs its intrinsic function of acknowledging a reception result, and yet can reduce transmission delay and the overall system load due to retransmission in the case where packet loss is relatively less important than transmission delay time, such as in the case of voice communication. To this end, a recipient compares a PER of a received packet signal with a threshold value. If the PER is higher than the threshold value, the recipient operates in the block ACK scheme, and if the PER is lower than the threshold value, the recipient determines a bitmap configuration scheme on the assumption that an erroneous frame has been successfully received. Also, using the determined bitmap configuration scheme, the recipient transmits a reception result for each received packet.

Abstract: A power saving apparatus and a method in a wireless communication system are provided. An Access Point (AP) buffers transmission frames for sleep-mode stations in a sleep-mode buffer. Upon wakeup from a sleep mode, a station sends a first control information frame indicating wakeup to the access point. The access point sends a second control information frame including a requested transmission length in response to the first control information frame to the station. The station generates a third control information frame, aggregates the third control information frame and user data frames to a first protocol data unit, and sends it to the AP. Then the AP generates a fourth control information frame, aggregates the fourth control information frame and buffered frames to a second protocol data unit, and sends it to the station.

Abstract: A buffering apparatus and method for packet aggregation are provided. A buffer buffers packet data to be transmitted on a frame basis. An aggregator represents the positions of the buffered packet data in an Access Category (AC) bitmap and a Traffic Identifier (TID) bitmap according to an AC and a TID of the buffered packet data, and provides a bitmap indicating the positions of packet data to be aggregated according to an aggregation condition to an aggregation controller. The aggregation controller aggregates the packet data based on the bitmap received from the aggregator, constructs an aggregation Physical Service Data Unit (PSDU) with the aggregated packet data, and transmits the aggregation PSDU to a destination.