Abstract: A link adaptation system using a Doppler frequency is provided. The link adaptation system includes: a Doppler frequency estimation unit to estimate a Doppler frequency of a signal transmitted via a wireless channel; a Signal to Noise Ratio (SNR) measurement interval determination unit to determine an SNR measurement interval of the signal transmitted via the wireless channel based on the estimated Doppler frequency; and an SNR measurement unit to measure an SNR of the signal based on the determined SNR measurement interval.

Abstract: A method for transmitting data at a high rate in a wireless LAN is provided. A wireless access point requests reliable node information from a wireless terminal having a transfer rate equal to or less than a predetermined transfer rate if data to be transmitted to the terminal occurs. The terminal produces a frame containing information related to reliable nodes that can communicate with the terminal and information of greatest transfer rates between the reliable nodes and the terminal, and transmits the frame to the access point. The access point selects an optimal relay node from the reliable nodes, based on the greatest transfer rates between the reliable nodes and the access point and transfer rates between the reliable nodes and the terminal, and determines if a relay gain exists when using the optimal node. If the relay gain exists, the access point performs relay transmission to the terminal; otherwise, it performs direct transmission to it.

Abstract: A system of controlling an antenna of a moving object is provided. The system includes: a plurality of communication antennas established in the moving object; an environmental information generation unit generating environmental information which includes strength information of a received signal and moving speed information of the moving object; an antenna use determination unit determining, with respect to the plurality of communication antennas, a number of antennas for each use based on the environmental information; and an antenna assigning unit assigning the plurality of communication antennas for each use according to the determined number of antennas.

Abstract: A semiconductor memory system includes an external memory, an internal memory, and a one-time programmable (OTP) memory. The external memory includes a kernel, a public key, first boot information used to authenticate the public key and generate a test secret key, and a second boot loader verifying integrity of the kernel. The internal memory includes a first boot loader that verifies integrity of the second boot loader and generates the test secret key. The OTP memory includes second boot information generated using the public key and a secret key. Since the secure boot method and the semiconductor memory system using the method do not need an additional OTP memory to store a secret key unlike conventional technology, the capacity and recording time of the OTP memory can be reduced to about half compared to the conventional technology.

Abstract: A method for generating packet-based transmission control parameters includes (a) receiving class information of an audio-video (AV) application and characteristic information of an AV packet, from the AV application, (b) receiving status information of a wireless channel and buffer storage time information of the AV packet, from a medium access control (MAC) layer, and (c) generating and outputting the packet-based transmission control parameters on the basis of the received information. In addition, a selective retransmission method includes (a) transmitting packets of an MPEG-2 frame in real-time, (b) checking for any transmission error after the transmission, and (c) if any transmission error is generated, retransmitting only packets of an I-frame. Therefore, it is possible to efficiently support AV service in wireless communication by dynamically controlling transmission control parameters according to a buffer status and by reflecting the characteristics of the AV frames.

Abstract: A handoff method is provided in a communication network including a plurality of fixed nodes attached to a router connected to at least one external network, and at least one mobile node associated with a current fixed node. The method detects movement of a mobile node; prepares a handoff of the mobile node from a current fixed node to potential fixed nodes upon detecting movement of the mobile node; decides whether to handoff to one of the potential fixed nodes as a target fixed node; and performs the handoff from the current fixed node to the target fixed node. The handoff method enables the mobile station to quickly move its association from one access point to another by minimizing a probe delay which is a primary contributor to handoff delay.

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 wireless communication system includes at least one AP assigned with a unique MAC address and a shared virtual MAC address; and at least one mobile station to search the at least one AP, receive AP information from the retrieved AP, and perform a handoff, wherein the mobile station transmits query data to the shared virtual MAC address, receives response data from the AP, determines whether the AP exists on a predetermined channel, and when the AP exists on the channel, requests the AP having the shared virtual MAC address for AP information, and receives the AP information from the AP.

Abstract: Handover in a mobile communication system, and more particularly, an apparatus and method that can broadcast handover information to a particular region using beamforming is provided. An apparatus for storing handover information in a mobile communication system includes: an estimation unit to estimate a direction of arrival (DOA) of a received signal with respect to a first base station based on the received signal, wherein the received signal is received from a terminal belonging to the first base station; and a storage unit to store the estimated DOA as handover information associated with a second base station when the terminal is handed over to the second base station. According to aspects of the present invention, a number of neighboring base stations that a terminal needs to search to perform handover may be reduced. Therefore, the terminal may perform handover more quickly and a communication disconnection time may be reduced.

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: Provided are a system and method of transmitting an Aggregated Media Access Control (MAC)Protocol Data Unit (A-MPDU) in a Wireless Local Area Network (WLAN) system. A MAC layer divides service data transferred from an upper layer into a plurality of MPDUs, forms a single transmission frame including the sequentially arranged MPDUs, delimiter information for distinguishing each of the MPDUs, and ACK request information for requesting for a reception result of the MPDUs, and transmits the formed transmission frame to a recipient. Accordingly, service coverage is extended, and a transmission delay is minimized, resulting in improved service efficiency.

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: An apparatus and method for controlling transmission rate by determining whether a data transmission failure is caused by a channel error or a data collision in order to reduce a collision-caused rate decrease or a collision-caused rate increase delay in a WLAN. A collision-caused data transmission failure and if the number of data transmission failures reaches a predetermined threshold, data is retransmitted by means of an RTS/CTS exchange.

Abstract: A method is provided for efficiently allocating a transmission period in a wireless network system. An access point (AP) transmits a PSMP frame indicating a downlink period provided to each station (STA) and a minimum amount of an uplink period allocated to each STA, and at least one sub PSMP frame indicating an uplink period additionally provided for an STA that transmitted a resource request message for remaining queued data in the uplink period indicated by the PSMP frame. If the uplink period indicated by the PSMP frame is insufficient to transmit the queued data, the STA transmits a data unit including a part of the queued data and a resource request message for the remaining queued data in the uplink period. After transmitting the resource request message, the STA receives the sub PSMP frame after the full period indicated by the sub PSMP frame, and transmits the remaining queued data to the AP in the uplink period indicted by the sub PSMP frame.

Abstract: The present invention relates to a power saving in a wireless local area network including a plurality of access points providing at least one mobile station in each access point cell boundary with access service, the mobile station transits between an active mode and an idle mode. The power saving method includes grouping the access points into at least one paging group with a paging group boundary; determining if the a mobile station is in the idle mode in which the mobile station switches between an awake state and a doze state every predetermined time interval, or the active mode in which the mobile station is in the awake mode; and if the mobile station is in the idle mode enabling an idle handoff which occurs only when the mobile station crosses the paging group boundary. In the present invention, the handoff occurs when the mobile terminal crosses the paging group boundary but not the access point cell in the idle mode, resulting in reduction of power consumption.

Abstract: An apparatus is provided for allocating a transmission period in a wireless network system. An access point (AP) transmits a PSMP frame indicating a downlink period and an uplink period allocated to each station (STA), and at least one sub PSMP frame indicating an allocated downlink period for at least one of a retransmission of downlink data and a transmission of an ACK indicating successful receipt of uplink data. After exchanging data with the AP in the downlink and uplink periods indicated by the PSMP frame, an STA receives the each sub PSMP frame, and performs at least one of a reception of the retransmitted downlink data and a reception of the ACK in the downlink period indicated by the each sub MAP frame.

Abstract: An apparatus is provided for efficiently allocating a transmission period in a wireless network system. An access point (AP) transmits a PSMP frame indicating a downlink period provided to each station (STA) and a minimum amount of an uplink period allocated to each STA, and at least one sub PSMP frame indicating an uplink period additionally provided for an STA that transmitted a resource request message for remaining queued data in the uplink period indicated by the PSMP frame. If the uplink period indicated by the PSMP frame is insufficient to transmit the queued data, the STA transmits a data unit including a part of the queued data and a resource request message for the remaining queued data in the uplink period. After transmitting the resource request message, the STA receives the sub PSMP frame after the full period indicated by the sub PSMP frame, and transmits the remaining queued data to the AP in the uplink period indicted by the sub PSMP frame.

Abstract: A method is provided for allocating a transmission period in a wireless network system. An access point (AP) transmits a PSMP frame indicating a downlink period and an uplink period allocated to each station (STA), and at least one sub PSMP frame indicating an allocated downlink period for at least one of a retransmission of downlink data and a transmission of an ACK indicating successful receipt of uplink data. After exchanging data with the. AP in the downlink and uplink periods indicated by the PSMP frame, an STA receives the each sub PSMP frame, and performs at least one of a reception of the retransmitted downlink data and a reception of the ACK in the downlink period indicated by the each sub MAP frame.