Abstract: In a handoff system and method for a dual mode terminal, the handoff system includes: a dual mode terminal which receives a message containing location information of a router of a second network while performing handoff from a first network to the second network, and which transmits a registration request message containing the location information of the router; and a home agent which transcodes data transmitted from a content providing server to be adapted for a bandwidth of the second network on the basis of information contained in the registration request message received from the dual mode terminal, and which transmits the transcoded data to the dual mode terminal.

Abstract: In a Voice over Internet Protocol (VoIP) video communication method and apparatus, first and second VoIP-based terminals store video event indexes and images mapped thereto with respect to state information of a user and terminal, and establish a session using session establishment information defining the video event. The first terminal then transmits a data packet including the video event index, and the second terminal receives the data packet and outputs an image mapped to the video event index of the images stored in advance. Thus, by transmitting and receiving a predefined index alone without transmitting user and terminal states as a real time data-type image, the VoIP video communication method and apparatus prevent unnecessary waste of bandwidth in video communication.

Abstract: In a Voice over Internet Protocol (VoIP) video communication method and apparatus, first and second VoIP-based terminals store video event indexes and images mapped thereto with respect to state information of a user and terminal, and establish a session using session establishment information defining the video event. The first terminal then transmits a data packet including the video event index, and the second terminal receives the data packet and outputs an image mapped to the video event index of the images stored in advance. Thus, by transmitting and receiving a predefined index alone without transmitting user and terminal states as a real time data-type image, the VoIP video communication method and apparatus prevent unnecessary waste of bandwidth in video communication.

Abstract: In a video conference system and method, a first terminal and second through Nth terminals maintain a session for a conference. The first terminal prevents an input of further information to the white board by the second through Nth terminals during a set time period from an input of information to the white board and the second through Nth terminals transmit further information, input during a buffering mode selected in an unlocked state, to other terminals participating in the session upon the input of information to the white board being allowed after the set time period has elapsed.

Abstract: A wireless network system and method to secure Quality of Service (QoS) according to a type of Wireless Local Area Network (WLAN) service in a WLAN communication system based on IEEE 802.11 includes: an authentication server adapted to set a priority for an access category of a wireless network service requested by a user to perform an authentication procedure in response to a user terminal requesting authentication for access to a wireless network; and an Access Point (AP) adapted to receive and store access category information of the user terminal authenticated by the authentication server and to compare access category information contained in a packet received from the user terminal to the previously stored access category information of the user terminal to control access to the wireless network.

Abstract: A network access method of Wireless Local Area Network (WLAN) terminals and a network system thereof which are designed to support network association between a terminal and an Access Point (AP) in an IEEE 802.11 WLAN environment includes: scanning at least one AP in the network and determining whether or not the AP uses a Wired Equivalent Privacy (WEP) Key; and converting to an Open System authentication mode or a Shared Key authentication mode according to the determination. Accordingly, the terminal can scan for the existence of a WEP Key from at least one AP and convert into a network-accessible Open System authentication mode and a Shared Key authentication mode so as to execute an association.

Abstract: A method and apparatus for transmitting frames in a Wireless Local Area Network (WLAN), each station in the WLAN determines whether there is another station in a hidden state. The station transmits a frame to an Access Point (AP) without performing an Request To Send/Clear To Send (RTS/CTS) mechanism when there is another station in a hidden state, thereby improving use efficiency of the wireless network and minimizing frame transmission delay.

Abstract: An inter-symbol interference cancellation method for an orthogonal frequency division multiple access system is provided. The inter-symbol interference cancellation method includes transmitting, at a base station, an OFDMA symbol having a first half part and a second half part divided in time; receiving, at a mobile station, the OFDMA symbol; and restoring the OFDMA symbol by repeating one of the first half part or the second half part. The ISI cancellation method for an OFDMA communication system of the present invention uses an OFDMA symbol having two identical parts sequentially arranged in time, whereby it is possible to recover a transmitted OFDMA symbol if at least one of the two parts is successfully received.

Abstract: An uplink signal receiving method and apparatus using successive interference cancellation (SIC) in a wireless transmission system based on Orthogonal Frequency Division Multiple Access (OFDMA) are provided.

Abstract: A method for exchanging media description information between user agents using a session initiation protocol (SIP) comprises the steps of: providing information on an OS and sound module of a first user agent so that the first user agent generates, in a media description field of a session description protocol (SDP), an SIP message including the information on the OS and sound module of the first user agent, and sends it to a second user agent; and setting a processing format for voice data of the second user agent so that the second user agent determines the voice data format supportable by the first user agent from the information on the OS and sound module of the first user agent, compares it with the voice data format supportable by the second user agent, and sets a format commonly supportable by the first and second user agents as the voice data format of the second user agent.

Abstract: In a wireless local area network (WLAN) and a channel selection method of a WLAN station, a station newly entering the WLAN captures packets from WLAN service channels, which packets are provided by at least one access point (AP) for a predetermined measuring time. The WLAN calculates, from the captured packets, busy factors indicative of the load on each WLAN service channel so as to confer a priority between WLAN service channels. The WLAN selects channels according to the conferred priority.

Abstract: A broadband wireless access system including: a base station that allocates an uplink bandwidth to each connected subscriber station according to at least one algorithm; and at least one subscriber station that when there is no voice information to be sent through the uplink bandwidth allocated from the base station according to an unsolicited grant service (UGS) algorithm, detects another packet based on another algorithm, encapsulates the detected packet, and sends the encapsulated packet in a payload field of a UGS packet to the base station through the uplink bandwidth. Thus, the broadband wireless access system maximizes utilization of the bandwidth allocated according to the UGS algorithm.

Abstract: An IP based voice/video communication system and call pickup/forwarding method and a program storage device, readable by a machine, tangibly embodying a program of instructions executable by the machine to perform the call pickup/forwarding method enables a subscriber can have voice/video communication irrespective of time or place by forwarding voice/video calls between voice/video communication terminals such as a TV, PDA and home pad, or by picking up a incoming call at a nearby terminal if it is difficult for the subscriber to answer the call at the originally called terminal from his/her location.

Abstract: An IP network and a communication method therein. The IP network includes a first terminal adapted to make an outgoing call and a second terminal adapted to transmit information on a plurality of serviceable communication modes other than a communication mode of the call incoming from the first terminal depending upon whether the incoming call is connected.

Abstract: Disclosed are a system and method for controlling transmission power in a wireless local area network (WLAN), and more particularly, a system and method for controlling transmission power in a WLAN that are capable of providing a WLAN service to terminals outside a service area by controlling the transmission power in the WLAN. Thus, link margin data of a station positioned at a hidden node of the WLAN is received from another station positioned in a service area, and the received link margin data is compared with preset link margin data for control of the transmission power in the WLAN.

Abstract: A method and apparatus save power in a multimode wireless terminal having plural communication modems for supporting different communication systems. The multimode wireless terminal performs its basic functions of reception and transmission, while only one of the communication modems is turned on and the others are turned off so as to reduce power consumption. This results in extension of the utilization time of the multimode wireless terminal.

Abstract: An Orthogonal Frequency Division Multiple Access (OFDMA)-based mobile terminal and a method for measuring reception channel quality for use in the OFDMA-based mobile terminal are provided. A mobile terminal includes a transceiver for exchanging frequency signal with a base station and a control unit for calculating a Carrier-to-Interference and Noise Ratio (CINR) of a data subcarrier with a second preamble of a downlink frame received through the transceiver. A mobile terminal and a method for measuring a channel quality for the mobile terminal enable calculating a CINR of data subcarriers using information contained in a second preamble that is provided in a downlink frame proposed, whereby the mobile terminal can provide a base station with more reliable channel quality information, resulting in avoiding degradation of communication quality and improvement of system throughput.

Abstract: A text messaging apparatus and method for a mobile terminal includes: transmitting a text message having a context identification number from a first mobile terminal to a second mobile terminal; receiving a response text message from the second mobile terminal in response to the text message, the response text message having a context identification number identical to that of the first text message; extracting the context identification number from the response text message; retrieving text messages linked to the context identification number; and displaying the response text message together with the retrieved text messages.

Abstract: An apparatus and method for estimating frequency offset in a mobile terminal are provided. The method includes collecting information on the locations of a base station and the mobile terminal; calculating a moving speed of the mobile terminal using the collected location information; and estimating the frequency offset using the calculated moving speed.

Abstract: An inter-symbol interference cancellation method for an orthogonal frequency division multiple access system is provided. The inter-symbol interference cancellation method includes transmitting, at a base station, an OFDMA symbol having a first half part and a second half part divided in time; receiving, at a mobile station, the OFDMA symbol; and restoring the OFDMA symbol by repeating one of the first half part or the second half part. The ISI cancellation method for an OFDMA communication system of the present invention uses an OFDMA symbol having two identical parts sequentially arranged in time, whereby it is possible to recover a transmitted OFDMA symbol if at least one of the two parts is successfully received.