Abstract: An apparatus and method for supporting a cooperative handover in a broadband wireless communication system. A method for operating a mobile station (MS) for a cooperative handover in a broadband wireless communication system includes determining a handover to a target BS and omitting a CID update process of the MS during the handover process to the target BS, wherein the CID of the MS is shared beforehand between a serving BS and the target BS.

Abstract: An apparatus and a method manage power of a small base station. Whether a notify message indicating that a subscribed terminal enters a macro base station that includes an off-small base station is received from the macro base station under a closed access mode is determined. When the notify message is received, whether a service is providable to the subscribed terminal is determined. When the service is providable to the subscribed terminal, the small base station is turned on. During the closed access mode or when a load of a macro cell is large during an open access mode, when a terminal that should be serviced does not exist in the neighborhood of a small base station, an interference and power consumption unnecessarily generated may be reduced by turning off the small base station.

Abstract: A method and system for managing an inactive interval of a Base Station (BS) are provided, in which the BS transmits a preferred Low-Duty Mode (LDM) pattern to a coordination server that manages LDM patterns of BSs, receives an LDM pattern from the coordination server, the LDM pattern being determined for the BS by the coordination server, taking into account the preferred LDM pattern and LDM patterns of neighbor BSs, and operates in an active interval and an inactive interval according to the received LDM pattern.

Abstract: An apparatus and method for supporting a cooperative handover in a broadband wireless communication system. A method for operating a mobile station (MS) for a cooperative handover in a broadband wireless communication system includes determining a handover to a target BS and omitting a CID update process of the MS during the handover process to the target BS, wherein the CID of the MS is shared beforehand between a serving BS and the target BS.

Abstract: An apparatus and a method for controlling an Energy Saving (ES) mode at a base station of a wireless communication system are provided. The method for controlling the ES mode includes predicting a traffic load of a next time, determining whether to enter the ES mode using the predicted traffic load, when determining to enter the ES mode, determining reliability of the predicted traffic load, and when the predicted traffic load is reliable, operating in the ES mode.

Abstract: An apparatus and a method manage power of a small base station. Whether a notify message indicating that a subscribed terminal enters a macro base station that includes an off-small base station is received from the macro base station under a closed access mode is determined. When the notify message is received, whether a service is providable to the subscribed terminal is determined. When the service is providable to the subscribed terminal, the small base station is turned on. During the closed access mode or when a load of a macro cell is large during an open access mode, when a terminal that should be serviced does not exist in the neighborhood of a small base station, an interference and power consumption unnecessarily generated may be reduced by turning off the small base station.

Abstract: An apparatus and a method for selectively retransmitting data according to a channel state in a wireless communication system are provided. The method includes determining retransmission information of a receiver from feedback information received from the receiver, determining a retransmission scheme for the receiver using the retransmission information of the receiver, and performing a retransmission process with the receiver according to the determined retransmission scheme. In a good channel state, the data is retransmitted using the retransmission scheme to thereby enhance the reliability of the data delivery and the reception performance. In a bad channel state, the data is not retransmitted to thereby reduce a waste of resources in the data retransmission.

Abstract: A method and system for managing an inactive interval of a Base Station (BS) are provided, in which the BS transmits a preferred Low-Duty Mode (LDM) pattern to a coordination server that manages LDM patterns of BSs, receives an LDM pattern from the coordination server, the LDM pattern being determined for the BS by the coordination server, taking into account the preferred LDM pattern and LDM patterns of neighbor BSs, and operates in an active interval and an inactive interval according to the received LDM pattern.

Abstract: A method for performing a handover by a subscriber station (SS) in a broadband wireless communication system including a serving base station (BS) communicating with the SS, and at least one neighbor BS neighboring the serving BS. The SS receives downlink signals from the serving BS and the neighbor BS; measures an arrival time difference between the downlink signal received from the serving BS and the downlink signal received from the neighbor BS; and transmits the measured arrival time difference to the serving BS.

Abstract: An apparatus and method for controlling operation states of a medium access control layer by a mobile subscriber station (MSS) in a broadband wireless access communication system. The method includes: state-transitioning into a sleep state or an idle state when there is no data transmitted between a base station and the MSS during a predetermined first time interval in an awake state; and performing a location change in the idle state when the mobile subscriber station moves from a first paging zone to a second paging zone, and state-transiting into the awake state when the mobile subscriber station in the idle state detects a paging to the mobile subscriber station. The method minimizes power consumption and maximizes efficiency in use of radio resources.

Abstract: An apparatus and a method for selectively retransmitting data according to a channel state in a wireless communication system are provided. The method includes determining retransmission information of a receiver from feedback information received from the receiver, determining a retransmission scheme for the receiver using the retransmission information of the receiver, and performing a retransmission process with the receiver according to the determined retransmission scheme. In a good channel state, the data is retransmitted using the retransmission scheme to thereby enhance the reliability of the data delivery and the reception performance. In a bad channel state, the data is not retransmitted to thereby reduce a waste of resources in the data retransmission.

Abstract: A method for receiving common control information from a base station to a plurality of subscriber stations in a wireless communication is provided. The common control information includes first information that all of the plurality of subscriber stations commonly receive and second information that the plurality of subscriber stations separately receive according to channel states of the plurality of subscriber stations. The first information is decoded by demodulating and decoding the common control information according to a modulation scheme and a coding scheme corresponding to an MCS (Modulation and Coding Scheme) level applied to the first information in the base station. The second information is decoded by demodulating and decoding the common control information according to a modulation scheme and a coding scheme corresponding to MCS levels applied to the second information in the base station.

Abstract: A method for transmitting common control information from a Base Station (BS) to an Mobile Station (MS) in a wireless mobile communication system is provided, in which the BS generates a MAP Information Element (IE) using common control information to be transmitted to the MS, the common control information being resource allocation information and control information, converts the MAP IE to a MAP IE message, applies an Modulation and Coding Scheme (MCS) level corresponding to the channel status of the MS, and transmits the MAP IE message with data to the MS.

Abstract: A mobile communication system using an orthogonal frequency division multiplexing (OFDM)/orthogonal frequency division multiple access (OFDMA) scheme. The method for assigning ranging codes in the OFDM/OFDMA communication system includes classifying rangings between a base station and a mobile subscriber station (MSS) of the OFDM/OFDMA communication system into an initial ranging, a periodic ranging, a bandwidth request ranging, and a handover ranging. A first number of ranging codes used for the rangings are created and a second number of ranging codes selected from the first number of ranging codes are assigned as handover ranging codes used for the handover ranging.

Abstract: A method is provided a ranging method in a communication system. The method includes measuring the state of a channel between an Mobile Station (MS) and a Base Station (BS) when recognizing a need for ranging with the BS after acquiring synchronization with the BS; setting a channel state information code corresponding to the measured channel state; and transmitting a ranging code message including the set channel state information code to the BS to perform the ranging.

Abstract: A method and apparatus for dynamically allocating and releasing a Channel Quality Information CHannel (CQICH) to and from a Mobile Station (MS) in a Base Station (BS) communicating with a plurality of MSs on a common radio channel in a wireless communication system are provided, in which the BS determines whether the MS is under a first group, when a CQICH is to be allocated to the MS, determines whether any data transmission has occurred for a CQICH allocation period preset for the first group and counted from a reallocation time, if the MS is under the first group, and groups the MS to a second group and reallocates a CQICH to the MS, the second group having a lower priority level than the first group, if no data transmission has occurred for the CQICH allocation period.

Abstract: An apparatus and a method for scheduling packets in a wireless communication system. The method includes the steps of dividing a transmission deadline of the packets for a destination into a first deadline, which is an end point of the transmission deadline, and a second deadline, which is allocated before the first deadline in consideration of a transmission channel state and a quality of service (QoS) of the packets, scheduling and transmitting the packets according to transmission priorities thereof, which are determined by a predetermined scheme, before the second deadline, and scheduling and transmitting the packets according to an approaching order of the packets with respect to the first deadline, if the packets have passed through the second deadline.

Abstract: A system for performing network re-entry upon handover of a mobile subscriber station (MSS) to a target base station (BS). Upon detecting handover of the MSS, the target BS detects network re-entry information necessary for network re-entry of the MSS from the serving BS, and transmits, to the MSS, the detected network re-entry information, information on an acknowledge (ACK) channel through which the MSS will respond that it has received the network re-entry information upon receipt of the network re-entry information, and ACK request information requesting the MSS to respond whether it has received the network re-entry information. The MSS receives the ACK channel information, and thereafter receives, from the target BS, the network re-entry information and the ACK request information, and a response transmits to the target BS which indicates that it has received the network re-entry information, through the ACK channel in response to the ACK request information.

Abstract: A method for performing a handover by a subscriber station (SS) in a broadband wireless communication system including a serving base station (BS) communicating with the SS, and at least one neighbor BS neighboring the serving BS. The SS receives downlink signals from the serving BS and the neighbor BS; measures an arrival time difference between the downlink signal received from the serving BS and the downlink signal received from the neighbor BS; and transmits the measured arrival time difference to the serving BS.

Abstract: An apparatus and method for controlling operation states of a medium access control layer by a mobile subscriber station (MSS) in a broadband wireless access communication system. The method includes: state-transitioning into a sleep state or an idle state when there is no data transmitted between a base station and the MSS during a predetermined first time interval in an awake state; and performing a location change in the idle state when the mobile subscriber station moves from a first paging zone to a second paging zone, and state-transiting into the awake state when the mobile subscriber station in the idle state detects a paging to the mobile subscriber station. The method minimizes power consumption and maximizes efficiency in use of radio resources.