Abstract: Disclosed is a handover method in a wireless portable Internet system. When a mobile subscriber station is in a drop state, a ranging request message including an identifier of a previous base station and a string generated by encoding the ranging request message using an authentication key of the previous base station is sent to a target base station. The target base station requests the previous base station to execute handover of the mobile subscriber station using the identifier of the previous base station included in the ranging request message. The previous base station carries out message authentication using the encoded string received from the target base station, and when the authentication is successful, transmits information about the mobile subscriber station that is required for handover to the target base station. Accordingly, a ceaseless service session can be provided even in the drop state.

Abstract: The present invention relates to a scheduling apparatus and a method thereof in an HPi system. A scheduling algorithm is applied appropriate to a characteristic of each multimedia service (e.g., real-time service, non real-time service, best-effort service, etc.) and a transmission order of the IP packets transmitted from a network is determined such that a transmit wait queue is generated. Radio resource allocation is performed in accordance with the order of the data items queued in the transmit wait queue, the size of transmittable data is determined such that a PDU is generated. In addition, frame data formed of bursts of PDUs is generated and transmitted to a physical layer. Therefore, a scheduling algorithm can be applied appropriate to characteristics of each multimedia service. In addition, packet scheduling is performed in two steps in order to schedule traffic corresponding to radio frames such that packets can be efficiently processed.

Abstract: The present invention relates to a subscriber station security-related parameter negotiation method in a wireless portable Internet system. The subscriber station security-related parameter negotiation method includes security-related parameters in transmitting/receiving basic capability negotiation request messages and basic capability negotiation response messages such that the subscriber station and the base station negotiate the subscriber station security-related parameters. The security-related parameters include an authorization policy support subfield used to negotiate an authorization policy between the subscriber station and the base station, and message authentication code mode subfields used to negotiate a message authentication code mode.

Abstract: Disclosed are a method for requesting, generating and distributing a service-specific traffic encryption key in a wireless portable Internet system, an apparatus for the same, and a protocol configuration method for the same. In the present invention, a subscriber station sends a Key Request message for requesting a service-specific traffic encryption key to the base station using a PKM-REQ MAC message, and a base station analyzes the Key Request message to generate the requested service-specific traffic encryption key. Subsequently, the base station sends a Key Reply message, including the generated service-specific traffic encryption key, to the subscriber station using a PKM-RSP MAC message. If the base station fails to generate the key, the base station sends a Key Reject message, including a reason for the failure, to the subscriber station.

Abstract: When a base station of a time division duplex based mobile communication system receives an initial ranging request signal from a subscriber station, the base station generates initial ranging information including delay time information to the subscriber station, and receives uplink data delayed and transmitted using a delay time from the subscriber station. Also, when the subscriber station transmits an initial ranging request signal to the base station and receives initial ranging information including delay time information from the base station, the subscriber station establishes a transmission parameter value by using the transmission parameter value included in the initial ranging information and transmits uplink data by using the established delay time.

Abstract: Disclosed are a terminal of an OFDMA-TDMA wireless Internet system capable of reducing transmission delay time while securing QoS for uplink data and a packet transmission method. A MAC layer of the terminal is divided into a MAC software part and a MAC hardware part to control priorities of data packets at a high level and low level. The high level priority controller carries out various fine control operations according to a QoS policy and the low level priority controller performs mechanical control operations based on a predetermined simple fixed priority policy.

Abstract: Disclosed is a method for allocating and accessing downlink resources in the OFDMA communication system. In the resource allocation method, bursts having the same modulation and channel encoding level are arranged in a predetermined temporal order on a physical layer. Information on the allocated unit resources is included in a common control block and is transmitted to a subscriber station, and the subscriber station then detects a number of the allocated unit resources to thus check the range of bursts to be received by the subscriber station. Therefore, power consumption by the subscriber station is reduced and signaling overheads of the common control information and unneeded residual resources are decreased.

Abstract: A method and authentication apparatus for sharing information for identifying an Authorization Key (AK) with a Base Station (BS) in a subscriber station are provided. The method includes, in the subscriber station, sharing a root key with the BS by performing an authentication with the BS, sharing an AK derived from the root key with the BS, sharing an AK sequence number of the AK with the BS, and sharing an AK Identifier (AKID) of the AK with the BS. The AK sequence number is generated by a sequence number of the root key. The AKID is generated by a parameter including the AK, the AK sequence number, a Medium Access Control (MAC) address of the subscriber station, and a BS Identifier (BSID) of the BS.

Abstract: The subscriber station of claim 15, wherein the uplink data includes data to be transmitted, and a header having information on the data and the subscriber, and the uplink data generator adds the subheader includDisclosed is a method and device for requesting and reporting channel quality information in a mobile communication system. An uplink radio resource for a subscriber station having data to transmit is allocated and a CQI indicator for requesting channel quality information is added to the allocation information to be transmitted to a subscriber station. The subscriber station having received the uplink radio resource allocation information generates channel quality information by measuring the radio channel quality for communication with the base station according to existence of the indicator and transmits desired uplink data having the generated channel quality information to the base station.

Abstract: The present invention relates to a digital clipping method for reducing a high peak-to-average power ratio (PAPR) of a transmission signal in a transmitter of an orthogonal frequency division multiplexing access (OFDMA) system. In the method, a) the transmission signal to be digitally clipped is divided into real and imaginary parts, b) magnitudes of the real and imaginary part signals are divided into a plurality clipping levels, and c) the transmission signal is respectively clipped by comparing the real and imaginary part signals with the plurality of clipping levels while allowing phase errors. In c), a plurality of comparators is used to respectively compare the real and imaginary parts of the complex number transmission signal with the plurality of clipping levels.

Abstract: A method for requesting and reporting channel quality information (CQI) in a wireless portable Internet system is disclosed. Timing of a channel quality information request by a base station is determined, existence of an automatic repeat request acknowledgment (ARQ_ACK) message of downlink data is determined on requesting the channel quality information from the subscriber station, the automatic repeat request acknowledgment message and the radio resource for the channel quality report to the subscriber station is allocated, the automatic repeat request acknowledgment message and the channel quality report information is received, and a modulating and coding level of downlink data is determined by extracting the channel quality report information form the automatic repeat request acknowledgment message.

Abstract: The present invention relates to a method for timing acquisition and carrier frequency offset estimation of an OFDM communication system and an apparatus using the same. For this purpose the present invention provides a method for calculating at least one auto-correlation and calculating an observation value by performing a sliding sum on the at least one auto-correlation, and calculating a peak point of an absolute value of the observation as frame timing. In addition, the present invention provides a method for generating a third OFDM symbol that is generated by delaying a second OFDM symbol, calculating an observation value through the second and third OFDM symbols, and calculating a phase difference from a result of multiplication of the observation value and a conjugate complex value of the observation value such that a carrier frequency offset can be estimated.

Abstract: Disclosed herein is a base station that extracts a ranging channel signal from a received signal partially correlates each of a plurality of ranging channel signals and each of ranging codes according to ranging modes, and selects a ranging channel signal greater than a first threshold value, the plurality of ranging channel signals being signals according to plurality of time delays of a ranging channel signal. In addition, the base station correlates each of the selected ranging channel signal and each of corresponding ranging code, selects a ranging channel signal having the maximum correlation value, and estimates receiving power by using a time delay corresponding to the selected ranging channel signal.

Abstract: An automatic gain control apparatus and method of a mobile station in an OFDM system are provided. The method includes identifying a preamble section and a data symbol section in a received frame signal; when a current symbol is the preamble section, measuring a power value of a preamble signal, comparing the measured power value of the preamble signal and a threshold value, and amplifying the received frame signal based on a predetermined gain; when a data symbol section includes a pilot carrier, measuring an average power value of the pilot carrier in the data symbol, comparing the measured average power value and the threshold value, and amplifying the received frame signal based on a predetermined gain; and when the data symbol section includes no pilot carrier, maintaining an existing gain, or performing an automatic gain control operation according to a gain estimated by using the pilot carrier during the data symbol section.

Abstract: A ranging method of an access terminal comprising receiving and analyzing UL-MAP/DL-MAP; selecting a given uplink sub-channel number and a symbol number from the UL_MAP when a ranging event is generated; requesting a ranging process by transmitting a CDMA code; receiving a ranging response message broadcasted from the access point; extracting a CDMA code, a sub-channel number, and a symbol number from the received ranging response message, comparing the extracted result and the stored ranging parameters, and adjusting transmission power, timing, and frequency offset on the basis of the extracted result or discarding the ranging response message; and terminating a ranging response message receipt operation.

Abstract: In a signal monitoring apparatus of a base station of a communication system having multiple antennas, a transmitting/receiving unit transmits a plurality of transmit signals by using the multiple antennas or processes a plurality of receive signals received through the multiple antennas. A radio frequency calibration unit calibrates the transmit signals transmitted through the multiple antennas, and processes at least one target transmit signal among the plurality of transmit signals so as to monitor the at least one target transmit signal. A signal monitoring unit receives at least one first signal or at least one second signal, and transmits the at least one first signal or the at least one second signal to user equipment. The at least one first signal is a signal processed from at least one target receive signal among the plurality of receive signals, and the at least one second signal is a signal processed from the at least one target transmit signal by controlling the radio frequency calibration unit.

Abstract: An apparatus and method for canceling a DC offset efficiently removes the DC offset by calculating the DC offset after acquiring synchronization in a terminal receiver used for an orthogonal frequency division multiplexing system. The apparatus for canceling the DC offset includes an adding/averaging unit (130), an accumulator (140), a synchronization determiner (150), and a pulse density modulation signal generator (160). The adding and averaging the added input data signals over one frame. The accumulator (140) outputs a DC offset control value by successively accumulating the DX offsets calculated from the adding and averaging unit. The synchronization determiner (150) determines whether to output the DC offset control value provided by the accumulator (140) based on synchronization information. The pulse density modulation signal generator (160) generates a digital pulse density modulation signal based on a representative value provided by the synchronization determiner (150).

Abstract: The present invention relates to a method for managing a group traffic encryption key (GTEK) in a wireless portable Internet system. In the method, for higher security of a group traffic service such as a multicast service, a broadcast service, and a multicast-broadcast service (MBS), a base station periodically generates and distributes a GTEK to a subscriber station served with the group traffic service. A lifetime of a group key encryption key (GKEK) used for encrypting a GTEK is set greater than that of the GTEK. That is, the GKEK is updated once while the GTEK is updated several times. According to the present invention, security for the group traffic service is increased while reducing radio resource consumption.

Abstract: Upper level protocol message transmitting method and apparatus are provided based on a new management message to be used in a portable Internet system. When a base station receives the upper level protocol message to be broadcast, it includes the same in the management message and transmits the included message to all the mobile terminals of a cell, and thus, the total number of the transmissions is decreased, thereby increasing a wireless efficiency.

Abstract: Disclosed is a method for a preamble-based bandwidth request. The present invention enables state control of a subscriber station based on the latest environment in a portable Internet system requesting a bandwidth using a preamble, and hence allows a subsequent more efficient transmission of user data. In addition, the present invention provides information for discrimination of the subscriber station transmitting the preamble as well as state control information of the subscriber station to the base station during a preamble-based bandwidth request by the subscriber station, and enables the base station to discriminate the subscriber station in the next time of data transmission with the subscriber station.