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: 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: 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: 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 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: The present invention relates to a multi-mode communication system and a method thereof. The multi-mode communication system uses a first mode among a plurality communication modes for accessing a first mobility control entity (MCE) among a plurality of MCEs, and communicates data with the first MCE. The multi-mode communication system receives a paging request that has been transmitted from a multi-mode control entity (MMCE) for accessing a second MCE from the first MCE and analyzes the paging request, and puts the first mode into a sleep mode and a second mode for accessing the second MCE into an awake mode based on the analysis. Subsequently, multi-mode UE accesses the second MCE by using the second mode in the awake mode. According to the present invention, an MMCE for multi-mode control is provided to integrate and manage an idle state for each access mode of multi-mode user equipment, thereby minimizing power consumption due to access of the multi-mode UE to a radio access system.

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: 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.

Abstract: The present invention relates to apparatus and method for providing a mobile instant messaging service. The apparatus includes a buddy status managing unit for recording and managing a status information of at least one mobile messenger subscriber; a buddy list managing unit cooperating with the buddy status managing unit for managing a buddy list of the mobile messenger subscriber based on a telephone number, and providing the buddy list to the mobile messenger subscriber; and a chatting service unit for providing a chatting service between the mobile messenger subscriber and a buddy selected by the mobile messenger subscriber in the buddy list provided to the mobile messenger subscriber by the buddy list managing unit.

Abstract: Disclosed are a subscriber station authentication method, a protocol configuration method, and a device thereof in a wireless portable Internet system. In the subscriber station authentication method, an authentication mode between a subscriber station (10) and a base station (20) is negotiated, and the authentication mode is negotiated by the base station (20) according to the authentication mode negotiation. The authentication modes include an authentication mode based on the IEEE 802.16 privacy standard protocol and an authentication mode based on the standardized authentication protocol of the upper layer. Authentication is performed by the base station (10) in the case of the authentication mode based on the IEEE 802.16 privacy standard protocol, and the authentication is performed through message transmission using a diameter protocol between a base station (10) and an authentication server (40) in the case of the authentication mode based on the standardized authentication protocol of the upper layer.

Abstract: A subcarrier allocating apparatus allocating data to be transmitted to a plurality of orthogonal subcarriers in an orthogonal frequency division multiplexing (OFDM) system is provided. The apparatus includes a logical index generator generating a logical index for allocating a data subcarrier to a physical index, the logical index being included with only data subcarriers and the physical index indicating a location of a substantial subcarrier within a symbol, an intermediate index converter converting the logical index into an intermediate index by performing a given operation on the generated logical index and a pilot location constant, and a physical index converter converting the intermediate index into a physical index based on the number of data subcarriers on the left and right sides of a null subcarrier for insertion of a guard interval formed by the null subcarrier.

Abstract: The present invention relates to a security association negotiation method of extensible authentication protocol (EAP) for authenticating a subscriber station user in a wireless portable Internet system. An exemplary security association negotiation method using a user authentication in a wireless portable Internet system according to an embodiment of the present invention includes following steps. A base station generates an authentication key for authenticating a user of a subscriber station. The base station receives a security association capability request message including security association capability information of the subscriber station from the subscriber station after generating the authentication key. The base station determines whether the base station is able to accept a security association capability of the subscriber station included in the security association capability request message.

Abstract: A sphere decoder sets a Euclidean distance between a lattice vector obtained by using an MMSE or ZF estimate and a received signal as an initial radius, further reduces the initial radius, and searches lattices points included inside a hypersphere with the further reduced initial radius. In addition, one lattice vector having a minimum Euclidean distance is output. One dimension is selected to reduce an initial radius, and estimates in other dimensions are kept fixed, excluding the selected dimension. Then candidate lattice points are searched in the selected dimension, excluding a current estimate, such that a minimum Euclidean distance and a lattice point estimate corresponding to the minimum Euclidean distance are obtained. The initial radius is updated by the minimum Euclidean distance, and a final lattice vector is constructed by combining a lattice point estimate corresponding to the initial radius and the lattice point estimates in other dimensions.

Abstract: A receiver according to an exemplary embodiment of the present invention receives a transmitted signal, converts the signal to a predetermined symbol, and estimates channel information including a channel gain of a channel of the transmitted signal. In addition, the receiver generates an intermediate processing value for decoding the signal based on the estimated channel information and the symbol, and normalizes the intermediate processing value to the channel gain to generate a reference value. The generated reference value is used for a soft-decision value for decoding the signal. In addition, when the signal is decoded by using a hard-decision value, a constellation point value that is closest to the reference values is generated and set as the hard-decision value.

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 and apparatus of an idle state of a mobile terminal. One embodiment relates to a method and apparatus that display message in an idle state of a mobile terminal. Another embodiment relates to a method and apparatus for driving an application for an idle state in a mobile terminal. A further embodiment relates to a method and apparatus for providing idle state contents to a mobile terminal.

Abstract: In a decoding apparatus in a portable Internet terminal, a channel encoded symbol received from a transmitter is decoded by one of a chase-combining scheme and a code-combining scheme selected based on an ID value of the subpacket indicating a start position of the symbol. In this case, the chase-combining scheme is partly used for the encoded symbol of the information bit. With such a mode, decoding can be performed at a low code rate.