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: 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: 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 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: 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: 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: 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: 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 cell search device using an appropriate preamble for a downlink of a cellular system using an orthogonal frequency division multiplexing access (OFDMA) scheme and a method thereof is disclosed.

Abstract: In a method for allocating transmission power in a communication system including multiple antennas, a plurality of subcarriers are grouped by a plurality of groups, and each group includes at least one subcarrier. A transmission power weight and an antenna transmission vector are calculated for each group by using channel information, a transmission power for each group of each antenna is calculated by using the transmission power weight and the antenna transmission vector for each group, and transmission signals are transmitted through the multiple antennas after determining which signals need to be transmitted from the multiple antennas by using the transmission power.

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.

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: A ranging method of an access terminal that requests a ranging to an access point through a wireless network and performs the ranging, the ranging method including a) initializing a ranging period, b) setting a timer with the ranging period and starting the timer, c) requesting a ranging by transmitting a given ranging code to the access point based on radio resource allocation information provided by the access point, d) receiving a ranging response message from the access point, and controlling transmission power, timing, and frequency offset of an access terminal according to transmission parameters included in the received ranging response message, e) estimating a downlink channel condition through which a signal from the access point is transmitted, f) resetting the ranging period according to the estimated downlink channel condition, and g) iteratively performing b) to f) according to the reset ranging period.

Abstract: A device and a method for estimating a Carrier to Interference-plus-Noise Ratio (CINR) in an Orthogonal Frequency Division Multiplexing (OFDM) system are provided. The CINR estimating method includes receiving a preamble symbol and transmitting subcarrier transmitted from a base station, calculating an interference power and noise power using the preamble symbol and transmitting subcarrier, calculating a receive power used for the base station to transmit a preamble and data symbol, estimating a preamble CINR value using an interference power, a noise power, and a receive power, calculating the noise power from a subcarrier not transmitting a preamble, and calculating an average CINR of data subcarriers using the preamble CINR value and the noise power. Accordingly, a precise CINR can be estimated using a preamble when the preamble power is amplified in comparison with the data symbol power.