Abstract: A method and apparatus for transmitting uplink acknowledge information (ACK) in a communication system using an orthogonal frequency division multiple access (OFDMA) scheme. The method includes receiving a data bit for the uplink ACK; outputting codewords corresponding to the data bit; performing quadrature phase shift keying (QPSK) modulation on symbols for ACK vector indexes corresponding to the codewords for the received data bit; performing inverse fast Fourier transform (IFFT) on a transmission signal having subcarrier clusters to which the modulated transmission symbols are allocated; and transmitting the IFFT-processed transmission signal.

Abstract: A method for measuring channel quality of a Base Station (BS) by using a ranging signal in a broadband wireless communication system is provided. The method includes estimating a time offset of the ranging signal received through a ranging channel, measuring channel quality by using the ranging signal including the time offset, determining whether distortion occurs in the measured channel quality by using the time offset, and compensating for distortion of the measured channel quality.

Abstract: A method of allocating bursts in a broadband wireless communication system is provided. The method includes dividing a downlink period into a plurality of regions according to a burst property, calculating a residual symbol axis size and a residual subchannel axis size of a first region conforming to two-dimensional allocation among the plurality of regions, allocating bursts to be allocated to the first region in a descending order, wherein the bursts are respectively allocated in a rectangular shape having a length corresponding to the number of residual symbols along a time axis or in a rectangular shape having a length corresponding to the number of residual subchannels along a frequency axis, and allocating bursts to be allocated to at least one region conforming to one-dimensional allocation among the plurality of regions to the at least one region conforming to one-dimensional allocation according to a scheduling priority.

Abstract: A resource allocation method of a Base Station (BS) in a wireless communication system is provided. The method includes estimating a size of a MAP message, and evaluating a size of an available burst allocation region according to the estimated size of the MAP message and allocating bursts in the evaluated-sized burst allocation region. Accordingly, when a DownLink (DL) subframe is used by being divining into a plurality of regions according to a burst characteristic, a throughput can be improved without waste of resources by estimating a resource amount occupied by a MAP message in the DL subframe.

Abstract: Disclosed is a method and an apparatus for generating a preamble sequence for an adaptive antenna system supporting a space division multiple access in an OFDMA communication system. Particularly, disclosed is a method for forming a preamble sequence identifying each of a plurality of mobile subscriber stations located within a cell or a sector of a communication system which includes a plurality of sub-channels assigned to the mobile subscriber stations, each of the sub-channels including a plurality of bins each of which includes n number of contiguous subcarriers in a frequency domain, the preamble sequence being transmitted before each of the sub-channels is transmitted, the method including the step of generating a preamble sequence by phase-shifting a predetermined sequence according to a predetermined phase shift sequence in the frequency domain.

Abstract: A digital predistortion apparatus is provided for predistorting a nonlinear characteristic caused by a wideband power amplifier that amplifies a input signal. The digital predistortion apparatus includes a predistorter, connected to the power amplifier via a digital-to-analog converter (DAC) and a frequency up-converter, for receiving the input signal and compensating for the nonlinear characteristic using a look-up table that depends upon a change in output power of the power amplifier. The digital predistortion apparatus further includes look-up table (LUT) updating block for adaptively updating the look-up table by comparing a feedback signal output from the power amplifier, connected thereto via an analog-to-digital converter (ADC), with the input signal output from the predistorter.

Abstract: An apparatus and method for transmitting uplink fast feedback information using a fast feedback channel in an orthogonal frequency division multiple access (OFDMA) communication system. A channel encoder selects information data for uplink fast feedback information, and determines a codeword from a pre-determined codeword set corresponding to the selected information data. A non-coherent modulator chooses transmission symbols by performing orthogonal modulation according to the determined codeword based on a predetermined modulation pattern, and maps the chosen symbols into sub-carriers. An inverse fast Fourier transform (IFFT) block performs an inverse fast Fourier transform (IFFT) on the mapped symbols and transmits the IFFT processed mapped symbols.

Abstract: An apparatus and method for estimating a Signal to Interference plus Noise Ratio (SINR) in a wireless communication system are provided. The method includes processing a received signal by Orthogonal Frequency Division Multiplexing (OFDM) demodulation to convert the received signal into frequency-domain data, selecting ranging data from the frequency-domain data, multiplying the selected ranging data by a ranging code to perform code demodulation, calculating at least one norm value and at least one coherent norm value by bundle for the code-demodulated data and estimating an SINR using the calculated at least one norm value and at least one coherent norm value.

Abstract: A method and apparatus are provided for calculating a log-likelihood ratio (LLR) for decoding in a receiver for a mobile communication system, wherein the method and apparatus determine selection bits for distinguishing four quadrants in a constellation representing signal points of transmission symbols, determine domain bits for distinguishing the signal points in each domain of the four quadrants according to a modulation order of the transmission symbols, repeat an operation of dividing a received signal into a real component and an imaginary component according to the number of determined domain bits, calculate and origin-shift absolute values of the real component and the imaginary component, and calculate LLRs for the selection bits. Further, the method and apparatus can subsequently calculate LLRs for corresponding domain bits each time the origin-shifted received signal is received.

Abstract: An apparatus and a method for estimating a channel using sliding windows in a broadband wireless communication system are provided. The apparatus includes an estimator, a first calculator, a second calculator, and a third calculator. The estimator estimates a speed of travel. The first calculator calculates a time correlation values using the estimated speed. The second calculator calculates weight factors using the time correlation values. The third calculator calculates a channel estimation value by multiplying corresponding pilot symbols by the weight factors and equalizing the pilot symbols.

Abstract: An apparatus and a method for interference cancellation in a broadband wireless communication system are provided. A receiving apparatus includes an estimator, a channel compensator, and a demodulator. The estimator estimates channels of a desired signal and at least one interference signal, estimates noise, calculates a mean interference power of each interference signal, and calculates a mean noise power. The channel compensator channel-compensates burst data. The demodulator calculates a noise variance value by adding the mean noise power to the at least one mean interference power and creates Log Likelihood Ratio (LLR) by demodulating the channel-compensated data.

Abstract: A method for generating a burst in a communication system. The method includes estimating a first allocable PDU according to scheduling priority; generating a first burst in which the first PDU is to be included; and determining whether a total size of bursts to be allocated to a downlink subframe including the generated first burst is less than a maximum size of bursts allocable to the downlink subframe.

Abstract: Disclosed is a method for controlling transmission power to be allocated to sub-carrier signals in a cellular communication system capable of dividing a frequency band into a plurality of sub-carrier bands and multiplexing the sub-carrier signals of the sub-carrier bands based on multiple frequency reuse factors.

Abstract: Provided is an outer loop power control apparatus and method for a signal transmitter in a communication system. The outer loop power control method includes determining a first setpoint of a kth frame according to whether or not an error occurs in a (k?1)th frame, updating a second setpoint of the kth frame with the first setpoint of the kth frame if a difference value between the first setpoint of the kth frame and a second setpoint of the (k?1)th frame is greater than a first reference value, and transmitting a transmit power control message to a signal receiver at the kth frame if the difference value between first setpoint of the kth frame and the second setpoint of the (k?1)th frame is greater than a second reference value.

Abstract: A cyclic delay diversity (CDD) technique in a multiple-antenna broadband wireless communication system is provided. An apparatus in the multiple-antenna broadband wireless communication system includes: a controller for selecting at least one sub-carrier to which CDD is applied; at least one shifter for shifting a phase of a signal mapped to the at least one selected sub-carrier; and an operator for converting the signal, which is mapped to the at least one selected sub-carrier and whose phase is shifted, and other signals mapped to the remaining sub-carriers into time-domain signals.

Abstract: Disclosed is a method for receiving a signal by a receiver in a communication system, the method includes receiving a signal; estimating a first noise value by using a reference signal included in the received signal; estimating a second noise value by using at least one subcarrier which has been unused for a transmission of data and the reference signal; and when a difference between the estimated first noise value and the estimated second noise value is greater than a threshold value, demodulating the data by using an interference removal algorithm.

Abstract: A preamble generation method and apparatus are provided for improving transmit diversity by changing a preamble structure in a broadband wireless communication system using multiple antennas based on a multiple input multiple output (MIMO) scheme. First pilot tones associated with different antennas are selected. The first pilot tones are multiplied by different first Walsh codes. Second pilot tones associated with the same antenna are sequentially selected along a frequency axis. The second pilot tones are multiplied by a second Walsh code. Preambles are generated by assigning, to at least two symbol durations, output signals multiplied by the first and second Walsh codes. Consecutive pilot tones during each of the at least two symbol durations are spaced by one pilot tone, and code streams of the first and second Walsh codes are alternately multiplied by the pilot tones. The preamble structure has orthogonality between the antennas using frequency, time and code domains.

Abstract: A method and apparatus for estimating a signal delay between a transmission signal which is to be processed in a predetermined communication device of a mobile communication system, and a feedback signal. Each of the transmission and feedback signals is sampled for a predetermined length, and signal power magnitude values are computed in a sample unit and are stored in first and second memory blocks. Mean squared error (MSE) values are computed from a plurality of samples, while a start sample position of one block is shifted on a basis of a start sample position of the other block. A sample delay value is estimated from a start sample position of the one block with a smallest MSE value such that a sample delay between a transmission signal and a feedback signal is closely estimated regardless of a frequency allocation (FA) value.

Abstract: A nano-size lead-free piezoceramic powder and a method of mechanochemically synthesizing the same are provided. The nano-size lead-free piezoceramic powder can have a basic component of (KxNa1-x)NbO3, where x ranges from 0 to 1. A weight ratio of a milling ball to a raw powder can be set, and then the milling ball and the raw powder can be provided into a milling container at the set ratio. Nano-size lead-free piezoceramic powder can be mechanochemically synthesized using a high-energy ball mill device.

Abstract: A method and apparatus for estimating noise in a signal reception apparatus of a communication system are provided. The method and apparatus include a channel estimator for estimating a channel for a signal vector received from multiple cells, and a noise estimator for estimating noise using the received signal vector, a number of the cells, a number of pilot subcarriers used for the channel estimation and pilot patterns used in the cells. As provided, the noise estimation method and apparatus improve decoding performance which improves cell capacity in a communication system.