Electronics and Telecommunications Research Institute

Samsung Electronics Co., Ltd.

Kt Corporation

Sk Telecom Company, Ltd.

Hanaro Telecom., Inc.

Ktfreetel Co., Ltd

Hanaro Technologies, Inc.

Young-Ha Lee

Youn-Ok Park

Jun-Woo Kim

Chang-Wahn Yu

Dae-Ho Kim

Seung-Ku Hwang

Young-Hoon Kim

Su-Chang Chae

Eon-Young Hong

The present invention relates to a signal transmitting apparatus, a method thereof, and an inverse fast Fourier transform (IFFT) apparatus for a signal transmitting apparatus. A signal transmitting apparatus according to an embodiment of the present invention receives data, and performs inverse fast Fourier transform (IFFT) on the data on the basis of a twiddle factor for shifting output data by the size of a cyclic prefix. In addition, the signal transmitting apparatus sequentially stores data corresponding to the size of the cyclic prefix starting with initial data among the transformed data, and generates an OFDM symbol on the basis of the stored data and the transformed data. According to the embodiment of the present invention, it is possible to efficiently reduce a time delay and a memory use amount when a cyclic prefix is added at a transmitting end, without changing the size of hardware and power consumption.

Signal transmitting apparatus, method thereof, and inverse fast fourier transform apparatus for signal transmitting apparatus

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.

Method and apparatus for uplink timing synchronization with ranging signal in mobile communication system

The present invention relates to a complex multiplier and a twiddle factor generator. The complex multiplier according to an embodiment of the invention includes: a first adder/subtracter that adds the real part of the complex number and a first twiddle factor or subtracts the first twiddle factor from the real part of the complex number according to a first signal; a second adder/subtracter that adds the imaginary part of the complex number and a second twiddle factor or subtracts the second twiddle factor from the imaginary part of the complex number according to a second signal; a first multiplier that multiplies the value obtained by the first adder/subtracter by a third twiddle factor and outputs the resulting value; a second multiplier that multiplies the value obtained by the second adder/subtracter by a fourth twiddle factor and outputs the resulting value; a multiplexer that selectively outputs the values output from the first and second multipliers as a real part output signal and an imaginary part output signal according to a third signal; and a controller that provides the first to third signals. According to the present invention, it is possible to achieve a complex multiplier having a simple hardware design.

Complex multiplier and twiddle factor generator

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.

Subcarrier allocation apparatus and method, subcarrier de-allocation apparatus and method in OFDM system

A base station demodulator according to the exemplary embodiment of the present invention includes a vector index demodulator, and a channel value detector. The vector index demodulator demodulates CQI or ARQ ACK/NACK channels by multiplying QPSK modulation signals transmitted as m subcarriers in a tile by m conjugate complexes corresponding to the m subcarriers, and determines the greatest value of the demodulation results as a vector index. The channel value detector inputs n vector indexes demodulated by the vector index demodulator to a first shift register, inputs n subsequent vector indexes to a second shift register, and detects a channel value for the CQI or the ARQ ACK/NACK by repeating the above vector index input to the first and second shift registers m-times.

Demodulator of base station in orthogonal frequency division multiple access

A receiving method and apparatus of an orthogonal frequency division multiplexing access system having multiple antennas that is capable of improving system design and realization of integration degree by reducing complexity of fast Fourier transform (FFT) and noncoherent combination is provided. The receiving apparatus of a communication system having multiple antennas includes a parallel/series converter for converting data received according to each receiving path from parallel to series data; a fast Fourier transform (FFT) unit for fast Fourier transforming the data converted from parallel to series data; a series/parallel converter for converting the fast Fourier transformed series data from series to parallel data; a series noncoherent combiner for noncoherently combining the fast Fourier transformed series data and outputting the noncoherent combined data; a channel estimator/compensator for channel-estimating/compensating the data converted to parallel according to respective receiving paths; and a coherent combiner for coherently combining the channel-estimated/compensated data and for outputting the coherent combined data.

Receiving apparatus and receiving method of communication system with multiple antennas

In the uplink of an OFDMA system, a preamble is used to estimate a channel and then the pilot tones of a data symbol are used for channel estimation to update the channel estimate. The channel estimate is used for channel compensation, and the phase of the channel is corrected using the channel estimate obtained from the pilot tones. In this way, the channel estimation performance and hence the compensation ability can be enhanced.

Uplink channel estimation system for orthogonal frequency division multiple access system and method thereof

Disclosed is a ranging system and method in an OFDMA system. The ranging system includes complex exponential twiddle storage units for respectively storing complex exponential twiddle factors corresponding to a timing error, complex multipliers for respectively complex-multiplying the complex exponential twiddle factors by received uplink ranging data, code correlators for respectively correlating the outputs of the complex multipliers and ranging codes, and threshold comparators for respectively comparing the outputs of the code correlators with a threshold.

Uplink ranging system and method in OFDMA system

Disclosed is an AGC (automatic gain control) device and method of an OFDM system with a DC offset compensation function, and a recording medium storing a program including the method. The AGC device calculates an energy of input signals with DC offsets as the summation of the square of the input signals, and calculates an energy of the DC offsets in the input signals as the summation of the square of the DC offsets. Pure signal energy without DC offsets is produced by subtracting the energy of the DC offsets from the energy of the calculated input signal. The energy and an AGC reference value are then compared, and feedback of a comparison result is performed.

Automatic gain control device and method in orthogonal frequency division multiplexing system with DC offset compensation function, and recording medium storing program containing the method

A method for calculating frequency offset using arc tangent calculations according to real part and imaginary part input values received externally. The method includes converting arc tangent equations for determining frequency offset into equations to perform log calculations; calculating frequency offset using linear approximation and the converted log equations; and dividing the real part input value to bit values of a predetermined size to realize a size similar to that of the imaginary part input value if a range of the frequency offset value to be calculated is small. With the use of the method, hardware area and power consumption may be reduced, and precise frequency offset may be calculated.

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Daejeon, South Korea

Young-Ha Lee