Abstract: Disclosed are a method and a system for transmitting/receiving signals in a mobile communication system using a multiple input multiple output adaptive antenna array scheme. A first receiver calculates a reception weight value by using a de-spread signal of a reception signal for creating a reception beam of the first receiver and calculates a transmission weight value by using the calculated reception weight value for creating a transmission beam of the second transmitter, thereby creating feedback information including the transmission weight value. A first transmitter transmits the feedback information to a second receiver. The second receiver receives the feedback information and the second transmitter detects the transmission weight value from the feedback information received in the second receiver, and creates the transmission beam corresponding to the detected transmission weight value in order to transmit a signal by applying the transmission beam to the signal.

Abstract: An apparatus and method for switching between an AMC mode and a diversity mode adaptively according to a channel environment in a broadband wireless communication system are provided. According to the present invention, a transmitter (a base station) determines a transmission mode according to frequency-domain and time-domain channel measurement information received from a receiver (a mobile station). If the transmission mode is the AMC mode, the transmitter selects a coding and modulation scheme according to a frequency-domain CQI received from the receiver. If the transmission mode is a diversity mode, the transmitter selects a predetermined coding and modulation scheme.

Abstract: A method for transmitting and receiving weight information for creating transmission/reception beams in a mobile communication system using a multiple input multiple output adaptive antenna array scheme. The method includes a receiver receiving a predetermined signal, and differentially providing weights to a first scheme and a second scheme for minimizing an error between the received signal and a predetermined reference signal, thereby obtaining a minimum error value. The receiver generates a despread signal by despreading the received signal, produces a reception weight for creation of a reception beam by the receiver through calculation using the despread signal and the minimum error value, and produces a transmission weight for creation of a transmission beam by a counterpart transmitter through calculation using the reception weight and the minimum error value.

Abstract: A method for receiving a signal from a radio unit in a base station having at least one reception antenna is disclosed. The method includes receiving a reception signal via the reception antenna, and generating an output signal using the reception signal and a reception beam weight for a previous time; calculating a cost function using a desired reception signal transmitted from the radio unit among the reception signal and the generated output signal; calculating a trace vector using the calculated cost function and the reception signal; updating the reception beam weight using the trace vector for a next time; and generating a reception beam by applying the updated reception beam weight.

Abstract: A transmitting and receiving apparatus and method for optimizing performance of an adaptive modulation and coding (AMC) in a multiple input and multiple output antenna (MIMO) communication system. When the AMC is applied to the MIMO system, the optimal scheme is different depending on the MIMO channel situation, the maximum transmission power, and the maximum modulation order. The transmitting apparatus includes an ordering selector that selects a successive interference cancellation (SIC) scheme in order to obtain a maximum MIMO-AMC performance, and the receiving apparatus includes a channel quality information (CQI) generator corresponding to the SIC scheme selected at the transmitting apparatus.

Abstract: An apparatus and method for generating an octal code for identifying cells in a mobile communication system. In the octal code generating apparatus, a binary code generator generates a binary code with a predetermined minimum Hamming distance. A column permutator permutes the order of columns of the binary code in a predetermined interleaving method. A 3-bit combiner generates a plurality of codewords using the column-permuted binary code as a generator matrix and groups the bits of each of the codewords by threes. An octal code generator converts the 3-bit grouped binary codewords to octal code sequences.

Abstract: Disclosed is a method for transmitting/receiving data by use of feedback information in a closed loop multi input multi output (MIMO) mobile communication system. The method includes the steps of feeding back transmission eigenvector selection information determined through a singular value decomposition (SVD) of a channel matrix and transmitting the transmission eigenvector selection information to a transmitter; and receiving the feedback transmission eigenvector selection information, selecting transmission data according to the received transmission eigenvector selection information, mapping the selected transmission data to at least one transmission antenna, and transmitting the transmission data to a receiver.

Abstract: An apparatus and method for transmitting/receiving a pilot pattern set to distinguish a base station in an FDM communication system. The method divides a total frequency bandwidth into at least two sub-bandwidths including a plurality of sub-carriers in an OFDMA (Orthogonal Frequency Division Multiple Access) mobile communication system, configures a single frame cell (FC) using one sub-bandwidth from among the sub-bandwidths and a plurality of OFDM (Orthogonal Frequency Division Multiplexing) symbol intervals, and assigns a pilot signal to a time-frequency cell comprised of at least one OFDM symbol and at least one sub-carrier within the FC. The method includes the steps of spreading a pilot signal and a data signal using different orthogonal codes, synthesizing the spread pilot and data signals, and performing a CDM (Code Division Multiplexing) process; and mapping the CDM-processed pilot and data signals to a predetermined time-frequency cell in the FC.

Abstract: An apparatus for generating a preamble sequence in an orthogonal frequency division multiplexing (OFDM) communication system using A subcarriers in a frequency domain. A preamble sequence generator generates a length?M+N+k preamble sequence, where M+N+k is less than A, by combining a length?N Golay complementary sequence with a length?M Golay complementary sequence. An inverse fast Fourier transform (IFFT) processor assigns elements constituting the preamble sequence to the M+N+k subcarriers among the A subcarriers on a one-to-one mapping basis, assigns null data to remaining subcarriers excluding the M+N+k subcarriers from the A subcarriers, and then IFFT-transforms the assigned result into time-domain data.

Abstract: A method for transmitting reference signals in a radio communication system in which a frequency band is divided into a plurality of sub-frequency bands. The reference signals are transmitted through at least one of the plurality of sub-frequency bands, and data signals are transmitted through the plurality of sub-frequency bands except for the at least one of the plurality of sub-frequency bands. The method includes the steps of: determining a reference signal pattern representing positions of the at least one of the plurality of sub-frequency bands through which the reference signals are transmitted in consideration of a preset time and a preset bandwidth; generating the reference signals using a PN code and a Walsh code; and transmitting the reference signals through the sub-frequency bands corresponding to the reference signal pattern.

Abstract: A method for generating a preamble sequence in an orthogonal frequency division multiplexing (OFDM) communication system having A subcarriers in a frequency domain. The method comprises generating a length-2×M×N preamble sequence, where 2×M×N is less than A, by using a length-N Golay complementary sequence and a length-M Golay complementary sequence; and assigning elements constituting the preamble sequence to 2×M×N subcarriers among the A subcarriers on a one-to-one mapping basis, assigning null data to the remaining subcarriers excluding the 2×M×N subcarriers from the A subcarriers, and then IFFT-transforming the assigned result into time-domain data.

Abstract: A mobile communication system receives a reception signal of a reception signal, and performs a control operation such that a weight for generating a reception beam is calculated using a first technique if a difference between an error sum value at a current time and an error sum value at a previous time is greater than an absolute value of a first threshold or the error sum value at the current time is greater than or equal to a second threshold, and performs a control operation such that the weight is calculated using a second technique if the different between the error sum value at the current time and the error sum value at the previous time is less than or equal to the absolute value of the first threshold and the error sum value at the current time is less than the second threshold.

Abstract: An apparatus and method for signal detection in a Broadband Wireless Access (BWA) system are provided, in which in a transmitter, a first preamble sequence generator generates preamble sequences, a low-Peak-to-Average Power Ratio (PAPR) preamble sequence selector selects a first low-PAPR preamble sequence from among the generated preamble sequences, a preamble sequence copier copies the first low-PAPR preamble sequence at least once and outputs the first low-PAPR preamble sequence and the at least one copy, a complex conjugator generates preamble sequences orthogonal to the first low-PAPR preamble sequence and the at least one copy by calculating complex conjugates of the first low-PAPR preamble sequence and the at least one copy, and a second preamble sequence generator generates at least one second low-PAPR preamble sequence using the first low-PAPR preamble sequence.

Abstract: A method for generating a preamble sequence in an OFDM (Orthogonal Frequency Division Multiplexing) communication system that uses A sub-carriers in a frequency domain and uses N Tx (Transmission) antennas, includes the steps of: generating N sequences, each having a length of ‘B/N’, by dividing B sub-carriers from among the A sub-carriers by the ‘N’ indicative of the number of the Tx antennas; and mapping, for each of the N sequences, individual components of the sequence to the B/N sub-carriers from among the A sub-carriers on a one by one basis in order to assign the components of the sequence to the B/N sub-carriers, and assigning null data to remaining sub-carriers other than the B/N sub-carriers from among the A-sub-carriers, such that a preamble sequence of a corresponding Tx antenna is generated.

Abstract: A method for generating a preamble sequence in an orthogonal frequency division multiplexing (OFDM) communication system having A subcarriers in a frequency domain. The method comprises generating a length -M×N preamble sequence, where M×N is less than A, by using a length-N Golay complementary sequence and a length-M Golay complementary sequence; and assigning elements constituting the preamble sequence to M×N subcarriers among the A subcarriers on a one-to-one mapping basis, assigning null data to the remaining subcarriers excluding the M×N subcarriers from the A subcarriers, and then IFFT-transforming the assigned result into time-domain data.

Abstract: A subcarrier assignment apparatus and a subcarrier assignment method, in which each of a plurality of Base Stations (BSs) constituting an Orthogonal Frequency Division Multiple Access (OFDMA) communication system provides services in the capacity of a serving BS to Mobile Stations (MSs). Channel quality information for the respective MSs are fed-back from the respective BSs. Subcarriers are assigned to the respective MSs according to a corresponding scheduling scheme in consideration of the channel quality information for the respective MSs, which are fed-back from the respective BSs, and then BSs which manage the subcarriers assigned to the respective MSs according to the corresponding scheduling scheme are selected. These operations provide site diversity to each of the MSs, and thus system capacity is maximized.

Abstract: A method for transmitting a signal by a transmitter in a frequency overlay communication system. The method includes generating y first signal groups by shuffling input information data with a length yN on an N-by-N grouping basis according to a first shuffling scheme; generating y second signal groups by performing N-point IFFT on each of the first signal groups; generating y third signal groups by multiplying each of the second signal groups by preset values; generating N fourth signal groups by de-shuffling the third signal groups on a y-by-y grouping basis according to a de-shuffling scheme; generating N fifth signal groups by performing y-point IDFT on each of the fourth signal groups; generating y sixth signal groups by shuffling the fifth signal groups according to a second shuffling scheme, and serial-converting the sixth signal groups; and performing a transmission RF process on the serial-converted signal and transmitting the RF-processed signal to a receiver.

Abstract: A ranging apparatus in a communication system is provided. A terminal generates a ranging code for ranging with a base station, maps the ranging code to at least one sub-carrier so the ranging code is repeated in a time domain, generates a ranging signal so the mapped ranging code has a size of one symbol interval, and transmits the generated ranging signal to the base station. The base station receives a ranging signal, extracts a half signal of a valid symbol interval of the ranging signal, generates a valid symbol interval signal by repeating the extracted half signal of the valid symbol interval, restores a ranging signal using the valid symbol interval signal, and performs ranging using the ranging signal.

Abstract: A system for performing cell acquisition in a frequency overlay communication system having a first frequency band and a second frequency band including the first frequency band. A base station (BS) generates a reference signal used for identifying a cell using a specific sequence in a predetermined frequency band, and transmits the reference signal. A mobile station (MS) receives the reference signal to determine whether the BS uses the first frequency band or the second frequency band, determines a reference signal having a maximum correlation value through correlation calculation with at least one predefined sequence, and detects a BS identifier (ID) corresponding to the determined reference signal.

Abstract: An apparatus and method for reducing pilot overhead in a broadband wireless communication system are provided. A data symbol mapper maps data symbols to be transmitted into subcarriers and detects values of the data symbols mapped into predefined subcarriers. A pilot generator determines masking codes for each pilot group by using the detected values of the data symbols and masks the determined masking codes into pilot symbols of the corresponding pilot group. A pilot symbol mapper maps the masked pilot symbols received from the pilot generator into subcarriers.