Abstract: An apparatus uses transmission antenna diversity to compensate for fading. An encoder according to a first embodiment forms 4 combinations each including 3 symbols so that 4 input symbols should be transmitted only once at each antenna and each time interval, and delivers the combinations to the 3 transmission antennas for 4 time intervals, and two or more symbols selected from the 4 input symbols are phase-rotated by predetermined phase values before being transmitted via the transmission antennas. An encoder according to a second embodiment forms 3 combinations each including 3 symbols so that 3 input symbols should be transmitted only once at each antenna and each time interval, and delivers the combinations to the 3 transmission antennas for 3 time intervals, and two or more symbols selected from the 3 input symbols are phase-rotated by predetermined phase values before being transmitted via the transmission antennas.

Abstract: A mobile communication system includes at least three transmission antennas of first to third transmission antennas, and uses an overlapped antenna scheme for grouping the first and second transmission antennas into a first transmission antenna group and grouping the second and third transmission antennas into a second transmission antenna group. First and second modulators modulate L information bit streams to be transmitted through the first transmission antenna group and output first and second modulation symbol streams. Third and fourth modulators modulate L other information bit streams to be transmitted through the second transmission antenna group and output third and fourth symbol streams. First to fourth puncturers puncture at least one modulation symbol in a predetermined position among the first to fourth modulation symbol streams.

Abstract: A mobile communication system having M transmission antennas for receiving P information bit streams and encoding the received information bit streams with a space-time trellis code (STTC) according to an optimal generator polynomial; modulating the encoded P information bit streams in a predetermined modulation scheme and outputting modulation symbol streams; and puncturing at least one modulation symbol in a predetermined position from each of the M modulation symbol streams, and transmitting the punctured modulation symbol streams through the M transmission antennas, thereby increasing a data rate while maintaining maximum diversity gain.

Abstract: A apparatus and method for estimating a sequence of transmitted quadrature amplitude modulation (QAM)-modulated signals and space-time block coded signals using an optimal expectation-maximization (EM)-based iterative estimation algorithm in a multiple-input and multiple-output (MIMO)-orthogonal frequency division multiplexing (OFDM) mobile communication system. An initial sequence estimation value is produced on the basis of a predetermined initial value using a pilot sub-carrier contained in each of OFDM signals received by a receiving side. A normalized value of a received signal on a channel-by-channel basis is produced by a predetermined equation using orthogonality between the OFDM signals received by the receiving side. At least one subsequent sequence estimation value is produced using the initial sequence estimation value and the normalized value of the received signal on the channel-by-channel basis.

Abstract: A receiver for receiving complex symbols in a radio communication system, in which a symbol arranger collects signals from at least three transmitter antennas through at least one receiver antenna over four time intervals; a channel estimator estimates at least three channel gains from the three transmitter antennas to the receiver antenna; first and second decoders each compute metrics for all possible pairs of symbols using the received signals and channel gains, and detect two symbols having a minimum metric; And a P/S (Parallel to Serial) converter arranges the detected symbols in the right order. Each decoder linearly operates the received signals and channel gains, pre-detects two symbols using threshold detection, and outputs the pre-detected symbols as final symbols if the product of the product of the pre-detected symbols and a constant determined by the channel gains is a minimum.

Abstract: An apparatus using transmitting antenna diversity to combat degradation due to fading in a wireless communication system. At least two symbols of four symbols to be transmitted through four transmitting antennas are rotated by predetermined phase values. An encoder configures four combinations for four input symbols so that a sequence of four symbols can be transmitted once by each transmitting antenna during each time interval. The combinations are transferred to the four transmitting antennas during four time intervals. Before the four input symbols are transmitted to the transmitting antennas, at least two symbols selected from the four input symbols are rotated by predetermined phase values. Therefore, the maximum diversity order can be obtained, a transmission delay time can be reduced, and the effect of fast fading can be reduced.

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: Disclosed is a method for generating a space-time trellis code (STTC) for maximizing space-time diversity gain and coding gain in a mobile communication system including at least two transmission antennas and generating a second number of STTC codes with an information data bit stream upon receiving the information data bit stream comprised of a first number of bits.

Abstract: A mobile communication system includes M transmission antennas, P encoders for receiving P information bit streams and encoding the received information bit streams with a space-time trellis code (STTC), and M modulators for modulating information bit streams output from the P encoders in a predetermined modulation scheme and outputting modulation symbol streams. A sequence used for channel estimation is generated, and the sequence is transmitted in substitute for at least one modulation symbol in a predetermined position through the M transmission antennas, for each of the modulation symbol streams output from the M modulators.

Abstract: According to one aspect of the present invention, there is provided a signal transmission apparatus for a mobile communication system. In the signal transmission apparatus, a frame segmentation section segments an input frame into Bk bit group, where k=1, . . . , K. A first group of encoders encodes Bk bit group and outputs encoded symbols. A second group of encoders encodes other Bk? bit group and output other encoded symbols. Each encoded symbol is encoded again to the transmit antennas using different functions. A transmission section includes a plurality of antennas in groups of a predetermined number of antennas, and the total number N of antennas is larger than the sum of the number of antenna groups. The transmission antennas transmit symbols encoded by one of the encoders.

Abstract: In a communication system, an apparatus for receiving a signal transmitted through a channel having time-varying characteristics and for restoring original user information included in the received signal, preferably includes: a first channel characteristic estimator for estimating a signal representing the delay characteristic of the channel; a first channel characteristic predictor for decimating the estimated signal applied thereto, for predicting the characteristic values of the channel, for interpolating the predicted channel characteristic values, and for outputting the interpolated result as a first predictive characteristic signal; and a first receiver for generating a decision value from the first predictive characteristic signal and the received signal, restoring the transmitted signal using the estimated decision value, and outputting a restored transmitted signal, which is fed back to the first channel characteristic estimator.

Abstract: Provided is a method of reducing a peak-to-average-power ratio in a multiple antenna orthogonal frequency division multiplexing communication system. The method includes: reducing a peak-to-average-power ratio of input serial data sequences; space-time coding the input serial data sequences with the reduced peak-to-average-power ratio to generate N symbols to be tranmitted via N antennas; receiving the serial data sequences of the N symbols to transform the serial data sequences into N parallel data sequences; allocating each of the N parallel data sequences to Ns sub-carriers and performing Inverse Fast Fourier Transform on the N parallel data sequences; transforming the N parallel data sequences into N serial data symbols; and replicating a portion of the serial data symbols to generate cyclic prefixes and interleaving the cyclic prefixes into starting portions of the serial data symbols to cyclically expand the N symbols.

Abstract: A transmission method based on random beamforming. A base station receives, from mobile stations, feedback information including channel-by-channel transmission rates for a weight vector arbitrarily set by the base station. The base station compares transmission rates of identical channels received from the mobile stations. The base station allocates an associated channel to a mobile station with a large transmission rate and transmits a signal through the allocated channel. The transmission method based on random beamforming can improve fairness and efficiency of a resource allocation by simultaneously allocating different channels to multiple terminals and can increase a total system capacity through the improved fairness and efficiency.

Abstract: A transmitter in a multiple input multiple output (MIMO) communication system is provided. The transmitter includes a multiplexer for multiplexing an input bit stream into a plurality of bit streams, and outputting the bit streams in parallel; a bit-order rearranger for reordering bits constituting the bit streams, which are output from the multiplexer in the same time period, and outputting the reordered bits as reordered bit streams; and a modulator for modulating the parallel reordered bit streams output from the bit-order rearranger according to their associated modulation schemes, and transmitting the modulated symbols via their associated antennas.

Abstract: An apparatus and method for transmitting and receiving signals using multi-antennas are disclosed. The signal transmitting apparatus for transmitting signals to a plurality of receiving apparatuses, using multi-antennas, includes: a V generator which generates a beamforming matrix V for a predetermined channel; a water filling unit which does not perform water filling for a training signal that is pre-known by the receiving apparatuses, and performs water filling for a user signal to be transmitted by using the V matrix and predetermined control values; a V operation unit, which multiplies a signal output from the water filling unit by the V matrix and transmits the multiplied result through the multi-antennas; and a control value detector, which extracts the control values from signals received from the receiving apparatuses through the multi-antennas, and outputs a maximum value among the extracted values to the water filling unit.

Abstract: A signal detection method and apparatus in a receiver in a MIMO mobile communication system. The receiver orders symbol combinations transmittable from a transmitter in an ascending order of the difference between the symbol combinations and transmit symbols produced by eliminating inter-symbol interference from a received signal, initializes a symbol combination with the minimum difference to an ML solution, calculates the distance between a first symbol combination and the transmit symbols and the cost of a second symbol combination, detects a symbol combination having a distance to the transmit symbols equal to the distance between the first symbol combination and the transmit symbols, and having a minimum distance, and decides the first symbol combination as the ML solution if the minimum distance exceeds the distance between the first symbol combination and the transmit symbols.

Abstract: An adaptive subchannel and bit allocation method in a wireless communication system. A mobile station analyzes channel quality information of a subchannel at a predetermined period and determines a feedback band index with a maximum decision criterion. The mobile station feeds back the determined feedback band index with the maximum decision criterion to a base station. The base station generates band allocation information using the feedback information from the mobile station, and transmits the band allocation information to the mobile station. The mobile station transmits AMC information using the band allocation information received from the base station. The base station estimates a channel using the AMC information transmitted from the mobile station and allocates bits to the allocated band according to the channel estimation result.

Abstract: Disclosed is a method for acquiring synchronization in a mobile communication system using an Orthogonal Frequency Division Multiplexing (OFDM) scheme. The method includes modeling a power delay profile in time-varying frequency selective fading channel conditions by a specific function; detecting a log probability distribution function of a timing offset and a frequency offset in consideration of a correlation between a received signal and the received multi-path signal in the time-varying frequency selective fading channel conditions having the power delay profile modeled as the specific function; and estimating a timing offset and a frequency offset which maximize the log probability distribution function of the timing offset and the frequency offset.

Abstract: A base station identification method for a frequency hopping-orthogonal frequency division multiple access (FH-OFDMA) based multi-input multi-output (MIMO) communication system that allocates a preamble, a pilot arrangement pattern and a pilot signal pattern per frame to each of base stations. A mobile station identifies a base station using at least one of the preamble, the pilot arrangement pattern, and the pilot signal pattern. The method divides the base stations into a plurality of preamble groups, and allocates the same preamble to base stations belonging to each preamble group.

Abstract: A data transmission apparatus and method using a full-diversity, full-rate STBC are provided. In the data transmission apparatus, a serial-to-parallel converter converts an input bit stream to parallel binary vectors. A bit/symbol mapper generates modulator input symbols by combining the bits of the binary vectors. A modulator modulates the modulator input symbols to complex symbols. A transmit matrix block encoder encodes the complex symbols using a transmit matrix and transmits the coded symbols through corresponding transmit antennas.