Abstract: There is provided a signal detecting method using constellation set grouping in a spatial multiplexing multiple input multiple output system. The signal detecting method includes dividing a set of candidate symbols, a constellation set into a plurality of subsets by grouping the constellation set; dividing a tree search process of a QR-decomposition with M-algorithm (QRDM) algorithm into a plurality of partial detection phases; and performing the plurality of divided partial detection phases in parallel or iteratively.

Abstract: A method for detecting signals in spatial multiplexing multiple-input multiple-output (MIMO) systems using a QR-decomposition with M (QRD-M) algorithm is provided. The method includes receiving signals, limiting upper and lower bounds of a complexity in a QR-decomposition with M (QRD-M) algorithm, and detecting the received signals using the QRD-M algorithm. The signal detecting method can effectively reduce the amount of operation generated while detecting signals, using the QRD-M algorithm where the upper and lower bounds of the complexity are limited.

Abstract: Provided are a synchronization apparatus and method for improving timing estimation performance in an OFDM-FDMA/CDMA/TDMA system, which can correctly estimate symbol timing through a more correct timing metric using a guard interval of a preamble. The synchronization apparatus includes an auto-correlator for calculating an auto-correlation value of a received signal and a signal delayed by a predetermined time, a power detector for calculating power of the received signal, a timing metric/normalizer for normalizing the auto-correlation value by dividing the auto-correlation value by the calculated power to obtain a timing metric, and a peak detector for finding a peak value of the timing metric to estimate a frame starting position and an initial symbol timing. The auto-correlator calculates an auto-correlation length as long as a length of a guard interval, considering the preamble characteristic that the patterns are repeated in the time domain.

Abstract: Provided are a dynamic channel/power allocation method for an FRP-based OFDMA system and a frame/slot structure. capable of supporting the dynamic channel/power allocation method. In the FRP-based OFDMA system, each of cells has an inner cell, an outer cell and a plurality of sectors and performs data communication with a plurality of MSs therein through one or more orthogonal subchannel groups. In the dynamic channel/power allocation method, a BS receives a feedback channel condition from an MS provided with a service of the BS and allocates a subchannel group with a high SINR to each MS in consideration of the fairness and the distance information of each MS. Power is allocated to each MS on the basis of the conditions of a channel allocated to each MS, thereby obtaining a multi-user diversity gain.

Abstract: Provided are a transmission method and apparatus for allocating a subchannel and forming a stationary beam to maximize transmission efficiency in an OFDMA based wireless communication system. The method includes determining the subchannel for the equipment of each user based on the channel state of the equipment of each user, determining a beam index for the equipment of each user, based on location information and direction of arrival information of the equipment of each user, generating an OFDM symbol by mapping a modulation symbol corresponding to the equipment of each user to the determined subchannel, and transmitting the generated OFDM symbol to a wireless space by forming a beam following the determined beam index. Using the method, the equipment of each user can be allocated with an advantageous subchannel, can remove an interference signal at low cost, and can increase total throughput of an OFDMA system downlink.

Abstract: Method for providing frequency-hopping OFDMA using symbols of comb patter, the method including the steps of: a) assigning frequency domain signal X(k) of comb pattern (comb symbol, k is frequency index) to modulated data sequence, the comb symbol comprising predetermined number of sub carriers (sub carrier group) which are placed with predetermined interval in the whole available frequency band; b) getting the comb symbol hopped for the comb symbol to have independent frequency offset; and c) inverse fast fourier transforming the comb symbol to time domain signal x(n) (n is time index) and transmitting the signal.

Abstract: Disclosed are an adaptive pilot symbol assignment method that flexibly controls the number of transmit antennas according to each user's moving speed, channel status, or user request, and assigns proper pilot symbols in the downlink of an OFDMA (Orthogonal Frequency Division Multiplexing Access) based cellular system; and a sub-carrier allocation method for high-speed mobile that allocates some sub-carriers to assign proper pilot symbols for ultrahigh-speed mobile users, and the rest of the sub-carriers to the other users to assign proper pilot symbols to the users, on the assumption that the ultrahigh-speed mobile users have a traffic volume almost insignificant to the whole traffic volume.

Abstract: Disclosed is a frequency hopping method in an OFDM system, comprising: (a) detecting a mutual interference degree between different cells, and determining whether to use different frequency hopping patterns between the cells for interference averaging according to the mutual interference degree interference degree; (b) determining a number P of the different frequency hopping patterns needed between all the cells in the system; (c) generating the frequency hopping patterns of more than the number P and allocating the generated frequency hopping patterns to each cell, the frequency hopping patterns having the same frequency collision times between two channels in the different frequency hopping patterns; and (d) frequency-hopping the channels in each cell according to the allocated frequency hopping pattern.

Abstract: Provided is a method for retransmitting data based on antenna scheduling in a MIMO system to which a spatial multiplexing technique is applied. The method includes the steps of: (a) at a transmitter side, modulating an input packet into transmittable data to transmit to a receiver side; (b) at the receiver side, estimating channel values from the packet transmitted from the transmitter side, and selecting transmitting and receiving antennas for transmitting the next packet from the estimated channel values; (c) detecting whether an error is present in the packet or not, and transmitting a feedback signal to the transmitter side, the feedback signal including information on whether or not to transmit the packet and a list of the selected transmitting antennas; and (d) at the transmitter side, retransmitting the transmitted packet or transmitting the next packet through the transmitting antennas designated by the receiver side depending on the feedback signal.

Abstract: In an OFDMA-based cellular system, a frame of a downlink signal includes a common slot and traffic slots. The common slot includes a synchronization preamble and a cell search preamble. The synchronization preamble has a structure for synchronizing time and frequency, and the cell search preamble has a cell search structure. The traffic slot includes pilot symbols provided on the time and frequency axes. A cyclic prefix is used to estimate initial symbol synchronization, and the initial symbol synchronization and the synchronization preamble are used to synchronize the frame. The synchronization frame and the cell search preamble are used to estimate time and frequency synchronization. The cell search preamble is used to search cells. When the initial synchronization is performed, the cyclic prefix is used to track the frequency, the synchronization preamble is used to track symbol synchronization, and the cell search preamble is used to track fine frequency synchronization.

Abstract: Provided are a dynamic resource allocation method based on frequency reuse partitioning for an Orthogonal Frequency Division Multiple Access (OFDMA) system, and a frame transmission method therefor. The dynamic resource allocation method includes: a) dividing a coverage into cells based on frequency reuse partitioning; b) selecting a candidate user to receive a channel allocated thereto based on the ratio; c) acquiring distance information for the candidate user; and d) checking whether the candidate user is in an inner or outer cell area based on the distance information. If the candidate user is in the inner cell area, a subchannel group among subchannel groups having a Frequency Reuse Factor (FRF) lower than a threshold value is selected and subcarriers of the selected subchannel group is allocated. If the candidate user is in the outer cell area, a subchannel group among subchannel groups having a FRF higher than the threshold value is selected.

Abstract: In this patent, we propose an efficient CCI cancellation algorithm capable of working in cellular OFDM systems in high interference environments especially for users at the cell edges. We propose modified BSs' transmitters (Txs) and MS receiver (Rx) structures. Adjacent BSs use different transmitting interleaving patterns. This leads to orthogonality in the frequency domain. Furthermore, the energy of every symbol is spread over two different subcarriers to get frequency diversity. At the MS Rx, the maximum likelihood estimator MLE CCI canceller is applied to cancel signals of interfering BSs using the same frequency band. A drawback of the MLE CCI canceller is that its performances is degraded when the received power of desired and interferer signals is nearly the same. To solve this problem, the MLE CCI canceller is assisted by a closed-loop power control (CPC) scheme. The newly proposed CPC scheme is capable of detecting and combating against the situation where the equal power is received.

Abstract: Disclosed is a transmitting and receiving method for reducing a time-varying channel distortion in an orthogonal frequency division multiplex (OFDM) system. In the present invention, the transmitter defines M sub-channels in one data group, mathematically analyzes a change of channel for each path causing a time-varying channel distortion in a high-speed mobile environment by approximation, calculates a weight value based on the mathematical analysis and assigns the calculated weight value to transmit data of each sub-channel. Subsequently, the receiver combines the signals of these M sub-channels and demodulates the combined signals. Accordingly, the present invention greatly reduces a distortion caused by the time-varying channel to improve a bit error rate and a channel estimation performance.

Abstract: Disclosed is a receiver digital filter for a digital IF signal processor suitable for the specification of each communication standard in a communication system that supports at least one communication standard. The filter for each standard is constructed as one block, and includes a block for externally implementing the constructed block. The coefficient of the digital filter constructed in one block is implemented with an external input or an internal filter coefficient calculator by a basic filter building block. In this manner, the common resources required in the digital filter used in each communication standard are shared, and only the additionally required resources are selectively implemented. Since the shared resources are calculated by dynamic programming, a considerably smaller number of additional resources are required.

Abstract: Provided are a dynamic channel/power allocation method for an FRP-based OFDMA system and a frame/slot structure capable of supporting the dynamic channel/power allocation method. In the FRP-based OFDMA system, each of cells has an inner cell, an outer cell and a plurality of sectors and performs data communication with a plurality of MSs therein through one or more orthogonal subchannel groups. In the dynamic channel/power allocation method, a BS receives a feedback channel condition from an MS provided with a service of the BS and allocates a subchannel group with a high SINR to each MS in consideration of the fairness and the distance information of each MS. Power is allocated to each MS on the basis of the conditions of a channel allocated to each MS, thereby obtaining a multi-user diversity gain.

Abstract: Provided are a multi-step channel prediction apparatus and method for adaptive transmission in an OFDM/FDD system. A channel prediction is preformed considering a time-varying characteristic of a channel changing within one slot, in addition to feedback and processing delay time between a transmitter and a receiver, and an adaptive transmission is performed. Therefore, a target PER performance can be maintained without degradation of the system performance.

Abstract: Provided are a synchronization apparatus and method for improving timing estimation performance in an OFDM-FDMA/CDMA/TDMA system, which can correctly estimate symbol timing through a more correct timing metric using a guard interval of a preamble. The synchronization apparatus includes an auto-correlator for calculating an auto-correlation value of a received signal and a signal delayed by a predetermined time, a power detector for calculating power of the received signal, a timing metric/normalizer for normalizing the auto-correlation value by dividing the auto-correlation value by the calculated power to obtain a timing metric, and a peak detector for finding a peak value of the timing metric to estimate a frame starting position and an initial symbol timing. The auto-correlator calculates an auto-correlation length as long as a length of a guard interval, considering the preamble characteristic that the patterns are repeated in the time domain.

Abstract: Disclosed is a hybrid multi-user interference cancellation method for canceling interference between a plurality of user signals, which comprises: receiving a plurality of external user signals, calculating powers of the user signals, and numbering the calculated signal powers in their intensity orders; sorting the user numbers in descending order; forming at least one user cluster so that the signal powers following the sorted user numbers may differ less from a central value or a mean value in the same cluster; and performing parallel interference cancellation on the respective user signals within the same cluster, and performing successive interference cancellation between the formed clusters.

Abstract: Disclosed is an implementation method for simplifying a complicated message-passing function in a decoder for decoding block codes encoded with low-density parity-check (LDPC) codes and only using a summator and a shifter to simplify the hardware structure of the decoder, in which method the input interval of the message-passing function for binary representation of a message input is divided and the respective divided intervals are linearized to allow the calculation of the output of the message-passing function without using a memory. Based on the fact that the message-passing function is similar in structure to an exponential function, the linearized intervals are set to make the maximum value expressible in each digit of the binary representation as the boundary of the intervals.

Abstract: Disclosed is an adaptive transmit and receive method and device in a multiple-antenna wireless communication system. A transmit mode comprises different main transmit modes each of which includes one or both of a sub-transmit mode based on STBC and a sub-transmit mode based on SM. A receiver calculates an STBC performance parameter and a SM performance parameter, and a transmitter uses the parameters to determine a main transmit mode with maximum data rates and select a sub-transmit mode for minimizing power consumption. The transmitter channel-encodes, modulates and antenna-maps input data according to the selected transmit mode, and outputs results to the receiver. The receiver antenna/symbol-demodulates and channel-decodes the received data.