Abstract: A sphere decoder sets a Euclidean distance between a lattice vector obtained by using an MMSE or ZF estimate and a received signal as an initial radius, further reduces the initial radius, and searches lattices points included inside a hypersphere with the further reduced initial radius. In addition, one lattice vector having a minimum Euclidean distance is output. One dimension is selected to reduce an initial radius, and estimates in other dimensions are kept fixed, excluding the selected dimension. Then candidate lattice points are searched in the selected dimension, excluding a current estimate, such that a minimum Euclidean distance and a lattice point estimate corresponding to the minimum Euclidean distance are obtained. The initial radius is updated by the minimum Euclidean distance, and a final lattice vector is constructed by combining a lattice point estimate corresponding to the initial radius and the lattice point estimates in other dimensions.

Abstract: The present invention relates to a multi-input multi-output (MIMO) system for enhancing transmission performance. The MIMO system uses space-time encoding and transmit antenna selection methods, and includes a transmitter (100) and a receiver (200). The transmitter (100) includes N transmit antennas (130-1, 130-4) that are more than M tansrni antennas (130-1, 130-3) used for transmitting a signal to space channel, selects the M transmit antennas (130-1, 130-3) among the N transmit antennas (130-3 130-4), and transmits symbol by space-time encoding the symbol. The receiver (200) includes M receive antenna (120-1, 210-2) for receiving a signal from the space channel, detects an information symbol by using the signal received through the receive antenna (210-1, 210-2), generates transmit antenna selection information for selecting M transmit antennas (130-1, 130-3) among transmit antennas (i30-1, . . . 7130-4) with reference to a channel estimate, and returns the information to the transmitter.

Abstract: A space-time code used for a transmitter to transmit a plurality of data symbols to a receiver in a MIMO system, the space-time code including a code word matrix for transmitting an amount of data symbols corresponding to a product of the number of transmit antennas and a spatial multiplexing rate during one block period, wherein a row index indicates combined signals transmitted through different transmit antennas and a column index indicates time slots that correspond to the number of transmit antennas, and wherein the number of data symbols allocated to each transmit antenna in a code block corresponds to the spatial multiplexing rate, and the data symbols are combined by different combining coefficients for each transmit antenna at every time slot, and simultaneously transmitted through different transmit antennas, and each transmit antenna transmits a different set of data symbols at every time slot.

Abstract: An interference canceller is herein disclosed wherein a baseband signal is input to a detector's fingers, and the fingers detect multi-path signals and estimate the baseband signal's channel. An MRC uses the finger's despread signal and the channel estimate to output a soft bit decision value, while a signal regenerator uses a hard bit decision value and the finger's channel estimate to regenerate the baseband signal. An SIR measurer uses a soft bit decision value and a despreader's channel estimate to measure an SIR. A signal selector compares each detector's SIR measurement value with a target SIR, and when the SIR measurement value is greater than the target SIR, it selects the detector's regeneration signal to group received signals. A subtractor subtracts the regeneration signal from the baseband signal.

Abstract: Disclosed is a MIMO-OFDM system, wherein the transmitter comprises a serial/parallel converter for converting continuously inputted symbols of the number of subcarriers to K parallel signals; a signal reproducer for reproducing K parallel signals by the number of transmit antennas L an eigenmode generator for generating eigenbeam of the reproduced signals outputted from the signal reproducer at each subcarrier, on the basis of Nf eigenbeam forming vectors which are fed back long-term and information of a best eigenbeam forming vector at each subcarrier which is fed back short-term, through the feedback device; and a plurality of inverse Fourier converters for receiving the signals outputted from the eigenmode generator and generating an OFDM symbol.

Abstract: An adaptive interference suppression receiver for a DS/CDMA system includes: input signal generators outputting a part of received signals of receiver antennas that has a coding block's transfer code; adaptive filter blocks filtering a complex signal output from the input signal generators with a tap weight updated based on a constraint MMSE criterion and estimating phase and amplitude components of a specific user channel using the filtering output signal to generate a channel-estimated signal; a signal restorer combining the channel-estimated signal and the filtering output signal and restoring an original signal; a signal selector for selecting known training data signal or the restored signal; and error generators comparing the channel-estimated signal and the filtering output signal and calculating an error between the two signals.

Abstract: A method for parallel type interference cancellation in a CDMA receiver, wherein minimum processing delay time is required while ensuring performance of an interference cancellation device, and space for embedding hardware for implementing the method can be reduced. The method for parallel type interference cancellation in a CDMA receiver, comprising: (a) when an over sample position of a received signal reaches the end of a symbol of a user, completing temporary detecting and recovering the symbol of the user; (b) generating a residual signal by using the recovered signal of the user and received signal state; and (c) detecting symbol information by obtaining an interference cancelled signal by adding the residual signal to the recovered signal of the user.

Abstract: The present invention relates to a receiver applicable to a code division multiple access system having multiple transfer rates. In a CDMA system, when performing a de-spreading process to extract information from received data in which various terminal signals or multiple path signals are asynchronously mixed, interference between a plurality of users or paths tends to occur. The present invention proposes an interference canceller for effectively canceling the interference between the users or paths. For this, the present invention implements a parallel interference canceller for estimating in parallel interference signals from asynchronously received signals and canceling the estimated interference signals from the received signals. In the present invention, when implementing a parallel interference canceller for asynchronously received signals, as bit information of the received signals is not aligned in the same time frame, the following conditions are considered.

Abstract: An adaptive RAKE receiving apparatus is constrained with at least one constraint for use in a mobile communication system.

Abstract: An interference cancellation receiver reduces the multiple access interference in a CDMA system. The receiver includes a demodulator for receiving a residual signal or a received signal from a calling terminal as an over-sample unit baseband spread signal and down-sampling the baseband spread signal on a chip basis to output a demodulation signal, a regenerator for performing a bit decision for the demodulation signal, regenerating signals through the channelization and scrambling and converting the regenerated signals to signals on the over-sample basis, an adder for summing up the over-sample unit signals, a filter for filtering the summed-up signal to output a band spread signal, a subtractor for subtracting the band spread signal from the received signal to output the residual signal and a delay for keeping timing with the residual signal by delaying the chip unit signals outputted from the regenerator.

Abstract: An apparatus and method for performing circular group-wise parallel interference cancellation in a multi-rate DS-CDMA system that reduce the multiple access interference in a CDMA system are disclosed. The invention provide a method of grouping received signals, which improves the interference cancellation efficiency of the signal receiver. The method of the invention groups a plurality of signals according to the magnitude of signals, and sequentially performs interference cancellation with respect to the groups in order of the signal magnitude. The apparatus and method determine the signal rank by using both the power estimation value of the received signal of each finger and the soft bit decision value being the output value of the maximal ratio combiner, perform grouping of the fingers selected by a finger selector, and finally perform interference cancellation. The soft bit decision value is independent of channel, and has the bit information at the time of signal transmission.

Abstract: A transmission apparatus for DS/CDMA system with MIMO antenna system is disclosed. The apparatus includes a transmitter for transmitting data by applying different scramble code to each transmitting data through a plurality of the transmitting antennas and receiver for receiving transmitted data by obtaining diversity gain based on the maximum order of the diversity in order to effectively detect data. The present invention has excellent detection performance by receiving data with full order of diversity, which is multiple of the number of receiving antennas and the number of multipath, without complicated operation such as a decision feed equalizer.

Abstract: An adaptive weighted parallel interference cancellation system for CDMA that decreases MAI (multiple access interference) and thereby increases general performance, including K stages for iterative cancellation of MAI in a received signal of a user. Each stage includes a detector, a regenerator, and a subtractor. The detector is configured to determine a tentative bit decision from a despread signal. The regenerator that is connected with the detector in parallel is configured to spread an unmodulated signal, multiply a channel phase, and multiply by the output of the detector. The subtractor uses weighted signals that are adjusted user by user and according to changing environments.

Abstract: An adaptive interference suppression receiver for a DS/CDMA system includes: input signal generators outputting a part of received signals of receiver antennas that has a coding block's transfer code; adaptive filter blocks filtering a complex signal output from the input signal generators with a tab weight updated based on a constraint MMSE criterion and estimating phase and amplitude components of a specific user channel using the filtering output signal to generate a channel-estimated signal; a signal restorer combining the channel-estimated signal and the filtering output signal and restoring an original signal; a signal selector for selecting known training data signal or the restored signal; and error generators comparing the channel-estimated signal and the filtering output signal and calculating an error between the two signals.

Abstract: An interference canceller. A baseband signal is input to a detector's fingers, and the fingers detect multi-path signals and estimate the baseband signal's channel. An MRC uses the finger's despread signal and the channel estimate to output a soft bit decision value, while a signal regenerator uses a hard bit decision value and the finger's channel estimate to regenerate the baseband signal. An SIR measurer uses a soft bit decision value and a despreader's channel estimate to measure an SIR. A signal selector compares each detector's SIR measurement value with a target SIR, and when the SIR measurement value is greater than the target SIR, it selects the detector's regeneration signal to group received signals. A subtractor subtracts the regeneration signal from the baseband signal.

Abstract: A method for canceling an interference signal by using a parallel multi-stage structure in a code division multiple access (CDMA) system, includes the steps of: a) delaying a receiving signal; b) receiving and predicting data and channel parameter from the individual user; c) regenerating the interference signal of the individual user by using the data and the channel parameter predicted by the multiple receiving and predicting; and d) canceling all the interference signals delayed and transferred through the delaying by the interference signal regenerated through the multiple interference regeneration.

Abstract: An adaptive apparatus and method for detecting a receiving signal employing constrained minimum mean square error (MMSE) criterion as an adaptive algorithm for detecting CDMA receiving signal. The apparatus comprises an adaptive filtering means; a channel estimating means; a signal restoring means; a selecting means; a reference signal generating means; an error calculating means; and a tap weight controlling means. In the apparatus, an adaptive filter can be normally operated even if compensating a phase and amplitude of a channel at the same time.

Abstract: An interference cancellation receiver reduces the multiple access interference in a CDMA system. The receiver includes a demodulator for receiving a residual signal or a received signal from a calling terminal as an over-sample unit baseband spread signal and down-sampling the baseband spread signal on a chip basis to output a demodulation signal, a regenerator for performing a bit decision for the demodulation signal, regenerating signals through the channelization and scrambling and converting the regenerated signals to signals on the over-sample basis, an adder for summing up the over-sample unit signals, a filter for filtering the summed-up signal to output a band spread signal, a subtractor for subtracting the band spread signal from the received signal to output the residual signal and a delay for keeping timing with the residual signal by delaying the chip unit signals outputted from the regenerator.

Abstract: In a method of the present invention for parallel type interference cancellation in a CDMA receiver, minimum processing delay time is required while ensuring performance of an interference cancellation device, and space for embedding hardware for implementing the method can be reduced. The method for parallel type interference cancellation in a CDMA receiver, includes the steps of: (a) when an over sample position of a received signal reaches the end of a symbol of a user, completing temporary detecting and recovering the symbol of the user; (b) generating a residual signal by using the recovered signal of the user and received signal state; and (c) detecting symbol information by obtaining an interference cancelled signal by adding the residual signal to the recovered signal of the user.

Abstract: An adaptive RAKE receiving apparatus is constrained with at least one constraint for use in a mobile communication system.