31 results about "Multiuser detector" patented technology

A Tree-structured multicarrier multiple access communication system in a multiple access environment having a number of interfering signals. In one embodiment an environment estimator estimates and tracks the number of interfering signals of the environment. A code selector determines an optimal spreading code represented by the environment, and identifies an actual spreading code that is closest to the optimal spreading code. A signal transmitter can then be used to transmit a multicarrier multiple access signals in accordance with the actual spreading code identified. On the receiver side, a multiuser detector (MUD) module performs tree structured multiuser detection signal processing, and produces a bit stream for each interfering signal.

A digital receiver automatically detects and non-coherently demodulates a multiplicity of interfering digitally modulated signals transmitted simultaneously at approximately the same carrier frequency. The receiver includes one or more antenna inputs (e.g., polarization and/or space diverse), a parameter estimator module, and a multiuser detector for estimating the data transmitted by each interfering signals and adapted to operate with at least one of a MUD algorithm with partially quantized prior information and a MUD algorithm based on prewhitened data.

A multi-user turbo decoder combining multi-user detection and forward error correction decoding is disclosed that utilizes iterative decoding of received, interfering signals, and the construction of a decoding tree of the decoder is changed for each iteration of the decoding based on the previous conditional probability estimates of the value of the data bits of each signal making up the received, interfering signals. Before each iteration of multi-user decoding, a probability estimate is calculated that the value of the bit in a signal has a certain value for all of the data bits. Using the probability estimate a new decoding tree is constructed before each iteration of decoding such that the signal bit having the most reliable estimate is assigned to the lowest or root level of the tree. Using the probability estimate for the other signal bits, the signal bit having the next most reliable estimate is assigned to the second level of the tree, and so forth, with the signal bit having the least reliable estimate being assigned to the highest level of the tree adjacent the terminating nodes or leaves of the tree. By building the decoding tree in this manner for each iteration of symbol decoding, a reduced complexity search is more likely to include paths (and nodes) in the tree containing the correct value for the channel symbols.

A multi-user decoder is disclosed in which interfering users are assigned to levels of a decoding tree constructed in the decoder dependent on the power levels of the user's received signals and for each symbol interval. By building the decoding tree in this manner for each symbol interval, a reduced complexity search is more likely to include paths and nodes in the tree containing the correct value for the channel symbols.

Performing approximate diagonalization of a correlation metric by user permutation to improve Multiuser Detector (MUD) processing. The system reorders the entries in the S-Matrix in order to move the bit decisions closer together in the decision tree. In one embodiment the reordering is a sequential pairwise correlation.

A multi-user turbo decoder combining multi-user detection and forward error correction decoding is disclosed in which randomly ordered indices are assigned to interfering users before a decoding tree is constructed in the multi-user decoder for each symbol interval for every iteration and for each new block of data. By building the decoding tree in this manner for each symbol interval, a reduced complexity search is more likely to include paths (and nodes) in the tree containing the correct value for the channel symbols. All users thus share in the benefit of root level placement in the decoding tree. In an alternative embodiment of the invention only one decoding pass is accomplished and there is no re-construction of the decoding tree based on further random index ordering for iterative decoding. No modification to the transmitted signaling method is needed.

A multiuser detector system with correlation based pruning including a parameter estimation module adapted to receive complex signals, and to produce estimated signature waveforms for each of K co-channel interfering signals. Pre-processing the estimated signature waveforms using an S-matrix module and producing a more valid set of hypotheses, wherein the S-matrix module uses apriori knowledge of an unnormalized cross correlation matrix, and processing the more valid set of hypotheses for pruning with an M-algorithm a multiuser detector module. An improvement to the M-algorithm in which the interference structure based on the signal correlation matrix used during the optimization process aids in selecting a better subset of hypotheses to test. This approach has the benefit of reducing computational complexity and improving performance over the existing M-algorithm

A multi-user detector for use in a CDMA receiver system includes a channel tap interpolator to generate interpolated channel taps for users of interest. The interpolated channel taps occur at integer multiples of a chip period from a sampling reference point. The channel tap interpolation allows detection processing to proceed in the chip domain, rather than in the sample domain, thus reducing the complexity of the multi-user solution significantly. In at least one approach, a number of low dimensionality “virtual” users are defined based on the recursive property of the spreading sequences. Solutions may then be developed for the virtual users using conventional detection (e.g., MMSE) techniques.

The embodiment of the invention provides a signal detection method and device applied to a non-orthogonal multiple access system. The method and device are applied to a multi-user detector. The method comprises the following steps: according to an evaluation probability predicted value on a log domain, currently saved by another user node connected with a resource block node to be updated currently, determining an evaluation probability predicted value on the log domain of the resource block node to be updated currently, transferred to the user node, and sending the value to the user node so as to be saved; according to the evaluation probability predicted value on the log domain, currently saved by the user node and a prior probability value on the log domain of the user node, determining an evaluation probability predicted value on the log domain, transferred to a next resource block node connected with the user node, of the user node; and sending the value to the next resource block node connected with the user node so as to be saved. By applying the embodiment of the invention, the convergence rate of an MPA algorithm can be effectively increased, and the processing delay of the multi-user detector can be reduced.

A multiple access processing system for a plurality of users employing a multiuser detector processing partial blocks of data within a window. The multiuser detector processes the data for all users within a processing window and is interrupted at successive frame boundaries. Once an entire block is processed by the MUD, the blocks for that user are decoded and the processing continues.

Windowed multiuser detection techniques are disclosed. A window of data is established, and certain central bits within the window are selected as reliable, while other side bits are ignored. The selected bits are demodulated. The windowed multiuser detector moves along to the next window in such a manner that the next group of central bit decisions lay contiguous with the previous set, and eventually every bit to be demodulated has at some point been a central bit decision. Most any type of MUD algorithm (e.g., MMSE algorithm MUD or M-algorithm MUD) can be used to compute estimates in the windowed data. Unreliable windowed data are distinguished from reliable data (e.g., weighting or other de-emphasis scheme).

A multiuser detector that detects and decodes synchronous or asynchronous CDMA subchannels having different spreading factors with reduced computational complexity. The multiuser detector is compatible with ZF-BLE, MMSE, decorrelating detectors and the like using Cholesky decomposition to minimize numeric operations. The system and method arranges the columns of system transmission response matrices representing the response characteristics of individual users into a total system transmission response matrix which represents a plurality of matched-filter responses for a given block of received data. The invention in conjunction with Cholesky decomposition reduces the number of required mathematic operations prior to parallel matched filtering.

The invention relates to a robust multiuser detector design method, which solves the technical problem of high error rate of the traditional robust multiuser detector in an impact noise channel environment. The robust multiuser detector design method comprises the steps of: initializing algorithm parameters; using an opposition-based learning method to initialize a parent population, and determining three wolves in the parent population; updating the parent population by adopting an improved gray wolf algorithm position updating equation, and sorting population individuals according to fitnessvalues from large to small; generating offspring crossover mutants by utilizing the parent population, performing position information differential operation on an evolutionary direction of the offspring crossover mutants and successful crossover mutation probabilistic information when the fitness values of the offspring crossover mutants are superior to that of the parent population, acquiring new evolutionary direction information and saving the new evolutionary direction information, and updating positions of the three wolves. With the adoption of the robust multiuser detector design method adopting a Huber theory and utilizing a residual non-rapid-increasing function to design a multi-user detector in an impact noise channel, the mentioned problem is effectively solved, and the robustmultiuser detector design method can be used in multi-user detector design.

The invention discloses an uplink multi-user detection method for a multi-beam satellite mobile communication system, and belongs to the technical field of satellite mobile communication. The method comprises the following steps of firstly, constructing a system model of multi-beam satellite communication, simplifying an uplink receiving channel matrix by utilizing the characteristic of energy concentration of an uplink beam domain channel, enabling the uplink receiving channel matrix to be equivalent to a periodic N diagonal matrix, and reducing the calculation complexity in LMMSE detection by utilizing a Jacobi iteration method. According to the uplink multi-user detection method, the system model is simplified, the number of required pilot frequency and channel estimation is effectively reduced, and the calculation complexity of a multi-user MMSE detector is greatly reduced.