86 results about "Multiuser detection" patented technology

An error correction decoding (ECC) processing scheme is disclosed that reduces computational complexity normally associated with multiuser detection (e.g., TurboMUD) solutions, without causing degradation in quality of service or decreasing the total throughput. Error correction decoding algorithms are applied only to portions of the estimates that were affected by the immediately previous MUD update process. Even though the MUD and/or ECC updating is targeted so as to reduce complexity of each iteration, all of the estimates are maintained and remain candidates for future updates. As such, there is no negative impact real-time or future performance. This targeting approach can be used in conjunction with many variations of MUD, including full-complexity or reduced complexity, and may include MUD with confidence ordering or voting, and other techniques for facilitating efficient and effective MUD processing.

A plurality of communications is received. The communications are transmitted in a wireless code division multiple access format. A channel response for each received communication is estimated. A system response matrix is constructed using codes and the channel responses of the received communications. An objective matrix is produced using the system response matrix. The received communications are matched filtered to produce a first input. The first input is processed with an interference cancellation matrix to produce a first set of symbols of the received communications. The first set of produced symbols are processed with a feedback interference construction matrix to produce feedback interference. The feedback matrix added to an inverse of the interference cancellation matrix equals the objective matrix. The feedback interference is subtracted from a result of the match filtering to produce a next input. The next input is processed with the interference cancellation matrix to produce a next set symbols of the received communications.

The present invention relates to a new parallel interference cancellation (PIC) configuration where the PIC is implemented after the rake reception and multipath combining. In the invention disclosed, the regenerated interference contributions (functions of signature sequence cross-correlations) for multiuser detection (MUD) in a multipath radio channel are explicitly filtered through the estimated multipath channels, and stored. These stored quantities already contain the effect of the channel, and only need updating according to the rate of change of channel dynamics, and not the symbol period. During each symbol period, interference is computed from each interfering user to each desired user using current estimates of symbol decisions and the aforementioned interference contributions. The precomputation of the interference contributions, which are valid for a sequence of symbols, allows for extremely low complexity baseband processing in the receiver.

A Parameter Estimator for accurately estimating signature responses of multiple co-channel interfering digital transmission signals. The Parameter Estimator is used in a Multiuser Detection (MUD) Receiver to significantly reduce the error rate. The Parameter Estimator comprises a plurality of software components, including a Signature Waveform Estimator, Training Sequence Locator, Noise Estimator, Active Users Tester, Initial Transformation Matrix Builder, a Transformation Matrix Rebuilder, and a Transformation Matrix Selector, and generates an estimated noise power, a training sequence index and estimated signature waveforms.

A method and apparatus are disclosed that apply multiuser detection (MUD) analysis to an aggregated RF response from a plurality of simultaneously queried RFID tags, so as to distinguish the individual tag responses. The claimed method thereby significantly reduces RFID detection latency when multiple tags are simultaneously queried. Some embodiments transmit carrier waves at more than one frequency, such as a plurality of equally-spaced frequencies, so as to enhance the MUD analysis by incorporating a multi-frequency dimension. Other embodiments incorporate additional spatial dimensions by deploying multiple RF detection antennae at separated locations. The number of colliding tag responses must be estimated before MUD analysis can be applied. In some embodiments other signal parameters must be estimated, such as signal bias and an impulse function for each responding tag that characterizes alterations of the RF signal while in transit due to propagation distance, passage through intervening objects, and reflections.

The invention provides a multiuser detection method based on a serial strategy for an SCMA (Sparse Code Multiple Access) uplink communication system, and belongs to the field of signal detection of wireless communication systems. The method is characterized in that nodes in a conventional SCMA factor graph are divided into J groups (J is a quantity of user nodes); each group comprises one user node and all resource nodes connected with the user node; and all nodes (one user node and all the resource nodes which are connected with the user node) of each group are updated in sequence in each iteration process. According to the multiuser detection method, already-updated node messages are utilized in each iteration process, so that a utilization ratio of the already-updated node messages can be effectively increased. The BER (Bit Error Rate) performance of the method is far superior to the BER performance of a method in the prior art under the condition of less iteration times. The calculation complexity of the method is much lower than the calculation complexity of the method in the prior art under the condition of hardly any loss of the BER performance.

A method and apparatus for enhancing the receiving and information identification functions of multiple access communications systems by employing one or more optical processors configured as a bank of 1-D correlators. The present invention is particularly useful in a DS/SS CDMA communications system, resulting in a multiuser CDMA system that approaches carrier to noise performance (C/N) as opposed to being limited by multiple access interference (MAI). The correlators are arranged in parallel to detect and/or demodulate the received signal, in conjunction with one or more complex algorithms to perform near-optimum multiuser detection, perform multipath combining and/or perform carrier Doppler compensation. An improved receiver in accordance with the present invention comprises means for receiving a plurality of signals transmitted through a communications channel; signal conversion means for converting the received signals into a form suitable for input to the multichannel correlator; a multichannel optical correlator for identifying the presence of particular waveforms and estimating the relative time delay or delays, carrier frequency offset from expected, RF amplitude and RF phase for each received spread spectrum waveform present in the received plurality of signals; a controller for determining and providing to the optical correlator the appropriate set of reference hypotheses; and one or more receiver algorithms depending on the exact receiver function to be performed.

The present invention is a digital communication method that increases the overall throughput of a Multiuser Detection (MUD)-based co-channel multiple access (MA) system in terms of the total number of bits transmitted through the shared medium by all the users of the MA system if signals are allowed to interfere. The total number of users can be increased if more dimensions are used for assigning the transmitted signals and the same dimensions are measured at the receiver. Specifically, the present invention does not require any coordination among transmitters but simply requires a transmitter to send its signal with either a randomly chosen polarization ellipse, or an assigned or randomly chosen amplitude level.

The invention belongs to the wireless communication signal detection technical field and relates to a block compressive sensing non-orthogonal multiple-address system multiuser detection method. The invention provides a sparseness adaptive detection method which can recombine structured sparseness into block sparseness. According to the block compressive sensing non-orthogonal multiple-address system multiuser detection method of the invention, a block sparseness-adaptive sub-space tracking algorithm is adopted for recombined block sparseness signals; according to the algorithm, a noise power setting threshold is utilized to realize the adaptive evaluation of the sparseness of users, and SER (Symbol Error Rate) performance is improved greatly compared with that of the prior art under a condition that the a priori information of sparseness degree is not required; and a simulation result indicates that the performance of the algorithm can reach an optimal theoretical value after a signal-to-noise ratio is increased to a certain extent.

The invention provides an optimal multiuser detection method based on an evolutionary chaotic quantum neural network. The method comprises the following steps: establishing an optimal multiuser detection model; initializing an initial parameter of the chaotic quantum neural network, and activating the chaotic quantum neural network to acquire an approximate optimal solution; initializing the individual quantum, assigning the binary measurement state of the first individual quantum as the output value of the chaotic quantum neural network; constructing a fitness function and computing the fitness; evolving the quantum state of the individual quantum and acquiring a new measurement state by using a simulated quantum revolving door; activating the quantum neural network evolution mechanism in evolutionary chaotic scrambling to produce a sub-optimal solution for the binary state of each individual quantum; computing the fitness function value of each individual quantum to find out the global optimal solution; and outputting the global optimal solution as an optimal result for the multiuser detection. The detection method provided by the invention has excellent multi-access interference resistance and far-near effect resistance, wide application range, and can acquire the optimal detection result within the short time.

This invention discloses one TD-SCDMA same frequency area down part interference offset channel estimation method, which comprises the following steps: for n areas to store memory sequences of s1,s2,s3...son; receiving signal Midamble train codes to form 128-code data; at certain time getting data from signal Midamble train codes for first area remaining part offset; then processing first area signal estimation then for first area to receive signal restore; restoring user terminal from first area to receive signal s1 and brushing s1 memory unit.

A method and apparatus for transmitting and receiving in black space is described. The asymmetric interference channel is an appropriate model for many realistic scenarios, especially those arising more frequently as dynamic spectrum access (DSA) becomes more prevalent. As DSA nodes evolve to become more cognitive (e.g. self aware, environment aware, and adaptive), the prevailing white space seeking and gray space adapting policies leave a significant portion of the spectrum, namely, the black space, untapped. Described herein is a throughput versus SINR result and a corresponding technique for jointly choosing a transmission rate and multiuser detection algorithm that allows computationally constrained cognitive DSA nodes high rate operation in spectrum black space. Also described is an information theoretic motivated policy for seemingly insignificant waveform design choices that greatly enhance the throughput of a secondary sender-receiver pair while fulfilling a given complexity requirement within the secondary node's receiver.

A method of providing medium access control for a wireless mobile ad hoc network includes defining a TDMA network timing frame including a data (DATA) zone having one or more time slots structured to support multiuser detection (MUD) of concurrent transmissions during each slot, a negative acknowledgment (NACK) zone during which nodes transmit requests for retransmission of packets destined to but not successfully received by the nodes, a broadcast (BC) zone during which network management messages are broadcast to the nodes, and a control (CTRL) zone. A primary master (PM) node is selected and operates as a source of network time for all the nodes. Each node synchronizes its time to that of the PM node during the CTRL zone in a distributed manner, by exchanging control messages with the PM node or other nodes located one or more hops from the PM node.

System and method for detecting transmissions from multiple users in a digital wireless communications system in the presence of interference. A preferred embodiment comprises derotating a received signal by a specified amount, determining channel estimates, which can include the determination of the number of users (interferers plus a desired user), and extracting information transmitted by the desired user from the received signal. Successive and parallel multiuser detection schemes are provided for extracting the information from the received signal.

The invention provides methods and apparatus for multiple user detection (MUD) processing. One aspect of the invention provides a multiprocessor, multiuser detection system for detecting user transmitted symbols in CDMA short-code spectrum waveforms. A first processing element generates a matrix (hereinafter, “gamma matrix”) that represents a correlation between a short-code associated with one user and those associated with one or more other users. A set of second processing elements generates, e.g., from the gamma matrix, a matrix (hereinafter, “R-matrix”) that represents cross-correlations among user waveforms based on their amplitudes and time lags. A third processing element produces estimates of the user transmitted symbols as a function of the R-matrix.

The invention relates to a particle filtering method used for asynchronous DS-CDMA system blind multiuser detection in the mobile communication technical field to inhibit multiple access interference and near-far effect and reduce system error rate. The method adopts the following main steps: firstly, a plurality of channel gains, time delays and random particles of a user symbol are generated, and the importance weighing of the random particles is initialized; secondly, a Markov Model, which is set up according to the characteristics of the physical channel of each user, combines with user symbol particle to complete Kalman filtering estimation of each channel gain and time-delayed particle, thereby reducing the deviation of particle distribution; thirdly, the joint posterior probabilityof the particle is obtained and the weighted mean of the particle in the estimated value of the user symbol, channel time delay and gain is completed; fourthly, during the process, update and normalization of particle weighting are completed, and importance resampling of the particle is carried out according to effective sampling size. The invention has the characteristics of stable performance and easy implementation.

A method of using a user equipment (UE) in a wireless time division duplex communication system. Each communication burst has a unique channelization code and a midamble code which is uniquely related to the channelization code, each such midamble code being uniquely related to one or more channelization code. The UE receives communication bursts and detects each midamble code in a received communication burst. The UE determines the channelization codes related to each detected midamble based on a mapping of midamble codes to related channelization codes. The UE detects channelization codes in the received communication burst from among the determined channelization codes.

What is provided is a system for maintaining acceptable error rates in a MUD-enabled ad-hoc network. In this system the power spread associated with all of the nodes is maintained within the dynamic range of the system, for instance 30 dB. Also, the signal-to-noise ratio at an intended receiver is maintained above a predetermined minimum SNR, for instance above 5 dB. If the dynamic range rule is not met, then the power at the transmitting node is attenuated such that the dynamic range rule is met, checking to see that the minimum SNR rule is also met, or the transmission from this node is pulled. If there is no power control solution, then power aware scheduling is applied. Alternatively, only power aware scheduling is utilized.