271 results about "Multi user detection" patented technology

Methods and systems are provided for reducing interference across coverage cells using base stations interconnected by a packet network. A wireless device monitors the channel signal strength of its serving cell and its neighboring cell. The serving cell collects measurements from the wireless devices within its cell and informs its neighboring cell when one of the wireless device may be causing significant interference to the neighboring cell. The neighboring cell collects this information and executes a multi-user detection and cancellation algorithm on a subset of these interfering wireless devices.

A modem that provides efficient use of wireless network bandwidth in the presence of multi-user interference and noise comprising a multi-user detection module (115), a data formatting module (120), a control processor (125) and a demultiplexer (135).

A Multi-User Detection device and method for DS-CDMA to allow enhanced signal reception under Multi-User Interference (MUI) at either the Remote Station or the Base Station is disclosed. The method includes the steps of relaying current channelization code use at Base Stations to Remote Stations operating in the vicinity of the Base Stations. This information is used by an MUD device at the Remote Station, to improve its ability to separate signals transmitted from different Base Stations. The downlink channelization code information is used to recreate the interference received by all neighboring Base Stations transmissions at the Remote Station. The same method can be applied at the Base Station side. The Uplink Channelization Code Usage information is relayed to each Base Station from its neighboring Base Stations. Recreating the total Remote Station interference at the Base Station allows a multistage interference cancellation based MUD to enhance its capability of receiving Remote Stations in its coverage area.

A radio communication network that requires no connection between base stations during handoff or when the cell is overloaded, is realized by using a receiver that has a multi-user detection function and a transmitter for synthesizing control information and user data to output the synthesized data. Upon reception of a signal that is transmitted from a mobile station located on the boundary with a neighboring cell, the base station synthesizes user data for a mobile station in its local cell and control information for controlling the handoff operation to transmit the synthesized data. In response to this transmission, a mobile station in the neighboring cell separates the control information by multi-user detection to detect the signal and transmits a handoff request to the base station.

A system is presented that provides real-time performance for iterative multi-user detectors, such as Turbo MUDs, which are used to separate simultaneous transmissions on the same frequency, by permitting the MUD to use a less computationally intense, fast-processing algorithm and to correct for errors caused by the fast processing. In order to reduce the errors, a voting system is coupled to the output of the multi-user detector within the iterative system. The voting system provides confidence values on a bit-by-bit basis for the estimates made by the multi-user detector, with the confidence values then being utilized as soft inputs to a bank of conventional single-user decoders.

Multi-user detection method with elimination of interference between users, each user transmitting modulated data in the form of symbols on a transmission channel, each transmission channel (k) comprising at least one propagation path (i) and each propagation path arriving at an array of reception antennae (l) according to a direction of arrival (θ_i,k), the method comprising at least one sequence of steps for each user (k), each sequence comprising:

• • (a) a reception step (600_k,700_k,800_k,800,900) decomposing each antenna signal into filtered signals (x_l,i,k) issuing from the different paths (i) of the said user (k) and combining the said filtered signals by means of a first plurality of coefficients (b_l,i,k, c_i,k) in order to form an estimation (z_k) of the signal transmitted by the user;
  • (b) a step of estimating (670_k,770_k,870_k,870,970) the contribution ((x_l,k)l=1 . . . L) of the user to the signals received by the different antennae from the said estimation of the signal transmitted and a second plurality of coefficients (u_i,k, w_l,i,k ) obtained from the said first plurality of coefficients;
  • (c) a step of eliminating interference (680_k′,780_k,880_k,880,980) subtracting from the antenna signals the contribution estimated at step (b) in order to obtain cleaned antenna signals;
  • the cleaned antenna signals supplied by at least one first sequence being used as antenna signals by at least one second sequence.

A method and apparatus for using a multi-user detector for reducing multiple access interference (MAI) in a direct sequence CDMA wireless system such as W-CDMA. A superconducting rapid single flux quantum (RSFQ) RF digital receiver operating in combination with an RSFQ successive interference canceller (SIC) is located in the base stations of the wireless system. In the present invention, the RSFQ SIC is a vector machine capable of processing the cross-correlation matrices using an iterative method to decorrelate the user binary code sequences from the input signal in which the interference components are removed. According, the reduction in interference results in a significant increase in system capacity while improving cellular coverage area.

In a spectrum allocation method in a cellular communication system, a cell pattern is divided into clusters each containing a plurality of adjacent cells. A pool of forward and return link bearers is allocated to each cluster and may be shared among cells within the cluster. Bearers are reused between blusters having a sufficiently high mutual isolation. Preferably, the same time slot in a return link bearer is allocated to multiple users within the cluster. The receiver of the shared return link bearer uses multi-user detection techniques to separately decode the signals from each user sharing a time slot, using the spatial diversity of the individual cells.

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 method (400) and arrangement (200) for mitigation of intercell and intracell interference in a 3GPP cellular communication system (100) by, in a receiver in a cell of the system, deriving for a first channel in the cell a signal, representative of first channel transfer function (A⁽¹⁾); deriving for at least a second channel originating in a different cell a signal (A^{(2 . . . M)}), representative of second channel transfer function, based on: deriving a cell specific scrambling code (s), deriving a channel impulse response (h), and deriving a channelisation code (c); and performing multi-user detection using the first and second signals. Where the channelisation code is unknown, a substitute channelisation code is preferably substituted. It will be appreciated that the technique can be applied to both downlink and uplink. This provides the advantage that both intra-cell interference and intercell interference are mitigated.

A method for multi-user detection includes receiving a complex input signal due to a superposition of waveforms encoding symbols in a real-valued constellation, which are transmitted respectively by a plurality of transmitters in a common frequency band. The complex input signal is sampled at sampling intervals over the duration of an observation period to provide a sequence of complex samples. The sequence of complex samples is processed to determine soft decision values corresponding to the symbols transmitted by the plurality of the transmitters in the observation period, while constraining the soft decision values to be real values. The soft decision values are then projected onto the constellation to estimate the transmitted symbols.

A unified minimum mean square error (MMSE) equalization/multi-user detection (MUD) approach for demodulating direct sequence CDMA (DS-CDMA) signals is described. In at least one embodiment, the unified approach is capable of generating a variety of cost-effective receiver demodulation techniques that may range from, for example, a low cost linear MMSE equalization technique to a relatively high complexity MMSE MUD.

A method, and a system of mitigating interference effects under a communication environment including a first spread spectrum (SS) transmission scheme and a second spread spectrum (SS) transmission scheme in the same frequency band are proposed in this present invention. Firstly, responsive to a received signal, output number of signal of the first SS transmission scheme and the second SS transmission scheme. Secondly, retrieve the timing, phase and amplitude information of signals of the first SS transmission scheme in the received signal, and the timing, phase and amplitude information of signals of the second SS transmission scheme. Generate a plurality of linearly-modulated signals based on a predetermined manner, correlate the received signal based on the plurality of linearly-modulated signals to generate a correlated outputs. Finally, selectively produce an estimated information sequence carried by the signals of the first SS transmission scheme and the signals of the second SS transmission scheme based on the correlated outputs in another predetermined manner. Such a method and a system not only extend the ability of conventional linear multi-user detection to the FH-CDMA (frequency hopping code division multiple access) and the DS-FH-CDMA (direct sequence and frequency hopping code division multiple access) multi-user communications systems, but also remove the limitations of the conventional linear multi-user detection on linearly modulated signals. In addition, the multi-user synchronizers proposed in this invention, which estimate the received timings, phases, and amplitudes of the interfering and the desired spread spectrum signals with feasible complexity, further complete the interference suppression communications system. This invention is applicable to various environments. For example: the source of DSSS signals could be derived from the IEEE 802.11b devices or perhaps the IEEE 802.15.3 devices; the source of FHSS signals could be derived from the IEEE 802.15.1 (Bluetooth) devices or the HomeRF devices. Moreover, this invention is not limited to the wireless communications as it is equally applicable to the optical communications systems (e.g. the HFC (hybrid-fiber-coax) networks) and the wired communications systems.

Methods and systems in a wireless receiver for enabling the reception of input signals at varied power levels in the presence of co-channel interference utilizing combinations of space-time adaptive processing (STAP), interference cancellation multi-user detection (MUD), and combined STAP/MUD techniques. In MUD, code, timing, and possibly channel information of multiple users are jointly used to better detect each individual user. The novel combination of adaptive signal reconstruction techniques with interference cancellation MUD techniques provides accurate temporal cancellation of interference with minimal interference residuals. Additional methods and systems extend adaptive signal reconstruction techniques to take Doppler spread into account. STAP techniques permit a wireless receiver to exploit multiple antenna elements to form beams in the direction of the desired signal and nulls in the direction of the interfering signals. The combined STAP-MUD methods and systems increase the probability of successful user detection by taking advantage of the benefits of each reception method. An additional method and system utilizes STAP techniques in the case where no pilot signal is available. This method compares the outputs of various hypothesized STAP solutions.

In a multi-user detection receiver, a multi-user detector DET receives a signal from a multiple access channel MA and the current soft estimates of each user's contribution to the received signal, and outputs updated soft estimates for each user by subtracting the current soft estimates of all the interfering users. The updated soft estimate or soft demodulated by soft demodulators DEM₁ . . . DEM_K, the coded by soft decoders DEC₁ . . . DEC_K which refine the probabilities of the coded bits derived from the soft demodulators DEM₁ . . . DEM_K, by taking into account the knowledge of the code, and output to soft modulators M₁ . . . M_K. For each iteration of the MUD receiver algorithm, an acquisition function ACQ acquires the timing of the estimates of each user's contribution to the channel for use by the detector DET in the next iteration, giving improved acquisition performance over conventional single-user techniques.

There is provided a system and method for multi-user detection by a plurality of base stations situated at different geographical locations through base station cooperation. An exemplary method comprises exchanging detected data iteratively while performing separate detection and decoding of received data streams.

A method and apparatus to compensate for interference between signals within a wireless communication system using dirty paper coding to compensate for interference on the downlink and multi-user detection to compensate for interference on uplink.

In signal detection system and method implemented to reduce the effects of interference in multi-user detection systems, a receiver defines a frame of symbols containing at least one window based upon a number of user signals contained in a received signal r(t). A symbol amplitude of a single-user in the multi-user system is approximated over the window of the frame based on a number of reflected signal paths of the received user signal. A perturbative correction value is calculated based upon a correlation matrix. An estimation of the symbol amplitude of the single-user signal is calculated over one or a number of windows of the frame. The single-user signal is detected when the symbol amplitudes of the entire signal within the frame has been calculated. To reduce the number of interfering users in a multicell CDMA system, the symbol codes are modified to include an even code and an odd code. The even and odd codes are symmetrically separated over the duration of the symbol to form an interference reduction window. If the delay offsets of the symbol codes are less than the interference reduction window and the even codes are assigned to a first cell, and odd codes to adjacent cells, then the adjacent cell interference vanishes.

The invention provides a multi-user detection method based on a ZC (Zadoff-Chu) sequence. The multi-user detection method based on the ZC sequence is applicable to the situation of a high speed. The multi-user detection method is an improvement of a ZC sequence multi-user detection method using three joint detection windows in an LTE high-speed scene. The multi-user detection method comprises the steps that a specific ZC sequence root serial number is selected to generate the ZC sequence, related peak values in a Doppler environment can shift to centralize within the detection range of a single detection window through the specific ZC sequence root serial number, and therefore multi-user detection can be carried out through the single detection window at the detection end. According to the multi-user detection method based on the ZC sequence, the disadvantage that energy of a main window is dispersed by frequency offset can be effectively avoided, and high performance still can be achieved under the conditions of high speed and high frequency offset.

A multi-user detection method eliminating interference between users transmitting modulated data of symbols on a transmission channel, each transmission channel including at least one propagation path arriving at an array of reception antennas in a direction of arrival. Each user (a) estimates the signal transmitted by the user from the antenna signals, effecting estimation of the direction of arrival and characteristics of propagation of each path of the transmission channel from the signals; (b) estimates the data transmitted by the user from the estimation of the signal transmitted; (c) estimates the contribution of the user to the signals received by the different antennas from the estimated data and the estimated direction of arrival and propagation characteristics; and (d) subtracts from the antenna signals the contribution estimated at (c) to obtain cleaned antenna signals, supplied by at least a first sequence, used as antenna signals by at least a second sequence.

The invention provides a power distribution method considering delay limitation in a millimeter wave (mmWave) uplink communication system assisted by an intelligent reflection surface (IRS). Accordingto the method, the power distribution problem is converted into three optimization steps through an alternating optimization (AO) thought by taking optimization of user power as a target and maximumdelay of a user as a constraint, and the method specifically comprises the steps of(1) fixing a multi-user detection matrix and an IRS passive beamforming variable, and obtaining an optimized power closed-form solution according to a transmission delay constraint; (2) fixing power and passive beamforming variables, and optimizing a multi-user detection matrix to eliminate inter-user interference;and (3) fixing power and a user detection matrix, and proposing a complex circulation waveform optimization (CCMO) algorithm for optimization of IRS beam forming. According to the invention, retransmission time delay caused by channel blocking can be effectively resisted in a low-cost and low-power-consumption mode by utilizing an almost passive IRS auxiliary link, and the proposed algorithm is suitable for being expanded to the problem of large-scale IRS auxiliary power distribution.

This invention provides a detection method and device for the training sequence in a downlink TDD/CDMA system. In some TDD/CDMA systems, Multi-user detection (MUD) can be applied in UE, but the conventional training sequence detection method of great complexity. This invention is to perform matched filter operation on the training sequence of the desired users at at possible positions to get the adaptive threshold values detecting training sequence intensity and the multi-path positions, which correspond to the output peak values of the matched filter. Afterwards it performs the matched filter operation for other possible training sequences only at those peak positions mentioned above. This invention uses adaptive threshold value to detect the training sequence intensity, and the algorithm is improved greatly.