185 results about "Multipath component" patented technology

A system and method for canceling interference present in a code-division multiple access (CDMA) channel signal received at a CDMA receiver that is caused by multipath components of a transmitted pilot channel signal or by soft handoff conditions is computationally efficient because it operates at symbol rates. The channel signal from which such multipath interference is canceled can be either a traffic (data) channel or the pilot channel itself. Interference signals are produced in groups corresponding to the fingers of the CDMA rake receiver. The interference signals corresponding to each finger are used to cancel interference in the other fingers.

A MIMO method based on distributed transmission sources for transmitting a downlink data stream between M transmitting antennas and a mobile terminal having P receiving antennas, M and P>1, channels from at least two transmitting antennas to one of receiving antennas have different multipath distributions, said method comprises transmitting corresponding M substreams to the mobile terminal by using the same spreading code; estimating the multipath channel matrix; and processing the signal according to the multipath channel matrix to restore the downlink data stream, the estimating including measuring the total number of actual multipath received components having different delays in the transmitted signals; constructing the multipath channel matrix by taking the number as the multipath number, so that if the signal transmitted by one of the transmitting antennas to the receiving antenna has no multipath component corresponding to one of the delays, the channel parameter corresponding to the transmitting antenna, the receiving antenna and the delay is set as 0, the transmitting comprises adjusting the gain of said M sub-data streams based on the average signal quality measurement of uplink signals from the mobile terminal to said M transmitting antennas, so that average path losses of respective downlink channels are substantially equal.

A method for enhancing the accuracy of Advanced Forward Link Trilateration (AFLT) position location calculations is disclosed. A position determination entity (PDE) constructs a statistical database of pilot phase measurements reported by mobile stations (MSs) located in a geographic region about a reference base station (BS). When a MS's location is to be calculated, the MS reports a set of PN phase offsets to the PDE. Using only that set of PN phase offsets, the PDE determines a rough estimate of the MS's location using conventional AFLT and also determines the region within which the MS is located. If the PDE determines that the MS did not report one or more earlier arriving PN phase offsets but reported a delayed multipath component, the PDE sends a message to the MS to look for an earlier arriving PN phase offset at a certain time prior to the reported PN phase offset.

The present invention relates to a method and apparatus for reducing interference arising from signal propagation delay in multipath signal environments in wireless communication systems. The present invention provides a method of operating a mobile communications base station which receives multipath components of signals from a number of high mobility subscriber terminals, the method comprising: for each subscriber terminal signal received, determining a best signal component; determining the difference in time between reception of said best signal component and a reference time; transmitting to said terminal a transmission timing offset in order to receive said best component at substantially said reference time.

The present invention relates to a method for estimating a propagation channel in the presence of transmit beam-forming within a receiver, accounting for the structure of two logical channels referred as to a common channel and a dedicated physical channel (CPICH, DPCH) and based on a common structure of corresponding propagation channels, said DPCH channel comprising two sub-channels (DPDCH, DPCCH), said propagation channels being modeled as a linear superposition of a finite number of discrete multipath components following an uncorrelated-scattering wide-sense stationary model, a multipath component being characterized by a time-varying multipath complex coefficient and a delay. Use: RAKE Receiver.

This invention generally relates to wired and wireless ultra wideband (UWB) data communications apparatus and methods, and in particular to UWB receiver systems and architectures, and to correlators therefore. An ultra wideband (UWB) receiver system comprising: a receiver front end to receive a UWB signal having a plurality of multipath components; and a correlator coupled to said receiver front end to correlate said UWB signal with a reference signal; and wherein said UWB signal comprises a plurality of pulses; wherein each said pulse has a plurality of multipath components; wherein said reference signal comprises a plurality of multipath components of a said pulse; and wherein said correlator comprises at least one correlator module configured to correlate a plurality of said multipath components of a said pulse with said reference signal.

The channel estimation method for millimeter-wave communication includes virtual multipath acquisition and sparse reconstruction. In the virtual multipath acquisition stage, instead of searching the real multipath components (MPCs), the virtual representation of the real MPCs is derived, and the hierarchical search is utilized to acquire the virtual MPCs based on a normal limited-resolution codebook. In the sparse reconstruction stage, the real MPCs are reconstructed from the virtual MPCs acquired in the virtual multipath acquisition stage. An enhanced sub-array scheme is used to design a hierarchical codebook under a strict constant-modulus constraint. The designed codebook can be used for both analog and hybrid beamforming/combining devices. The training overhead of channel estimation and the complexity of the search are significantly reduced, and the size of the dictionary matrix is greatly reduced by exploiting the results of the virtual multipath acquisition.

In one embodiment, a rake receiver for a spread-spectrum (SS) signal has a plurality of rake fingers corresponding to different multipath components of the SS signal and sampling circuitry generating a stream of samples corresponding to the SS signal. A first rake finger has a detection path detecting symbols based on the samples, a synchronization (synch) path, and a weighting controller. Front-end circuitry in the synch path applies three or more time delays, weighting, and SS correlation to the stream of samples to generate front-end output signals. Back-end circuitry in the synch path generates one or more control signals for controlling the timing of the sampling circuitry based on the front-end output signals. The weighting controller adaptively controls the weighting applied by the front-end synch circuitry to minimize effects of one or more other multipath components associated with one or more other rake fingers of the rake receiver.

System and methods are disclosed for passively determining the location of a moveable transmitter utilizing a pair of phase shifts at a receiver for extracting a direction vector from a receiver to the transmitter. In a preferred embodiment, a phase difference between the transmitter and receiver is extracted utilizing a noncoherent demodulator in the receiver. The receiver includes an antenna array with three antenna elements, which preferably are patch antenna elements spaced apart by one-half wavelength. Three receiver channels are preferably utilized for simultaneously processing the received signal from each of the three antenna elements. Multipath transmission paths for each of the three receiver channels are indexed so that comparisons of the same multipath component are made for each of the three receiver channels. The phase difference for each received signal is determined by comparing only the magnitudes of received and stored modulation signals to determine a winning modulation symbol.

A receiver comprises a plurality of antenna elements for receiving a data signal. Each antenna element has a plurality of Rake fingers. Each Rake finger processes a received multipath component of the received data signal of its antenna element by applying a complex weight gain to that received multipath component. A complex weight gain generator determines the complex weight gain for each Rake finger for each antenna element using an input from all the Rake fingers. A summer combines an output of each Rake finger to produce an estimate of the data signal.

A method for reducing multipath when determining a location of a stationary or near stationary position, includes receiving a signal from an antenna moving continuously with respect to the stationary or near stationary position, the signal including a multipath component, processing the received signal including the multipath component, wherein multipath error in the received signal is reduced during the processing and determining a location of the stationary or near stationary position based on the processed received signal with the multipath error reduced.

The invention provides a GNSS reflected signal parameter estimation method and a device. The recursive least square (RLS) filtering is carried out on the correlation value which is obtained by demodulating and dispreading a short-distance multipath signal to estimate the parameters of the multipath signal; the parameters includes the information such as the tracking errors of the code and the carrier phase of a direct branch, the amplitude and the delay of each multipath component relative to a direct signal, carrier frequency, phase position and the like; the estimated multipath component information can be used as the utilization of a reflected signal; and the estimated information of the tracking errors of the direct signal enables a receiver still to accurately track the code and the carrier under the environment of short distance multipath to eliminate the interference of the multipath signal and improve the tracking accuracy. When the system is changed, the basic structures of correlated modules are not changed, and the sending signals and the direct signals can be estimated and tracked through regulating part of parameters and functions. The invention is a estimation proposal suitable for various GNSS systems.

Multipath components of signals transmitted through time-varying digital radio channels are received with individual delays, and signals through a given channel comprise a code identifying that channel. A delay profile indicating a magnitude (Y) for delay values in a search window is calculated repetitively for known channels; the delays of multipath components for known channels estimated; a signal strength indicator calculated; and a search for new multipath components not already estimated performed at regular time intervals. When a new multipath component is found, its identification code is compared to the codes of the known channels. If the code of the new component is identical to the code of a known channel, a delay profile and a signal strength indicator is calculated for a window transposed to include the new multipath component. In this way as many multipath components as possible are included in the search window for a new cell.

A method for compensating for multipath components in a received CDMA signal comprising a repetitive PRN code uses delay times in addition to the early, late and prompt delay times for determining if a multipath component is present in the received signal, and if so, making an adjustment to the delay time of the replica code generated by a receiver so as to minimize the difference between the correlation values for a delay time equal to −1 chip and a delay time more negative than −1 chip. In this manner, adjustments to the estimation time for the start of the PRN code can be made in a manner which minimizes the effects of multipath components. A system using additional delays and correlators in association with the code phase detector, a code numerical control oscillator and replica code generator is described for performing the above methodology. The methodology is particularly suitable for GPS receivers and may further be used in receivers that receive any type of digital sequence spread spectrum, code division multiple access signals. Compensation for multipath components with 180 degree phase shifts is also made as well as compensation due to smoothing of the triangular correlation function due to RF characteristics and non-ideal PRN codes.

Methods, a base station and computer programs for performing multiple access in wireless OFDM cellular systems over multipath wireless channels considering both space and frequency domains,

The base station 100 comprises a large number of antennas 103 in the form of a two-dimensional array and transmits a given number of signals to a number of users 106, so that each one receives its intended signal (or set of intended signals) without interference to/from the other users 106. The base station 100 includes a scheduler in space-time-frequency dimensions 101 as well as an orthogonal space-frequency processing technique 102 for addressing the users 106. The cellular scenario is assumed where the wireless channel 105 presents significant multipath, thereby resulting in multiple signal components being received by each user 106. Orthogonality of the beams is achieved upon transmission by properly discretizing the spatial domain, while inter-user interference is avoided by exciting only those beams that result in multipath components received by one single user 106.

Methods and Systems for tracking symbol timing of an OFDM signal are disclosed. In one embodiment, a wireless receiver includes signal tracking and timing logic to facilitate the timing of a demodulation operation such that the demodulation operation occurs on the proper symbol boundary, particularly when the OFDM signal has multipath components and the second component has greater power than the first.

Method and system are disclosed for detecting a situation where it is likely that additional multipath components are available in the channel, but are not included in the RAKE processing. In some embodiments, the invention uses the interference estimates for all RAKE fingers associated with tracked multipath components to detect the fraction of the available signal energy that is captured by the path searcher. The invention provides an activation signal to the path searcher if the fraction of the available power that is captured by the tracked paths falls below a predefined threshold.