158 results about "Multipath delay" patented technology

A single frame format is employed by a millimeter wave communication system for single-carrier and OFDM signaling. A Golay-coded sequence in the start frame delimiter (SFD) field identifies the data transmission as single carrier or OFDM. Complementary Golay codes are employed in a channel estimation field to allow a perfect estimate of the multipath channel to be made. Marker codes generated from Golay codes are inserted periodically between slots for tracking and/or for reacquiring timing, frequency, and multipath channel estimates. The length of the marker codes may be adapted relative to the multipath delay spread.

A method and apparatus are provided for adaptively allocating pilots in a pilot-aided channel estimation system. A multipath delay is measured between a base station (BS) and a mobile station (MS). A distribution density of pilots of a signal to be transmitted between the BS and the MS is controlled. When the multipath delay is large, the pilot distribution density is relatively raised. However, when the multipath delay is small, the pilot distribution density is relatively lowered. The pilot distribution density is adaptively controlled according to the multipath delay, such that resources are effectively utilized and throughput is improved.

Disclosed is a transceiver for a base station with a smart antenna having a plurality of antennas. The transceiver comprises: a multipath searching unit for searching multipath delay information for each demodulation channel; a demodulating unit for forming an adaptive beam for each demodulation channel by using the multipath delay information for each demodulation channel for receiving signals and performing demodulation to the received signals and outputting at least one adaptive beam weight vector; a controlling unit for selecting at least one downlink beam index for each channel; and a modulating unit for selecting the downlink switched beams and forming switching beam for modulating signals of each channel and outputting the modulated signals in downlink.

The invention relates to a system for evaluating the performance of a satellite navigation system. The system has a real-time evaluation mode and a playback evaluation mode and comprises a system positioning accuracy evaluation module, a system velocity measurement accuracy evaluation module, a system availability evaluation module, a system completeness evaluation module, a configuration holding capacity evaluation module and a multipath delay evaluation module, wherein the system positioning accuracy evaluation module evaluates system positioning accuracy by calculating a user equivalent range error and using a statistical method; the system velocity measurement accuracy evaluation module obtains a system velocity measurement accuracy conclusion by calculating a user pseudo-range error and using the statistical method; the system availability evaluation module respectively calculates the availability of the common mode and a wide area differential mode to obtain a system availability conclusion; the system completeness evaluation module obtains a system completeness conclusion by calculating the completeness of three parts, namely a satellite, a ground operational control system and a receiver; the configuration holding capacity evaluation module obtains a configuration holding capacity conclusion by counting constellation occupied time percentage; and the multipath delay evaluation module obtains a multipath delay conclusion by calculating the delay, amplitude and phase difference of a multipath signal relative to a direct signal. The system is easy to implement in engineering and can effectively evaluate the performance of the satellite navigation system.

Multipath delay estimation of a direct sequence spread spectrum (DS-SS) signal transmitted in a multipath fading channel is accomplished by measuring the envelope of the signal to determine a new delay estimate. Delay estimates are also obtained in ray strength order, by subtracting out the influence of the stronger rays on the weaker ones. This subtraction approach can be performed iteratively, allowing further refinement of the delay estimates. Delay estimates can also be determined by minimizing the mean square error (MSE) between a measured correlation function and a modeled correlation function. The minimum mean square error (MMSE) approach can performed iteratively, to further refine the delay estimates. Maximum likelihood (ML) delay estimates can also be obtained by exploiting side information regarding the transmit and receive pulse shapes.

A receiver for a multi-carrier CDMA system receives a signal transmitted having a known pilot sequence on plural sub-carriers. The system includes plural down-converters for down-converting the received signal to baseband signals. A delay and channel estimator correlates at least one of the baseband signals with a single wideband pilot signal, the single wideband pilot signal including all of the known pilot sequences, to produce an estimate of channel gain and multi-path delay. Plural demodulators, one for each of the plural sub carriers, are operatively coupled to the delay and channel estimator, each for demodulating one of the plural baseband signals using the estimate of channel gain and multi-path delay.

A method and apparatus reduces error in a communication system that includes multiple orthogonal subcarriers by suppressing a subcarrier in a transmitting communication device and by equalizing a received signal in a receiving communication device. Subcarrier suppression is based on a determination of a signal quality metric with respect to each subcarrier or is based on a determination of excessive signal power overdriving an amplifier of the receiving communication device. Equalization of the received signal is based on an equalization function that reduces a multipath delay introduced to the transmitted signal when the multipath delay exceeds a tolerable multipath delay.

The invention belongs to the technical field of radio signal identification, in particular to a communication protocol signal identification method based on a depth residual network. The method comprises the following steps of: performing time-frequency analysis on a communication protocol signal in a sample library, and converting a time-frequency spectrum diagram of the signal into a gray-scaleimage; training The depth residual network model by gray-scale image. The trained depth residual network model is used to detect and identify the specific communication protocol signals trained in thetransmission process. As that depth residual network is applied to the field of communication signal identification, the invention overcomes the defect of high signal quality requirement and high prior information requirement of the traditional method, etc. At low SNR, multipath delay, When Doppler frequency offset and some features of signal are obscured by strong interference noise, Doppler frequency offset can still accurately identify the protocol type, and it does not depend on the prior information of received signal, so it can directly process the received IF signal, and has robust performance and high efficiency, which provides ideas for the subsequent research in this field, and has strong practical application value.

The invention provides a method and the device for estimating a channel. The method comprises the following steps of: acquiring channel rough estimation at the position of a reference signal; acquiring multipath delay estimation of the channel rough estimation at the position of the reference signal in a time domain, and determining limiting frequency of a frequency domain interpolation filter needing to be adopted according to the multipath delay estimation; selecting a first frequency domain interpolation filter corresponding to the limiting frequency from a stored frequency domain interpolation filter bank; and performing interpolation processing by adopting the channel rough estimation at the position of the reference signal of the first frequency domain interpolation filter and a time domain interpolation filter to acquire the channel estimation at the positions of all the resource particles. The method and the device greatly reduce computation complexity of a system on the premise of ensuring performance of channel estimation.

The present invention provides an adaptive user autonomous integrity monitoring method. The method comprises: converting the system time of different navigation systems into the same as that of the main system; converting the reference coordinates of different navigation systems to be consistent with the main coordinates; respectively estimating a satellite clock difference, a troposphere delay, an ionosphere delay, and a multipath delay; obtaining a PDOP (position dilution of precision ) value through observation data and satellite ephemeris data; when PDOP<3, using the positioning domain-based location solving method; when 3<PDOP<6, using the measurement domain-based location solving method; when 6<PDOP, determining that the system is not available; using the parity vector method for fault detection; and using the maximum likelihood estimation for fault identification. According to the method provided by the present invention, the exploitation and utilization of observation information can be maximized, and the influence of the gross error on the positioning result can be reduced, so that the performance of the autonomous integrity monitoring of a receiver can be enhanced.

A timing recovery scheme demarcates a complete range of inter-symbol interference free (ISI-free) sampling positions available in a cyclically extended symbol. The timing recovery scheme computes an ensemble correlation between the cyclic extension and the data part of symbols to estimate timing. The ensemble correlation function retains delay-spread and timing information by separately maintaining the correlation value for each sample position within the symbol duration and combines the correlation values for identical sample positions over an ensemble of symbols. In this manner, the scheme not only provides timing estimates, but can also provide estimates of the multipath delay-spread in a channel. The delay-spread estimates provide valuable information about the nature of the channel. A receiver can use this information, for example, to adjust the frequency-domain channel interpolation filter bandwidth in order to improve performance for the given channel condition.

The invention relates to a method and a device for weakening the influence of multipath on the positioning accuracy of a receiver antenna. Under the condition that crude doppler frequency shift and code phase information are obtained, the method obtains advanced data, instant data and delay data of a local code generator, as well as local complex sinusoidal signals, product signal data between intermediate frequency signals received by a receiver and a local oscillator from a traditional closed loop expanding frequency intermediate frequency digital receiver; the data is sent to a digital signal processer to be processed; accurate multipath delay, multipath fading and phase estimation are obtained, then the estimation is combined with a local code of a receiving system, a code relative to carrier wave tracking loop and data of a carrier wave phase accumulator to calculate a value correction value of the codes and the carrier wave phase accumulator, and the data after being corrected is sent to a post processor and a user interface to be processed, therefore the positioning accuracy of the receiver antenna is enhanced. The device comprises a traditional expanding frequency receiver, a digital signal processor, a data output interface connected with the traditional expanding frequency receiver, and a data input interface connected with the traditional expanding frequency receiver.

The interference cancellation (IC) system (500) includes a plurality of IC units, for which IC is applied. Each IC unit has its spread spectrum code generator, delay devices, correlators or matched filters (MF), spreading circuits and subtracting and adding devices. The IC process in accordance with the invention includes using a bank of MF to despread the received signal at every time instant corresponding to every identified multipath of every user's transmitted signal. Based on the despread signals, an initial decision for the present information symbol of every user can be made using a single-user receiver such as, for example, the conventional Rake receiver or an equalizer. Based on the initial decisions, IC regenerates the multipath signals for each user using timed versions of the spread spectrum code, the delays of the multipaths, and the corresponding channel medium estimates. By adding the regenerated signal estimates for the multipaths of all users, an estimate of the received signal at the input of the receiver prior to despreading can be reconstructed. Each IC unit despreads the regenerated received signal using timed versions of the corresponding spread spectrum code for each multipath delay. The result is subsequently subtracted from the initial despread signal and, to avoid removing the desired user path component, the reconstructed, interference-free, desired despread signal path is also added. The above IC process may be repeated several times (e.g., using several IC stages). Performing interference cancellation after despreading the regenerated estimate of the received signal leads to substantially smaller complexity than the prior art approach where the interference cancellation occurs prior to dispreading.

The invention provides a dynamic resource distributing method used in an LTE-A (Long Term Evolution Advanced) system on the basis of resource blocks. In the dynamic resource distributing method, the sizes of time domains and frequency domains of the resource blocks are regulated in real time according to two parameters, i.e. a Doppler frequency shift and a multipath delay spread, of a channel; in the process of processing the resource blocks, each resource block is abstracted into one point, all subcarriers are equally treated inside the point, powers and bits are equally distributed, and a gain of the block is represented by an average value of gains of all carriers; and in the process of distributing the resource blocks, firstly, the best blocks are distributed for all users by using a greedy algorithm, and then a priority is established for each user for the blocks shared by a plurality of users, so that each user is mediated, and thus, not only is the complexity reduced, but also the fairness of each user is ensured.

The invention discloses an indoor pseudo-satellite signal multipath microscopic parameter analysis system based on a statistical model. A software system comprises an indoor structured scene modelingmodule, which is used for carrying out three-dimensional scene modeling with an office area as a target research environment, and is provided with a pseudo-satellite launcher and a pseudo-satellite data collection point; a multipath signal tracking module for carrying out multi-path signal tracking by adopting an image method; a multipath signal extraction module used for extracting multipath signals based on time and power judgment; and a data derivation and statistics analysis module used for matching a deterministic model obtained by inductive statistics with a theoretical model, and verifying the correctness of a multipath microcosmic parameter theoretical model suitable for a pseudo-satellite signal system. Based on the system disclosed by the invention, channel characteristics of pseudo-satellite multipath of a multipath delay extended model, a multipath power delay model and the like in indoor environments can be revealed, and the design of a pseudo-satellite receiver and a simulator is facilitated.

The invention relates to an interference clearance method and device. The core of the invention is that PN sequence after the received available data blocks is superposed to the start position of the available data blocks to ensure that the cyclic convolution relation is formed between the available block data and the multipath delay; at the same time, the interference caused by the multipath delay when PN sequence passes through the channels is considered as the cyclic convolution of the PN sequence and the multipath delay of the channels. In this way, signal of the multipath delay when PN sequence passes through the channels is directly reproduced through Fourier transform/inverse transform. Accordingly, linear convolution operation in the prior art is prevented; complicated operations during the receiving treating process are reduced so that the receiving treating process is very simple.

The invention discloses an exploration method of geological information, comprising the following steps of: selecting a specific sequence code; processing the specific sequence code and then modulating to a low-frequency carrier signal in a spectrum spreading way, and amplifying the modulated carrier signal; converting an amplified electrical signal into an elastic wave containing certain exploration information by a loudspeaker (an elastic wave transmitting antenna), and coupling into an earth channel to carry out transmission; receiving elastic wave signals with different paths which are transmitted by the earth and reflected by stratum interfaces by a sound pick-up (an elastic wave receiving antenna); converting the obtained elastic wave signals into the electric signals again; removing the noise and the interference of the obtained electric signals by using a frequency-selective filter, and carrying out equalization processing, frequency spectrum analysis and digital signal processing on the obtained electric signals; and then computing the parameters, i.e. multipath delay, signal energy, noise energy and signal-to-noise ratio of a multipath signal according to a relevant algorithm of multipath signal processing after microcomputer data processing and fusion.

In order to suppress out-of-band radiation within a range of a spectrum mask regulation without reducing transmission signal power or the like even when a wireless communication is performed in a white space by using OFDM or the like, the present invention is characterized by including an RF circuit characteristic analysis unit, a multipath delay detection unit, a digital filter setting unit, and a transmission power setting unit and further including: a windowing function/windowing duration selection unit configured to select a windowing function and a windowing duration based on the analysis result by the RF circuit characteristic analysis unit, the detection result by the multipath delay detection unit, and the setting by the digital filter setting unit and the transmission power setting unit; a guard interval duration selection unit configured to select a guard interval duration; and a transmission power selection unit configured to select transmission power.

The invention discloses a low earth orbit satellite space-ground communication channel modeling model and modeling method. The model comprises a Doppler frequency shift and change rate module, a multipath delay and gain module, a Rician module, a lognormal module, a state transition control module and a Gauss white noise module. According to the invention, based on the Markov chain process, switching among a direct irradiation state, a medium shadow state and a depth shadow state can be realized; and the transmission time delay, the noise, the large Doppler frequency offset and the frequency offset change rate are considered at the same time, so that not only can stationary and non-stationary orbit satellite communication channel characteristics be described, but also broadband and narrowband communication conditions can be described, and the transmission characteristics of a low-orbit satellite mobile communication channel can be described more accurately.

The embodiment of the invention relates to the technical field of simulation test, and discloses a wireless multipath fading channel simulation system and a method. The system comprises a host computer, a frequency conversion unit and a baseband processing unit. The host computer comprises a user control unit and a channel coefficient generation unit. The user control unit is used for setting thechannel model parameters, and the channel coefficient generating unit is used for calculating the impulse response coefficient of the channel fading model according to the channel model parameters. The frequency conversion unit is used for converting a radio frequency test signal into a signal of a preset frequency band and transmitting the signal to a baseband processing unit. The baseband processing unit is used for performing multipath delay processing on the signal of the preset frequency band, and calculating the faded baseband signal according to the impulse response coefficient and thesignal of the preset frequency band processed by the multipath delay processing. By adopting the embodiment of the invention, the wireless communication performance of the equipment can be comprehensively tested, the test is convenient and the cost is low.

The interference cancellation (IC) system (500) includes a plurality of IC units, for which IC is applied. Each IC unit has its spread spectrum code generator, delay devices, correlators or matched filters (MF), spreading circuits and subtracting and adding devices. The IC process in accordance with the invention includes using a bank of MF to despread the received signal at every time instant corresponding to every identified multipath of every user's transmitted signal. Based on the despread signals, an initial decision for the present information symbol of every user can be made using a single-user receiver such as, for example, the conventional Rake receiver or an equalizer. Based on the initial decisions, IC regenerates the multipath signals for each user using timed versions of the spread spectrum code, the delays of the multipaths, and the corresponding channel medium estimates. By adding the regenerated signal estimates for the multipaths of all users, an estimate of the received signal at the input of the receiver prior to despreading can be reconstructed. Each IC unit despreads the regenerated received signal using timed versions of the corresponding spread spectrum code for each multipath delay. The result is subsequently subtracted from the initial despread signal and, to avoid removing the desired user path component, the reconstructed, interference-free, desired despread signal path is also added. The above IC process may be repeated several times (e.g., using several IC stages). Performing interference cancellation after despreading the regenerated estimate of the received signal leads to substantially smaller complexity than the prior art approach where the interference cancellation occurs prior to dispreading.

The invention discloses a signal generation method of a low-interference multispeed multi-cell quasi-synchronous code division multiple access (CDMA) communication system. The method comprises the steps: a spread spectrum sequence code group is an Hadamard matrix set with certain idealized characteristics formed by Bent functions and a Walsh-Hadamard orthogonal sequence set; a sequence set with the characteristic of a similar zero correlation zone (ZCZ) sequence is obtained by calculating with a pair of complementary sequence sets by utilizing the Hadamard matrix set; and a plurality groups of sequence sets with the similar ZCZ sequence characteristics are obtained by carrying out Cartesian convolution operation with the orthogonal sequence set by utilizing the similar ZCZ sequence set. When a system maximum synchronization error and a channel maximum multipath delay spread are in the stated range, the system interference can be reduced greatly. The parameters of the spread spectrum sequence code group and the system efficiency can be adjusted and flexibly selected according to the practical factors. Therefore, the requirements of power control and synchronization by the CDMA communication system are reduced, and the complexity of system realization is lowered.