299 results about "Narrowband interference" patented technology

A system and / or a method for detecting interference using correlation may be used in a communication system to protect against, or to report the presence of, narrowband interference, which has deleterious effects on the performance of the wideband communication system. The interference detection system described herein may be used to determine presence of narrowband interference by calculating correlation factors for a plurality of narrowband channels disposed within the wideband communication system and comparing the correlation factors with a threshold correlation factor.

An adaptive notch filter (ANF) module selectively filters a received wideband communication signal to eliminate narrowband interference that lies within the frequency spectrum of the wideband communication signal. To determine the presence of narrowband interference, the ANF module scans various known narrowband channels that lie within the frequency spectrum of the wideband communication signal and determines signal strengths for each of the narrowband channels. The signal strengths from the narrowband channels are compared to a threshold that is derived from the narrowband signal strengths. Narrowband channels having signal strengths that are greater than the threshold are determined to have interference.

The present invention relates to a blind adaptive filter for narrowband interference cancellation, which includes an adaptive filter, a delay unit coupled to the adaptive filter for generating a delayed signal with a predetermined delay length from the output signal of the adaptive filter, and an error calculation unit coupled to the adaptive filter and the delay unit. The error calculation unit compares the output signal from the adaptive filter and the delayed signal from the delay unit to extract error information, and feedback the first error information to the adaptive filter. The first error information is formed of a transfer function including a number of coefficients, and used to adjust the adaptive filter and remove interference in the next input signal. The disclosed technique is also applicable in wideband receivers, as well as resisting multiple strong narrowband interferences having a frequency sweep rate of tens of milliseconds.

A method for suppressing narrowband interference in OFDM receivers is provided including the steps of acquiring a sample of received data, estimating parameters of each of a number of narrowband interferers from the acquired sample of data, forming an excision filter using the estimated parameters and inserting the excision filter into an OFDM receiver.

A packet detector joint detects 802.11a packets, 802.11b packets and interference that is within a monitored frequency range but is not formatted as 802.11a packets or 802.11b packets. The packet detector can use signals from one or more antennas. Detection of signals is done using differentially detected correlations. In addition to packet detection, the packet detector can identify signal levels, noise levels and locations of narrowband interference. The process of packet detection and identifying other indicators can be done simultaneously and as the signal is being received.

A wireless device receives an input signal representing a signal of interest (e.g., one or more portions of a packet) on a wireless medium. The input signal may, in addition, contain narrowband interference signals. The wireless device removes the signal of interest from the input signal to produce a residue signal, and analyzes the residue signal to determine the presence of any interference bands in which narrowband interference signals may be present. The wireless device then removes the detected interference bands from the input signal. The residue signal may reveal the presence of interference signals, which might otherwise be hard to distinguish in the input signal. Thus, interference signals with power levels much lower than the power of the signal of interest may be detected and removed.

A technique for reducing interference between a direct-sequence ultra-wideband communications system and a narrowband communications system uses interference-rejecting spreading codes to reduce signal power in a frequency band associated with the narrowband communications system. A method of operating an ultra-wideband communications system includes applying an interference-rejecting spreading code to a signal for transmission. The interference-rejecting spreading code is configured to reduce power in a particular frequency band of a transmit or receive power spectral density associated with the ultra-wideband signal without substantially reducing power outside that particular frequency band of the transmit or receive power spectral density associated with the ultra-wideband signal.

A wideband signal comprising both a wanted signal and narrowband interference is received in a wideband receiver. The receiver comprises an interference detection unit comprising a set of sub-band filters. With the aid of the sub-band filters the received signal is processed to detect a sub-band containing the narrowband interference in time domain.

A receiver receives spread spectrum signals which include unwanted narrowband signals, for example, radio signals which comprise a mixture of signals from signal sources using the Group Special Mobile (GSM) ETSI standard coding and from signal sources using Code Division Multiple Access (CDMA) coding. Both despreading of the spread spectrum signal and attenuating of predetermined frequencies (corresponding to the narrowband signal) of the spread spectrum signal are performed prior to downconverting. In another approach to decoding a spread spectrum signal in which an unwanted narrowband signal has been coded using a coding scheme with error correction capabilities, the narrowband signal is decoded, regenerated and subtracted prior to despreading of the spread spectrum signal.

Cancellation of interference in a communication system with application to S-CDMA. A relatively straight-forward implemented, and computationally efficient approach of selecting a predetermined number of unused codes is used to perform weighted linear combination selectively with each of the input spread signals in a multiple access communication system. If desired, the predetermined number of unused codes is always the same in each implementation. Alternatively, the predetermined number of unused codes are selected from within a reordered code matrix using knowledge that is shared between the two ends of a communication system, such as between the CMs and a CMTS. While the context of an S-CDMA communication system having CMs and a CMTS is used, the solution is generally applicable to any communication system that seeks to cancel narrowband interference. Several embodiments are also described that show the generic applicability of the solution across a wide variety of systems.

The invention discloses a single-wavelength four-Raman laser radar detection system and a detection method. The system combines three laser radar technologies of atmospheric temperature measurement via pure-rotation Raman scattering, vapor measurement via vibration Raman scattering, and measurement of atmosphere aerosol optical characteristics via Raman Mie scattering and an inversion method. The laser radar system employs 355 nm single-wavelength pulse laser as a detection light source and a large-diameter optical reception telescope with high transmittance for measuring the wavelength to collect atmospheric back scattering light signals, four wavelength atmospheric Raman scattering light signals and Mie scattering echo light signals of 353 nm, 354 nm, 355 nm, 386 nm, and 407 nm are mutually separated via an angle separation method of color separation filters and interference filters by a following optical path, the above five-wavelength scattering light signals are gated via narrowband interference filters, photoelectric conversion of photomultipliers of the same type is accomplished, and data acquisition is accomplished by a five-channel data collector.

The system and method of the preferred embodiments may be directed to improving the signal-to-noise ratio in frequency spectrum regions where narrowband interference may be present. The system and method of the preferred embodiments includes reducing the narrowband interference by determining a noise estimate. In accordance with the noise estimate and output of a frequency domain equalizer, a noise-cancelled output may be obtained.

The available modulation schemes of a network are analyzed to determine which ones contain excessive phase noise or narrowband interference. A network element is selected and assigned to a test channel at a first modulation scheme at a predetermined power level to achieve a predetermined PER. The network element transmits a test signal and the network controller measures the signal to noise ratio (SNR) in the received test signal. If the SNR is not within a predetermined tolerance range of an estimated SNR for the modulation scheme at the predetermined PER, the modulation scheme is determined to have excessive phase noise or narrowband interference. Each available modulation scheme is tested by instructing the network element to transmit the test signal using each modulation scheme and assigning the power level of each modulation scheme. The suitable modulation schemes may be determined.

Disclosed are an indication method, system and device for a dynamic idle frequency. After a TD-LTE network side determines a usable idle frequency band, the idle frequency band is used as an auxiliary carrier, wherein the idle frequency band includes frequencies occupied by other narrowband systems; then a main carrier sends auxiliary carrier configuration information, which includes an auxiliary carrier center frequency point and bandwidth, to a terminal, wherein the auxiliary carrier center frequency point is a center frequency point of the usable idle frequency band and the auxiliary carrier bandwidth is a non-LTE-standard bandwidth; and at last, auxiliary carrier resources are scheduled for the terminal and scheduling information is notified to the terminal through the main carrier, wherein the scheduling information is capable of indicating all resource blocks of the non-standard-bandwidth auxiliary carrier and narrowband interference signals in an auxiliary carrier frequency range can be avoided. The TD-LTE is capable of using an idle frequency band with a non-LTE-standard width as an auxiliary carrier and capable of scheduling and indicating all resource blocks capable of avoiding the narrowband interference signals on the auxiliary carrier so as to allocate to the terminal.

A positioning system receiver that mitigates narrowband interference by dynamically choosing the mitigation technique that yields the best interference mitigation capability with the least signal degradation to maximize receiver performance parameters such as receiver sensitivity, multipath resolution, and low power.

The invention discloses a method for automatically identifying and learning abnormal radio signal types. The method is characterized by completing feature extraction of a radio signal in virtue of analysis and actual measurement of the frequency spectrum data of the radio data in combination with experiential knowledge of radio monitoring experts and a feature extraction method. In the characteristic space of the radio signal, clustering analysis is executed on actually-measured sweep-frequency interference, broadband interference, narrowband interference, and invalid intervention signals by using a clustering analysis method. By means of a result of the clustering analysis, the method may provide a radio monitoring device with a capability of automatically identifying abnormal radio signal types. With accumulation of the frequency spectrum data of the actually-measured radio data and increase in identification errors, the method provides a capability of automatically learning the results of the clustering analysis regularly. According to an identification result in combination with a communication device, the method provides an automatic alarming capability for a monitoring device. The method, used in a radio monitoring device, improves an information processing capability of the radio monitoring device, may achieve unmanned operation of the radio monitoring device, and decreases the workload of monitoring technicians.

A narrowband interference excision method and apparatus. According to one embodiment, a method for narrowband interference excision is disclosed. The method comprising transforming time domain data into a frequency domain vector having a plurality of frequency bins. The method further comprises estimating a plurality of power values corresponding to frequency bins of the frequency domain vector to obtain a current power vector. Then, calculating an average power vector from the current power vector and at least one selected previous power vector. Further, excising selected frequency bins of the frequency domain vector to produce an excised frequency domain vector. Moreover, determining whether to include the average power vector in future average power vector determinations. In another embodiment, a narrowband interference excision apparatus is disclosed.

An adaptive data stream filter removes narrowband interference from the CATV return path prior to these paths being combined in the network. A method for removing narrowband interference from the CATV return path detects potential narrowband interference in real-time and adapts a filter to remove this potential narrowband interference. An exemplary embodiment of the above method uses previously created filters that are combined based on detected interference in an adaptive manner to continually adapt to new interference sources. Another exemplary embodiment of the above method calculates new filter coefficients for the data stream filter based on detected interference. In another embodiment, two filters are operated in a ping-pong manner for each band of interference identified as above threshold. This enables updating of one filter while another filter is performing the data stream filter operation.

The invention provides a timing synchronization method and a timing synchronization system for power line carrier communication. The system comprises an analog-to-digital converter, an I / O (Input / Output) demodulator, a narrowband interference detector, an adaptive filter, a normalization module, an auto-correlation calculation module, a comparator and a postprocessor, wherein an OFDM (Orthogonal Frequency Division Multiplexing) carrier signal is converted into an OFDM carrier frequency domain signal by the analog-to-digital converter, the I / O demodulator and the narrowband interference detector. The method comprises the following steps: 1, acquiring average power P of each OFDM subcarrier f; 2, performing narrowband interference detection on the OFDM subcarrier f; 3, filtering the OFDM signal and then performing normalization processing; 4, acquiring start time of the OFDM carrier signal and outputting an OFDM carrier synchronization signal. Compared with the prior art, the timing synchronization method and the timing synchronization system for power line carrier communication have the advantage of higher robustness under various different channel environments of narrowband interference, pulse noise, multi-path propagation and violent change or nonlinear input signal amplitude.

A method for reducing interference from at least one narrowband interferer in a pilot symbol assisted receiver (10) includes the steps of; receiving a stream of received data, passing the stream of received data through an adaptive filter that reduces interference from any narrowband interferer, passing the filtered data through a correlator (7, 8) arranged to detect pilot symbols, when a pilot symbol is detected passing the stream of received data to a receiving apparatus without first passing the received data through the adaptive filter (3), and wherein the pilot symbol includes one or more repetitions of known data or pseudo noise.

The invention discloses a free space optical communication device based on a passive optical network (PON) technology, which aims at the situation that the current free space optical communication system is operated in an SDH system and is not suitable for a PON broadband access network technology. The free space optical communication device comprises a PON interface module, an optical emitting module, an optical emitting antenna, an optical receiving antenna, an optical receiving module, a system control module and an alignment module, wherein both the optical emitting module and the opticalreceiving module adopt infrared lasers with different wavelengths, which are respectively light with the wavelength of 850nm and light with the wavelength of 20nm, and the interference resistance andthe stability of the system are strengthened; the optical emitting module and the optical receiving module perform the transmission and the receiving by four beams of light and drive the lasers in a receiving channel by applying corresponding narrowband interference optical filters and a double-end pulse interval modulation drive circuit; the interference resistant effect of the device on severe weather is strengthened, and the device can be more favorably applied to the wireless communication of a Chinese PON broadband access network.

A wireless communication system may include first and second wireless communications devices communicating with one another via a wireless communications link having a settable link characteristic. The first and second wireless communications devices may include respective first and second wireless transceivers and respective first and second controllers coupled thereto. The first controller may be for detecting received interference, for determining a type of the interference from among interference types comprising wideband interference and narrowband interference, and for setting the settable link characteristic to compensate for the interference based upon the interference type.

A spur detection and spur cancellation apparatus in a multiple sub-carrier digital communication receiver includes a spur detection block that estimates, using one or more Fourier transforms, a frequency location of a narrowband interference spur in a received digital signal that includes a plurality of sub-carriers, and a spur cancellation block that attenuates the estimated narrowband interference spur. The spur detection block may use a fast Fourier transform (FFT) and / or a discrete Fourier transform (DFT) to locate a frequency and to measure a discrete power spectra of the narrowband interference spur. A channel state information block in the receiver may adjust a channel state information metric based on the located frequency and / or the measured discrete power spectra of the narrowband interference spur.

The invention relates to a method for inhibiting MPSK narrowband interference of a direct sequence spread spectrum system (DSSS), and belongs to the technical field of anti-interference of communication. In the method, a main lobe and a side lobe of a MPSK narrowband interference signal are inhibited respectively by adopting a method of combining a frequency domain and a time domain. The method comprises the following steps of: by adopting a method of segmentation overlay processing, inhibiting the main lobe of the MPSK narrowband interference signal as many as possible, and simultaneously ensuring that the energy loss of the useful signal is reduced as much as possible by using the difference between the noise characteristics of the DSSS communication signal in the frequency domain and the energy focusing characteristics of the MPSK narrowband interference signal; and inhibiting the side lobe of the MPSK narrowband interference signal in the time domain so as to effectively separate the interference signal from the useful signal, achieve high performance of bit error rate and guarantee reliable communication of the DSSS by using the characteristics that the frequency spectrum of the side lobe of the MPSK narrowband shows an impulse form. In addition, the method has low computational complexity and is easily implemented by the system in real time.

The invention provides a method for eliminating time-domain narrowband interference of a direct sequence spread spectrum communication system, which comprises the following steps of: 1) dividing received spread spectrum signals into two paths of same signals, wherein one path of signals are delayed and then output to an interference estimating module, and the other path of signals are taken as reference signals; 2) estimating interference signals in the first path of the spread spectrum signals by a transverse filter with unequal interval taps through a time-domain arithmetic, and outputting the interference signals; and 3) subtracting the interference signals from the reference signals, and obtaining the spread spectrum signals of which the narrowband interference is eliminated. In addition, the invention also provides a device for eliminating the time-domain narrowband interference of the direct sequence spread spectrum communication system. The method and the device have the advantages of little computation workload, no need of complicated hardware structure and easy digitalization. The transverse filter with the unequal interval taps can adapt to estimating more types of narrowband interference, and solves the problems of complicated realization of variable tap intervals and poor system continuous work performance at the same time.

A device and method for measuring power of a received broadband signal including narrowband interference in a mobile communication system is provided. An interference eliminator removes the narrowband interference from the received broadband signal through a filter. A power compensator calculates a compensation value for compensating for at least one portion of the received signal removed when the narrowband interference was removed. A received power measurement unit measures power of the received signal received from the interference eliminator, and compensates for a measurement error in the measured power due to the removed at least one portion using the compensation value, and then outputs the received broadband signal having the compensated power.