System and method for extraction of communication interference

A method for the extraction of communication interference, may include converting a digital baseband signal into an analog signal, transmitting the analog signal; receiving the analog signal, converting the analog signal after receipt into a received digital signal, modulating the digital baseband signal to generate a reference signal, estimating a delay between the received digital signal and the reference signal, generating an aligned reference signal based on the reference signal and the delay, estimating a transmission gain of the received digital signal based on the received digital signal and the aligned reference signal, multiplying the aligned reference signal by the transmission gain to generate a scaled reference signal, and subtracting the scaled reference signal from the received digital signal to generate an estimated interference present in the received digital signal.

TECHNICAL FIELD

The present disclosure relates generally to wireless communication and, more particularly, to extraction of communication interference.

BACKGROUND

Satellite communications systems and other wireless communications are used in a variety of telecommunications systems, television, radio and other media systems, data communication networks, military and defense communications systems, and other systems to convey information between remote points using transmitters and receivers. A transmitter is an electronic device which, usually with the aid of an antenna, propagates an electromagnetic signal such as radio, television, or other telecommunications. Transmitters often include signal amplifiers which receive a radio-frequency or other signal, amplify the signal by a predetermined gain, and communicate the amplified signal. On the other hand, a receiver is an electronic device which, also usually with the aid of an antenna, receives and processes a electromagnetic signal. In certain instances, a transmitter and receiver may be combined into a single device called a transceiver.

Because wireless communications are transmitted “over-the-air,” such communications may be subject to interference, whether such interference is incidental or a result of unauthorized use and/or tampering. Accordingly, methods and systems to identify and quantify such interference may be critical to the accuracy and security of communications.

SUMMARY

In accordance with some embodiments of the present disclosure, a method for extraction of communication interference may include converting a digital baseband signal into an analog signal. The method may also include transmitting the analog signal. The method may additionally include receiving the analog signal. The method may further include converting the analog signal after receipt into a received digital signal. The method may also include modulating the digital baseband signal to generate a reference signal. Moreover, the method may include estimating a delay between the digital received signal and the reference signal. The method may additionally include generating an aligned reference signal based on the reference signal and the delay. The method may further include estimating a transmission gain of the received digital signal based on the received digital signal and the aligned reference signal. Additionally, the method may include multiplying the aligned reference signal by the transmission gain to generate a scaled reference signal. The method may also include subtracting the scaled reference signal from the received digital signal to generate an estimated interference present in the received digital signal.

Technical advantages of one or more embodiments of the present disclosure may include the ability to replicate a reference signal component within the received signal using the transmitted reference signal and estimates of delay and scale factor. The precision of this replication may allow for high fidelity extraction of the reference signal from the received signal leaving any interfering signal available for characterization and further processing.

It will be understood that the various embodiments of the present disclosure may include some, all, or none of the enumerated technical advantages. In addition, other technical advantages of the present disclosure may be readily apparent to one skilled in the art from the figures, description and claims included herein.

DETAILED DESCRIPTION

FIG. 1illustrates a schematic diagram of an example of communication system100, in accordance with certain embodiments of the present disclosure. As shown inFIG. 1, system100may include one or more terminals110and140, one or more terrestrial base stations120, and one or more satellites130. For simplicity, only three terminals110and140, two base stations120, and three satellites130are shown inFIG. 1. A terminal110and140may include any device, system, or apparatus configured to process, transmit, and/or receive wireless communications signals, and may also be referred to as a remote station, a mobile station, an access terminal, user equipment (UE), a wireless communication device, a cellular phone, or some other terminology. In some embodiments, a terminal140may be specially configured to extract interference from a transmitted signal. Terrestrial base stations120may include any ground-based system configured to transmit, receive, repeat, and/or amplify wireless communications signals, and may also be referred to as a fixed station, an access point, or some other terminology. Satellites130may include any artificial satellite in orbit about the Earth that is configured to transmit, receive, amplify, repeat, and/or amplify wireless communications signals.

InFIG. 1, each terminal110and140is shown as simultaneously receiving signals from multiple transmitting sources, where a transmitting source may be terrestrial base station120or satellite130. In certain embodiments, terminal110or140may also be a transmitting source. In general, terminal110,140may receive signals from zero, one, or multiple transmitting sources at any given moment.

FIG. 2illustrates a block diagram of selected components of an example of transmitting and/or receiving element200(e.g., a terminal140), in accordance with certain embodiments of the present disclosure. Given the functionality of element200, element200may be considered a transmitter, and a receiver.

As depicted inFIG. 2, element200may include a transmit path having a modulator212a, an upconverter208and a digital-to-analog converter (DAC)204. Modulator212amay be configured to modulate a baseband digital signal received from digital circuitry202and generate signal S1(t). Upconverter208may be configured to frequency upconvert the signal received from modulator212ausing an oscillator signal provided by oscillator210. DAC204may be configured to receive the signal from upconverter208and convert such digital signal into an analog signal for transmission via antenna218a. Antenna218amay receive the analog signal and transmit such signal via communication channel220(e.g., to one or more of terminal110, base station120, and/or satellite130).

Similarly, element200may include a receive path having an analog-to-digital converter (ADC)224and a downconverter228. ADC224may be configured to receive a transmitted analog signal from communications channel220via antenna218band convert such analog signal into a modulated digital signal. Downconverter228may be configured to frequency downconvert the modulated digital signal into a received digital signal based on an oscillator signal provided by oscillator210. In order to detect and quantify interference, element200may transmit a reference signal S1(t) (e.g., from a terminal140to a satellite130) and receive back the same signal. As shown inFIG. 2, in such a case, the received digital signal may be represented by the equation aS1(t−τ)+bS2(t), where S1(t−τ) is a time-delayed version of transmitted signal S1(t) delayed by a delay τ, a is a gain resulting from transmission and receipt of the signal, and bS2(t) is scaled interference. WhileFIG. 2depicts various signals S1(t), S1(t−τ), and bS2(t) as continuous signals, it is noted that such signals may also represent snapshots of digital data streams.

Oscillator210may be any suitable device, system, or apparatus configured to produce an analog waveform of a particular frequency for modulation or upconversion of an analog signal to a wireless communication signal, or for demodulation or downconversion of a wireless communication signal to an analog signal. In some embodiments, oscillator210may be a digitally-generated sample sequence.

Digital circuitry202may include any system, device, or apparatus configured to process digital signals and information received via the receive path, and/or configured to process signals and information for transmission via the transmit path. Such digital circuitry202may include one or more microprocessors, digital signal processors, and/or other suitable devices. In some embodiments, one or more of the other components of element200described in this disclosure may be a part of digital circuitry202.

In addition to the components above, element200may include an interference extractor having a memory206, a modulator212b, a delay module230, a delay estimator232, a gain estimator234, a multiplier236, and a summer238. In some embodiments, one or more components of the interference extractor may be implemented in a general purpose processor, a specialized processor (e.g., a digital signal processor or a graphics processing unit) or in a field-programmable gate array (FPGA).

Memory206may be communicatively coupled to digital circuitry202and may include any system, device, or apparatus configured to retain program instructions and/or data for a period of time (e.g., computer-readable media). Memory206may include random access memory (RAM), electrically erasable programmable read-only memory (EEPROM), a PCMCIA card, flash memory, magnetic storage, opto-magnetic storage, or any suitable selection and/or array of volatile or non-volatile memory that retains data for later use after power to element200is turned off. In operation, memory206may store a baseband digital signal for processing by the interference extractor.

Modulator212bmay be configured to modulate a the baseband digital signal stored in memory206to generate a copy of reference signal Ŝ1(t). Modulator212bmay be similar or identical to modulator212a.

Delay estimator232may be any system, device or apparatus configured to compare the reference signal Ŝ1(t) generated by modulator212bto the received digital signal aS1(t−τ)+bS2(t) generated by downconverter228in order to determine an approximate delay τ necessary to align the two signals (e.g., align the information embedded within the two signals). Delay estimator232may communicate the determined delay to delay module230. In some embodiments delay estimator232may implement a fast correlation between the reference signal and the received digital signal, determine if the maximum correlation peak is statistically significant, and, if so, may determine the time delay τ necessary to align the signals.

Delay module230may be any system, device or apparatus configured to receive the reference signal Ŝ1(t) generated by modulator212band the delay τ and based on such inputs, generate an aligned signal Ŝ1(t−τ). In some embodiments, delay module230may generate an aligned signal by discarding an appropriate number of digital samples from reference signal Ŝ1(t).

Gain estimator234may be any system, device or apparatus configured to receive the aligned reference signal Ŝ1(t−τ) and the received digital signal aS1(t−τ)+bS2(t) and based on such inputs, generate a gain â approximately equal to the actual signal gain a. In certain embodiments, gain estimator234may implement an adaptive algorithm to estimate the multiplicative factor â necessary to scale the aligned reference signal Ŝ1(t−τ) to the non-interference portion of the received digital signal aS1(t−τ)+bS2(t). For example, in one embodiment, the aligned reference signal and the received digital signal may be independently scaled by automatic gain control (AGC) circuits to normalize their amplitudes. Subsequently, these AGC results may be applied to an adaptive least mean square (LMS) to allow convergence of the gain estimate and to estimate the gain.

Multiplier236may be any system, device or apparatus configured to receive estimated gain â and aligned reference signal Ŝ1(t−τ) and based on such inputs, generate a scaled reference signal âŜ1(t−τ).

Summer238may be any system, device or apparatus configured to subtract the scaled reference signal âŜ1(t−τ) from the received digital signal aS1(t−τ)+bS2(t) to generate an interference signal approximately equal to the interference bS2(t). The interference signal may be communicated to digital circuitry for further processing.

FIG. 3illustrates a flow chart for an example method300for extracting interference, in accordance with embodiments of the present disclosure. According to some embodiments, method300may begin at step302. As noted above, teachings of the present disclosure may be implemented in a variety of configurations of system100and/or element200. As such, the preferred initialization point for method300and the order of the steps302-320comprising method300may depend on the implementation chosen.

At step302, modulator212amay modulate a digital baseband signal generated by digital circuitry202, upconverter208may translate the modulated signal to standard intermediate frequencies (IF). DAC204may convert the translated signal to an analog signal, and antenna218amay transmit the modulated analog signal via communications channel220. At step304, memory206may store the digital baseband signal generated by digital circuitry202. At step306, modulator212bmay modulate the stored digital baseband signal to generate a reference signal.

At step308, antenna218bmay receive the transmitted signal from communications channel220. At step310, ADC224may convert the received signal to the digital domain, and downconverter228may translate the signal to generate a digital received signal.

At step312, delay estimator232may estimate the delay between the digital received signal and the reference signal. At step314, delay module230may generate an aligned reference signal based on the reference signal and the estimated delay. At step316, gain estimator234may estimate the transmission gain of the digital received signal based on the received digital signal and the aligned reference signal.

At step318, multiplier236may multiply the aligned reference signal by the estimated gain to generate a scaled reference signal. At step320, summer238may subtract the scaled reference signal from the received digital signal to generate an estimated interference. At step322, extraction parameters and statistics may be computed and saved to refine acquisition and processing parameters for subsequent iterations to allow improved extraction. After completion of step322, method300may end.

AlthoughFIG. 3discloses a particular number of steps to be taken with respect to method300, method300may be executed with greater or lesser steps than those depicted inFIG. 3. In addition, althoughFIG. 3discloses a certain order of steps to be taken with respect to method300, the steps comprising method300may be completed in any suitable order.

Method300may be implemented using element200or any other system operable to implement method300. In certain embodiments, method300may be implemented partially or fully in software and/or firmware, embodied in a memory or other computer-readable media and executable by a processor or other suitable device (e.g. digital circuitry202).

Modifications, additions, or omissions may be made to system100and/or element200from the scope of the disclosure. The components of system100and/or element200may be integrated or separated. In addition, the components of system100and/or element200may be implemented in hardware, firmware, and/or software. Moreover, the operations of system100and/or element200may be performed by more, fewer, or other components. As used in this document, “each” refers to each member of a set or each member of a subset of a set.

Although the present disclosure has been described with several embodiments, various changes and modifications may be suggested to one skilled in the art. It is intended that the present disclosure encompass such changes and modifications as fall within the scope of the appended claims.