Abstract: The present invention relates a remote sensing system, or particularly a satellite-formation-based remote sensing system, wherein comprising: a master satellite provided with an SAR system as a payload thereof, a first concomitant satellite, and a second concomitant satellite, wherein the first concomitant satellite and the second concomitant satellite fly around the master satellite, and the master satellite is located on major axes of motion trajectories of the first concomitant satellite and the second concomitant satellite, so as to define a first spatial baseline and a second spatial baseline that have an identical cross-track baseline component. The present invention enables high-precision, wide-range, three-dimensional imaging based on the satellite-formation, while acquires spatiotemporal features of variation of a ground region according to the synchronization in terms of time, frequency, and space.

Abstract: A method and system for emulating physical layer (L1) connectivity between distant computing devices. Existing solutions require that the computing devices or end points directly connect to a same interconnecting (or network) device and/or employ network devices requiring awareness of the communication protocol used between the end points. Further, existing solutions typically fail to match the ingress and egress clock rates. These restrictions limit scaling of the solutions, confine the end points to a physical co-location, and/or fail to transport or replicate the physical properties (e.g., errors, proprietary signaling, clock frequency, etc.) of the data stream transmitted between the end points. The disclosed method and system overcome these limitations through implementation of a L1 connectivity abstraction between computing devices across a network, and through clock rate reconstruction using a data buffer state controlled phase lock loop (PLL) mechanism.

Abstract: A mobile device includes; a power line communication ( ) module that communicates data with an external device via a power line, receives a first preamble signal from the external device during a first preamble interval, receives a voltage signal as the data during a data reception interval following the first preamble interval, and demodulates the voltage signal to provide a demodulated voltage signal, a frequency/duty detector that detects a frequency and a duty of the first preamble signal, and a control circuit that performs signal a data determination operation on a demodulated voltage signal during a data period and using the first detected frequency and the first detected duty.

Abstract: A method of selecting a frequency block includes determining a first value representing a lowest noise level of a radio channel at a first or second node, calculating a first metric representing a ratio between a first desired signal strength and the first value, determining a second value representing a lowest noise level of a radio channel at the first or second nodes, calculating a second metric representing a ratio between a second desired signal strength and the second value, selecting, on the basis of at least the first and second metrics and amongst a set of frequency blocks including at least the first and second frequency blocks, a frequency block for transmission of a message between the first and second nodes, indicating a sub-band of the selected frequency block, and causing transmission of the message on the indicated sub-band.

Abstract: Power is provided from a power source and a status of the power source is signaled by controlling a waveform of an AC voltage generated from the power source. The status may include, for example, a capacity of the power source. In some embodiments, a frequency of the AC voltage may be controlled to signal the status. The power source may include, for example, an uninterruptible power supply (UPS), and signaling a status of the power source may include controlling an inverter of the UPS to signal the status. Related systems are also described.

Abstract: A backscatter communication method and apparatus based on pattern-based demodulation is disclosed. The backscatter communication method includes receiving a communication signal, and demodulating the communication signal based on a slope of the communication signal at an edge of each time interval.

Abstract: A compensator for compensating line or coupling losses of a signal transmission path for transmitting a communication signal between an antenna and an electronic control unit, including at least one first interface for connecting to the antenna and a second interface for connecting to the electronic control unit, and which is furthermore notable in that, in addition to the communication signal, the compensator is configured to output a position signal for position determination. An electronic circuit arrangement for operating at least one antenna and an antenna device is also disclosed.

Abstract: The present technique relates to an image sensor, an data transmission method thereof, an information processing apparatus, an information processing method, an electronic device, and a program with which it is made possible to improve flexibility in compression and to make connectivity between an image sensor and a DSP better. Data Pixel4*N to Pixel4*N+3 in a 12-bit original image data format of four pixels is converted into six-bit compression data and is arranged by two pixels into a 12-bit compression data format including a structure identical to that of a 12-bit original image data format, whereby data Data2*N and Data2*N+1 is configured. Moreover, upper eight bits of each of compression data formats Data2*N and Data2*N+1 are read and arranged into data Byte3*N and Byte3*N+1. Lower four bits of each of the compression data format Data2*N and Data2*N+1 are arranged into data Byte3*N+2. The present technique can be applied to an imaging apparatus.

Abstract: Systems and methods for synchronizing a power line communication system including a power line and one or more devices communicatively coupled to the power line. A mains frequency of the power line is estimated at the devices, and corresponding local frequencies of the devices are adjusted based on the corresponding estimated mains frequency. Data signals are transmitted from or received by the devices based on the adjusted local frequencies.

Abstract: A PLC/power-supply hybrid device includes a power supply circuit. The power supply circuit includes a switching part for chopping a voltage of a voltage input terminal side, and a control circuit that controls the chopping by controlling switching of the switching part. The control circuit is operated in a normal mode and a transmission mode. The normal mode is a mode in which voltage conversion is performed. The transmission mode is a mode in which data transmission is performed through PLC using a power line that leads to the voltage input terminal. In the transmission mode, the control circuit modulates the switching of the switching part in accordance with transmission data.

Abstract: A way to deliver traffic to a mobile node that is undergoing a hand off between two Access Routers (AR) is described. The method of the present invention operates to perform some or all of the following: decrease, e.g., minimize, delays between the time the old link breaks and the first packet is sent from the new link; reduce and/or eliminate packet bursts from old to new AR when an old (existing) link breaks; ensure that packets are neither lost nor duplicated during hand off; maintain QoS control of delivery order to the MN; make good or best use of multiple links during make-before-break hand-off; and support both uplink and downlink traffic.

Abstract: A frequency range for Fourier transform is controlled and a digital signal is subjected to fast Fourier transform within the controlled range, whereby a plurality of frequency components (FFT signals) in the digital signal are detected. A transmission rate of a received signal is determined using the detected FFT signals and the FFT signals are demodulated by an operation at a speed corresponding to the determined transmission rate.

Abstract: A method for supporting Time-Quadrature Amplitude Modulation (TQAM) in a wireless communication system includes generating a transmission symbol identified by a combination of a QAM symbol and a position of a time resource to which the QAM symbol is mapped, shifting at least one QAM symbol among QAM symbols contained in the transmission symbols with respect to a time axis, and readjusting a constellation point of the QAM symbol on the basis of a shifting quantity. A method for operating a receive end comprises receiving a reception symbol identified by a combination of a QAM symbol and a position of a time resource to which the QAM symbol is mapped, restoring at least one QAM symbol shifted in a transmit end for uniformizing of the time-axis distribution of QAM symbols contained in the reception symbols, generating decoding metrics for the reception symbol, and performing decoding the reception symbol using the decoding metric.

Abstract: An frequency shift keying (FSK) transceiver for use in a hearing aid is capable of automatic tuning of the transceiver frequency. The automatic tuning makes use of a phase difference detector and a tuning manager adapted to control the frequency of a resonant circuit of the FSK transceiver according to information received from the phase difference detector. The phase difference detector measures the phase difference across a component of the resonant circuit of the FSK transceiver. If the phase difference of a binary FSK symbol is equal to the phase difference of the opposite binary FSK symbol, the resonant circuit is tuned, otherwise the tuning manager performs a tuning procedure in order to minimize the difference in phase differences, and adjusts the frequency of the resonant circuit accordingly.

Abstract: A memristor-based emulator including a memristor circuit for use in digital modulation that includes a first current feedback operational amplifier (CFOA) having multiple terminals in communication with a capacitor Cd and in further communication with a resistor Ri. A second CFOA having multiple terminals is in communication with the first CFOA and is adapted to be in further communication with a voltage vM to provide an input current iM for integration by a capacitor Ci. A nonlinear resistor is in communication with the second CFOA. A third CFOA having multiple terminals is in communication with the nonlinear resistor and is in further communication with the first CFOA and a resistor Rd. The third CFOA and the resistor Rd act as an inverting amplifier associated with the nonlinear resistor to increase a current gain to increase a difference between ON and OFF values of a resistance of a realized memristor.

Abstract: A signal transmission system including a transmitting device and a receiving device, including: the transmitting device including: a first modulator that modulates a frequency of a control signal; and a first multiplexer that multiplexes the frequency-modulated control signal onto a DVI (Digital Visual Interface) signal to be transmitted to the receiving device via a single network cable; and the receiving device including: a first separator that separates the frequency-modulated control signal from the multiplexed DVI signal; and a first demodulator that demodulates the separated control signal.

Abstract: In at least one embodiment, a method includes receiving a first transmission from a device, the first transmission transmitted at a first frequency. In response to receiving the first transmission, a transceiver is disabled and a second transmission is transmitted to the device, the second transmission transmitted at a second frequency. The method further includes receiving a third transmission from the device, the third transmission transmitted at the second frequency.

Abstract: A communication system having a configurable bandpass filter is disclosed. The system includes a bandpass filter and a bandpass controller. The bandpass filter has an adjustable center frequency. The bandpass controller is configured to identify a frequency shift in a master in or received signal and to shift the center frequency of the bandpass filter according to the identified frequency shift.

Abstract: The invention relates to the field of radio signal receivers for use in wireless communication networks. In particular to a receiver unit having at least one antenna input for receiving multipath radio signals via a radio unit and at least one antenna from one or more user equipments is provided. The receiver unit comprises: a despreading unit configured to despread a multipath radio signal in the received multipath radio signals using a number of despreading fingers corresponding to a number of delay positions in the multipath radio signal which corresponds to a number of paths in the multipath radio signal, and a combining unit configured to apply at least one weight to the output of each of the number of allocated despreading fingers and combine the weighted outputs into a resulting equalized radio signal.

Abstract: A non-contact power supply transmitter system 100 transmitting an electric power from a transmitting device (TX) 200 to a receiving device (RX) 300 with a non-contact power supply transmitter method, the TX 200 including: a transmitting coil 202; a driver 204 causing the transmitting coil to generate a power signal of the electromagnetic field; and an FSK modulation unit 240 transmitting an FSK signal Sf through the transmitting coil, the RX 300 including: a receiving coil 302; a rectifier circuit 320 rectifying an electric current induced by the receiving coil; an FSK demodulation unit 340 demodulating the FSK signal received through the receiving coil; and a controller 312 controlling so that a rectifying mode of the rectifier circuit is switched to a diode rectifying mode during the FSK communication. The non-contact power supply transmitter system 100 and the RX 300 can execute a stable FSK communication.

Abstract: A non-contact power supply transmitter system 100 transmitting an electric power from a transmitting device (TX) 200 to a receiving device (RX) 300 with a non-contact power supply transmitter method, the TX 200 including: a transmitting coil 202; a driver 204 causing the transmitting coil 202 to generate a power signal of the electromagnetic field; and an FSK modulation unit 240 transmitting an FSK signal Sf through the transmitting coil 202, the RX 300 including: a receiving coil 302; an FSK demodulation unit 330 demodulating the FSK signal Sf received through the receiving coil 302; and a controller 312 inputting the FSK signal demodulated by the FSK demodulation unit 330, the FSK demodulation unit 330 is composed of an analog circuit. The non-contact power supply transmitter system, the receiving device, and the analog circuit can realize a low power, space-saving FSK communication.

Abstract: A method selects a codebook for transmit beamforming. The method constructs an estimated channel matrix based on a codebook, selects a channel submatrix from the estimated channel matrix, calculates a selection matrix from the channel submatrix; and assigns a steering matrix based on the selection matrix. The method may construct an estimated channel matrix, select a channel submatrix, and calculate a selection matrix for each of multiple codebooks, then select an optimal codebook. The steering matrix is assigned based on the optimal codebook. The steering matrix may be used in steering a transmitted packet. The method may also calculate a post-MIMO equalizer signal-to-noise ratio for a data stream, based on the estimated channel matrix and the selected codebook. A related system is also disclosed. Other embodiments are provided, and each of the embodiments described herein can be used alone or in combination with one another.

Abstract: The present invention employs hierarchical modulation to simultaneously transmit information on different modulation layers using a carrier RF signal. Initially, first data to be transmitted is assigned to a first modulation layer and second data is assigned to a second modulation layer. In one embodiment of the present invention, the first and second data are assigned based on reliability criteria. The first and second modulation layers are hierarchical modulation layers of the carrier RF signal. Once assigned, the first data is transmitted using the first modulation layer of the carrier RF signal and the second data is transmitted using the second modulation layer of the carrier RF signal. In one embodiment of the present invention, information may be transmitted to one end user using one modulation layer, and information may be transmitted to a different end user using a different modulation layer.

Abstract: The invention provides transmission methods of messages between a tanker aircraft and receiver aircraft that facilitate air refueling operations using a boom device in, particularly, radio silence environments. In the case of data messages, the method comprises steps for transmitting a message from the aircraft that emits the message to the target aircraft as an analog signal via the electro-magnetic connection which is used for contact detection and disconnection and audio communications between the tanker aircraft and the receiver aircraft in radio silence environments. In the case of audio and data messages it is transmitted a signal resulting from mixing analog signals corresponding to both messages in a way that allows their separation at the target aircraft.

Abstract: A Bluetooth receiver comprises a RF front end configured to receive a Bluetooth signal including a preamble and 34-bit pseudo-number (PN); a DC estimator communicatively coupled to the RF front end; and a frame synchronizer communicatively coupled to the DC estimator. The DC estimator is configured to perform DC offset estimation by determining an average value of samples of the preamble and the frame synchronizer is configured to use the 34-bit PN for frame synchronization.

Abstract: One embodiment of the present invention relates to a communications system. The system includes a Highway-Addressable Remote Transducer (HART) transmitter comprising a direct memory access (DMA) module configured to access at least one transmitter lookup table (LUT) using DMA transfers to modulate a HART data packet into a frequency-shift keying (FSK) data signal. The system also includes a HART receiver configured to demodulate a received FSK data signal into a demodulated HART data packet.

Abstract: In an FSK receiver according to the present invention, a correction operation for a DC offset component is performed based on a maximum value and a minimum value of a demodulation signal. If a difference between the maximum and minimum values is less than a predetermined threshold value TH1, the correction operation is halted. Thus, the FSK receiver can rapidly perform an appropriate offset removal from a multi-level FSK signal.

Abstract: A repeater includes a clock-and-data recovery element and a phase interpolator to extract an embedded clock frequency from a data stream. The phase interpolator determine a frequency offset and sends such offset as phase interpolator codes to a filter and scaler. The filtered, scaled phase interpolator codes are used to produce a reference clock frequency for retransmission.

Abstract: A multiple-antenna receiver can enable and disable receive radio frequency front-end and analog front-end circuits of specific antenna receiving routes according to a predetermined scheme during the receive data phase. The predetermined scheme calculates signal quality indices of the receiving route antennas according to a preamble sequence, and derives the modulation and coding scheme and the number of spatial streams via the information provided by a header sequence. Indications of the signal quality indices are compared with threshold values to determine which receiving routes are to be turned on and which receiving routes are to be turned off.

Abstract: Systems and methodologies are described that facilitate mitigation of interference through uplink scheduling in a wireless communication environment. Access points can assign multiple terminals to a single tile or segment of shared resource (e.g., a time frequency region) to maximize the number of terminals supported. However, combinations of certain types of terminals can cause a significant increase in interference. In particular, allocating multiple terminals having a relatively high velocity (e.g., terminals located in moving vehicles) to a single tile can cause an unacceptable increase in interference. To mitigate interference, high velocity terminals can be identified. Once identified, terminals can be allocated to the available tiles based at least in part upon avoiding combinations that result in a significant increase in interference.

Abstract: A signal processing arrangement is designed to process a digitalized phase-modulated and/or digitalized spreaded input signal (1) and has a complex channelizer (2) which despreads and/or demodulates the input signal (1) in the time range on the basis of a folding operation.

Abstract: A distortion compensation device which reduces a distortion of an amplifier which is added to an output signal of the amplifier, the distortion compensation device including: a plurality of distortion compensation coefficient storage circuits which stores a plurality of distortion compensation coefficients and outputs the distortion compensation coefficients according to an amplitude of an input signal of the amplifier, a distortion compensating processing circuit which adds the distortion compensation coefficient output from each of the plurality of distortion compensation coefficient storage circuits to the input signal of the amplifier, and a distortion compensation coefficient updating circuit which performs weighting processing on the distortion compensation coefficient output from each of the plurality of distortion compensation coefficient storage circuits to reduce the distortion compensation coefficient and which calculates an update value of the distortion compensation coefficient by using the disto

Abstract: The high sensitivity FSK radiofrequency signal receiver includes an antenna for receiving FSK radiofrequency signals, a LNA amplifier receiving signals picked up by the antenna, a local oscillator for supplying oscillating signals, a mixer for mixing the incoming signals with the oscillating signals to produce intermediate signals. The receiver includes a broadband or poly-phase filter for filtering the intermediate signals, and a sampler for supplying sampled intermediate signals to a high sensitivity demodulation stage, which supplies data signals. The receiver includes a processing circuit for performing a discrete Fourier transform of sampled intermediate signals. The selector at the processing circuit output determines the difference between the signal amplitude peak frequency above a determined threshold and the expected frequency of the intermediate signals.

Abstract: Circuitry for use in aligning bytes in a serial data signal (e.g., with deserializer circuitry that operates in part in response to a byte rate clock signal) includes a multistage shift register for shifting the serial data signal through a number of stages at least equal to (and in many cases, preferably more than) the number of bits in a byte. The output signal of any shift register stage can be selected as the output of this “bit slipping” circuitry so that any number of bits over a fairly wide range can be “slipped” to produce or help produce appropriately aligned bytes. The disclosed bit slipping circuitry is alternatively or additionally usable in helping to align (“deskew”) two or more serial data signals that are received via separate communication channels.

Abstract: The present invention provides a method of estimating a frequency offset. The method comprises receiving a wireless signal timed according to a first frequency; generating a local signal timed according to a second frequency; and performing a plurality of synchronization searches, each search comprising obtaining a set of correlation results indicative of a correlation between the wireless signal and the local signal at different timing offsets of the wireless signal relative to the local signal. The method the no comprises finding a series of results, with a result from each of a plurality of the synchronization searches, for which the difference in; timing offset between results from adjacent searches in the series is within a maximum specified value. A frequency off set between the first and second frequencies can be determined from the series.

Abstract: Provided is a communication system that includes setting a detection threshold according to a distribution of at least one logic value of a transmission signal corresponding to an on-off keying (OOK) scheme or a frequency shift keying (FSK) scheme, and determining a type of noise source influencing a reception signal using the detection threshold and the distribution of at least one logic value.

Abstract: A wireless communication system is provided. The wireless communication system includes a wireless relay and a mobile terminal. The wireless relay is coupled to a phone network. The mobile terminal is physically coupled to the wireless relay to make a voice communication with the phone network via the wireless relay. Further, the mobile terminal and the wireless relay exchange control data and voice data corresponding to the voice communication over a short-range wireless link based on one of a transparent mode and a translation mode. A signaling connection is established on an asynchronous connection-oriented logical (ACL) transport channel between the mobile terminal and the wireless relay for exchanging the control data, and a voice connection is established on a synchronous connection oriented (SCO) channel between the mobile terminal and the wireless relay for exchanging the voice data.

Abstract: A method of performing a service scan for available channels across a bandwidth of an input signal, the method comprising the steps of: acquiring a power spectrum of the input signal bandwidth; analyzing the power spectrum to identify a list of candidate channels, each candidate channel being identified by at least a center frequency; processing each of the candidate channels in a receiver unit to extract service information, if present, relating to the candidate channel; and storing the service information for the channel in a memory.

Abstract: There is provided a solution for dual channel transmission in a radio communication device. Both transmission signals to be transmitted on different channels are mixed two times by using oscillator signals having the same frequencies for both transmission signals, and the transmission circuitry is arranged to process the signals so that the transmission signals are nevertheless up-converted to different frequency channels.

Abstract: A method and apparatus for decoding binary frequency shift key signals in which an exclusive-OR of the sign of a real waveform with a sign of the imaginary waveform at a time shortly after the real (or, alternatively, the imaginary) waveform crosses zero is used to determine a bit represented by the signal. In some embodiments, particularly those in which the bit period is about one-half of the carrier signal frequency, both the real and imaginary waveforms are monitored to detect the zero crossing in order to account for the situation in which data transitions prevent zero-crossings on one of the waveforms.

Abstract: Systems and methods and memory media for performing modulation type detection. An attempt is made to estimate an underlying symbol rate of a received signal. The received signal is compensated for carrier frequency offset. Two candidates for symbol timing offset are estimated from the compensated signal. The compensated signal is downsampled using each offset candidate. A set of features is computed for each of the two downsampled signals. For each downsampled signal, the set of features is compared to a corresponding set of thresholds to obtain a corresponding set of comparison results. The two sets of comparison results are used to determine the modulation type of the received signal. A second method for estimating symbol rate may be performed if the modulation type is found to be FSK.

Abstract: Improvements are disclosed for in-band signaling, i.e., transmission of data in a voice channel of a digital wireless network during a voice call session. A family of narrow-band signaling methods, some employing tapered waveforms, is disclosed to successfully pass data-carrying signals through the low-bit rate modes of the EVRC-B vocoder commonly used in CDMA wireless channels. These features can be used in cell phones or other wireless communication devices, including automotive applications.

Abstract: A wireless relay apparatus is provided. The wireless relay apparatus includes a telephone module configured to couple with a public switched telephone network (PSTN) to receive a telephone call, and a wireless module coupled to the telephone module to process the telephone call and configured to wirelessly connect to a mobile terminal such that the telephone call is forwarded to the mobile terminal over a short-range wireless link. Further, the wireless module is configured to operate in one of a transparent mode and a translation mode so as to exchange voice data with the mobile terminal.

Abstract: The radio transmitting apparatus includes a first initial phase value setting circuit that sets, in the first modulator, an initial value of the phase of the first modulated signal, which is a value at the start of the modulation according to the first modulation scheme. The radio transmitting apparatus includes a second initial phase value setting circuit that sets, in the second modulator, the phase stored in the phase storing circuit as an initial value of the phase of the second modulated signal, which is a value at the start of the modulation according to the second modulation scheme. The radio transmitting apparatus includes a signal gathering circuit that selects and outputs the first modulated signal output from the first modulator and then selects and outputs the second modulated signal output from the second modulator.

Abstract: A receiver for detecting and recovering data from Orthogonal Frequency Division Multiplexed (OFDM) symbols. The receiver comprises a demodulator, symbol synchronization unit, frequency transform processor, and coarse frequency offset detector. The demodulator generates sampled symbols. The symbol synchronization unit has correlators, which receives the sampled symbols, and a correlation detection processor. Each correlator auto correlates each sampled symbol, and the correlation detection processor determines a start point of each symbol. The frequency transform processor receives the sampled symbols and performs a frequency transform on each symbol.

Abstract: Improved control apparatus and methods transfer information between devices, such as controllers and field devices, utilizing a modulator that generates a pulse width modulated (PWM) signal containing information to be transferred by a first of the devices, e.g., the controller, to the second device. A transformer or other inductive device transfers the PWM signal across the isolation barrier, where it is demodulated to analog form for application to the second device, e.g., the field device. Information transferred from the second device to the first device can be transferred in an amplitude modulated (AM) signal that utilizes, as its carrier, a fixed duty cycle output of the modulator that generates the PWM signal.

Abstract: An apparatus for providing a data encoding scheme may include an encoder. The encoder may be configured to determine, for a digital input value comprising a particular number of bits, whether more than half of the bits of the digital input value have a high value. The encoder may be further configured to encode the digital input value by inverting each of the bits of the digital input value in response to a determination that more than half of the bits of the digital input value have the high value. Corresponding method and computer program product, and a decoder and decoding method are also provided.

Abstract: Improved control apparatus and methods transfer information between devices, such as controllers and field devices, utilizing a modulator that generates a pulse width modulated (PWM) signal containing information to be transferred by a first of the devices, e.g., the controller, to the second device. A transformer or other inductive device transfers the PWM signal across the isolation barrier, where it is demodulated to analog form for application to the second device, e.g., the field device. Information transferred from the second device to the first device can be transferred in an amplitude modulated (AM) signal that utilizes, as its carrier, a fixed duty cycle output of the modulator that generates the PWM signal.

Abstract: A technique for wirelessly transmitting management data without cables in a data center is provided. Management data is obtained at a device in the data center. A wireless management data signal is generated from the management data. The wireless management data signal is configured to be transmitted at frequencies matching an ambient electromagnetic noise emitted by the data center, such that the wireless management data signal is masked in the ambient electromagnetic noise emitted by the data center. The wireless management data signal is wirelessly transmitted to another device.

Abstract: Determining a frequency offset of a received signal utilizing two or more multipath components of the received signal is provided herein. By way of example, the received signal can be correlated with a synchronization sequence in a time domain or a frequency domain, resulting in separation of the two or more multipath components of the received signal. Analysis of at least one of the multipath components can provide a frequency offset of the received signal. Furthermore, by analyzing the multipath components, estimation of the frequency offset can be improved as compared with single-signal analysis techniques.