Abstract: A logging tool is positioned downhole in a wellbore, where the logging tool communicates with a computer on the Earth's surface over an analog signal path. Tool data is received from a sensor associated with the logging tool and encoded into a symbol signal. The symbol signal is transmitted to a receiver system via the analog signal path. The receiver system has one or more filters to filter the symbol signal. The one or more filters includes an equalizer filter indicative of an analog signal path response of the analog signal path. The filtered symbol signal is decoded into second tool data. The second tool data is encoded into second symbols and based on the second symbols, an updated analog signal path response of the analog signal path is generated to update the equalizer filter.

Abstract: Systems, apparatus, and methods are described for formatting and for performing data communications between a surface modem and one or more modems located in a logging tool of a bottom hole assembly for use in a wellbore environment.

Abstract: A logging tool is positioned downhole in a wellbore, where the logging tool communicates with a computer on the Earth's surface over an analog signal path. Tool data is received from a sensor associated with the logging tool and encoded into a symbol signal. The symbol signal is transmitted to a receiver system via the analog signal path. The receiver system has one or more filters to filter the symbol signal. The one or more filters includes an equalizer filter indicative of an analog signal path response of the analog signal path. The filtered symbol signal is decoded into second tool data. The second tool data is encoded into second symbols and based on the second symbols, an updated analog signal path response of the analog signal path is generated to update the equalizer filter.

Abstract: One or more adjustment to a set of telemetry communication parameters utilized for providing communications between a surface modem and at least one downhole modem of a borehole logging system are described. The one or more adjustments to the telemetry communication parameters may be made following completion of an initial training of the modems and without the need to power down the surface modem or any of the downhole modem(s) included in the at least one downhole modem.

Abstract: One or more adjustment to a set of telemetry communication parameters utilized for providing communications between a surface modem and at least one downhole modem of a borehole logging system are described. The one or more adjustments to the telemetry communication parameters may be made following completion of an initial training of the modems and without the need to power down the surface modem or any of the downhole modem(s) included in the at least one downhole modem.

Abstract: Systems, apparatus, and methods are described for formatting and for performing data communications between a surface modem and one or more modems located in a logging tool of a bottom hole assembly for use in a wellbore environment.

Abstract: In an example implementation, communications between a downhole logging tool and surface computing subsystem can be provided through a cable that includes one or more electrical conductors. To allow multiple channels of data to be transmitted along a single multi-conductor cable, data can be divided into two or more different channels, and each channel of data can be transmitted along the conductors. Due to the length of the cable, the electrical conductors of the cable may be subject to strong capacitive and inductive coupling. As a consequence of this coupling, signals sent downhole along any two arbitrary conductors may be subject to distortion, and can produce significant “crosstalk” on the other conductors. The effects of crosstalk can be reduced in a variety of ways, for example using QR decomposition.

Abstract: An identification method comprising: when an object is in a whole process from entering to separating from a region inducted by the low-frequency electromagnetic field, receiving the low-frequency signal of the low-frequency electromagnetic field in real time; extracting the attribute code and signal intensity corresponding to the low-frequency signal received and conducting associate storage; and after the object separates from the region inducted by the low-frequency electromagnetic field, determining the route direction along which the object passes through the vector beacons according to the attribute code and signal intensity stored.

Abstract: In an example implementation, communications between a downhole logging tool and surface computing subsystem can be provided through a cable that includes one or more electrical conductors. To allow multiple channels of data to be transmitted along a single multi-conductor cable, data can be divided into two or more different channels, and each channel of data can be transmitted along the conductors. Due to the length of the cable, the electrical conductors of the cable may be subject to strong capacitive and inductive coupling. As a consequence of this coupling, signals sent downhole along any two arbitrary conductors may be subject to distortion, and can produce significant “crosstalk” on the other conductors. The effects of crosstalk can be reduced in a variety of ways, for example using QR decomposition.

Abstract: A technique for frame synchronization in a communication system includes performing symbol correlation on received signal samples. A determination is made as to whether a magnitude of the symbol correlation is greater than a first threshold. In response to the magnitude of the symbol correlation being greater than the first threshold, an indication is provided that the received symbol is a valid symbol (e.g., a SYNCP symbol or SYNCM symbol). In response to the magnitude of the symbol correlation being less than the first threshold, an indication is provided that the received symbol is an indeterminate symbol (e.g., an invalid symbol or a SYNCM/2 symbol).

Abstract: Methods and systems are disclosed for frequency-domain symbol and frame synchronization for multi-carrier communication systems. Received signals are sampled and converted into frequency components associated with subcarriers within the multi-carrier communication signals. Symbol synchronization is performed in the frequency domain by performing correlation(s) between frequency components of the received signal and frequency-domain synchronization symbol(s). After symbol synchronization, frame synchronization correlation is also performed in the frequency domain between frequency components of the received signal and frequency-domain synchronization symbol(s). The disclosed embodiments are particularly useful for symbol and frame synchronization in multi-carrier received signals for power line communication (PLC) systems and/or other harsh noisy communication environments.

Abstract: An identification method comprising: when an object is in a whole process from entering to separating from a region inducted by the low-frequency electromagnetic field, receiving the low-frequency signal of the low-frequency electromagnetic field in real time; extracting the attribute code and signal intensity corresponding to the low-frequency signal received and conducting associate storage; and after the object separates from the region inducted by the low-frequency electromagnetic field, determining the route direction along which the object passes through the vector beacons according to the attribute code and signal intensity stored.

Abstract: A technique for frame synchronization in a communication system includes performing symbol correlation on received signal samples. A determination is made as to whether a magnitude of the symbol correlation is greater than a first threshold. In response to the magnitude of the symbol correlation being greater than the first threshold, an indication is provided that the received symbol is a valid symbol (e.g., a SYNCP symbol or SYNCM symbol). In response to the magnitude of the symbol correlation being less than the first threshold, an indication is provided that the received symbol is an indeterminate symbol (e.g., an invalid symbol or a SYNCM/2 symbol).

Abstract: Methods and systems are disclosed for frequency-domain frame synchronization for multi-carrier communication systems. Received signals are sampled and converted into frequency domain components associated with subcarriers within the multi-carrier communication signals. A sliding-window correlation (e.g., two-dimensional sliding window) is applied to the received symbols represented in the frequency domain to detect frame boundaries for multi-carrier signals. The sliding-window frame synchronization can be applied by itself or can be applied in combination with one or more additional frame synchronization stages. The disclosed embodiments are particularly useful for frame synchronization of multi-carrier signals in PLC (power line communication) systems.

Abstract: Methods and systems are disclosed for frequency-domain amplitude normalization for symbol correlation in multi-carrier communication systems. Digital samples associated with input signals received from a communication medium are processed using a Fast Fourier Transform (FFT) to generate complex frequency components. Each complex frequency component is normalized with respect to its amplitude, and the frequency-domain, amplitude-normalized frequency components are multiplied with frequency components for reference symbol(s) to generate frequency-domain correlation values. These frequency-domain correlation values are analyzed to determine if a correlation exists between the amplitude-normalized frequency components and the predetermined reference frequency components. A correlation detection output is then generated that indicates whether or not a symbol synchronization was achieved.

Abstract: A transmitter and method for processing a digitally modulated communication signal, which may reduce peak-to-average-power-ratio (PAPR) while maintaining acceptable error rates is disclosed. After subcarrier mapping, a first digital representation of the signal is upsampled into a second digital representation, which is transformed into a first time domain representation. Samples whose magnitudes exceed a magnitude limit are limited to that limit to produce a second time domain representation. The second time domain representation is transformed to a third frequency domain representation, which is downsampled into a fourth frequency domain representation. In addition to the in-band subcarriers, some out-of-band subcarriers adjacent to the frequency band are preserved while the remaining out-of-band subcarriers are eliminated to produce a fifth frequency domain representation.

Abstract: Methods and systems are disclosed for frequency-domain frame synchronization for multi-carrier communication systems. Received signals are sampled and converted into frequency domain components associated with subcarriers within the multi-carrier communication signals. A sliding-window correlation (e.g., two-dimensional sliding window) is applied to the received symbols represented in the frequency domain to detect frame boundaries for multi-carrier signals. The sliding-window frame synchronization can be applied by itself or can be applied in combination with one or more additional frame synchronization stages. The disclosed embodiments are particularly useful for frame synchronization of multi-carrier signals in PLC (power line communication) systems.

Abstract: Methods and systems are disclosed for frequency-domain carrier blanking in multi-carrier communication systems. When excessive energy is detected in one or more subcarriers within a received symbol for multi-carrier communications, those subcarriers are blanked for subsequent demodulation in order to avoid corruption of the demodulated data. A conversion from time-domain digital samples to frequency-domain values using an FFT (Fast Fourier Transform) and a threshold detector are utilized to detect corrupted subcarriers. Further, this frequency-domain carrier blanking can be implemented dynamically on a symbol-by-symbol basis to further improve demodulation performance by reducing decoding errors. The disclosed embodiments are particularly useful for improving demodulation performance in power line communication (PLC) systems.

Abstract: Methods and systems are disclosed for frequency-domain amplitude normalization for symbol correlation in multi-carrier communication systems. Digital samples associated with input signals received from a communication medium are processed using a Fast Fourier Transform (FFT) to generate complex frequency components. Each complex frequency component is normalized with respect to its amplitude, and the frequency-domain, amplitude-normalized frequency components are multiplied with frequency components for reference symbol(s) to generate frequency-domain correlation values. These frequency-domain correlation values are analyzed to determine if a correlation exists between the amplitude-normalized frequency components and the predetermined reference frequency components. A correlation detection output is then generated that indicates whether or not a symbol synchronization was achieved.