Embodiments related to retransmission in a communication system are described and depicted. In one embodiment, a retransmission entity repeats a transmission of a data transfer unit by the device after a predetermined number of other transmitted data transfer units has been transmitted. The retransmission entity may also determine whether a measure for a time period since the first transmission of the data transfer unit by the device has exceeded a predetermined threshold and to provide a final transmission of the data transfer unit based on the determining that the measure for the time period has exceeded the predetermined threshold.

A quadrature demodulator includes a quadrature demodulating circuit configured to generate an analog in-phase signal and an analog quadrature signal based on an output signal of a low noise amplifier, and a controller configured to cause a thermal noise, instead of the output signal of the low noise amplifier, to be input to the quadrature demodulating circuit, when a correction parameter to correct a mismatch between the in-phase and quadrature signals is being calibrated.

The invention comprises real-time down-hole intelligent communication based on the characterization of signal attenuation caused by a coaxial cable used as a communication medium and by frequency response changes of the electronic components of the transmitters and receivers, generated by the down-hole operating environment. The invention relates to a method for the real-time characterization of the attenuation response of a two-way communication system using a coaxial cable, consisting in: generating test tones for the real-time characterization of the attenuation response of a two-way communication system in the transmission and reception bands, measuring the signals received, estimating noise and the ratio to the communication signal, comparing with reference responses, adjusting the transmission and reception frequencies in order to maintain the communication with the maximum signal-to-noise ratio. The invention also relates to an adaptive two-way transmitter/receiver system for communication using coaxial cable as a link means, formed by: a transmitter with automatic adjustment of the operating band by means of the real-time characterization of the attenuation response of a two-way communication system. The invention further relates to adjustable filtering and coupling devices for optimizing the transmission and reception bands, and a control module capable of measuring the transmission and reception attenuation responses.

A method or system is disclosed to assess transmission errors in a visual media input. Domain knowledge is obtained from the visual media input by content analysis, codec analysis, distortion analysis, and human visual system modeling. The visual media input is divided into partitions, which are passed into deep neural networks (DNNs). The DNN outputs of all partitions are combined with the guidance of domain knowledge to produce an assessment of the transmission error. In one or more illustrative examples, transmission error assessment at a plurality of monitoring points in a visual media communication system is collected and assessed, followed by quality control processes and statistical performance assessment on the stability of the visual communication system.