digital carrier

digital carrier

(hardware, communications)
A medium which can carry digital signals; broadly equivalent to the physical layer of the OSI seven layer model of networks. Carriers can be described as baseband or broadband. A baseband carrier can include direct current (DC), whereas broadband carriers are modulated by various methods into frequency bands which do not include DC.

Sometimes a modem (modulator/demodulator) or codec (coder/decoder) combines several channels on one transmission path. The combining of channels is called multiplexing, and their separation is called demultiplexing, independent of whether a modem or codec bank is used. Modems can be associated with frequency division multiplexing (FDM) and codecs with time division multiplexing (TDM) though this grouping of concepts is somewhat arbitrary.

If the medium of a carrier is copper telephone wire, the circuit may be called T1, T3, etc. as these designations originally described such.

T1 carriers used a restored polar line coding scheme which allowed a baseband signal to be transported as broadband and restored to baseband at the receiver. T1 is not used in this sense today, and indeed it is often confused with the DS1 signal carried.
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According to the considered functional structure, the digital carrier of the reconstructed digital input signal (equivalent of event timing information) is formed by the ADC at the stage of transmitted data reconstruction.
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There is no known archival digital medium (in part because no digital carrier can be interpreted without hardware and software specific to that carrier.
This dual-capacity cellular phone works in digital mode when the digital carrier is available.
The remaining loops can be economically served by digital carrier systems out to a remote point from the central office.
Some highly integrated tuner/demodulator SoCs include channel filtering, digital carrier and timing recovery, channel selectivity, gain control, and LO (local oscillator) generation, which eliminates the need for an external low-noise amplifier.

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