Dissemination refers to a physical data transfer (digital bit stream) in the form of signals from one point to another or to several points via data transmission channel, as a rule, for subsequent processing by means of computer technology.
Examples of such channels include copper wires, fiber optic lines, wireless data channels and storage.
Dissemination can be analogue or digital and can be modulated either by analogue modulation or by digital coding.
Although analogue communication refers to the transmission of an ever-changing digital signal, dissemination is a continuous transmission of messages. Messages are either a sequence of pulses, meaning a linear code, or limited to a set of continuously changing waveforms using a digital modulation method. This method and the corresponding demodulation are carried out by modem equipment.
The data in question can be digital messages coming from one data source or another – for example, from a keyboard. This could be an analogue signal — a video signal or a phone call digitised into a bitstream using pulse-coding modulation (PCM) or more advanced source-coding schemes. Source coding and decoding are performed by coding equipment.
Serial dissemination is a sequence of transmission of signal elements representing a symbol or other data object. Digital serial transmission is the sequential sending of bits over a single wire, optical path or frequency. Since this requires less signal processing and reduces the chances of error in comparison with parallel transmission, the data transfer for each individual path can be faster. This mechanism can be used at longer distances, because the check digit or parity bit can easily be transmitted.
Parallel dissemination is the simultaneous communication of the corresponding elements of a signal along two or more paths. Using multiple electrical wires, you can transmit several bits simultaneously, allowing you to achieve higher transmission speeds than with serial transmission. This method is used inside the computer, for example, in internal data buses, and sometimes in external devices such as printers. The main problem is the “skew”, caused by the wires in parallel transmission having slightly different properties. This can lead to some bits arriving earlier than others, which in turn can damage the message. The parity bit can help reduce errors. However, an electrical wire with parallel data transmission is less reliable over long distances, as the transmission carries a much higher probability of being broken.