There are two possible ways of signal transmission in data network – digital and analog.
Computers use electrical signals for communication over the network. The voltage of the signal determines its strength and pressure. While computer generates electrical signal, it is possible that data would travel in electric current form, light pulses form, or wavelength form, depending on the type of network.
Both types of signal transmission are using voltage. However, analog signal is more continuous and is in a form of wave over time. Like any waveform, analog signal has four characteristics:
Amplitude – is a strength of the signal. Maximum amplitude is defined by the voltage.
Frequency – measured in Hz and defines how many times wave cycles per some period of time (seconds). Higher frequency means faster waves.
Wavelength – is measured in meters and defines how big is the distance between one point and the same point in next cycle. Easiest way to measure by checking the peak distances. The higher is frequency the lower the wavelength.
Phase – the difference in the same point of the wave over time. It is measured in degrees with 360 degrees to one complete wave. It can be seen from Figure 1.
Figure 1.
While having a benefit of lesser energy consumption compared to digital signal, analog signal is too imprecise and would have greater noise interference. It is unacceptable for computers that require precision.
Digital signal is made of pulses, the value might be either one or zero as shown in Figure 2.
If there is voltage, computer interprets it as one, if there is none – zero. This allows computer communicate in binary form. Each value is called bit – the smallest unit of data. Eight bits form a byte. Computers recognize commands in bits and bytes forms. Multiple bytes together form a message. Bytes can be translated to text, image, or other form by computer.
Benefits of digital transmission:
Precise pulses represent precise bits
Less noise affection
Fewer errors
Less overhead data
Overhead is information added to data in order to be sent and received correctly over the network. Many layers in the OSI model add headers and/or trailers to data. They are the parts of transmission overhead.
