signals

a physical form of a message.

signal Types

Analogue

a smooth continuum of values consists of a wave with amplitude that represents the values of interest.

pros	cons
high accuracy	susceptible to noise and interference in the channel
	difficult to process using digital electrinics
An analogue signal can be represented digitally by:

• Sample the signal at a suitable rate(can be done through the (sampling theorem)
• Quantise to the nearest permissible value
• Converting to digital format

Digital Signals

a sequence of discreet symbols consists of a sequence of discrete symbols from a fixed set, rather than arbitrary values.

Modulation

used to map digital signals onto a analogue channel

Binary Encoding

digital signals in computing systems use binary encoding with two symbols 0,1

Non-binary Encoding in Networks

Networked systems often use more complex encoding schemes(wireless links may use modulation schemes with 16,64 or 256 symbols)

• Baud Rate: The number of symbols transmitted per second(different from bit rate)

NRZ modulation (Non Return to Zero Modulation): A method of encoding digital data for transmission where the signal does not return to zero voltage between bits