Computer Networks Media

Computer Network Media

• Twisted-pair (TP) cable and Coaxial cable use metallic (copper) conductors to receive and transmit signals in the form of electrical current.
• Fiber-optic cables carry data signals in the form of light, which is propagated along the inner core by reflection.

Wireless Communication

• Wireless communication employs an antenna for transmission and reception of signals through air, vacuum, or water.
• The antenna radiates electromagnetic waves from the surrounding medium for transmission.
• The antenna picks up electromagnetic waves from the surrounding medium for reception.

Analog and Digital Signaling

• Information can be transmitted via one of two signaling methods: analog or digital.
• The strength of an analog or digital signal is measured by its voltage.
• Analog signal examples include speech, sirens, and live music.
• Analog data signals have voltage that varies continuously, with properties including amplitude, frequency, wavelength, and phase.

Analog Signal Characteristics

• Amplitude refers to the strength of an analog wave.
• Frequency refers to the number of times amplitude cycles over a fixed time period, measured in hertz (Hz).
• Wavelength refers to the distance between corresponding wave cycle points, which is inversely proportional to frequency and expressed in meters or feet.

Analog Signal Benefits and Drawbacks

• Analog signals have the benefit of being more variable.
• However, they are susceptible to transmission flaws, such as noise.

Digital Signaling

• Digital signal pulses consist of pulses of voltages, where positive voltage represents a 1 and zero voltage represents a 0.
• Digital signals use a binary system, where 1s and 0s represent information, and each bit (binary digit) has a possible value of 1 or 0.

Digital Signal Benefits and Drawbacks

• Digital signals have the benefit of being more reliable and less susceptible to noise interference.
• However, they require many pulses to transmit the same information, and have an overhead of non-data information, such as addressing information.

Transmission Flaws Affecting Data Signals

• Noise refers to any undesirable influence that degrades or distorts a signal.
• Common transmission flaws affecting data signals include signal noise, attenuation, and latency.

Sources of Interference on Data Signals

• Electromagnetic interference (EMI) is caused by EMI waves that emanate from electrical devices or cables carrying electricity.
• Radiofrequency interference (RFI) is caused by radio waves.
• Severe thunderstorms can also cause interference.

Crosstalk and Attenuation

• Crosstalk occurs when a signal traveling on one wire or cable infringes on the signal traveling over an adjacent wire or cable.
• Attenuation refers to the loss of a signal's strength as it travels away from its source.
• Amplifiers can be used to strengthen analog signals, but they also amplify noise.