Chapter 2 - The Physical Layer Flashcards
Redefine the physical layer.
The physical layer is the foundation on which the network is built. It defines the electrical, timing, and other interfaces by which bits are sent as signals over channels.
List physical mediums
- Wires
- Air
What are electromagnetic signals?
Used to send information from transmitter to receiver through a transmission medium.
The amplitude of a wave is how ____ it is.
High
The period of the wave is the ___ between two trough.
DIstance
Frequency is the ____ the signal makes a complete cycle within a frame.
Number of times
Phase it the measure of the ____ of a waveform at a given moment within the ___ of the signal.
Position; Period
The range of frequencies that a signal contains.
Spectrum
The width of the spectrum
Absolute bandwidth
Telephone equipment allows voice bandwidth of___.
4000 Kilo Hz (guard-band around voice bandwidth)
Voice Bandwidth is _____.
300-3400 Kilo Hz
___ Mega Hz is the minimum bandwidth required to transmit video signals with guard-bands that carry it up to __ Mega Hz.
4;6
What affects information transmission?
Noise
What are types of noise?
Crosstalk, Impulse, Thermal, Intermodulation
Transmission media that rely on a physical cable or wire are often called___.
Guided media
Transmission media that rely on wireless mediums (air) are often called___.
Unguided media
What signal quality impairments affect guided media?
Attenuation, delay distortion, noise
Define attenuation?
Reducing of a signal (weakens) as distance increases
Define delay distortion.
Signals arriving to early or too late due to impairments in transmission medium. In voice signals this is called jitter.
What is a repeater?
A repeater amplifies signals
What is a regenerator?
Cleans signal noise
What signal quality impairments affect unguided media?
Free-space loss, atmospheric absorption, multipath, refraction,thermal noise
Channel capacity is base on ___.
data rate, noise, bandwidth and error rate
Wireless transmission is the use of __ waves to transmit signals.
EM (Electromagnetic)
Explain ways wireless transmission is carried out?
- Frequency Hopping spread spectrum
- Direct Sequence spread spectrum
- Ultra-wideband
Outline spectrum for wireless transmission.
- Radio transmission - omnidirectional waves, penetrate walls, travel long distances
- Microwave - directional waves requiring repeaters, do not penetrate
- Infrared - unguided waves used for short distances, relatively directional, do not penetrate walls
- Light
Nyquist Theorem specifies the maximum data rate for noiseless condition. The formula:
2Blog (base 2) V bits/sec
Shannon’s Theorem specifies the maximum data rate under a noise condition. The formula:
Blog (base 2) (1 + S/N) bits/sec
Ethernet and fast internet uses ___ encoding
Manchester
