Chapter 2 - The Physical Layer

Question 1

Redefine the physical layer.

Answer 1

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.

Question 2

List physical mediums

Answer 2

1. Wires
2. Air

Question 3

What are electromagnetic signals?

Answer 3

Used to send information from transmitter to receiver through a transmission medium.

Question 4

The amplitude of a wave is how ____ it is.

Answer 4

High

Question 5

The period of the wave is the ___ between two trough.

Answer 5

DIstance

Question 6

Frequency is the ____ the signal makes a complete cycle within a frame.

Answer 6

Number of times

Question 7

Phase it the measure of the ____ of a waveform at a given moment within the ___ of the signal.

Answer 7

Position; Period

Question 8

The range of frequencies that a signal contains.

Answer 8

Spectrum

Question 9

The width of the spectrum

Answer 9

Absolute bandwidth

Question 10

Telephone equipment allows voice bandwidth of___.

Answer 10

4000 Kilo Hz (guard-band around voice bandwidth)

Question 11

Voice Bandwidth is _____.

Answer 11

300-3400 Kilo Hz

Question 12

___ Mega Hz is the minimum bandwidth required to transmit video signals with guard-bands that carry it up to __ Mega Hz.

Answer 12

4;6

Question 13

What affects information transmission?

Answer 13

Noise

Question 14

What are types of noise?

Answer 14

Crosstalk, Impulse, Thermal, Intermodulation

Question 15

Transmission media that rely on a physical cable or wire are often called___.

Answer 15

Guided media

Question 15

Transmission media that rely on wireless mediums (air) are often called___.

Answer 15

Unguided media

Question 16

What signal quality impairments affect guided media?

Answer 16

Attenuation, delay distortion, noise

Question 17

Define attenuation?

Answer 17

Reducing of a signal (weakens) as distance increases

Question 18

Define delay distortion.

Answer 18

Signals arriving to early or too late due to impairments in transmission medium. In voice signals this is called jitter.

Question 19

What is a repeater?

Answer 19

A repeater amplifies signals

Question 20

What is a regenerator?

Answer 20

Cleans signal noise

Question 21

What signal quality impairments affect unguided media?

Answer 21

Free-space loss, atmospheric absorption, multipath, refraction,thermal noise

Question 22

Channel capacity is base on ___.

Answer 22

data rate, noise, bandwidth and error rate

Question 23

Wireless transmission is the use of __ waves to transmit signals.

Answer 23

EM (Electromagnetic)

Question 24

Explain ways wireless transmission is carried out?

Answer 24

1. Frequency Hopping spread spectrum
2. Direct Sequence spread spectrum
3. Ultra-wideband

Question 25

Outline spectrum for wireless transmission.

Answer 25

1. Radio transmission - omnidirectional waves, penetrate walls, travel long distances
2. Microwave - directional waves requiring repeaters, do not penetrate
3. Infrared - unguided waves used for short distances, relatively directional, do not penetrate walls
4. Light

Question 26

Nyquist Theorem specifies the maximum data rate for noiseless condition. The formula:

Answer 26

2Blog (base 2) V bits/sec

Question 27

Shannon’s Theorem specifies the maximum data rate under a noise condition. The formula:

Answer 27

Blog (base 2) (1 + S/N) bits/sec

Question 28

Ethernet and fast internet uses ___ encoding

Answer 28

Manchester