Physical Layer - CH 3 (EXAM 1)

Question 1

What is the physical layer?

Answer 1

layer 1 in the internet model

contains physical and logical circuits to send transmission to data link layer

Question 2

What are the 2 types of circuit configuration?

Answer 2

point to point (wired) - server – client computer

multipoint (wireless) - client computer - client computer

Question 3

What is simplex data flow?

Answer 3

data flow in ONE direction

Question 4

What is half-duplex data flow?

Answer 4

data flow in BOTH directions (one at a time)

Question 5

What is a full-duplex?

Answer 5

data flows simultaneously in BOTH directions

Question 6

What is multiplexing?

Answer 6

dividing high speed circuits into slower logical ones

saving $$$

frequency and time

Question 7

What is frequency division multiplexing?

Answer 7

creates channels from the LARGER frequency band

guardbands separate channels to prevent interference

Question 8

What is wavelength division multiplexing?

Answer 8

a variant of FDM in fiber optics circuits

makes use of MULTIPLE wavelengths to divide circuits into channels

Question 9

What is time-division multiplexing?

Answer 9

circuit divided by devices taking turns
more efficient than FDM
equal turns

Question 10

What is statistical time division multiplexing?

Answer 10

variant of TDM
reduce time slots based on network usage

may cause delays when usage does not match allocated slots

Question 11

What is inverse multiplexing?

Answer 11

combines low-speed circuits into high-speed

Question 12

What is media?

Answer 12

physical manner to carry vice or data transmission

Question 13

What is guided media?

Answer 13

transmission flows along physical media

Question 14

What is wireless media?

Answer 14

transmission flow through the air

Question 15

What is a twisted pair cable?

Answer 15

guided media

(twisted-pair cable)wires bundled together
used for telephones and LAN

Question 16

What is a coax cable?

Answer 16

guided media

single copper core, outer insulation, shielding, inner insulation

less prone to interference

cable tv / internet

Question 17

What is a fiber optic cable?

Answer 17

guided media

optical core made of glass or plastic
data transmitted through LED’s
extremely fast data rates

Question 18

What are fiber optics?

Answer 18

multimode
graded-index multimode
single-mode

Question 19

What is a radio?

Answer 19

wireless media

wireless transmission of electrical waves through air
mobile network communication
cordless, wireless LAN

Question 20

What is a microwave?

Answer 20

high-frequency radio communication

requires line of sight which requires antennas and towers

Question 21

What is a satellite?

Answer 21

special form of microwave communication

long distance leads to delays

Question 22

What are the factors of media selection?

Answer 22

network type
cost
transmission distance
security
error rates
speeds

Question 23

What is a digital-analog?

Answer 23

discrete binary values (01)

Question 24

What is an analog?

Answer 24

transmission involves continuous waves (sin, cos)

Question 25

What is a parallel transmission mode?

Answer 25

multiple bits transmitted simultaneously

Question 26

What is a serial transmission mode?

Answer 26

bits transferred sequentially one at a time

Question 27

What do the sender and receiver have to agree on?

Answer 27

``` set of symbols (voltages or light pulses) symbol rate (how often sent) ```

Question 28

What is a unipolar signaling technique?

Answer 28

voltage is 0 or positive | represents binary bits

Question 29

What is a bipolar NRZ signaling technique?

Answer 29

voltage is positive or negative but NOT zero

Question 30

What is a bipolar RZ signaling technique?

Answer 30

voltage is positive or negative returning to 0 between each bit

Question 31

What is a bipolar AMI signaling technique?

Answer 31

voltage is 0, positive, negative, returns 0 between each bit, and alternates between a negative and positive voltage

Question 32

What is a manchester signaling technique?

Answer 32

voltage is positive or negative and bits are indicated by a mid bit transition

Question 33

What system was built for analog data?

Answer 33

telephone | needs a modem to convert analog to digital

Question 34

What are the 3 characteristics of waves?

Answer 34

amplitude (height of the wave) frequency (waves/second) phase (wave direction in degrees)

Question 35

What is a carrier wave?

Answer 35

basic wave transmitted through a circuit

Question 36

What is modulation?

Answer 36

modification of carrier wave's fundamental characteristics in order to encode information

Question 37

What are the 3 ways to modulate information?

Answer 37

``` amplitude modulation (AM) frequency modulation (FM) phase modulation (PM) ```

Question 38

What is a symbol?

Answer 38

+1 modifications to a carrier wave used to encode data one bit defining two different symbols

Question 39

What is 2-bit amplitude modulation?

Answer 39

2 bits transmitted per symbol (4 levels defined as symbols)

Question 40

What is the data rate?

Answer 40

data rate = symbol rate * (#bits/symbol)

Question 41

What are codecs?

Answer 41

device or software converting analog signals into digital form and vice versa

Question 42

What is pulse code modulation?

Answer 42

converts analog to digital sampling analog signal measuring amplitude of each sample encoding amplitude as binary data

Question 43

What is quantizing error?

Answer 43

difference between an original analog signal and approximated digital signal

Question 44

How can you reduce quantizing error?

Answer 44

sampling more frequently | using more levels of amplitude in encoding