Digi Comms SA1

Question 1

The need for ___ and ____ transmission of information is essential and important

Answer 1

fast; reliable

Question 2

Alphabets/Symbols are ____ in analog and ____ in digital systems

Answer 2

uncountably infinite; discrete

Question 2

Signals are ____ in analog and ____ in digital (hint: characteristic)

Answer 2

Continuous; Discrete

Question 3

Fidelity is measured in ____ in analog systems while it is measured in ____ in digital systems

Answer 3

SNR;BER

Question 4

T or F: Digital Systems in general are resistant to noise

Answer 4

True

Question 5

T or F: The source output in a digital communication system is an analog signal

Answer 5

False. It can also be a digital signal

Question 6

____efficiently converts an analog signal into a sequence of binary bits

Answer 6

Source Encoder

Question 7

Another term for data compression

Answer 7

lossy

Question 8

Another term for data compaction

Answer 8

lossless

Question 9

This element removes redundant information from the message signal, and is responsible for the efficient use of the channel

Answer 9

Source Encoder

Question 10

3 parts of the source encoder

Answer 10

sampling, quantization, and source coding

Question 11

____ converts an analog signal into a corresponding sequence of samples usually spaced uniformly in time`

Answer 11

sampling

Question 12

the output of sampling is ____ in amplitude and ___ in time

Answer 12

continuous; discrete

Question 13

process of transforming the sample amplitude into a discrete amplitude is called

Answer 13

quantization

Question 14

the output produced in quantization is ____ in amplitude and ___ in time

Answer 14

discrete; discrete

Question 15

what are the two types of quantization?

Answer 15

midtread and midrise

Question 16

T or F: Efficient use of channel means removing redundancy in the signal

Answer 16

True

Question 17

Element in the digital communication system which uses redundancy in a controlled manner

Answer 17

Channel Encoder

Question 18

T or F: Redundancy can be used at the receiver to overcome the effects of noise and interference

Answer 18

True

Question 19

Channel Encoder increases reliability and improves the ____ of the received signal`

Answer 19

fidelity

Question 20

The resulting sequence of symbols from the channel encoder is called

Answer 20

channel codeword

Question 21

This serves as the interface to the communication channel

Answer 21

digital modulator

Question 22

Digital Communication element whose primary purpose is to map the binary information sequence into signal waveforms

Answer 22

Digital Modulator

Question 23

each symbol in the channel codeword is represented by an ____ symbol

Answer 23

analog

Question 24

type of digital modulation technique used for data transmission in which instead of one bit, two or more bits are transmitted at a time

Answer 24

M-ary modulation

Question 25

The ______ ________ is the physical medium used to send the signal from the transmitter to the receiver

Answer 25

communication channel

Question 26

Communication channels can either be ____ (wired communications) or _____ (wireless communications)

Answer 26

guided; unguided

Question 27

Effect in communication channel described as a decrease in power as the inverse of square distance; measured in dB

Answer 27

Attenuation

Question 28

Effect in communication channel described as an additive in nature that falls within the passband of the signal

Answer 28

Noise

Question 29

Noise is typically modeled using what mathematical model?

Answer 29

White Gaussian Noise (WGN)

Question 30

Effect in communication channel where the channel has a smaller bandwidth compared to the signal bandwidth

Answer 30

Filtering

Question 31

Form of distortion of a signal in which one symbol interferes with the subsequent symbols

Answer 31

Intersymbol Interference (ISI)

Question 32

____ is the variations of the channel strength over time and over frequency

Answer 32

Fading

Question 33

Large-scale fading is due to path loss of a signal as a function of distance and ____ by large objects such as buildings and hills

Answer 33

Shadowing

Question 34

small-scale fading is due to the interference of the _____ signal paths between transmitter and receiver

Answer 34

multiple

Question 35

These channels cause signal fading

Answer 35

Time-varying channels

Question 36

______ processes the channel-corrupted transmitted waveform and translates the waveforms into a sequence of numbers

Answer 36

Digital Demodulator

Question 37

T or F: The channel encoder attempts to reconstruct the original information sequence

Answer 37

False, channel decoder dapat

Question 38

The channel decoder performs what two processes?

Answer 38

error-detection and error-correction

Question 39

Another term for when the source decoder attempts to reconstruct the original signal from the source

Answer 39

decompression

Question 40

T or F: The output of the source decoder is an accurate copy of the original source output

Answer 40

False, it is only an approximation

Question 41

The difference of original and reconstructed signals is a measure of ____

Answer 41

distortion

Question 42

Common Communication Channels

Answer 42

Wireline channel Fiber-optic channel Wireless electromagnetic channels Underwater acoustic channels Storage channels

Question 43

Mathematical models are used in the design of the _____ and _____ at the transmitter and ____ and ____ at the receiver

Answer 43

channel encoder; modulator; demodulator; channel decoder

Question 44

Simplest mathematical model for a communication channel

Answer 44

Additive noise Channel

Question 45

Thermal noise is statistically characterized as a _____ noise process

Answer 45

Gaussian

Question 46

Mathematical model that ensures transmitted signals do not exceed specified bandwidth limitations and thus do not interfere with one another

Answer 46

LTI Filter Channel with Additive Noise

Question 47

Mathematical model used for physical channels that exhibit time-variant multipath propagation

Answer 47

LTV Filter Channel with Additive Noise

Question 48

Average power of the transmitted signal

Answer 48

Transmit Power

Question 49

width of the passband channel

Answer 49

Channel bandwidth

Question 50

2 types of power-limited channels

Answer 50

wireless channels and satellite channels

Question 51

2 examples of bandwitdh-limited channels

Answer 51

Telephone and Television channels

Question 52

Give an example off the challenges in designing communication channels

Answer 52

Limited Spectrum, Power consumption, Interference, Seamless access, system on chip design

Question 53

Good communication system should have: ____ signal power ____ bandwidth ____ data rate ____ distortion ____ cost

Answer 53

small small large low low

Question 54

It is a measure of how efficiently a limited frequency spectrum is utilized

Answer 54

Bandwidth Efficiency

Question 55

Unit of measurement used in energy efficiency

Answer 55

bits/joule

Question 56

Defined as the ratio of transmitted data to consumed energy

Answer 56

Energy efficiency

Question 57

T or F: Power efficiency is more important than spectral efficiency in cellular transmission because sending data with more power can interfere with adjacent cells

Answer 57

True

Question 58

____ means the digital systems can withstand the effects of channel noise and signal distortion

Answer 58

Ruggedness

Question 59

Digital Systems permit the use of ____ which can eliminate degrading effects of channel noise and signal distortion

Answer 59

regenerative repeaters

Question 60

T or F: Digital Systems are more efficient in terms of tradeoff between bandwidth and SNR

Answer 60

True