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Question 1 of 60 Quiz ID: q1

What is the primary disadvantage of parallel transmission over longer distances?

It is too slow for modern applications

It requires complex error correction mechanisms

It becomes costly and impractical due to signal degradation and wiring needs

It cannot be used with digital signals

Question 2 of 60 Quiz ID: q2

In asynchronous transmission, what is the purpose of the start bit?

To signal the end of a data group

To synchronize the clocks of the sender and receiver for the entire session

To change the line state from idle (1) to active (0), signaling the beginning of a data group

To carry parity information for error checking

Question 3 of 60 Quiz ID: q3

How does isochronous transmission guarantee timely delivery of data?

By using very large frame sizes to reduce overhead

By assigning a fixed, guaranteed bandwidth after an initial start packet is transmitted

By employing complex forward error correction algorithms

By dynamically rerouting data through the fastest available path

Question 4 of 60 Quiz ID: q4

What is the fundamental principle that makes Frequency Division Multiplexing (FDM) possible?

The data rate of the medium must be lower than the sum of the source data rates

The useful bandwidth of the medium must exceed the combined bandwidth of the signals to be transmitted

All signals must be converted to a digital format before multiplexing

Signals must be synchronized to a common clock source

Question 5 of 60 Quiz ID: q5

Why is Wavelength Division Multiplexing (WDM) considered a form of FDM?

It uses time slots instead of frequencies

It multiplexes multiple beams of light, each at a different frequency (wavelength), onto a single fiber

It converts optical signals to electrical signals for multiplexing

It is only used for analog signal transmission

Question 6 of 60 Quiz ID: q6

In Synchronous TDM, what is a significant drawback compared to Statistical TDM?

It requires more complex hardware for multiplexing and demultiplexing

It cannot support devices with different data rates

It wastes capacity by transmitting empty time slots for sources with no data to send

It is unsuitable for long-distance communication

Question 7 of 60 Quiz ID: q7

What is the primary purpose of 'pulse stuffing' in TDM systems?

To add extra bits for error detection

To synchronize data sources with different clocks or data rates to a common rate

To encrypt the data stream for security

To compress the data to save bandwidth

Question 8 of 60 Quiz ID: q8

How does Statistical TDM (STDM) improve link efficiency over Synchronous TDM?

By using a higher frequency carrier wave

By dynamically allocating time slots only to active input devices

By eliminating the need for a framing pattern

By using analog modulation instead of digital

Question 9 of 60 Quiz ID: q9

What key feature distinguishes ADSL (Asymmetric Digital Subscriber Line) from a traditional leased line?

ADSL provides symmetric upstream and downstream data rates

ADSL uses existing telephone lines but reserves a band for POTS and uses FDM for data

ADSL can only be used for digital data, not voice

ADSL requires fiber optic cables to the premises

Question 10 of 60 Quiz ID: q10

How does Discrete Multitone (DMT) modulation, used in ADSL, adapt to line conditions?

It switches between analog and digital transmission based on noise

It tests each subchannel and allocates more bits to channels with better SNR

It uses echo cancellation to double the effective bandwidth

It dynamically changes the TDM frame size

Question 11 of 60 Quiz ID: q11

In a full-duplex transmission mode, what is possible?

Data can flow in both directions, but only one way at a time

Data can flow in both directions simultaneously

Data can only flow in one predetermined direction

Data flow alternates directions based on a priority scheme

Question 12 of 60 Quiz ID: q12

What is a major source of overhead in asynchronous transmission?

Large frame synchronization headers

Start and stop bits added to each small group of data bits

Complex error-checking sequences for every bit

The need for pulse stuffing to synchronize clocks

Question 13 of 60 Quiz ID: q13

In the context of FDM, what is 'intermodulation noise'?

Noise caused by crosstalk between adjacent channels

Noise generated within a channel due to poor shielding

Noise caused by the nonlinear effects of amplifiers generating spurious frequencies in other channels

Background noise from the transmission medium itself

Question 14 of 60 Quiz ID: q14

Why is a 'framing pattern' or 'sync bits' necessary in a Synchronous TDM stream?

To provide addressing information for each data source

To allow the demultiplexer to identify the start and end of each frame and correctly route the time slots

To compress the data within the frame

To encrypt the TDM stream for security

Question 15 of 60 Quiz ID: q15

In the TDM example with 11 sources, why is pulse stuffing applied to the 7.2 kbps digital sources?

To add error correction codes to their data

To lower their data rate to match the analog sources

To raise their data rate to a common multiple (8 kbps) for efficient multiplexing

To encrypt their data for transmission

Question 16 of 60 Quiz ID: q16

What is a key functional difference between a Multiplexer (MUX) and a Demultiplexer (DEMUX)?

A MUX combines signals, while a DEMUX separates a combined signal

A MUX modulates signals, while a DEMUX demodulates them

A MUX amplifies signals, while a DEMUX attenuates them

A MUX converts analog to digital, while a DEMUX converts digital to analog

Question 17 of 60 Quiz ID: q17

For which type of data traffic is isochronous transmission MOST critical?

Batch file transfers

Web browsing

Real-time audio and video streaming

Email communication

Question 18 of 60 Quiz ID: q18

What is the primary reason multiplexing is considered cost-effective?

It eliminates the need for error detection

It allows multiple low-data-rate devices to share a single high-data-rate line, which has a lower cost per kbps

It simplifies the network protocol stack

It automatically encrypts all shared data

Question 19 of 60 Quiz ID: q19

In the FDM example with voice signals, why is only one sideband (e.g., the lower) transmitted?

The upper sideband is always corrupted by noise

Transmitting one sideband is sufficient to reconstruct the original signal and it conserves bandwidth

Modulation equipment for single sideband is simpler and cheaper

Regulations forbid transmitting both sidebands for voice signals

Question 20 of 60 Quiz ID: q20

How does echo cancellation enable full-duplex operation on a single wire pair in ADSL?

It physically separates the transmitting and receiving wires

It uses a special modem that filters out its own transmitted signal from the received signal

It assigns vastly different frequency bands for upstream and downstream

It uses TDM to alternate transmission directions very rapidly

Question 21 of 60 Quiz ID: q21

What is the fundamental unit of data organization in synchronous transmission?

Byte

Bit

Frame

Packet

Question 22 of 60 Quiz ID: q22

Which multiplexing technique is inherently digital and interleaves data in time?

FDM

WDM

TDM

CDM

Question 23 of 60 Quiz ID: q23

In statistical TDM, what information must be included in each time slot or subframe that is NOT necessary in synchronous TDM?

Framing bits

The address of the destination device for the data in that slot

Error correction codes

A start bit

Question 24 of 60 Quiz ID: q24

The 'POTS' band in ADSL is reserved for voice. What is the primary reason for allocating more than the necessary 4 kHz?

To allow for high-fidelity audio transmission

To provide a guard band that prevents crosstalk between the voice and data channels

To accommodate multiple voice calls using TDM

To provide bandwidth for a dial-up modem backup

Question 25 of 60 Quiz ID: q25

What is a key advantage of serial transmission over parallel transmission for long-distance communication?

Higher potential data rate

Simpler synchronization of bits

Lower cost and greater reliability due to fewer wires

Built-in error correction

Question 26 of 60 Quiz ID: q26

Which component in a WDM system is responsible for amplifying all optical signals simultaneously without converting them to electrical signals?

Electrical Repeater

Multiplexer (MUX)

Optical Amplifier

Demultiplexer (DEMUX)

Question 27 of 60 Quiz ID: q27

In the TDM process, what is the purpose of the 'scan operation' shown in the transmitter diagram?

To check for errors in the data

To sequentially collect bits or bytes from the input buffers to form the composite TDM stream

To modulate the digital signal onto an analog carrier

To compress the data before transmission

Question 28 of 60 Quiz ID: q28

Why is flow control not typically a responsibility of the TDM multiplexer and demultiplexer themselves?

Flow control is handled by the physical layer protocol

The data rate on the multiplexed line is fixed, and the MUX/DEMUX are designed to operate at that rate regardless of device readiness

TDM includes automatic flow control in every time slot

Flow control is only needed for statistical TDM, not synchronous TDM

Question 29 of 60 Quiz ID: q29

What does the 'asymmetric' in ADSL directly refer to?

The physical shape of the wires

The use of different modulation techniques for upstream and downstream

The difference in data rate between the downstream (to user) and upstream (from user) directions

The fact that it works with older, imperfectly balanced telephone lines

Question 30 of 60 Quiz ID: q30

According to the lecture, what is the main reason for the popularity of multiplexing?

It enhances security through obscurity

It simplifies network management software

The cost per kbps decreases with an increase in the data rate of a facility

It is a requirement for international data standards

Question 31 of 60 Quiz ID: q31

What problem does a guard band aim to solve in FDM?

Clock skew between channels

Crosstalk between adjacent channels

Excessive overhead from framing bits

Intermodulation noise from amplifiers

Question 32 of 60 Quiz ID: q32

In the HDLC frame structure used for statistical TDM, what is the role of the 'Address' field in a subframe?

The IP address of the destination network

The MAC address of the destination device

An identifier for the specific data source or output channel the data belongs to

The address of the multiplexer itself

Question 33 of 60 Quiz ID: q33

What is the consequence of a demultiplexer losing frame synchronization in a Synchronous TDM system?

All data transmission stops until resynchronized

Only the data in the current frame is lost

The demultiplexer will misassign all subsequent time slots to the wrong output channels until synchronization is regained

The system automatically switches to asynchronous transmission mode

Question 34 of 60 Quiz ID: q34

Which transmission mode is characterized by unpredictable time intervals between data groups?

Synchronous

Asynchronous

Isochronous

Duplex

Question 35 of 60 Quiz ID: q35

What is the primary technical challenge that pulse stuffing addresses?

Differing data rates from various sources

High error rates on analog lines

The need for encryption in TDM systems

Synchronizing the multiplexer and demultiplexer clocks

Question 36 of 60 Quiz ID: q36

How does Statistical TDM potentially support more devices than Synchronous TDM on a link of the same data rate?

By using a more efficient modulation scheme

By using data compression on each channel

By statistically leveraging the fact that not all devices transmit simultaneously, allowing more devices to be pooled

By eliminating the need for framing bits

Question 37 of 60 Quiz ID: q37

What is the primary function of the 'FCS' field in an HDLC frame?

Flow Control Signaling

Frame Check Sequence (for error detection)

Frequency Carrier Synchronization

Frame Channel Selector

Question 38 of 60 Quiz ID: q38

In the context of DMT in ADSL, what does a subchannel's 'bit loading' refer to?

The physical weight of the modem

The number of bits assigned to be transmitted per symbol on that subchannel

The amount of data buffered for transmission on that subchannel

The electrical current required to transmit on that subchannel

Question 39 of 60 Quiz ID: q39

What is a major application of half-duplex transmission?

Telephone networks

Broadcast television

Walkie-talkies or police radio

Fiber optic backbone links

Question 40 of 60 Quiz ID: q40

What is the role of the 'control' field in a generic synchronous frame structure?

To carry network layer addressing information

To contain information for managing the data link layer (e.g., sequence numbers, acknowledgments)

To perform physical layer synchronization

To indicate the type of application data in the payload

Question 41 of 60 Quiz ID: q41

Why is a simple alternating bit pattern like 101010... often suitable for a TDM framing pattern?

It is easy for hardware to generate

It has a high probability of occurring naturally in a user data stream, ensuring frequent synchronization

It is a pattern that is unlikely to be sustained in a user data channel, making it easy to distinguish from data

It provides the best possible error detection capabilities

Question 42 of 60 Quiz ID: q42

What is the fundamental trade-off between Synchronous and Statistical TDM?

Speed vs. Security

Simplicity vs. Efficiency

Cost vs. Range

Analog vs. Digital

Question 43 of 60 Quiz ID: q43

In the FDM process, what is the 'composite baseband signal'?

The original unmodulated voice signal

The sum of all the individually modulated subcarrier signals

The signal after it has been demodulated by the receiver

The signal from the highest frequency channel

Question 44 of 60 Quiz ID: q44

What property of twisted-pair telephone lines does ADSL exploit that traditional modems did not?

Their ability to carry signals with frequencies up to 1 MHz, far beyond the 4 kHz used for voice

Their built-in error correction capability

Their symmetric electrical characteristics

Their use of digital switching

Question 45 of 60 Quiz ID: q45

What is the primary purpose of the 'scan operation' in the TDM receiver?

To check for viruses in the data

To synchronize with the transmitter's clock

To distribute the demultiplexed data from the time slots to the correct output buffers

To modulate the incoming signal

Question 46 of 60 Quiz ID: q46

Which of these is NOT a common component of a generic synchronous frame?

Synchronization bits

Start and Stop bits

Error checking bits

Data bits

Question 47 of 60 Quiz ID: q47

What is the main reason for using TDM for digitized voice signals (as in the example)?

TDM is the only way to transmit digital signals

It allows multiple digital voice channels to share a single high-speed digital link

It improves the audio quality of the voice signal

It encrypts the voice conversation

Question 48 of 60 Quiz ID: q48

How does WDM increase the capacity of a single optical fiber?

By making the light travel faster

By using time division multiplexing on a laser beam

By transmitting multiple signals simultaneously on different wavelengths of light

By increasing the power of the laser source

Question 49 of 60 Quiz ID: q49

What is the defining characteristic of simplex transmission?

Data can flow in both directions simultaneously

Data can flow in both directions, but only one way at a time

Data flows in only one predetermined direction

Data flow direction is randomly determined

Question 50 of 60 Quiz ID: q50

In the ADSL frequency allocation diagram, what does the 'echo cancellation' method allow?

Upstream and downstream to use overlapping frequency bands

The complete elimination of the POTS band

The use of TDM instead of FDM

The upstream band to be larger than the downstream band

Question 51 of 60 Quiz ID: q51

What is the primary mechanism used to prevent buffer overflow in Statistical TDM when input rates exceed the output line capacity?

Pulse stuffing

Flow control protocols at a higher layer (e.g., HDLC)

Dropping frames randomly

Increasing the output line speed dynamically

Question 52 of 60 Quiz ID: q52

Which multiplexing technique is most susceptible to errors caused by nonlinear amplification?

Synchronous TDM

Statistical TDM

FDM

All are equally susceptible

Question 53 of 60 Quiz ID: q53

What is the key difference between the 'data' in a Synchronous TDM slot and the 'data' in a Statistical TDM subframe?

Synchronous TDM data is always analog

Statistical TDM data includes the user's address information within it

Synchronous TDM data has no structure, while Statistical TDM data is highly structured

The data in a Synchronous TDM slot is 'pure' user data, while a Statistical TDM subframe's data is encapsulated with addressing overhead

Question 54 of 60 Quiz ID: q54

Why might the effective data rate experienced by a user on a Statistical TDM link be lower than the nominal output line rate?

Due to the addressing overhead added to each subframe

Because statistical multiplexers always operate at half-duplex

Due to pulse stuffing requirements

Because it uses analog modulation

Question 55 of 60 Quiz ID: q55

In the context of the lecture, what does 'PCM' stand for and what is its role in the TDM example?

Pulse Code Modulation; it is the method used to convert analog voice signals into a 64 kbps digital stream for TDM

Parallel Channel Multiplexing; it is an alternative to TDM

Phase Change Modulation; it is used for the main carrier

Packet Control Mechanism; it handles flow control

Question 56 of 60 Quiz ID: q56

What is the primary function of the 'Flag' field in an HDLC frame?

To indicate the priority of the frame

To carry network layer addressing

To mark the beginning and end of the frame (framing/synchronization)

To specify the type of data in the information field

Question 57 of 60 Quiz ID: q57

How does the 'stop bit' in asynchronous transmission differ from the 'idle state' of the line?

The stop bit is always a 0, while the idle state is a 1

The stop bit is always a 1, which is the same as the idle state, ensuring the line returns to idle

The stop bit carries parity information

There is no difference; they are the same

Question 58 of 60 Quiz ID: q58

What is a major advantage of using a hierarchical TDM system (e.g., multiplexing multiple T1 lines into a T2 line)?

It simplifies network management

It allows for the creation of very high-speed backbone links by aggregating lower-speed multiplexed streams

It reduces the need for error checking

It makes the system fully analog

Question 59 of 60 Quiz ID: q59

In the FDM demultiplexing process, what is the role of the bandpass filter?

To amplify the selected channel

To convert the signal from analog to digital

To isolate a specific channel by filtering out all frequencies outside its assigned band

To demodulate the signal and extract the original baseband signal

Question 60 of 60 Quiz ID: q60

Considering the entire lecture, what is the single most unifying concept behind all multiplexing techniques?

To convert analog signals to digital

To share the capacity of an expensive, high-performance transmission medium among multiple users to improve cost-effectiveness

To increase the absolute speed of a single communication channel

To provide error-free communication

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