Which of the following is not a common application of frequency-division multiplexing?
4 1-Mbps connections are multiplexed together. A unit is 1 bit. Find the duration of the output
timeslot.
In synchronous time-division multiplexing, if a source does not have data to send, the corresponding slot in
the output frame is _____.
Which is not true about synchronous time-division multiplexing?
Which statement is correct
In statistical time-division multiplexing, slots are dynamically allocated to _____.
Five 10-kbps connections are multiplexed together. A unit is 1 bit. How many slots are there in each
frame?
How many voice channels are multiplexed in a T2 line.
A technique used to make the highest input data rate the dominant data rate and then add dummy bits
to the input lines with lower rates.
Five 10-kbps connections are multiplexed together. A unit is 1 bit. Determine the rate of the
transmission link in kbps.
The bit-rate of a DS-1 signal over a T-1 line is:
Digital multiplexing is based on the principle of __________ from two or more digital signals.
It is the process of receiving single signal and produces output on multiple channels simultaneously.
Five 10-kbps connections are multiplexed together. A unit is 1 bit. Determine the frame rate in
frames/sec
Five 10-kbps connections are multiplexed together. A unit is 1 bit. Determine the duration of each frame
in micro seconds.
A jumbo group is equivalent to how many master group?
A master group supports how many voice channels?
1 supergroup is formed when combining how many groups?
Compute for the guardband in between channels in a Master group with 2.52MHz total bandwidth
how many voice channel has a supergroup have?
It is a dial-up service most often encountered when using a home telephone. It uses two-wire (or fourwire) twisted pair cable to connect the subscriber's handset to the network via an exchange. The
connection is often called local loop.
10 supergroups forms a ________
offers customers the opportunity to lease a line that is permanently connected to another customer.
Although the connection still passes through the switches in the telephone network, subscribers
experience it as a single line because the switch is always closed; no dialing needed.
The total bandwidth ( in Khz) of combining 12 voice channels
in FDM Hierarchy, 12 voice channel can be combined to formed a ______
Which of the following is true about quantization?
A. Actual quantization error is the same all throughout the process.
B. The signal to noise ratio is the same all throughout the quantization process.
C. The smaller the resolution the less quantization error is introduced
D. All of the choices
Which of the following is not true about PCM?
D. None of the above
B. Increasing n, will increase the dynamic range
A. Higher dynamic range will result if resolution is increased
C. Increasing n will increase SQR
What causes aliasing?
C. When the original analog signal is outside the voice band frequency range
A. When each cycle of the analog input signal is not sampled at least twice.
D. Is produced when the magnitude of a sample is rounded off to closest available level.
B. The Sample and Hold circuit naturally introduces alias of the input
A type of sampling where the input voltage is sampled with a narrow pulse and then held relatively
constant until the next sample is taken.
Flat-top Sampling
Which of the following is true about sample and hold circuit?
D. All of the choices
B. The capacitor is the hold circuit
A. A sample and hold circuit is a non-linear device with two inputs and consequently, heterodyning
occurs between these two signals
C. It introduces aperture error as a result of mixing two signals
What is the overhead used for a DS
Which statement is correct
A PCM system has the following parameters
Which is not true about synchronous time-division multiplexing?
What is the maximum data rate of a DDS
64?
5 10-kbps connections are multiplexed together. A unit is 1 bit.
It is the process of rounding off the amplitude of flat-top samples
The bit-rate of a DS-1 signal over a T-1 line is:
For a resolution of 0.02V, determine the voltage (in V) and
The total bandwidth (in khz) of combining 12 voice channels
Offers customers the opportunity to lease a line that is permanently connected
Ten 100-kbps connections are multiplexed together
A European version where the 2 systems are conceptually
When calculating the maximum number of users
A master group supports how many voice channels?
It follows a pattern, frame to frame, that allows
In a sample and hold circuit, which component
In a sample and hold circuit, which part/component
Asymmetrical digital subscriber line divides the bandwidth
Which of the following is not true about PCM
In statistical time-division multiplexing
A jumbo group is equivalent
Which statement is true about Symmetric (single-line)
Which of the following is true about sample and hold circuit
Determine the coding efficiency required for the following dynamic ranges
Which of the following is true about Signal-to-Noise ratio (not sure)
Six 50-kbps connections are multiplexed together
What causes aliasing
A technology that uses existing telecommunication networks
Six 100-kbps connections are multiplexed together
It is a level in an analog hierarchy
In order to directly reduce quantizing noise
A technique used to make the highest input data
In synchronous time-division multiplexing
It is a 6.312-Mbps service, where it can be used as a single
A PCM system has the following parameters: a maximum analog input frequency
10
Compute for the guardband in between channels
200.33
When an analog signal with infinite amplitude
256
High bit rate DSL uses what type
2B1Q
An alternative approach that is similar to ADSL
It is a technique used when the data rate of an input line
Multilevel
Which block of the PCM transmission system
ADC
Which of the following is not a common application of frequency
It is a dial-up service most often encountered when using a home telephone
Analog switched service
Which of the following is true about quantization
Smaller the resolution or all of the choices d sure
Which of the following is not true about Digital Transmission
A PCM system has the following parameters
How many voice channels are multiplexed in a T2 line
A part of PCM transmitter that serves as anti-aliasing circuit (not sure)
When the number of bits in a PCM code
16.90
The process of receiving single signal that produces multiple channels simultaneously
-
Demultiplexing
When calculating the maximum number of users , a limiting factor in FDM is:
-
The bandwidth of each signal
It refers to the portion of a link that carries a transmission between a given pair of lines
-
Channel
A DS-0 single-channel PCM system uses a 12 kHz sampling rate and an eight-bit PCM code for PCM-TDM
transmission. What is the produced PCM line speed of the said system?
-
96kbps
It is designed to be used in wireless applications that also combine signals from different sources to fit
into a larger bandwidth.
-
Spread spectrum
It is the basic building block of the FDM hierarchy
-
Message channel
It is the most significant circuit in a demultiplexer.
-
Bandpass filter
The bit-rate of a DS-1 signal over a T-1 line is:
-
1.536 Mbps
The acronym DSL stands for
-
Digital Line Subscriber
It follows a pattern, frame to frame, that allows the demultiplexer to synchronize with the incoming
stream so that it can separate the time slots accurately.
-
Framing bits
A digital hierarchy where the service is a single digital channel of 64kbps.
-
DS-0
A technique used to make the highest input data rate the dominant data rate then add dummy bits to
the input lines with lower rates
-
Bit Stuffing
Which of the following is not a common FDM application?
-
Secure communications
Spread-spectrum can be done by using:
-
All of the above
CDMA stands for
-
Code Division Multiple Access
The process of receiving single signal that produces multiple channels simultaneously
-
Multiplexing
How many voice channels are there in a master group
-
600
The term “chip rate” is used in describing:
-
Direct-sequence method
For a given data rate, direct-sequence systems, compared to standard RF systems, use:
-
Much more bandwidth
6 channels each with a 150-kHz bandwidth are to be multiplexed together. What is the minimum
bandwidth of the link if there is a need for a guard band of 20 kHz between the channels to prevent
interference?
-
1000khz
In synchronous time-division multiplexing, if a source does not have data to send, the corresponding slot
in the output frame is
-
Left empty
A technique where the bandwidth of the original signal also expands, but the process is different
-
DSSS
It is a 6.312-Mbps service, where it can be used as a single service for 6.312-Mbps transmissions or can
be used to multiplex 4 DS1-Channels, 96 DS-6 Channels or a combination of this type
-
DS-2
Which is not true about synchronous time-division multiplexing?
-
None of the above
Each narrowband channel is converted to a different location in the total frequency spectrum
-
Frequency-Division multiplexing
It is a technique used when the data rate of an input line is a multiple of others.
-
Multilevel-Multiplexing
A technique that uses M-different carrier frequencies that are modulated by the source signal
-
FHSS
FDM uses
-
modulation
FM
It is a type of multiplexing where in transmission from multiple sources occurs on the same facility but
not at the same time.
-
Time division multiplexing
Which statement is correct
-
Multiplexing uses multiple channels to transmit single signal
Is a digital multiplexing technique for combining several low-rate channels into one high-rate one.
A) FDM
B) TDM
C) WDM
D) None of the above
4 voice channels, each occupying a bandwidth of 4 KHz, are to be multiplexed together. What is the
minimum bandwidth of the link if there is a need for a guard band of 1.5 KHz?
a. 16
KHz
b.
20.5
KHz
c.
17.5
KHz
d. 21
KHz
A 10 MHz link is occupied by 7 channels having a bandwidth of 950 KHz each and guard bands.
How many are the guard bands and what is their bandwidth?
a. 5,
678.53
KHz
b. 6,
478.57
KHz
c. 7, 50
KHz
d. 6,
558.33
KHz
In frequency
division
multiplexing,
multiple signals
share the
bandwidth of a
common
communication
channel.
True
A)
False
B)
Which multiplexing technique transmits analog signals?
A) FDM
B) TDM
C) WDM
D) (a) and
(c)
A Jumbo group has a bandwidth of:
a. 15.984 MHz
b. 16.984 MHz
c. 15.12 MHz
d. 16.52MHz
Which of the following cannot be used for sources sending digital signals?
a. FDM
b. WDM
c. Both a and b
d. None of the above
It is the modulation used in FDM telephone
system.
FM
The
technique uses M different carrier frequencies that are modulated by the source signal. At
one moment, the sign modulates one carrier frequency; at the next moment, the signal modulates
another carrier frequency.
A) FDM
Frequency-Division Multiplexing
B) DSSS
Direct Source Spread Spectrum
C) FHSS
Frequency Hopping Spread Spectrum
D) TDM
Time-Division Multiplexing
Which multiplexing technique shifts each signal to a different carrier frequency?
A) FDM
B) TDM
C) Both (a) and (b)
D) None of the above
In synchronous TDM, if a source does not have data to send, the
corresponding slot in the output frame is:
a. removed
b. empty
c. occupied
d. full
It is a type of multiplexing wherein transmissions from multiple sources
occur on the same facility but not at the same time.
a. Frequency Division Multiplexing
b. Wavelength Division Multiplexing
c. Time Division Multiplexing
d. None of the above
In TDM, the transmission rate of the multiplexed path is usually
the sum of the transmission rates of the signal sources.
A) greater than
B) less than
C) equal to
D) not related to
is designed to use the high bandwidth capability of fiber-optic cable.
In a multiplexed system, lines share the bandwidth of
link.
A) 1; n
B) 1; 1
C) n; 1
D) n; n
A Master group has a bandwidth of:
a. 2.40 MHz
b. 240 KHz
c. 2.42 MHz
d. 2.52 MHz
FHSS stands for:
a. Frame Hopping Spread Spectrum
b. Frequency Hopping Spread Spectrum
c. Frame Hierarchy Spread Spectrum
d. None of the above
The word
transmission
refers to the portion of a
that carries a
channel; link
In
, we combine signals from different sources to fit into a larger
bandwidth.
A) spread spectrum
B) line coding
C) block coding
D) none of the above
In
TDM, slots are dynamically allocated to improve bandwidth
efficiency.
A) synchronous
B) statistical
C) isochronous
D) none of the above
It is the most significant circuit in a demultiplexer.
a. VCO
b. Bandpass filter
c. PLL
d. Discriminator
There are 9 sources, each creating 250 characters per second. If the
interleaved unit is a character and 1 synchronizing bit is added to each
frame, find the data rate of each source:
a. 250 Kbps
b. 4.5 Mbps
c. 450 Kbps
d. 4.5 Kbps
Which multiplexing technique involves signals composed of light beams?
A) FDM
B) TDM
C) WDM
D) none of the above
How many voice channels are there in a master group?
a. 12
b. 60
c. 600
d. 3600
it is the basic building block of the FDM hierarchy.
a. Message
channel
b. Group
c.
Baseband
channel
d. None of
the above
Bits that are usually added to the beginning of each frame
for synchronization are called:
a. Timing bits
b. Parity bits
c. Framing
bits
d. None of
the above
It usually accomplishes frequency modulation
in frequency division multiplexing systems.
a. VCO
b. PLL
c. Rectifier
d. Reactance modulator
Which multiplexing technique transmits
digital signals?
A) FDM
B) TDM
C) WDM
D) None of the above
In
TDM, each input connection has an allotment in
the output even if it is not sending data.
A) synchronous
B) statistical
C) isochronous
D) none of the above
can be applied when the bandwidth of a link (in
hertz) is greater than the combined bandwidths of the
signals to be transmitted.
A) TDM
B) FDM
C) Both (a) or (b)
D) Neither (a) or (b
is designed to be used in wireless applications in
which stations must be able to share the medium without
interception by an eavesdropper and without being subject
to jamming from a malicious intruder.
A) Spread spectrum
B) Multiplexing
C) Modulation
D) None of the above.
It is the circuit that performs demultiplexing in an FDM
system.
a. Oscillator
b. Bandpass filter
c. Discriminator
d. None of the above
is the set of techniques that allows the
simultaneous transmission of multiple signals across a single
data link.
A) Demodulating
B) Multiplexing
C) Compressing
D) None of the above
Which of the following is not a data rate management
strategy?
a. Multiple Multiplexing
b. Bit Padding
c. Multiple-slot Allocation
d. None of the above
The
technique expands the bandwidth of a signal by
replacing each data bit with n bits.
A) FDM
B) DSSS
C) FHSS
D) TDM
It is the most effective frequency demodulator.
a. Radio detector
b. PLL discriminator
c. limiter
d. all of the above
How many groups are there with a 600 voice channels?
a. 1
b. 5
c. 50
d. 300
The sharing of a medium and its link by two or more devices is called
.
A) modulation
B) encoding
C) line
discipline
D)
multiplexing
can be achieved by using multiplexing;
spreading.
can be achieved by using
A) Efficiency; privacy and
antijamming
B) Privacy and
antijamming; efficiency
C) Privacy and efficiency;
antijamming
D) Efficiency and
antijamming; privacy
Each signal in an FDM modulates a subcarrier.
a. True
b. False
c. Maybe
d. None of the above
Strips of unused bandwidth that separates channels in FDM
are called:
a. Frequency bands
b. Guard bands
c. Signal bands
d. None of the above
A Super group is composed of how many voice channels?
a. 48
b. 72
c. 60
d. None of the above
In synchronous TDM, for n signal sources of the same data
rate, each frame contains
slots.
A) n
B) n + 1
C) n - 1
D) 0 to n
Is a technique used when the data rate of an input line is not
a multiple of others:
a. Multiple-Slot Allocation
b. Pulse Stuffing
c. Interleaving
d. None of the above
DWDM stands for:
a. Digital Wavelength Division Multiplexing
b. Direct Wavelength Division Multiplexing
c. Dense Wavelength Division Multiplexing
d. Either a or b
Which of the following cannot be used for sources sending
analog signals?
a. FDM
b. WDM
c. TDM
d. None of the above
The sharing of a
medium and its
link by two or
more devices is
called
.
A)modulation
B)encoding
C)line discipline
D)multiplexing
2 INCORRECT Which multiplexing technique transmits analog signals?
A)FDM
B)TDM
C)WDM
D)(a) and (c)
3 CORRECT
Which multiplexing technique transmits digital signals?
A)FDM
B)TDM
C)WDM
D)None of the above
4 CORRECT
Which multiplexing technique shifts each signal to a different carrier frequency?
A)FDM
B)TDM
C)Both (a) and (b)
D)None of the above
5 CORRECT
In synchronous TDM, for n signal sources of the same data rate, each frame contains
slots.
A)n
B)n + 1
C)n - 1
D)0 to n
6 CORRECT
In TDM, the transmission rate of the multiplexed path is usually
the transmission rates of the signal sources.
A)greater than
B)less than
C)equal to
the sum of
D)not related to
7 CORRECT
Which multiplexing technique involves signals composed of light beams?
A)FDM
B)TDM
C)WDM
D)none of the above
8 CORRECT
utilization is the use of available bandwidth to achieve specific goals.
A)Frequency
B)Bandwidth
C)Amplitude
D)None of the above
9 INCORRECT
can be achieved by using multiplexing;
spreading.
can be achieved by using
A)Efficiency; privacy and antijamming
B)Privacy and antijamming; efficiency
C)Privacy and efficiency; antijamming
D)Efficiency and antijamming; privacy
10 CORRECT
is the set of techniques that allows the simultaneous transmission of
multiple signals across a single data link.
A)Demodulating
B)Multiplexing
C)Compressing
D)None of the above
11 CORRECT
In a multiplexed system,
lines share the bandwidth of
link.
A)1; n
B)1; 1
C)n; 1
D)n; n
12 CORRECT
The word
refers to the portion of a
that carries a transmission.
A)channel; link
B)link; channel
C)line; channel
D)line; link
13 CORRECT
can be applied when the bandwidth of a link (in hertz) is greater than the
combined bandwidths of the signals to be transmitted.
A)TDM
B)FDM
C)Both (a) or (b)
D)Neither (a) or (b)
14 CORRECT
FSM is an
technique.
A)analog
B)digital
C)either (a) or (b)
D)none of the above
15 CORRECT
is designed to use the high bandwidth capability of fiber-optic cable.
A)FDM
B)TDM
C)WDM
D)None of the above
16 CORRECT
is an analog multiplexing technique to combine optical signals.
A)FDM
B)TDM
C)WDM
D)None of the above
17 CORRECT
is a digital process that allows several connections to share the high
bandwidth of a link.
A)FDM
B)TDM
C)WDM
D)None of the above
18 CORRECT
is a digital multiplexing technique for combining several low-rate channels into
one high-rate one.
A)FDM
B)TDM
C)WDM
D)None of the above
19 CORRECT
We can divide
into two different schemes: synchronous or statistical.
A)FDM
B)TDM
C)WDM
D)none of the above
20 CORRECT
In
TDM, each input connection has an allotment in the output even if it is
not sending data.
A)synchronous
B)statistical
C)isochronous
D)none of the above
21 CORRECT
In
TDM, slots are dynamically allocated to improve bandwidth efficiency.
A)synchronous
B)statistical
C)isochronous
D)none of the above
22 CORRECT
In
, we combine signals from different sources to fit into a larger
bandwidth.
A)spread spectrum
B)line coding
C)block coding
D)none of the above
23 CORRECT
is designed to be used in wireless applications in which stations must be
able to share the medium without interception by an eavesdropper and without
being subject to jamming from a malicious intruder.
A)Spread spectrum
B)Multiplexing
C)Modulation
D)None of the above.
24 CORRECT
The
technique uses M different carrier frequencies that are modulated by
the source signal. At one moment, the sign modulates one carrier frequency; at the
next moment, the signal modulates another carrier frequency.
A)FDM
B)DSSS
C)FHSS
D)TDM
25 CORRECT
The
technique expands the bandwidth of a signal by replacing each data bit
with n bits.
A)FDM
B)DSSS
C)FHSS
D)TDM
Which of the following statement is not true
about digital companding?
The
is the number of bits sent in one
second.
-none of the above
-bit rate
In digital compression how many positive codes
are possible if a sample is coded at segment 6?
Which of the following statement is not true
about digital transmission?
-512
-It uses radio wave propagation
Determine the 8 bit compressed code of the
101010110010
When the 12 bit PCM code 0000101101100 is
compressed into 8 bits, which segment does it
belong?
-11100101
Which of the following is not true about signalto-noise ratio?
-all of the above
Which of the following is not true about PCM
codes?
-with linear coding SQR is sacrificed for high
amplitude signals to achieve more accuracy for
the low amplitude signals
When an analog signal with infinite amplitude
possibilities is quantized and is given 7-bit PCM
code how many limited number of
combinations are possible?
-128 ?
When the maximum voltage magnitude in
quantization is 3.5V and the resolution is 0.15 V,
what is the maximum SQR?
-46.67
For a compressor with μ=255 determine the
compressed output voltage for a maximum
input of 4 V and an input of 1 V.
-4.9979
Which encoding format uses positive to
negative transition to represent binary 1, and
negative to positive transition to represent
binary 0.
-manchester encoding
-segment 4
A type of encoding where 0 is represented by a
presence of transition at the beginning of the
bit and 1 if otherwise. Transition at the middle o
the interval is present but is used for
synchronization
-differential manchester
Determine the alias frequency if the sample
rate is 14 KHz and the analog input frequency is
9 KHz
-5 KHz
Determine the actual no. of PCM bits assigned
to the magnitude for a dynamic range of 60 db
-10
What do you call the error introduced by the
sampling process which alters the frequency
spectrum and prevents exactly reproducing the
analog signal at the receiver
-aperture error
When the no. of bits in PCM code, n, is 4, what
is the DR in db?
-23.521 dB
In unipolar encoding, if binary 1 is represented
by positive voltage how is binary 0
represented?
-zero voltage or idle
In this encoding format, no transition at the
beginning of the bit represents binary 0 and
transition of a voltage level represents binary 1
For a resolution of 0.04 V determine the seven
bit sign magnitude pcm code for a sample of 2.12 V
-NRZ-I
-0110101
The
is the time required to send one bit
-bit interval
In all codes possible in segment 5, how many
codes can be decoded exactly at the receiver?
-16
In a frequency-domain plot a composite signal
consisting of 12 sine wave (all of different
frequency and amplitude) there are
vert.
bars.
-12
In this encoding, 1 is represented by positive
and negative voltage alternately and zero using
zero volt
-bipolar encoding
With this pulse modulation technique, the
active portion of the pulse is varied
proportional to the amplitude of the analog
signal at the time the signal is sampled
-PPM
Which block of PCM transmission system is
used to convert the parallel pcm codes to
multilevel pam signals?
-sample and hold circuit
One disadvantage of this encoding is higher
bandwidth is required since it needs 2 signal
changes to encode binary 1 and 0
-biphase encoding
The value of a simple sinewave at time zero is it
maximum positive value. The phase shift is
therefore
degrees
-90
If the max value of a simple sine wave is 10
volts, the voltage values
-ranges from -10 to 10
A signal has a constant value of 10 volts, its
frequency is Hz
-0
With this pulse modulation technique , the
pulses are fixed length and fixed amplitude. It
uses binary system where a pulse or lack of
pulse within a prescribed time slot represents
either logic 1 or logic 0 condition
-pcm
It is the distortion created when using too low
sampling rate when coding an analog signal for
digital transmission
-fold-over distortion
Which of the following is true about pcm?
-the smaller the resolution the less
quantization error is introduced
How is binary 1 represented in NRZ-L?
-either positive or negative
Which of the following statement is true about
digital transmission?
-all of the above
What causes aliasing?
-when each of the analog input is not sampled
at least twice
Which of the following 12 bit pcm codes belong
to segment 3?
-000001010101
In digital compression, what is the compression
ratio of segments?
-16:1
Which of the following sampling rate will result
into foldover distortion if the maximum analog
input is 3 KHz?
-≥ 6KHz
The minimum sampling rate needed for an
analog signal whose frequency ranges from 100
Hz- 3000Hz is
-6000 Hz
Which of the following is not true about sample
and hold circuit?
-none of the above
A digital signal has a bit rate of 200bps. The bit
interval is
seconds
-0.005
Among the 4 methods of pulse modulation
which method is used in digital transmission?
-pcm
Which encoding uses 3 signal levels (+, -, zero
volts) positive to zero is used to represent
binary 1 and negative to zero is used to
represent binary 0
-bipolar encoding
Which of the following is true about
quantization?
-
All of the above
The minimum bandwidth for a 32PSK
modulated signal with a baud rate of 3000 baud
is – 3000Hz
The inputs to an 8-QAM modulator is C=0 I=0
Q=1 with a reference of –sinwct. The output isc. 0.765V, -45
In FSK, the
of the information signal
modulates the
of the carrier signal.- b.
amplitude, frequency
In 8PSK, what is the output of the I-product
modulator when the input is 011, reference is –
coswct?- d. 1.307 coswct
If the bit rate for modulation scheme A is two
times the bit rate for modulation scheme B, the
required bandwidth for scheme A is
the
one for scheme B. – we cannot tell
How many bits are needed to represent a
signaling element when the input bit rate is
50kbps and the output symbol rate is 5kbaud? –
10
If the symbol rate for 8PSK is 8kbaud, the bit
interval of the binary input is approximately –
24 kbps
The inputs to an 8- QAM modulator is C=1 I=0
Q=1 with a reference carrier of coswct. The
output is- b. 1.307sinwct+1.307coswct
What is the output pahe of an 8PSK signal when
the input is 000, reference carrier of sinwct but
uses a -90 degree phase shifter- -112.5 E
When the input to 16QAM is I=1 Q=0 I’=0 na
Q’=1, the 16 QAM output is when the reference
is –sinwct- c. 0.85V, -75E
Determine the center carrier frequency (in KHZ)
of an FSK signal with a mark frequency of 32
kHz, a space frequency of 24 khz and a bit rate
of 4kbps. - 28
In FSK, if the mark frequency is equal to 24kHz
and the space frequency is 16KHz, what is the
carrier frequency? – b. 20KHz
What is the output of the phase shifter when
the reference is coswct?- c. –sinwct
In ASK, if the reference carrier is cowct, and +1V
is used for binary 0 ad -1V for binary 1, when
the input is binary 1 what is ASK output?- a. 0
What is the BW efficiency of an 8 PSK signal for
a baud rate of 12kbaud? – A. 3bits/cycle
In a 64 QAM, the number of points in the
constellation per quadrant is – c. 16
A 16 QAM modulator has the following inputs I=
1 Q=1 I’=0 Q’=1 with a reference of –coswct, the
output phase is- c. 0.850V, 75
ASK is sometimes called digital AM or – ook
If the baud rate for modulation scheme A is two
times the baud rate for modulation scheme B,
the required bandwidth for scheme A is
the one for scheme B. – a. twice
In binary FSK, - a. The carrier amplitude remains
constant while frequency is shifting between 2
values
When the BW efficiency is equal to 8bits/cycle,
what type of system was used? – 256 QAm
When the reference is coswct, what is the QPSK
output when the input is I-1 Q-1 – b. sinwct+coswct
Cellular Mobile Communication is an example
of – c. Dgital to Analog Encoding
If the bit rate is 1200 bps and there are 2 bits
for each signal element, the symbol rate is –
600 baud
A 128-QAM modulated signal has a buad rate of
2000;there are
bits per baud. – 7
A QPSK modulator has the following inputs I=0
Q=1, reference carrier of coswct the output is –
c. –sinwct-coswct
If the bit interval of a digital input is equal to
1000 us, what is the baud rate for QPSK? -500
baud
What is the output of the Q-balanced
modulator when the input is I=1 Q=0 1’=0 Q’=1,
with –coswct
In FSK, if the mark frequency is equal to 24kHz
AND THE SPACE FREQUNCY is 16kHz, WHAt is
the carrier freq? – c. 22kHz
c. 0.821sinwct
In Binary PSK, if reference carrier is –coswct,
what is the output when the input is binary 1?in-PHASE
What is the bandwidth efficiency of 128QAM
systems? – 7
What is the output phase of an 8PSK system
where the reference carrier is –coswct with
input bit patterns IQC= 101 - -22.5
For the 8psk modulator, with a (-) 90 deg phase
shifter and reference of (-)sinwct, what is the
input combination (IQC) of the 8PSk signal equal
to-0.541sinwct+ 1.307 coswct – 110
In which type of modulation can the bit rate be
half the baud rate? – not applicable
When the BW efficiency is equal to 8bits/cycle
what type of system was used- 256QAM
What is the output phase of an 8PSK when the
reference carrier is –coswct with input bit
patterns IQC=101 – -22.5
In
modulation, the baud rate is ¼ times the
bit rate. – b. 16PSk
What is the bandwidth efficiency of 128 QAM
systems – 7
The inputs to an 8PSK modulator is C=0 I=0 Q=1
with a reference carrier of sinwct, the output
phase is – c. 112.5
In binary systems, the baud rate at the output
of the modulator is equal to – bit rate
In 8 PSK, what is the output of the 2-4 level
converter in the Q channel when the reference
carrier is –sinwct and the input is I=0 Q=1 C=0 –
c. +0.541 V
Determine the peak frequency deviation (in
KHZ) of an FSK signl with a mark frequency of
32kHz, A space frequency of 24 kHz, AND A BIT
RATE OF 4KBPS. – 4
-4
The process of receiving single signal that
produces multiple channels simultaneously
-
Demultiplexing
When calculating the maximum number of
users , a limiting factor in FDM is:
-
The bandwidth of each signal
It refers to the portion of a link that carries a
transmission between a given pair of lines
Determine the frequency deviation of an FSK
signal when the mark frequency is 18 kHz and
the space frequency is 22k Hz. – 2KhZ
The modulation affected by noise is - ASK
In binary FSK, how many output frequencies are
expected? - 2
-
Channel
A DS-0 single-channel PCM system uses a 12
kHz sampling rate and an eight-bit PCM code
for PCM-TDM transmission. What is the
produced PCM line speed of the said system?
-
96kbps
It is designed to be used in wireless applications
that also combine signals from different sources
to fit into a larger bandwidth.
-
Spread spectrum
It is the basic building block of the FDM
hierarchy
-
Message channel
It is the most significant circuit in a
demultiplexer.
-
Bandpass filter
The bit-rate of a DS-1 signal over a T-1 line is:
-
1.536 Mbps
The acronym DSL stands for
-
Digital Line Subscriber
It follows a pattern, frame to frame, that allows
the demultiplexer to synchronize with the
incoming stream so that it can separate the
time slots accurately.
-
Framing bits
A digital hierarchy where the service is a single
digital channel of 64kbps.
-
DS-0
A technique used to make the highest input
data rate the dominant data rate then add
dummy bits to the input lines with lower rates
-
-
Multiplexing
How many voice channels are there in a master
group
-
600
The term “chip rate” is used in describing:
-
Direct-sequence method
For a given data rate, direct-sequence systems,
compared to standard RF systems, use:
-
Much more bandwidth
6 channels each with a 150-kHz bandwidth are
to be multiplexed together. What is the
minimum bandwidth of the link if there is a
need for a guard band of 20 kHz between the
channels to prevent interference?
-
1000khz
In synchronous time-division multiplexing, if a
source does not have data to send, the
corresponding slot in the output frame is
-
Left empty
A technique where the bandwidth of the
original signal also expands, but the process is
different
-
DSSS
Bit Stuffing
Which of the following is not a common FDM
application?
-
Secure communications
Spread-spectrum can be done by using:
-
All of the above
CDMA stands for
-
Code Division Multiple Access
The process of receiving single signal that
produces multiple channels simultaneously
It is a 6.312-Mbps service, where it can be used
as a single service for 6.312-Mbps transmissions
or can be used to multiplex 4 DS1-Channels, 96
DS-6 Channels or a combination of this type
-
DS-2
Which is not true about synchronous timedivision multiplexing?
-
None of the above
Each narrowband channel is converted to a
different location in the total frequency
spectrum
-
-
Time division multiplexing
Which statement is correct
-
Multiplexing uses multiple channels to
transmit single signal
Frequency-Division multiplexing
It is a technique used when the data rate of an
input line is a multiple of others.
-
Multilevel-Multiplexing
A technique that uses M-different carrier
frequencies that are modulated by the source
signal
-
FHSS
FDM uses
modulation
It is a type of multiplexing where in
transmission from multiple sources occurs on
the same facility but not at the same time.
-
s a digital multiplexing technique for combining several low-rate channels into one high-rate
one.
A) FDM
B) TDM
C) WDM
D) None of the above
4 voice channels, each occupying a bandwidth of 4 KHz, are to be multiplexed together. What is the
minimum bandwidth of the link if there is a need for a guard band of 1.5 KHz?
a. 16
KHz
b.
20.5
KHz
c.
17.5
KHz
d. 21
KHz
A 10 MHz link is occupied by 7 channels having a bandwidth of 950 KHz each and guard bands.
How many are the guard bands and what is their bandwidth?
a. 5,
678.53
KHz
b. 6,
478.57
KHz
c. 7, 50
KHz
d. 6,
558.33
KHz
In frequency
division
multiplexing,
multiple signals
share the
bandwidth of a
common
communication
channel.
True
A)
False
B)
Which multiplexing technique transmits analog signals?
A) FDM
B) TDM
C) WDM
D) (a) and
(c)
A Jumbo group has a bandwidth of:
a. 15.984 MHz
b. 16.984 MHz
c. 15.12 MHz
d. 16.52MHz
Which of the following cannot be used for sources sending digital signals?
a. FDM
b. WDM
c. Both a and b
d. None of the above
It is the modulation used in FDM telephone
system.
FDM
The
technique uses M different carrier frequencies that are modulated by the source signal. At
one moment, the sign modulates one carrier frequency; at the next moment, the signal modulates
another carrier frequency.
A) FDM
B) DSSS
C) FHSS
D) TDM
Which multiplexing technique shifts each signal to a different carrier frequency?
A) FDM
B) TDM
C) Both (a) and (b)
D) None of the above
In synchronous TDM, if a source does not have data to send, the
corresponding slot in the output frame is:
a. removed
b. empty
c. occupied
d. full
It is a type of multiplexing wherein transmissions from multiple sources
occur on the same facility but not at the same time.
a. Frequency Division Multiplexing
b. Wavelength Division Multiplexing
c. Time Division Multiplexing
d. None of the above
In TDM, the transmission rate of the multiplexed path is usually
the sum of the transmission rates of the signal sources.
A) greater than
B) less than
C) equal to
D) not related to
is designed to use the high bandwidth capability of fiber-optic cable.
In a multiplexed system, lines share the bandwidth of
link.
A) 1; n
B) 1; 1
C) n; 1
D) n; n
A Master group has a bandwidth of:
a. 2.40 MHz
b. 240 KHz
c. 2.42 MHz
d. 2.52 MHz
FHSS stands for:
a. Frame Hopping Spread Spectrum
b. Frequency Hopping Spread Spectrum
c. Frame Hierarchy Spread Spectrum
d. None of the above
The word
transmission
refers to the portion of a
that carries a
channel; link
In
, we combine signals from different sources to fit into a larger
bandwidth.
A) spread spectrum
B) line coding
C) block coding
D) none of the above
In
TDM, slots are dynamically allocated to improve bandwidth
efficiency.
A) synchronous
B) statistical
C) isochronous
D) none of the above
It is the most significant circuit in a demultiplexer.
a. VCO
b. Bandpass filter
c. PLL
d. Discriminator
There are 9 sources, each creating 250 characters per second. If the
interleaved unit is a character and 1 synchronizing bit is added to each
frame, find the data rate of each source:
a. 250 Kbps
b. 4.5 Mbps
c. 450 Kbps
d. 4.5 Kbps
Which multiplexing technique involves signals composed of light beams?
A) FDM
B) TDM
C) WDM
D) none of the above
How many voice channels are there in a master group?
a. 12
b. 60
c. 600
d. 3600
it is the basic building block of the FDM hierarchy.
a. Message
channel
b. Group
c.
Baseband
channel
d. None of
the above
Bits that are usually added to the beginning of each frame
for synchronization are called:
a. Timing bits
b. Parity bits
c. Framing
bits
d. None of
the above
It usually accomplishes frequency modulation
in frequency division multiplexing systems.
a. VCO
b. PLL
c. Rectifier
d. Reactance modulator
Which multiplexing technique transmits
digital signals?
A) FDM
B) TDM
C) WDM
D) None of the above
In
TDM, each input connection has an allotment in
the output even if it is not sending data.
A) synchronous
B) statistical
C) isochronous
D) none of the above
can be applied when the bandwidth of a link (in
hertz) is greater than the combined bandwidths of the
signals to be transmitted.
A) TDM
B) FDM
C) Both (a) or (b)
D) Neither (a) or (b
is designed to be used in wireless applications in
which stations must be able to share the medium without
interception by an eavesdropper and without being subject
to jamming from a malicious intruder.
A) Spread spectrum
B) Multiplexing
C) Modulation
D) None of the above.
It is the circuit that performs demultiplexing in an FDM
system.
a. Oscillator
b. Bandpass filter
c. Discriminator
d. None of the above
is the set of techniques that allows the
simultaneous transmission of multiple signals across a single
data link.
A) Demodulating
B) Multiplexing
C) Compressing
D) None of the above
Which of the following is not a data rate management
strategy?
a. Multiple Multiplexing
b. Bit Padding
c. Multiple-slot Allocation
d. None of the above
The
technique expands the bandwidth of a signal by
replacing each data bit with n bits.
A) FDM
B) DSSS
C) FHSS
D) TDM
It is the most effective frequency demodulator.
a. Radio detector
b. PLL discriminator
c. limiter
d. all of the above
How many groups are there with a 600 voice channels?
a. 1
b. 5
c. 50
d. 300
The sharing of a medium and its link by two or more devices is called
.
A) modulation
B) encoding
C) line
discipline
D)
multiplexing
can be achieved by using multiplexing;
spreading.
can be achieved by using
A) Efficiency; privacy and
antijamming
B) Privacy and
antijamming; efficiency
C) Privacy and efficiency;
antijamming
D) Efficiency and
antijamming; privacy
Each signal in an FDM modulates a subcarrier.
a. True
b. False
c. Maybe
d. None of the above
Strips of unused bandwidth that separates channels in FDM
are called:
a. Frequency bands
b. Guard bands
c. Signal bands
d. None of the above
A Super group is composed of how many voice channels?
a. 48
b. 72
c. 60
d. None of the above
In synchronous TDM, for n signal sources of the same data
rate, each frame contains
slots.
A) n
B) n + 1
C) n - 1
D) 0 to n
Is a technique used when the data rate of an input line is not
a multiple of others:
a. Multiple-Slot Allocation
b. Pulse Stuffing
c. Interleaving
d. None of the above
DWDM stands for:
a. Digital Wavelength Division Multiplexing
b. Direct Wavelength Division Multiplexing
c. Dense Wavelength Division Multiplexing
d. Either a or b
Which of the following cannot be used for sources sending
analog signals?
a. FDM
b. WDM
c. TDM
d. None of the above
The sharing of a
medium and its
link by two or
more devices is
called
.
A) modulation
B)encoding
C)line discipline
D)multiplexing
2 INCORRECT
Which multiplexing technique transmits analog signals?
A)FDM
B)TDM
C)WDM
D)(a) and (c)
3 CORRECT
Which multiplexing technique transmits digital signals?
A)FDM
B)TDM
C)WDM
D)None of the above
4 CORRECT
Which multiplexing technique shifts each signal to a different carrier frequency?
A)FDM
B)TDM
C)Both (a) and (b)
D)None of the above
5 CORRECT
In synchronous TDM, for n signal sources of the same data rate, each frame contains
slots.
A)n
B)n + 1
C)n - 1
D)0 to n
6 CORRECT
In TDM, the transmission rate of the multiplexed path is usually
the transmission rates of the signal sources.
A)greater than
the sum of
B) less than
C) equal to
D) not related to
7 CORRECT
Which multiplexing technique involves signals composed of light beams?
A)FDM
B)TDM
C)WDM
D)none of the above
8 CORRECT
utilization is the use of available bandwidth to achieve specific goals.
A)Frequency
B)Bandwidth
C)Amplitude
D)None of the above
9 INCORRECT
can be achieved by using multiplexing;
spreading.
A)Efficiency; privacy and antijamming
can be achieved by using
B)Privacy and antijamming; efficiency
C)Privacy and efficiency; antijamming
D)Efficiency and antijamming; privacy
10 CORRECT
is the set of techniques that allows the simultaneous transmission of
multiple signals across a single data link.
A)Demodulating
B)Multiplexing
C)Compressing
D)None of the above
11 CORRECT
In a multiplexed system,
A)1; n
lines share the bandwidth of
link.
B)1; 1
C)n; 1
D)n; n
12 CORRECT
The word
refers to the portion of a
that carries a transmission.
A)channel; link
B)link; channel
C) line; channel
D) line; link
13 CORRECT
can be applied when the bandwidth of a link (in hertz) is greater than the
combined bandwidths of the signals to be transmitted.
A)TDM
B)FDM
C)Both (a) or (b)
D)Neither (a) or (b)
14 CORRECT
FSM is an
technique.
A)analog
B)digital
C)either (a) or (b)
D)none of the above
15 CORRECT
is designed to use the high bandwidth capability of fiber-optic cable.
A)FDM
B)TDM
C)WDM
D)None of the above
16 CORRECT
is an analog multiplexing technique to combine optical signals.
A)FDM
B)TDM
C)WDM
D)None of the above
17 CORRECT
is a digital process that allows several connections to share the high
bandwidth of a link.
A)FDM
B)TDM
C)WDM
D)None of the above
18 CORRECT
is a digital multiplexing technique for combining several low-rate channels into
one high-rate one.
A)FDM
B)TDM
C)WDM
D)None of the above
19 CORRECT
We can divide
into two different schemes: synchronous or statistical.
A)FDM
B)TDM
C)WDM
D)none of the above
20 CORRECT
In
TDM, each input connection has an allotment in the output even if it is
not sending data.
A)synchronous
B)statistical
C)isochronous
D)none of the above
21 CORRECT
In
TDM, slots are dynamically allocated to improve bandwidth efficiency.
A)synchronous
B)statistical
C)isochronous
D)none of the above
22 CORRECT
In
, we combine signals from different sources to fit into a larger
bandwidth.
A)spread spectrum
B)line coding
C)block coding
D)none of the above
23 CORRECT
is designed to be used in wireless applications in which stations must be
able to share the medium without interception by an eavesdropper and without
being subject to jamming from a malicious intruder.
A)Spread spectrum
B)Multiplexing
C)Modulation
D)None of the above.
24 CORRECT
The
technique uses M different carrier frequencies that are modulated by
the source signal. At one moment, the sign modulates one carrier frequency; at the
next moment, the signal modulates another carrier frequency.
A)FDM
B)DSSS
C)FHSS
D)TDM
25 CORRECT
The
technique expands the bandwidth of a signal by replacing each data bit
with n bits.
A)FDM
B)DSSS
C)FHSS
D)TDM
PQ#8 - 95/100
1. In synchronous time-division multiplexing, if a source does not have data to send, the corresponding
slot in the output frame is _____.
- left empty
2. It is a 6.312-Mbps service, where it can be used as a single service for 6.312-Mbps transmissions or
can be used to multiplex 4 DS1-Channels, 96 DS-6 Channels or a combination of this type.
- DS-2
3. Which is not true about synchronous time-division multiplexing?
- In synchronous TDM, the multiplexer combines light signals using a fiber channel and produces
unidirectional light.
4. Four 1-kbps connections are multiplexed together. A unit is 1 bit. Find the duration of a time
slot. - 250usec
Solution:
Bit duration = T
fb = bit rate
T = 1/fb = 1/1kbps = 1 ms
Output slot duration = T/n = 1ms/4 = 0.25 ms = 250 usec
5. Which statement is correct
- Multiplexing uses multiple channels and a single path
6. In statistical time-division multiplexing, slots are dynamically allocated to
_____. - improve the bandwidth efficiency
7. It is a level in an analog hierarchy where it has a bandwidth of 2.52MHz
- Master group
8. offers customers the opportunity to lease a line that is permanently connected to another customer.
Although the connection still passes through the switches in the telephone network, subscribers
experience it as a single line because the switch is always closed; no dialing needed.
- Analog Leased Service
9. Compute for the guardband in between channels in a Master group with 2.52MHz total
bandwidth - 200.33 or 599
Solution:
Total Bandwidth = (No. of Voice Channels x Bandwidth) + (No. of Voice Channels -1) Guard
Band 2.52MHz = (600x4 KHz) + (599) "X"
X = 200.33
10. Which of the following is not a common application of frequency-division
multiplexing? - Local Area Network
11. A jumbo group is equivalent to how many master group?
-6
12. Four 1-kbps connections are multiplexed together. A unit is 1 bit. How many slots are there in each
frame
-4
13. Digital multiplexing is based on the principle of __________ from two or more digital
signals. - Interleaving symbols
14. An analog multiplexing technique where the optical fiber data rate is higher than the data rate of
metallic transmission cable. It is also used to combine optical signals.
- b. WDM
15. It is the process of receiving single signal and produces output on multiple channels
simultaneously. - Demultiplexing
16. FDM uses ______ modulation.
- a. Single-Sideband Suppressed Carrier
17. How many voice channels are multiplexed in a T2 line.
- 96
18. Four 1-kbps connections are multiplexed together. A unit is 1 bit. Find the duration of a
frame. - 1ms
Bit duration = T
fb = bit rate
T = 1/fb = 1/1kbps = 1 ms
19. Each narrowband channel is converted to a different location in the total frequency
spectrum. - a. Frequency-Division Multiplexing
20. It is a dial-up service most often encountered when using a home telephone. It uses two-wire (or four
wire) twisted pair cable to connect the subscriber's handset to the network via an exchange. The
connection is often called local loop.
⎯ Analog Switched Service
PQ#9 - 100
1. A type of sampling where the input voltage is sampled with a narrow pulse and then held
relatively constant until the next sample is taken.
⎯ Flat-top Sampling
2. Which of the following is true about sample and hold circuit?
⎯ D. All of the choices
A sample and hold circuit is a non-linear device with two inputs and consequently, heterodyning
occurs between these two signals
The capacitor is the hold circuit
It introduces aperture error as a result of mixing two signals
3. Which of the following is not true about PCM?
⎯ A. Higher dynamic range will result if resolution is increased
4. What causes aliasing?
⎯ A. When each cycle of the analog input signal is not sampled at least twice.
5. Which of the following is true about quantization?
⎯ C. The smaller the resolution the less quantization error is introduced
OT
1. A technique used to make the highest input data rate the dominant data rate and then add dummy bits
to the input lines with lower rates.
⎯ Bit stuffing
2. Five 10-kbps connections are multiplexed together. A unit is 1 bit. Determine the rate of the
transmission link in kbps.
⎯ 50
Solution:
Transmission rate of the link = n * fbin = 5 * 10 kbps = 50 kbps
3. Five 10-kbps connections are multiplexed together. A unit is 1 bit. How many slots are there in each
frame?
⎯5
4. Five 10-kbps connections are multiplexed together. A unit is 1 bit. Determine the duration of each
frame in micro seconds.
⎯ 100
Solution:
T = 1/fb = 1/10 kbps = 100 us
Duration of each frame = n * (T/n) = 100 us
5. Five 10-kbps connections are multiplexed together. A unit is 1 bit. Determine the frame rate in
frames/sec. ⎯ 10000
Solution:
Output frame rate = 1/frame duration = 1/100 us = 10000
6. The bit-rate of a DS-1 signal over a T-1 line is:
⎯ 1.544 Mbps
7. A master group supports how many voice channels?
⎯ 600
8. how many voice channel has a supergroup have?
⎯ 60
9. 10 supergroups forms a
⎯ Mastergroup
10. 1 supergroup is formed when combining how many groups?
⎯5
11. In FDM Hierarchy, 12 voice channel can be combined to formed a
⎯ Group
12. The total bandwidth ( in Khz) of combining 12 voice channels
⎯ 48
13. What is the overhead used for a DS 1 service
⎯ 8 kbps
14. A PCM system has the following parameters: a maximum analog input frequency of 4.5kHz, a
maximum decoded voltage at the receiver of +- 5V, and a minimum dynamic range of 60 dB. Determine
the following: a) Minimum sampling rate (in Hz)
⎯ 9000
Solution:
The maximum analog input frequency is, fm = 4.5 kHz.
Let us denote the sampling rate as fs.
The minimum sampling rate is, fs = 2(fm) = 2(4.5 kHz) = 9 kHz = 9000 Hz.
15. What is the maximum data rate of a DDS?
⎯ 64 kbps
16. 5 10-kbps connections are multiplexed together. A unit is 1 bit. Find the duration of the output
timeslot. ⎯ 20 us
Solution:
T = 1/fb = 1/10 kbps = 100 us
Output slot duration = T/n = 100 us/5 = 20 us
17. It is the process of rounding off the amplitude of flat-top samples
⎯ Quantization
18. For a resolution of 0.02V, determine the voltage (in V), and the for the following 6-bit sign-magnitude
PCM codes: b) 011100. Do not include the unit in final answer.
⎯ -0.56
Solution:
19. Ten 100-kbps connections are multiplexed together. A unit is 1 bit. Determine the frame rate in
frames/sec
⎯ 100000
Solution:
T = 1/fb = 1/100kbps = 10us
Frame duration = T = 10 us
Frame rate = 1/frame duration = 1/10us = 100000
20. A European version where the 2 systems are conceptually identical but their capacities
differ ⎯ E-Lines
21. When calculating the maximum number of users, a limiting factor in FDM is
⎯ The bandwidth of each signal
22. It follows a pattern, frame to frame, that allows the demultiplexer to synchronize with the incoming
stream so that it can separate the time slots accurately.
⎯ Framing bits
23. In a sample and hold circuit, which component serves as the hold circuit?
⎯ Capacitor
24. In a sample and hold circuit, which part/component is the hold circuit?
⎯ Capacitor
25. Asymmetric Digital Subscriber Line divides the bandwidth of a twisted pair cable (1 MHz) into 3bands:
which band is used for downstream communication?
⎯ (250 KHz - 1 MHz)
26. Which statement is true about Symmetric (single-line) digital subscriber line (SDSL)
⎯ Same as HDSL but one uses single pair twisted cable, available to most residential subscriber to
achieve the same data rate as HDSL
27. Determine the coding efficiency required for the following dynamic ranges: b)40dB. Use 2 decimal
places
⎯ 95.75 or 95.73
Solution:
Other Sol’n:
28. Which of the following is true about Signal-to-noise ratio?
⎯ In linear codes, as the amplitude of a sample increases, SQR remains essentially constant
29. Six 50-kbps connections are multiplexed together. A unit is 1 bit. Determine the duration of each
frame in micro seconds.
⎯ 20
Solution:
T = 1/fb = 1/50 kbps = 20 us
Duration of each frame = T = 20 us
30. A technology that uses existing telecommunication networks to accomplish high-speed delivery of
data, voice and multimedia.
⎯ DSL
31. Six 100-kbps connections are multiplexed together. A unit is 1 bit. Determine the rate of the
transmission link in kbps.
⎯ 600
Solution; Transmission rate of the link = n * fbin = 6 * 100 kbps = 600 kbps
32. In order to directly reduce quantizing noise, one must
⎯ Increase the number of standard amplitudes
33. A PCM system has the following parameters: a maximum analog input frequency of 4.5kHz, a
maximum decoded voltage at the reciever of +-5V, and a minimum dynamic range of 60dB. Determine
the following c) actual number of bits used in the PCM code (excluding the sign)
⎯ 10
34. When an analog signal with infinite amplitude possibilities is quantized and is given a 5-bit PCM code,
how many limited number of combinations are possible?
⎯ 32
35. High bit rate DSL uses what type of encoding
⎯ 2B1Q
36. An alternative approach that is similar to ADSL; uses coaxial, fiber-optic or twisted pair cable for short
distances (300 to1800 meters)
⎯ Very High Bit Rate DSL
37. It is a technique used when the data rate of an input line is multiple of
others. ⎯ Multilevel-Multiplexing
38. Which block of the PCM transmission system is used to convert the multilevel PAM samples to binary
PCM Code?
⎯ ADC
39. Which of the following statement is not true about Digital Transmission?
⎯ None of the choices (Eto ata)
⎯ It uses pulse code modulation to convert analog to digital
⎯ It requires physical facility between a transmitter and a receiver
⎯ The original information may analog or digital in form
40. A PCM system has the following parameters: a maximum analog input frequency of 4.5kHz, a
maximum decoded voltage at the receiver of ±5V, and a minimum dynamic range of 60dB. Determine the
following: b) minimum number of bits used in the PCM code. Use 2 decimal places
⎯ 9.97
SOLUTION:
Minimum Dynamic Range = 20log(Vmax/Vmin)
60 dB = 20log(Vmax/Vmin)
3 = log(Vmax/Vmin)
103= Vmax/Vmin ---- 1000
Number of bits = log(1000+1)/log(2)
= 9.96722659 or 10 (including bit sign)
41. A part of PCM transmitter that serves as anti-aliasing circuit
⎯ BPF
42. When the number of bits in a PCM code, n, is 3, what is the dynamic range in dB?
⎯ 16.90
SOLUTION:
Number of bits = log(x+1)/log(2)
3 = log(x+1)/log(2)
X=7
20log(7) = 16.9019608