Wireless Communications for Everybody Answer

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Wireless Communications for Everybody Answer

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Week- 1

Graded Quiz for Introduction and History of Cellular Communication Systems

 

1.
Question 1
Which concept did ‘Bell lab.’ propose in first generation communication system?

1 point
Enter answer here

cellular telephone

2.
Question 2
What does BW stand for in communication field?

1 point

• BandWidth
• BroadWay
• BodyWeight
• Business Week

3.
Question 3
Which are the drawbacks of 1G? (Choose Three)

1 point

• Large Size Phone
• Poor Battery Performance
• Expensive Service Fee
• Wireless Communication

4.
Question 4
Which is the wrong one?

1 point

• FDMA: Frequency Division Multiple Access
• TDMA: Time Division Multiple Access
• CDMA: Code Division Multiple Access
• SMS: Social Message Service

5.
Question 5
What is a specialized agency of the United Nations (UN), which is responsible for information and communication technology issues?

1 point

• ITU
• 3GPP
• 3GPP2
• Verizon

6.
Question 6
Fill in the blanks of following sentence.

The 2G system was developed to voice service, but the 3G system was focused on ( ~ ) communication.

1 point
Enter answer here

Global System for Mobile communication

7.
Question 7
Which are the keywords and key technologies used in 3G cellular systems? (Choose Three)

1 point

• Smartphone
• CDMA
• TDMA
• MMS

8.
Question 8
What does LTE stand for?

1 point
Enter answer here

Long Term Evolution

9.
Question 9
Accordign to 3GPP, what is the target data rate for 5G cellular system?

1 point

• 10 Gbps
• 20 Gbps
• 30 Gbps
• 40 Gbps

10.
Question 10
Which one is not a key technology for 5G system?

1 point

• NOMA
• Many Cell
• New Waveform
• TDMA

11.
Question 11
Which one is an incorrect keyword for 5G system? See the blank of the following sentence.

The main targets for 5G (by 2020) are spectral efficiency, peak ( a ) massive ( b ), high ( c ) support, and low transmission ( d ).

1 point

• time
• connectivity
• mobility
• delay

 

Week- 2

Graded Quiz

 

1.
Question 1
The amount of information obtained by knowing the result of a random experiment is the same to the amount of (A)_________ on the result. In the case of tossing coin it is maximized when the coin is (B)________ and the corresponding amount of information is (C)___ bit.

1 point

(A) certainty, (B) fair, (C) 1

(A) certainty, (B) fair, (C) 0

(A) certainty, (B) unfair, (C) 1

(A) uncertainty, (B) fair, (C) 1

(A) uncertainty, (B) unfair, (C) 0

2.
Question 2
Suppose that the maximum frequency component of a signal is WW [Hz]. According to the sampling theorem, if the sample rate is above or equal to (A)_____, called the Nyquist rate, the original signal can be recovered perfectly.
Representing a continuous value requires (B)_______ number of bits because the resolution is (B)_______. If we increase the resolution of a quantizer, the distortion is (C)_________ but the information rate will be (D)_________.
1 point

(A) WW, (B) finite, (C) increased, (D) decreased

(A) WW, (B) infinite, (C) decreased, (D) increased

(A) 2W2W, (B) finite, (C) increased, (D) decreased

(A) 2W2W, (B) infinite, (C) increased, (D) decreased

(A) 2W2W, (B) infinite, (C) decreased, (D) increased

3.
Question 3
For wireless communications, we use an electrical device called antenna which converts an electrical current into a(n) (A)___________ and vice versa. A(n) (A)___________ can propagate a long distance with the speed of light. By doing this, we can deliver information wirelessly.
Mathematically, we can decompose a signal according to its constituent (B)________ components. The power spectrum of a signal indicates the power distribution of the information bearing signal according to (B)________.
Here, the range of non-zero power distribution is called the signal (C)_______ and it determines the speed of change in the signal. Remember that this is one resource we need to pay for transferring information.
If we increase the (D)_______ of the transmit signal, the intensity of the propagated radio wave increases, which implies longer propagation distance and better immunity for non-ideal effects. So, (D)_______ is another resource we need to pay.
1 point

(A) radio wave, (B) frequency, (C) power, (D) bandwidth

(A) radio wave, (B) frequency, (C) bandwidth, (D) power

(A) radio wave, (B) time, (C) power, (D) bandwidth

(A) acoustic wave, (B) frequency, (C) bandwidth, (D) power

(A) acoustic wave, (B) time, (C) power, (D) bandwidth

4.
Question 4
The PSD of the thermal noise is (A)_____. The noise power contained within the bandwidth of WW is (B)_____. Using the bandwidth of WW is equivalent to use (C)_____ independent samples. Then, the Shannon capacity is given as (D)_______ when the received signal power is PP.

1 point

 

​

5.
Question 5
What is the right order of processing
sequence at the transmitter?

1 point

(Channel Encoding) – (Constellation Mapping) – (Waveform Mapping) – (Up Converting & Power Amp)

(Channel Encoding) – (Waveform Mapping) – (Constellation Mapping) – (Up Converting & Power Amp)

(Waveform Mapping) – (Constellation Mapping) – (Channel Encoding) – (Up Converting & Power Amp)

(Constellation Mapping) – (Waveform
Mapping) – (Up Converting & Power Amp) – (Channel Encoding)

(Constellation Mapping) – (Channel
Encoding) – (Up Converting & Power Amp) – (Waveform Mapping)

6.
Question 6
Consider the case where a detection fails but the channel decoder recovers it. The noisy received symbols close to the (A)__________ are very probable to produce bit errors. But, the channel decoder may find that the erroneous bit sequence is not a possible candidate sequence and correct the errors by mapping to the closest (B)________ sequence. Although such mapping can fail either, such probability vanishes as the information bit size k (C)______.

1 point

(A) original symbols, (B) erroneous, (C) increases

(A) original symbols, (B) possible, (C) decreases

(A) original symbols, (B) possible, (C)
increases

(A) boundaries, (B) erroneous, (C) decreases

(A) boundaries, (B) possible, (C)
increases

7.
Question 7
Select the correct answer(s).

1 point

If we divide the area into many cells and
use one base station per each cell, much more power is required.

If users in different cells reuse the same frequency channels, the required bandwidth becomes much reduced.

Supporting many users in a large area by
only one transmitter is the power efficient way.

Cellular structure is bandwidth-efficient way to support many users in a large area but is not power-efficient.

8.
Question 8
The base station selects one among the
predetermined (A)______ based on the (B)_______ and transferring information by
using it. This is called (C)______.

1 point

(A) AMC (B) MCS (C) CQI

(A) AMC (B) CQI (C) MCS

(A) MCS (B) AMC (C) CQI

(A) MCS (B) CQI (C) AMC

(A) CQI (B) MCS (C) AMC

9.
Question 9
In frequency division multiple access (FDMA), (A)______ channels are allocated by dividing frequency
In time division multiple access (TDMA), (B)______ channels are allocated by dividing time.
In code division multiple access (CDMA), typically (C)______ codes are allocated to users so that each user can use the whole time and bandwidth.
1 point

(A) orthogonal (B) orthogonal (C) orthogonal

(A) orthogonal (B) orthogonal (C) quasi-orthogonal

(A) orthogonal (B) quasi-orthogonal (C) orthogonal

(A) quasi-orthogonal (B) orthogonal (C) quasi-orthogonal

(A) quasi-orthogonal (B) quasi-orthogonal (C) quasi-orthogonal

10.
Question 10
Compare the two-user rate region of CDMA, FDMA, and TDMA.

1 point

CDMA ≥ FDMA ≥ TDMA

CDMA ≥ TDMA ≥ FDMA

FDMA ≥ CDMA ≥ TDMA

FDMA ≥ TDMA ≥ CDMA

TDMA ≥ FDMA ≥ CDMA

 

 

 

 

Week- 3

1.
Question 1
Which action is better to cope with the so called “cocktail effect”?

1 point

Shutdown every transmission

Scheduling of transmission (e.g., round-robin way of transmission, allowing only some group of transmitters to transmit, etc)

2.
Question 2
In a single channel radio network, as the number of communicating pairs increases, it is impossible to support every pair. Which is the better solution for such overwhelming interference scenario?

1 point

Shrink the communication distance (such as multi-hop relay)

Make every node “move” randomly and wait for the source node to be close to its destination node.

3.
Question 3
Why does the cellular system look like as of today?

1 point

To handle large amount of interference

To save the power consumption of mobile terminals

4.
Question 4
What are the drawbacks to have stationary access points in the wireless network?

1 point

Increasing transmission power of mobile terminals.

Frequent handover (switching to a new access point) as mobile terminals move around the service area.

5.
Question 5
Increasing the base station density will increase the capacity of the cellular system?

1 point

Yes, if the number of mobile terminals is fixed and their demand is fixed.

Yes, even if the number of mobile terminals and their demand increase.

6.
Question 6
Select the two most unique features for the next generation cellular system (5G).

1 point

Ultra-dense base stations

mmWave transmission

Long-distance transmission

Frequent handover

7.
Question 7
The uplink power control is a typical example of radio resource management. When in the two-user case, is it optimal to shut off one of the users?

1 point

The target SIR is too high.

One mobile is too close to the base station.

8.
Question 8
In the distributed power control (DPC) algorithm, who measures the SIR (signal to interference), and reports it to whom?

1 point

The base station measures it and report to the mobile terminal.

The mobile terminal measures it and report to the base station.

9.
Question 9
To balance between fairness and throughput-maximization, which objective could be used in packet scheduling?

1 point

Maximize the minimum throughput of users

Proportional fairness

10.
Question 10
What is the most important gain from the packet scheming in the cellular system?

1 point

Increasing “average” data rate of each user.

Save the power consumption of base stations.

 

 

 

 

Week- 4

 

1.
Question 1
Which
correctly names the types of antennas shown below?

1 point

A: Whip B: PCB C: Feedhorn D: Monopole E: Dipole

A: Chip B: Dipole C: Microstrip D: Cassegrain E: Monopole

A: Monopole B: Dipole C: PCB D: Feedhorn E: Cassegrain

A: Whip B: Monopole C: PCB D: Dipole E: Cassegrain
2.
Question 2
What cannot be the antenna gain for the directed antenna below in dBi?

1 point

5 dBi

3 dBi

8 dBi

10 dBi
3.
Question 3
Given the antenna configuration shown below, if we want to send the signal from
the Tx to
the Rx, which of the following should have high value for good performance? (S
is the S-parameter) (Choose two)

1 point

S11

S31

S32

S21

4.
Question 4
If
antenna gain of 10 dBi was
achieved using a single antenna, what would be the ideal gain of an array of antennas under identical conditions if the signal power was boosted by 100
times?
1 point

50 dBi

1000 dBi

20 dBi

30 dBi

15 dBi
5.
Question 5
Which of the statements is erroneous? (Choose two)
1 point

The directivity of an antenna is determined by the beamwidth.

Circular array and linear array generate identical radiation patterns.

Radiation pattern can be only controlled by amplitude distribution.

With very closely spaced receiver antennas (perfectly correlated channels) for SIMO (single-input-multiple-output), an array gain of 3dB can be achieved.

Array gain can be used to reduce signal interference to other users.
6.
Question 6
For a perfectly uncorrelated (multipath) channel with 2 Tx antennas and 2 Rx antennas, how many paths can we exploit at maximum?
1 point

2

1

8

4

6
7.
Question 7
If
we have a 2 by 2 MIMO system with modulation scheme of 2 bps/Hz per symbol,
what is the achievable maximum spectral efficiency?
1 point

8 bps/Hz

2 bps/Hz

1 bps/Hz

4 bps/Hz

8.
Question 8
Which of the statements is erroneous? (Choose two)
1 point

Diversity can be achieved in space, time, and frequency.

Tx diversity can be the same as Rx diversity.

Multi-user MIMO can only be formed when a base station and a user both have multiple antennas at their sides.

Diversity gain can be made by antenna selection.

Alamouti coding is a type of antenna selection.

9.
Question 9
Which
of the following does not achieve maximum sum rate?

1 point

A

B

C

D

10.
Question 10
Which
of the following is a non-degraded channel?

1 point

A

B

C

D

 

 

 

Week- 5

 

1.
Question 1
Which of the following statements is not correct about LTE OFDM?

1 point

OFDM is a parallel transmission method using multiple subcarriers.

1200 subcarriers with 15KHz subcarrier spacing are used when the system bandwidth is 20MHz.

The OFDM symbol length, which is the inverse of the system bandwidth, is 50ns when the system bandwidth is 20MHz.

The cyclic prefix helps to keep the orthogonality among the multiple subcarriers in most typical practical cellular environments.

2.
Question 2
Which of the following statements is not correct about LTE MCS?

1 point

BPSK, QPSK, 16QAM, and 64QAM can be used for each subcarrier in an OFDM symbol.

Turbo code with various code rates is used as the channel code in LTE.

Each LTE MCS is mapped to its own channel quality information index.

The data rate of an LTE MCS is determined by the modulation order.

3.
Question 3
Select the most appropriate one for the
procedure of LTE H-ARQ.

1 point

(CQI report) →(Scheduling) →(Data transmission) →(ACK or NACK) →(Retransmission if NACK)

(Data transmission) → (Scheduling) → (CQI report) → (ACK or NACK) → (Retransmission if NACK)

(Scheduling) → (CQIreport) → (Datatransmission) → (ACKor NACK) → (Retransmissionif NACK)

(CQI report) → (Datatransmission) → (Scheduling)→ (ACKor NACK) → (Retransmissionif NACK)

4.
Question 4
Which of following
statements is not correct about
LTE frame structure and multiple access?

1 point

The basic resource unit is 1ms in time and 12 subcarriers in frequency.

In downlink, orthogonal frequency division multiple access is used.

In uplink, every user transmits with the same transmission power.

In uplink, single carrier frequency division multiple access is used.

5.
Question 5
Which of the Tx structure is appropriate for the following scheme of SFBC (Space-Frequency-Block-Coding) ?

1 point

6.
Question 6
Which of the following statements does not correspond to LTE-Advanced key items?

1 point

Coordinated multipoint transmission/reception, called CoMP.

Further enhancement of downlink MU-MIMO (R10 main issue).

Peak spectrum efficiency of 20 bps / Hz for downlink, and 30 bps / Hz for uplink.

Extension of downlink diversity to 8 antennas.

Uplink diversity utilizing up to 4 antennas.

7.
Question 7
Which of the following is incorrect?

1 point

A: Transmit diversity (TM2)

B: Closed loop spatial multiplexing (TM3)

C: CL rank = 1 (TM6)

D: Open loop spatial multiplexing (TM4)

8.
Question 8
What is the main reason to have open loop power control?

1 point

Fast set-up for initial power level.

Fast support of moving users.

9.
Question 9
Why is PF scheduler “proportionally” fair?

1 point

It prioritizes less received users.

It always gives more chances to users closer to the base station.

 

 

 

Week- 6

 

1.
Question 1
Which of the following best describes the advantage of circuit switching?

10 points

It provides a reliable communication channel.

It efficiently handles bursty traffic.

It doesn’t waste bandwidth.

2.
Question 2
Choose the one that best describes the disadvantage of circuit switching.

10 points

Connection setup delay

Best-effort delivery

Out-of-order delivery

3.
Question 3
Which of the following best describes the advantage of packet switching?

10 points

Data forwarding mechanism is simple.

Per-packet overhead is low.

It allows multiplexing.

4.
Question 4
Which of the following directly communicates with UE (user equipment) in LTE network?

10 points

eNodeB

SGW

MME

PGW

5.
Question 5
Which of the following acts as an interface between the external Internet and LTE network?

10 points

eNodeB

SGW

MME

PGW

6.
Question 6
What is the name of the process that connects a moving UE from one eNodeB to the other eNodeB without service disconnection?

10 points

Handover

Anchoring

Cell coverage

7.
Question 7
Which of the following is the name of the process that translates domain names into IP addresses?

10 points

IP address allocation

DNS resolution

Initial attachment

8.
Question 8
Choose the term that represents saving requested web pages for subsequent use.

10 points

Proxying

Caching

Load balancing

9.
Question 9
Which of the following is NOT related to traffic reduction in LTE network?

10 points

Handover

DNS resolution

Proxy forwarding

10.
Question 10
Which of the following is NOT a benefit of using LTE and WiFi together?

10 points

It better supports user mobility.

It provides more bandwidth hence, better throughput.

It reduces operating costs.