2023 – 2024 Coursera Wireless Communications For Everybody – Quiz Answers
Week 1: Introduction and History of Cellular Communication Systems quiz answers
In this part of the course, we will learn the introduction and history of cellular communication system. First, we will take a example of cellular communication system with cell phone. And then, learn about the what a cellular system is and how it has been developed so far. Lastly, we will briefly look into the concepts of future cellular systems.
Question 1. Which concept did ‘Bell lab.’ propose in first generation communication system?
Enter answer here
Question 2. What does BW stand for in communication field?
- Business Week
Question 3. Which are the drawbacks of 1G? (Choose Three)
- Large Size Phone
- Poor Battery Performance
- Expensive Service Fee
- Wireless Communication
Question 4. Which is the wrong one?
- FDMA: Frequency Division Multiple Access
- TDMA: Time Division Multiple Access
- CDMA: Code Division Multiple Access
- SMS: Social Message Service
Question 5. What is a specialized agency of the United Nations (UN), which is responsible for information and communication technology issues?
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.
Enter answer here
|Global System for Mobile communication|
Question 7. Which are the keywords and key technologies used in 3G cellular systems? (Choose Three)
Question 8. What does LTE stand for?
Enter answer here
|Long Term Evolution|
Question 9. According to 3GPP, what is the target data rate for 5G cellular system?
- 10 Gbps
- 20 Gbps
- 30 Gbps
- 40 Gbps
Question 10. Which one is not a key technology for 5G system?
- Many Cell
- New Waveform
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 ).
Week 2: Principles of Wireless Communication Theory quiz answers
In this part of the course, we will learn the fundamental principles of wireless communication theory. I will raise five fundamental questions in the first lecture as follows: i) ‘how can we represent information into a binary format?’, ii) ‘how can information be transferred?’, iii) ‘how does wireless digital MODEM work?’, iv) ‘how can high-rate data be delivered reliably?’, and v) ‘how can many users access simultaneously?’. During the following 5 lectures, you will have the answers.
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.
- (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
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)_________.
- (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
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.
- (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
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.
Question 5. What is the right order of processing sequence at the transmitter?
- (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)
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)______.
- (A) original symbols, (B) erroneous, (C) increases
- (A) original symbols, (B) possible, (C) decreases
- (A) original symbols, (B) possible, (C)
- (A) boundaries, (B) erroneous, (C) decreases
- (A) boundaries, (B) possible, (C)
Question 7. Select the correct answer(s).
- 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.
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)______.
- (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
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.
- (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
Question 10. Compare the two-user rate region of CDMA, FDMA, and TDMA.
- CDMA ≥ FDMA ≥ TDMA
- CDMA ≥ TDMA ≥ FDMA
- FDMA ≥ CDMA ≥ TDMA
- FDMA ≥ TDMA ≥ CDMA
- TDMA ≥ FDMA ≥ CDMA
Week 3: Principles of Wireless Resource Management quiz answers
In this part of the course, we will discuss the basic concept of wireless resource management. I will raise six interesting questions as follows: i) ‘how does the interference affect the capacity of wireless networks?’, ii) ‘why does the cellular system look like as of today?’, iii) ‘Increasing the number of cells increases the capacity?’, iv) ‘how is 5G cellular being shaped?’, v) ‘how does the interference management increase the capacity?’ and Ⅵ) ‘how does scheduling increase the average capacity?’.
Question 1. Which action is better to cope with the so called “cocktail effect”?
- Shutdown every transmission
- Scheduling of transmission (e.g., round-robin way of transmission, allowing only some group of transmitters to transmit, etc)
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?
- 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.
Question 3. Why does the cellular system look like as of today?
- To handle large amount of interference
- To save the power consumption of mobile terminals
Question 4. What are the drawbacks to have stationary access points in the wireless network?
- Increasing transmission power of mobile terminals.
- Frequent handover (switching to a new access point) as mobile terminals move around the service area.
Question 5. Increasing the base station density will increase the capacity of the cellular system?
- 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.
Question 6. Select the two most unique features for the next generation cellular system (5G).
- Ultra-dense base stations
- mmWave transmission
- Long-distance transmission
- Frequent handover
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?
- The target SIR is too high.
- One mobile is too close to the base station.
Question 8. In the distributed power control (DPC) algorithm, who measures the SIR (signal to interference), and reports it to whom?
- The base station measures it and report to the mobile terminal.
- The mobile terminal measures it and report to the base station.
Question 9. To balance between fairness and throughput-maximization, which objective could be used in packet scheduling?
- Maximize the minimum throughput of users
- Proportional fairness
Question 10. What is the most important gain from the packet scheming in the cellular system?
- Increasing “average” data rate of each user.
- Save the power consumption of base stations.
Week 4: Multiple Antenna Technologies quiz answers
In this part of the course, we will learn how multiple antennas can be efficiently used in different strategies for communication system enhancement. First, we look in to the basics of antenna, and then learn about the three main gains that are achievable by multiple antennas: array, diversity, and spatial multiplexing. Lastly, we briefly look in to the concepts of single-user MIMO and multi-user MIMO.
Question 1. Which correctly names the types of antennas shown below?
- 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
Question 2. What cannot be the antenna gain for the directed antenna below in dBi?
- 5 dBi
- 3 dBi
- 8 dBi
- 10 dBi
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)
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?
- 50 dBi
- 1000 dBi
- 20 dBi
- 30 dBi
- 15 dBi
Question 5. Which of the statements is erroneous? (Choose two)
- 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.
Question 6. For a perfectly uncorrelated (multipath) channel with 2 Tx antennas and 2 Rx antennas, how many paths can we exploit at maximum?
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?
- 8 bps/Hz
- 2 bps/Hz
- 1 bps/Hz
- 4 bps/Hz
Question 8. Which of the statements is erroneous? (Choose two)
- 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.
Question 9. Which of the following does not achieve maximum sum rate?
Question 10. Which of the following is a non-degraded channel?
Week 5: Physical Layer Design of LTE systems quiz answers
In this part of the course, we will learn how the fundamental principles of wireless communication theory, resource management, and multiple antenna technology are implemented in the LTE system.
Question 1. Which of the following statements is not correct about LTE OFDM?
- 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.
Question 2. Which of the following statements is not correct about LTE MCS?
- 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.
Question 3. Select the most appropriate one for the procedure of LTE H-ARQ.
- (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)
Question 4. Which of following statements is not correct about LTE frame structure and multiple access?
- 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.
Question 5. Which of the Tx structure is appropriate for the following scheme of SFBC (Space-Frequency-Block-Coding) ?
Question 6. Which of the following statements does not correspond to LTE-Advanced key items?
- 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.
Question 7. Which of the following is incorrect?
- A: Transmit diversity (TM2)
- B: Closed loop spatial multiplexing (TM3)
- C: CL rank = 1 (TM6)
- D: Open loop spatial multiplexing (TM4)
Question 8. What is the main reason to have open loop power control?
- Fast set-up for initial power level.
- Fast support of moving users.
Question 9. Why is PF scheduler “proportionally” fair?
- It prioritizes less received users.
- It always gives more chances to users closer to the base station.
Week 6: LTE Cellular Networks and Services quiz answers
In this course, we will discuss LTE cellular networks.
Question 1. Which of the following best describes the advantage of circuit switching?
- It provides a reliable communication channel.
- It efficiently handles bursty traffic.
- It doesn’t waste bandwidth.
Question 2. Choose the one that best describes the disadvantage of circuit switching.
- Connection setup delay
- Best-effort delivery
- Out-of-order delivery
Question 3. Which of the following best describes the advantage of packet switching?
- Data forwarding mechanism is simple.
- Per-packet overhead is low.
- It allows multiplexing.
Question 4. Which of the following directly communicates with UE (user equipment) in LTE network?
Question 5. Which of the following acts as an interface between the external Internet and LTE network?
Question 6. What is the name of the process that connects a moving UE from one eNodeB to the other eNodeB without service disconnection?
- Cell coverage
Question 7. Which of the following is the name of the process that translates domain names into IP addresses?
- IP address allocation
- DNS resolution
- Initial attachment
Question 8. Choose the term that represents saving requested web pages for subsequent use.
- Load balancing
Question 9. Which of the following is NOT related to traffic reduction in LTE network?
- 10 points
- DNS resolution
- Proxy forwarding
Question 10. Which of the following is NOT a benefit of using LTE and WiFi together?
- It better supports user mobility.
- It provides more bandwidth hence, better throughput.
- It reduces operating costs.