Questions

SAMPLE EXAMINATION QUESTIONS


The following questions are typical of those that will be used on IEEE WCET® certification examinations. An answer key may be found at the end of this page.


Q1. A mobile terminal moving at a speed of 30 m/sec is receiving a signal with a center frequency of 2 GHz, having a bandwidth of 5 MHz. The received signal has a delay spread of 2 µsec. The full Doppler spread of the received signal is approximately:

1. 0.5 MHz
2. 200 Hz
3. 400 Hz
4. 2.5 MHz 


Q2. In a CDMA cellular system, the coverage region of a cell located in a dense urban environment at 5:00 PM (busy hour) is most likely to be:

1. the same as the coverage at 3:00 AM (dead hour) because transmit power remains the same.
2. the same as the coverage at 3:00 AM (dead hour) because propagation remains the same.
3. smaller than the coverage of 3:00 AM (dead hour) because of higher cell loading.
4. smaller than the coverage at 3:00 AM (dead hour) because of more signal fading due to more cars on the street.


Q3. To overcome the near-far-problem, the CDMA implementation for cellular telephony uses:

1. signal spreading.
2. power control.
3. codeword orthogonality.
4. frequency re-use.


Q4. The choice of a duplexing method depends on the:

1. chosen multiple access technology.
2. nature of the available spectrum and of the traffic in uplink/downlink.
3. modulation type and error-correction statistics.
4. modulation type and the multiple access technology.


Q5. Fourth-generation (4G) standards are being developed under the umbrella of the ITU using which of the following names?

1. IMT-2000 (International Mobile Telecommunications 2000)
2. FPLMTS (Future Public Land Mobile Telecommunication System)
3. IMT-Advanced (International Mobile Telecommunications — Advanced)
4. LTE (Long Term Evolution)


Q6. In 802.11 using RTS/CTS as an access scheme where the duration of RTS, CTS, and an ACK are all equal to T, the Short Interframe Spacing duration equals S and the data packet duration of the transmitting source is D, the total period allocated to the transmitting terminal and no others is:

1. 3T+4S+D
2. 3T+3S+D
3. 3T+S+D
4. 3T+2S+D

Q7. The relationship among the IEEE 802.11 timing parameters is:

1. SIFS<PIFS<DIFS. 
2. PIFS<SIFS<DIFS.
3. SIFS>PIFS>DIFS.
4. SIFS<DIFS<PIFS.
 

Q8. Consider a receiver with an effective noise temperature of 33° C (306 K) and a 7-kHz bandwidth. Boltzmann’s constant is 1.38 × 10–23 Joules/degree K. The equivalent thermal noise of the receiver input is:

1. –135.3 dBW
2. –173.7 dBW
3. –165.3 dBW
4. –203.7 dBW
 

Q9. A fundamental architectural difference between Mobile IPv4 and Mobile IPv6 is that:

1. Mobile IPv6 does not require Home Agent (HA).
2. Mobile IPv4 dynamic home agent discovery returns a single reply to the mobile node.
3. Mobile IPv6 provides secure but less optimized routes than Mobile IPv4.
4. Mobile IPv6 does not require Foreign Agent (FA).


Q10. A mobile terminal in a CDMA network transmits a channel with a data rate of 12.2 kbps and has an
activity factor of 67%. If the target Eb/N0 is 5 dB and the chip rate is 3.84 Mcps, the channel’s load
factor is:

1. 1.0 × 10-2
2. 1.6 × 10-2
3. 3.2 × 10-3
4. 6.7 × 10-3


Q11. A communication satellite is operating at 12.75 GHz with EIRP=48 dBW. The ground terminal is 35786
km from the satellite and has a receive antenna with 33.37 dBi gain. The receiver noise temperature is
22.43 dBK. Based on these data, what is the received carrier to noise-spectral density C/N0?

1. 15.17 dB
2. 65.28 dB
3. 81.91 dB
4. 141.91 dB


Q12. The maximum Doppler shift of a signal with a carrier frequency of 28 GHz as received by a vehicle
moving at 36 km/h is:

1. 75.6 Hz.
2. 933 Hz.
3. 2968 Hz.
4. Cannot be determined with the given information.


Q13. Which of the following transmitter antenna systems is the most efficient?

1. An antenna system that has a return loss of 9.54 dB
2. An antenna system that has a voltage standing wave ratio of 1.5:1
3. An antenna system that has a reflection coefficient of 1/3
4. An antenna system that has a voltage standing wave ratio of 2:1


Q14. The multiple access method used in Global System for Mobile (GSM) communications standards is:

1. Othgogonal Frequency Division Multiple Access (OFDMA).
2. Time Division Multiple Access (TDMA).
3. Frequency Division Multiple Access (FDMA).
4. Code Division Multiple Access (CDMA).


Q15. Bluetooth is an example of a Personal Area Network (PAN) that:

1. can form a wireless network over a limited distance.
2. uses 5.8 GHz frequency band for communication.
3. can enable soft handover (i.e., handoff) between two PANs.
4. is an essential feature of 3G specification.


Q16. Universal garage door openers operating in the 30 - 40 MHz are manufactured in Europe. What action
should be recommended before the units could be sold in the USA?

1. to get Underwriter Lab (U/L) certification is recommended but not an essential prerequisite.
2. No action is needed since a universal garage door opener operates over a short range and it
operates in an unlicensed band.
3. A homologation process is needed since ETSI and FCC standards for testing the device do not have
a one-to-one correspondence.
4. Since units are built to metric measurements, verify that they are compatible with the standards of
the local distributor. 


Q17. An encryption technique that does NOT rely on the source and destination system sharing the same
encryption key is:

1. private key encryption.
2. secret key.
3. public key.
4. open key. 


Q18. Radio Jamming attack works at what layer?

1. Physical Layer
2. Session Layer
3. Presentation Layer
4. Network Layer


Q19. The error protection/recovery strategy most appropriate for a wireless link characterized by poor
signal quality and high propagation delay is:

1. forward error correction.
2. stop-and-wait ARQ.
3. selective repeat ARQ.
4. go-back-N ARQ.


Q20. Which one of the following statements best explains the frequency selective fading phenomenon?

1. It arises when the coherence time of the channel is large relative to the delay constraint of the
channel.
2. The coherence bandwidth of the channel is smaller than the bandwidth of the signal.
3. The coherence bandwidth of the channel is greater than the bandwidth of the signal.
4. It occurs when the coherence time of the channel is small relative to the delay constraint of the
channel. 


Answers: Q1 – 3; Q2 – 3; Q3 – 2; Q4 – 2; Q5 – 3; Q6 – 2; Q7 – 1; Q8 – 3; Q9 – 4;  Q10 – 4; Q11 – 3; Q12 – 2; Q13 – 2; Q14 – 2; Q15 – 1; Q16 – 3; Q7 – 3; Q18 – 1; Q19 – 1; Q20 - 2