Ecet 380- assuming that samples are taken at intervals of

Question

Question 1. Multipath occurs in a radio channel creating small-scale fading due to the following factor:
Rapid changes in signal strength
Random frequency modulation
Time dispersion
All of the above
None of the above

Question 2. Wavelength is ________________ proportional to frequency.
directly
inversely
not
equally

Question 3. A vehicle is traveling at 25 m/s directly toward the transmitter while receiving a mobile signal at 1900 MHz. What is the received frequency?
1900.00158 MHz
1900 MHz
1899.99842 MHz
1900.000158 MHz
None of the above

Question 4. The coherence bandwidth of a communication channel is estimated to be 2 kHz. Small scale propagation measurements are made in real time from a vehicle moving at 70 m/s. Assuming that samples are taken at intervals of 1/4 the Coherence time to ensure correlation of consecutive samples, how many samples are taken over a 20 m travel distance?
1600
800
3200
2400
None of the above

Question 5. Multipath occurs in a radio channel creating small-scale fading due to the following factor:
Rapid changes in signal strength
Random frequency modulation
Time dispersion
All of the above
None of the above

Question 6. Wavelength is ________________ proportional to frequency.
directly
inversely
not
equally

Question 7. A vehicle is traveling at 25 m/s directly toward the transmitter while receiving a mobile signal at 1900 MHz. What is the received frequency?
1900.00158 MHz
1900 MHz
1899.99842 MHz
1900.000158 MHz
None of the above

Question 8. The coherence bandwidth of a communication channel is estimated to be 2 kHz. Small scale propagation measurements are made in real time from a vehicle moving at 70 m/s. Assuming that samples are taken at intervals of 1/4 the Coherence time to ensure correlation of consecutive samples, how many samples are taken over a 20 m travel distance?
1600
800
3200
2400
None of the above

Question 9. Assume a discrete channel impulse response is used to model an urban RF radio channel with excess delays as large as 125 µs. If the number of multipath bins is fixed at 64, what is the maximum RF bandwidth which the model can accurately represent?
2.048 MHz
1.024 MHz
4.096 MHz
512 kHz
None of the above

Question 10. A spread spectrum system using sliding correlation has the following properties: Chip Rate = 32 Mbps; Slide factor 10-4; 24 shift registers in the sequence generator. What is the time between maximum correlations (ΔT)?
68.3 µs
57.6 µs
25.4 µs
46.5 µs
None of the above

Question 11. In small scale fading based on Doppler spread, fast fading has the characteristics of:
Low Doppler spread
Coherence time less than symbol period
Channel variations slower than baseband signal variations
Both b and c
None of the above

Question 12. _________________ diversity can be created without using additional bandwidth.
Frequency
Time
Spatial
all of the above
None of the above

Question 13. A certain transmission channel has a bandwidth of 2 MHz. What is the channel capacity if the SNR is 37 dB?
12.3 Mbps
18.6 Mbps
24.58 Mbps
36.3 Mbps
None of the above

Question 14. Multiple input, multiple output (MIMO) diversity gains can be obtained with the following:
multiple receive antennas
multiple transmit antennas
both a and b
neither a nor b

Question 15. What is the bandwidth of a raised cosine filter pulse with a symbol time of 64 µs and a roll-off factor of 0.25?

19.5 kHz
80 MHz
26.4 kHz
19.5 MHz
None of the above

Question 16. Linear predictive coders (LPC) belong to the ____________ domain class of vocoders.
frequency
spatial
hybrid
time
None of the above

Question 17. A frequency hopping spread spectrum system has a spread spectrum bandwidth of 2.1 MHz and each hop bandwidth is 7 kHz. How many frequency hop slots are there in this system?
21
15
250
300
None of the above

Question 18. What is the processing gain (in dB) of a spread spectrum system that has system bandwidth of 400 MHz and an information bandwidth of 200 KHz?

33 dB
27 dB
-33 dB
-27 dB
None of the above

Question 19. PN sequences in a spread spectrum communication system ______________ repeat after the period of the sequence is generated.
never
occasionally
always
annually

Question 20. A correlation function equals _______________ if the two codes have nothing in common.
one
64
zero
None of the above

Question 21. Frequency division duplexing (FDD) provides __________ distinct bands of frequencies for every user.
One
Three
Five
Seven
None of the above

Question 22. A TDMA system has a 25 MHz bandwidth with single channels of 250 kHz bandwidth each, with each frequency channel containing eight TDMA conversation channels. If each user is assigned one transmit and one receive slot within each frequency channel, calculate the number of users this system can support. Assume there is no separate guard band.
100
800
400
200
None of the above

Question 23. A system has eight trailing bits, eight guard bits, 32 synchronizing bits, and three traffic bursts of 64 bits of data per time slot. What is the frame efficiency if there are eight time slots per bit frame?
20%
40%
60%
80%
None of the above

Question 24. In a cellular system, channels are reused within _________________.
same cell
same cluster
coverage area
Never

Question 25. One of the differences between 2G Mobile Radio Networks and 2.5G Mobile Radio Networks is:

Internet browsing is not supported in 2G systems
Different transmit frequencies are used
Different multiple access technologies are used
All of the above
None of the above

Question 26. CDMA systems increase a user's data throughput by _____________________
assigning more frequencies
increasing spatial separation between users
increasing the length of a PN code
allowing the use of multiple Walsh codes
None of the above.