A certain channel has 5MHz bandwidth with SNR of 15 by 9S760l


									                      AL- QUDS UNIVERSITY                   First Exam          Time: 70 Min.
                      Faculty of Engineering               March 22, 2011        Marks: 25
                  Course: Fundamentals of
                                                          Instructor: Dr. Ali Jamoos
               Communication Systems (0701454)
Q1) Circle the correct answer:                                                       [15 points]
1. The cellular mobile communication systems are usually assigned a carrier frequency in the:
   (a) 3–30 MHz band (b) 30–300 MHz band (c) 300–3000 MHz band (d) 10 – 100 GHz band
2. The mobile network is connected to the public switching telephone network through the:
   (a) mobile station (b) base station (c) mobile switching center (d) none of the above
3. If the carrier signal frequency is 1800MHz, the corresponding wavelength is:
     (a) 3 m (b) 6 m        (c) 1/3 m      (d) 1/6 m
4. Given a channel with 2MHz bandwidth, the Nyquist data rate when using quaternary signals:
   (a) 1Mbps (b) 2Mbps           (c) 4Mbps       (d) 8Mbps
5. A certain channel has 5MHz bandwidth with SNR of 15, the Shannon channel capacity:
   (a) 5Mbps (b) 10 Mbps           (c) 20 Mbps       (d) 40Mbps
6. If a signal with a power level of 10W is inserted onto a transmission line and the measured
    power some distance away is 0.1W, then the loss is:
   (a) 10 dB (b) 20dB         (c) 30dB (d) 40dB
7. The bandwidth allocated for the 3G mobile systems is 5MHz. To obtain a spectral efficiency
     of 2 bps/Hz the transmitted data rate should be:
   (a) 2 Mbps (b) 5 Mbps          (c) 10 Mbps       (d) 20 Mbps
8. The frequency range of voice signal can be limited to:
   (a) 88–108 MHz band (b) 0.6–1.6 MHz               (c) 900–2400 MHz       (d) 300–3400 Hz
9. The device that converts digital data into analog signal and visa versa is known as:
   (a) codec (b) modem          (c) amplifier (d) repeater
10. The channel capacity of a certain channel with 200KHz bandwidth and 11.8dB signal-to-noise
    ratio is approximately:
   (a) 800 KHz band (b) 600 KHz             (c) 400 KHz       (d) 200KHz
11. A mobile receives a signal whose power is -100dB; this signal power is equal to:
   (a) -70dBm (b) -90dBm            (c) -110dBm          (d) -130dBm
12. The bandwidth of a coaxial cable is up to:
   (a) 500Hz (b) 50KHz (c) 500MHz (d) 500THz
13. A 1 Watt signal is applied to one end of a 0.5mm twisted pair cable and a 0.0001 Watt is
received at the other end, if the cable yields an attenuation of 20dB/Km then the cable length is:
   (a) 100m (b) 1Km          (c) 2Km       (d) 10Km
14. The microwave frequency range is:
   (a) 0Hz – 4KHz        (b) 30MHz – 1GHz (c) 1GHz – 40 GHz (d) 0.3THz – 200THz
15. The distance from earth to a satellite in a geo-stationary orbit is about:
   (a) 30Km (b) 34Km           (c) 36Km       (d) 38Km
16. The maximum distance between two antennas-each with 100m height-for LOS transmission:
   (a) 41Km (b) 82Km           (c) 123Km (d) 164Km
17. Transmission of signals is carried out in the ____________ of the OSI network model:
   (a) network layer (b) data link control layer         (c) physical layer (d) application layer
18. The wireless local area networks (WLAN) use carrier frequencies in the range:
   (a) 2.4KHz (b) 2.4MHz            (c) 2.4GHz (d) 2.4THz
19. When increasing the frequency of an electromagnetic wave, the corresponding wave energy:
   (a) will increase (b) will decrease (c) does not change
20. The Television broadcasting uses:
   (a) simplex transmission (b) half-duplex transmission (c) full-duplex transmission (d) none
21. Analog signal strength falls with distance due to attenuation, to increase it we use:
   (a) amplifier (b) repeater (c) modem (d) codec

22. Multipath propagation of radio waves results in:
  (a) Inter-symbol interference (b) amplitude distortion (c) delay distortion (d) all of the above
23. The impulsive noise:
  (a) has short duration (b) does not affect much the analog signals
  (c) major source of errors for digital signals (d) all of the above
24. When a signal is affected by impulsive noise, increasing the data rate will
  (a) increase the error rate (b) decrease the error rate      (c) not change the error rate
25. A receiver with an effective noise temperature of 294K and 10MHz bandwidth, the noise
    power at the output of the receiver is approximately (Boltzmann constant = 1.38×10-23 J/K):
  (a) -134dBm (b) -104dBm (c) -74dBm (d) -164dBm
26. The bandwidth of a twisted pair cable is up to:
  (a) 1KHz (b) 1MHz           (c) 1GHz (d) 1THz
27. The minimum Eb/N0 required to achieve a spectral efficiency of 2bps/Hz is:
  (a) 1dB (b) 1.5dB (c) 2dB (d) 2.5dB
28. The shielded twisted pair (STP):
  (a) suffers from EM interference (b) easy to handle
  (c) more expensive than unshielded twisted pair (UTP)            (d) all of the above
29. The fiber optic cable:
  (a) suffers from EM interference (b) yields lower attenuation than twisted pair cable
  (c) needs smaller repeater spacing than coaxial cable         (d) all of the above
30. The isotropic antenna:
  (a) is a theoretical point source antenna (b) used as a reference for other antennas
  (c) radiates in all directions equally with spherical radiation pattern       (d) all of the above

Q2) A microwave transmitter has an output of 0.1 Watt at 2GHz. Assume that this
    transmitter is used in a microwave communication system where the
    transmitting and receiving antennas are parabolas, each 1.2 m in diameter and
    has an effective area of Ae  0.56r 2 with r is the radius:
    1) what is the gain of each antenna in decibels
    2) Taking into account the antenna gain, what is the effective radiated power
       of the transmitted signal
    3) If the receiving antenna is located 24Km from the transmitting antenna over
       a free space path, find the available signal power out of the receiving
       antenna.                                                          [6 points]

Q3) For voice communications with Phase Shift Keying (PSK) modulation, the
    accepted maximum bit error rate (BER) is 10-4 (one bit error out of every
    10000 bits). If the effective noise temperature is 290K and the data rate is 2400
    bps, what received signal power level is required, express it in dBm. [4 points]


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