Computer Science 825
                           Quiz 1           Name _______________________

Terminology:  the very highest layer is the APPLICATION LAYER = Layer N
              the very lowest  layer is the PHYSICAL LAYER    = Layer 1

1. a. Which of the seven layers of the ISO-OSI model is the LOWEST
      layer that is typically found in each host computer but not
      found in an IMP.



   b. At which layer is it necessary that a common protocol
      be supported within all hosts and IMPs of a network.




2. Suppose a channel is equipped with high and low pass filters
   that pass only harmonics in the range 10,000 hz to 16,000 hz.
   On this channel what is the MINIMUM sampling rate required
   to reconstruct the exact signalling function.










3. a. What is the minimum number of signalling states necessary to transmit
      32,000 bits per second on a noise free channel that has a bandwidth of
      4000hz.








    b. What would be the BAUD rate of a modem performing this function.













4. What bandwidth is required to support a bit rate of 10000 BPS
   on a channel with a 20dB SNR?






5. Suppose a PCM scheme supports a bit rate of 140,000 bps and
   quantizes the signal into 1024 distinct levels.  What is the
   highest frequency that it can carry?












7. The main reason digital channels have much lower error rates than analog
   when used over long distances is:

   a. Digital signalling is baseband   c. Digital signals are amplified
      instead of analog.                  rather than regenerated.

   b. Digital signals are regenerated  d. Digital channels have much higher
      rather than amplified.              SNR's than analog.


8. The use of very small slot sizes in TDM multiplexing is

   a. Inefficient and shouldn't       b. Generally shouldn't be used for
      be used in either STDM or ATDM     SDTM but is OK for ATDM

   c. Generally shouldn't be used     d. Perfectly OK for both
      for ATDM but is OK for STDM


9. In the standard T1 (or DS1) channel a FRAME consists of

   a. 8 bits                          b. 8 slots

   c. 24 bits                         d. 24 slots


10. The transmission rate on the OC-1 (STS-1) channel is:

   a. 8000 bits per second            b. 8000 slots per second

   c. 8000 frames per second          d. 8000 bytes per second


11. Diagram an example of a 1 (ONE!) bit per baud phase shift modulation
    scheme which is self clocking and one which is not.

    a. Self clocking:





    b. Not self clocking: