Computer Science 825
                         Quiz 3              Name _______________________


1. Suppose a new  "high fidelity" voice telephone service has a bit rate
   of 2 ** 20 (1M) bits per second.  Suppose that the system is
   designed to carry frequencies up to 16384 = (2 ** 14)hz.  Into how many
   discrete levels can the PCM signal be quantized.





2. Suppose I have a 1000000 bits of data that I need to send.
   The path will be routed 4 intermediate switching centers and
   thus consists of 5 hops.

   Me ---  SC1 --- SC2 --- SC3 --- SC4 --- SC5 --- Dest

   If bit transmission rate is 100000 bits / second, how many seconds
   will the transmission take using message switching and
   and packet switching (100000 bit packets). Assume no interference
   competing traffic.

   Message:




   Packet:





3. Select the multiplexing scheme (FDM, ATDM, STDM) that applies
   in each of the following cases:

   a. The scheme most suitable for use with analog (as opposed
      to digital channel).


   b. The type of multiplexing that is, in effect, being used
      when multiple IBM type terminals are connected to a remote
      host computer through a single dedicated phone line.


   c. The type of multiplexing which imposes the LEAST overhead
      on the available bandwidth/bit rate.


4. The cell reley paper describes several aspects of the tradeoffs
   between large and small cell (frame) sizes.  Answer the following
   related T/F questions.

   ___ a. For a given sustained data rate, large cells require lower
          sustainable switching rates  than small ones.

   ___ b. The use of large cells makes it easier to do very precise
          allocation of bandwidth.

   ___ c. The use of large cells reduces the percentage of bandwidth
          used for carrying header/control information compared to
          end user data.