Computer Science 825
                         Quiz 2              Name _______________________

1. What is the minimum number of distinct signalling states that can
   be used to transmit data at a rate of 24,000 bits per second on a
   channel with a bandwidth of 4000 hz (show work for partial credit).









2. What is the minimum SNR (in db) that will sustain a data rate of
   24,000 bits per second on a 4000hz channel?







3. Write the expression for a general modulated sine wave carrier
   and identify the parameters that are varied in each of the
   standard  modulation schemes: (the answers to b, c, and d should
   be variables in the expression you provide in a.)

   a. f(t)  =

   b. Phase

   c. Amplitude

   d. Frequency


3. Give an example of a 1 bit per baud phase shift modulation scheme
   which is self clocking and one which is not.

   a. Self clocking:




   b. Not self clocking:




4. The relationship between the efficiency of asynchronous versus
   synchonous signalling is (efficiency = %bandwidth used to transmit
   data as opposed to being used for synchronization):

   a. Asynchronous is always         b. Synchronous is always more
      more efficient.                   efficient.

   c. Asynchonous is more efficient  d. Synchonous is more efficient
      for byte sized packets but        for byte sized packets but
      synchronous is more efficient     asynchronous is more efficient
      for large blocks                  for large blocks


5. In the model of synchonous transmission that we described in class

   a. the clock on the receiver       b. the clock on the receiver
      modem was driven by the            USART was driven by the
      receiving USART.                   receiver modem.

   c. independent clocks were used    d. No clocking at all was
      in the modem and the USART.        required.


6. In the models of synchronous and asynchonous transmission
   signalling between the U(S)ART and modem using the RS-232 interface
   is best described as:

   a. Base band and parallel          b. Base band and serial

   c. Modulated carrier and parallel  d. Modulated carrier and serial.


7. The suitability of using independent clocks in a UART and an
   asynchonous modem when compared to the use of independent clocks
   in a usart and a synchronous modem is:

   a. independent clocks are more     b. independent clocks are
      suitable in asynch because         more suitable in asynch
      resynchronization must occur       because lower bit rates
      after each byte is transmitted.    are used.

   c. independent clocks are more     d. they are perfectly suitable
      suitable in synchronous because    in both.
      there is less starting and
      stopping.                       e. they are totally unsuitable
                                         in both.