test review2.txt

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test review2.txt
2011-10-26 14:44:56
Data Computer Communications

Test II Review Data Comm
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  1. is a data encoding scheme in which a negative voltage is used to represent binary one and a positive voltage is used to represent binary zero.
    Non return-to-zero-level (NRZ-L)
  2. For____scheme, a binary 0 is represented by no line signal, and a binary 1 is represented by a positive or negative pulse.
    bipolar-AMI scheme
  3. In the ______code, there is a transition at the middle of each bit period; a low-to-high transition represents a 1, and a high-to-low transition represents a 0.
  4. A ________ converts digital information into an analog signal, and conversely.
  5. With _______ keying, binary values are represented by two different amplitudes of carrier frequencies.
  6. ______Takes advantage of the fact that it is possible to send two different signals simultaneously on the same carrier frequency, by using two copies of the carrier frequency, one shifted by 90� with respect to the other.
  7. __________ modulation and ________ modulation are special cases of angle modulation.
    Frequency (FM), Phase (PM)
  8. _________ transmission requires an overhead of two or three bits per character, and is, therefore, significantly less efficient than synchronous transmission.
  9. The ______ has more bits and therefore provides more redundancy. That is, it provides more information that can be used to detect errors.
  10. An (n, k) block code encodes _________ data bits into _____________ bit codewords.
    k, n
  11. The process under which the sending station does not send frames at a rate faster than the receiving station can absorb them is called.
    Flow Control
  12. The ______ approach requires acknowledgments after each frame.
  13. The ________ flow control technique can send multiple frames before waiting for an acknowledgment.
  14. __________ is a signal processing technique that allows transmission of digital signals in both directions on a single transmission line simultaneously.
    Echo cancellation
  15. A ______________ interleaves bits from each signal and takes turns transmitting bits from each of the signals in a round robin fashion.
    synchronous time division multiplexer (Synchronous TDM)