- There are 2 signaling levels
in binary digital transmission:
- low (= 0)
- high (= 1)
- However:
- There are different ways to signal data using these 2 signal levels !!
- We will look at some
commonly used
schemes
- Each
signaling scheme
has its strengths and
also, it's
weakness(es)
(The law of "conservation of misery" --- Herman Bavinck)
- Each
signaling scheme
has its strengths and
also, it's
weakness(es)
- The
Non-return-to-zero (NRZ) encoding scheme:
(It's the most intuitive code :))
- Example:
- Advantage:
- The highest frequency of
the transmitted signal is
relatively low
Explanation:
- The signal will vary
at its fastest rate when you
transmit as string of
0101010101....:
- Compare to other signalling codes (that you will learn later), this signal form varies at the lowest rate possible !
- The signal will vary
at its fastest rate when you
transmit as string of
0101010101....:
- The highest frequency of
the transmitted signal is
relatively low
- Disadvantage:
- There are situations where the receiver
cannot synchronize
its clock
with the sender's clock:
Example:
(There is no transmission in the signal so the receiver can not perform re-synchronization !)
- There are situations where the receiver
cannot synchronize
its clock
with the sender's clock:
- Common Practice:
- Because of its shortcoming, the NRZ code is only used for very short transmissions (e.g., transmit 1 byte (= 8 bits))