- The Manchester
transmission code:
- Example:
- Advantage:
- The receiver can always
synchronize
its clock at
every transmitted bit:
Reason: there is a transition at the middle of the signal (which is detectable)
- Therefore:
- The Manchester code is ideal for very long digital transmissions (packet length of several Kbytes).
- Practice in real life:
- Ethernet packets
can be as long as
1500 bytes
- Ethernet uses the Manchester code !!!
- Ethernet packets
can be as long as
1500 bytes
- NOTE:
- The synchronization operation
using
Manchester code will
reset the
receiver's clock to the
middle
of a clock period
(It's easy to do, take CS355 if you want to learn more about this).
- The synchronization operation
using
Manchester code will
reset the
receiver's clock to the
middle
of a clock period
- The ability to synchronize clocks does not come cheaply....
- The receiver can always
synchronize
its clock at
every transmitted bit:
- Disadvantage:
- The highest frequency of
the transmitted signal is
relatively high
In fact:
- The highest frequency used by the Manchester scheme is twice as large as the highest frequency used in the NRZ method
- Example: the highest frequency
signal using Manchester code is achieved when
you transmit a string of
00000000...:
I drew the highest frequency of a signal using NRZ below in the above figure.
You can see the Manchester code signal has 2 times the frequency as the NRZ code signal.
- The highest frequency of
the transmitted signal is
relatively high