07-12-2012, 12:28 PM
Line and Block Coding, Digital Transmission Modes
Self-Synchronization
(Clocking)
to correctly interpret signal received from
sender receiver’s bit interval must exactly
correspond to sender’s bit intervals
• if receiver clock is faster/slower, bit intervals
not matched ⇒ receiver misinterprets signal
• self-synchronizing digital signals include
timing information in itself, to indicate the
beginning & end of each pulse
Manchester
inversion at the middle of each bit interval is used
for both synchronization and bit representation
• 0 = pos-to-neg transition, 1 = neg-to-pos transition
• perfect synchronization ☺
• there is always transition at the middle of the bit, and
maybe one transition at the end of each bit
• fine for alternating sequences of bits (10101), but
wastes bandwidth for long runs of 1-s or 0-s