4.1.2: Line Coding Schemes Flashcards
What is a Unipolar Line Coding Scheme?
All signal levels are one on side of the time axis, either above or below.
What is Unipolar NRZ? What are its disadvantages?
Positive voltage = bit 1. Zero voltage = bit 0.
Signals does NOT return to zero at the middle of the bit.
DISADVANTAGES: baseline wandering, no synchronization
What is a Polar Line Coding Scheme?
Signal levels are on both sides of the time axis. For example, positive voltage = bit 1, negative voltage = bit 0.
What is Polar NRZ-Levels? What are its disadvantages?
The level of the voltage determines the value of the bit. For example, positive voltage = bit 1, negative voltage = bit 0.
DISADVANTAGES: baseline wandering, synchronization, polarity change.
What is Polar NRZ-Invert? What are its disadvantages?
The change or lack of change determines the value of the bit. If there’s no change, the bit value is 0; if there’s change, the bit value is 1.
DISADVANTAGES: baseline wandering (for 0s only), synchronization.
What is RZ? What are its disadvantages?
Uses three values: positive, zero, and negative. The signal returns to zero in the middle of the bit.
DISADVANTAGES: more complex, more bandwidth, polarity change.
What is Biphase Manchester?
Combines RZ and NRZ-L.
Duration of a bit is divided into two halves. Voltage remains at one level during first half, then moves to the other level for the second half. The transition allows for synchronization.
What is Biphase Differential Manchester?
Combines RZ and NRZ-I.
Always a transition in the middle of the bit. If the next bit is 0, there is a transition; if the next bit is a 1, there is no transition.
What is a Bipolar Line Coding Scheme?
There are three voltage levels: positive, negative, zero.
Voltage level for one data element is 0; voltage level for the other data element alternatives between positive and negative.
