Home of RF and Wireless Vendors and Resources

One Stop For Your RF and Wireless Need

Advantages of RZ line coding | Disadvantages of RZ encoding

This page covers advantages and disadvantages of RZ (Return to Zero) pulse shape in line coding. It mentions benefits or advantages of RZ encoding and drawbacks or disadvantages of RZ line coding.

Introduction: Digital signal is sequence of discrete, discontinuous voltage pulses. It is used to map data bits by various encoding techniques such as NRZ, RZ, biphase etc.

What is RZ encoding ?

In this line encoding type, the binary data is represented by pulse having transition rather than constant level voltage. In RZ, transition happens exactly at the center of the bit period. Hence it is known as 'Return to Zero'. Further the rules of unipolar, polar and bipolar signaling applies before encoding the binary data as per RZ encoding technique.

Unipolar RZ

As shown, using unipolar RZ encoding, binary '1' is mapped using positive pulse of amplitude 'V' for half bit period and returns to zero for next half bit period. Binary '0' is mapped by absence of pulse for entire bit period.
Example of Unipolar RZ encoding :
INPUT : [1 0 1 0 0 1 1 1 0] , Bit period : Tb
OUTPUT : [+ve pulse (over Tb/2 time duration) DC (Tb/2), DC (over Tb duration), +ve pulse (Tb/2) DC (Tb/2), DC (Tb) , DC (Tb), +ve pulse (Tb/2) DC (Tb/2) , +ve pulse (Tb/2) DC (Tb/2) , +ve pulse (Tb/2) DC (Tb/2) , DC (Tb) ]

Polar RZ

As shown, using polar RZ encoding, binary '1' is mapped using positive pulse of amplitude 'V' in the first half and return to zero in the second half where as binary '0' is mapped using negative pulse of amplitude 'V' in the first half bit period and return to zero in the next half bit period.
Example of Polar RZ coding :
INPUT : [1 0 1 0 0 1 1 1 0]
OUTPUT : [+ve pulse (Tb/2) DC (Tb/2), -ve pulse (Tb/2) DC (Tb/2), +ve pulse (Tb/2) DC (Tb/2) , -ve pulse (Tb/2) DC (Tb/2), -ve pulse (Tb/2) DC (Tb/2), +ve pulse (Tb/2) DC (Tb/2), +ve pulse (Tb/2) DC (Tb/2), +ve pulse (Tb/2) DC(Tb/2), -ve pulse(Tb/2) DC (Tb/2) ]

Bipolar RZ

As shown, using Bipolar RZ encoding, binary '1' is mapped using positive pulse and negative pulse of amplitude 'V' based on its alternate positions during first half bit period unlike NRZ. For the next half bit period it remains at zero DC level. The binary '0' is mapped by absence of pulse for entire bit period.
Example of Bipolar RZ line coding :
INPUT : [1 0 1 0 0 1 1 1 0]
OUTPUT : [+ve pulse (over 'Tb/2') DC ('Tb/2'), DC (over 'Tb'), -ve pulse ('Tb/2') DC ('Tb/2'), DC ('Tb'), DC ('Tb'), +ve pulse ('Tb/2') DC ('Tb/2') , -ve pulse ('Tb/2') DC ('Tb/2') , +ve pulse ('Tb/2') DC ('Tb/2'), DC ('Tb')]

Benefits or advantages of RZ encoding

Following are the benefits or advantages of RZ encoding:
➨It is simple line coding technique.
➨In polar RZ and bipolar RZ, no low frequency components are present.
➨Bipolar NRZ/RZ signaling waveform occupies lower bandwidth than unipolar NRZ and polar NRZ waveforms.
➨Signal drooping does not happen in Bipolar coding. Hence this line coding is suitable for data transmission over AC coupled lines.
➨Single error detection is possible using this line coding technique.

Drawbacks or disadvantages of RZ line coding

Following are the drawbacks or disadvantages of RZ line coding:
➨Signal droop occurs when signal is non-zero at 0 Hertz.
➨Unipolar/Polar RZ occupy twice bandwidth than Unipolar/polar NRZ respectively.
➨No error correction.
➨No clock is available.
➨Loss of synchronization occurs due to long string of ones and zeros in the binary data.



Line coding techniques

Difference between Unipolar Polar and Bipolar coding    RZ vs NRZ vs Manchester coding    RZ vs NRZ pulse shapes    Advantages and disadvantages of NRZ encoding    RZ encoding    2B1Q coding    8B6T coding    4D PAM5 coding    MLT-3 coding    4B/5B encoding    8B/10B encoding    R8ZS scrambling    HDB3 scrambling   


Advantages and Disadvantages of other wireless technologies

IrDA    HomeRF    Bluetooth    Radar    RF    Wireless    Internet    Mobile Phone    IoT    Solar Energy    Fiber Optic    Satellite    GPS    RFID    AM and FM    LTE   

What is Difference between

difference between OFDM and OFDMA
Difference between SC-FDMA and OFDM
Difference between SISO and MIMO
Difference between TDD and FDD
FDMA vs TDMA vs CDMA
FDM vs TDM
CDMA vs GSM

RF and Wireless Terminologies


Share this page

Translate this page