LINE CODING - ggn.dronacharya.info€¦ · Line coding (binary data to digital signals) Improve the...
Transcript of LINE CODING - ggn.dronacharya.info€¦ · Line coding (binary data to digital signals) Improve the...
![Page 1: LINE CODING - ggn.dronacharya.info€¦ · Line coding (binary data to digital signals) Improve the efficiency of line coding Sampling (a technique for changing analog data to binary](https://reader035.fdocuments.in/reader035/viewer/2022071102/5fdc2b828f9f0067865316a3/html5/thumbnails/1.jpg)
LINE CODING
![Page 2: LINE CODING - ggn.dronacharya.info€¦ · Line coding (binary data to digital signals) Improve the efficiency of line coding Sampling (a technique for changing analog data to binary](https://reader035.fdocuments.in/reader035/viewer/2022071102/5fdc2b828f9f0067865316a3/html5/thumbnails/2.jpg)
Data encoding is method to convert the data into signal form.
The signal may be of digital or in analog form. An analog signal is transmitted over a long
distance . But if we use, digital transmission , then we required a repeater between every 40 to 50 km.
Data encoding
![Page 3: LINE CODING - ggn.dronacharya.info€¦ · Line coding (binary data to digital signals) Improve the efficiency of line coding Sampling (a technique for changing analog data to binary](https://reader035.fdocuments.in/reader035/viewer/2022071102/5fdc2b828f9f0067865316a3/html5/thumbnails/3.jpg)
transmissionA computer network is designed to send information from one point in the network to another.
While designing a network, we have two choices
•Convert data into digital signal
•Convert data into analog signal
![Page 4: LINE CODING - ggn.dronacharya.info€¦ · Line coding (binary data to digital signals) Improve the efficiency of line coding Sampling (a technique for changing analog data to binary](https://reader035.fdocuments.in/reader035/viewer/2022071102/5fdc2b828f9f0067865316a3/html5/thumbnails/4.jpg)
Digital transmission includes
Line coding (binary data to digital signals)
Improve the efficiency of line coding
Sampling (a technique for changing analog data to binary data)
![Page 5: LINE CODING - ggn.dronacharya.info€¦ · Line coding (binary data to digital signals) Improve the efficiency of line coding Sampling (a technique for changing analog data to binary](https://reader035.fdocuments.in/reader035/viewer/2022071102/5fdc2b828f9f0067865316a3/html5/thumbnails/5.jpg)
Data Encoding
Digitalto
Digital
Digitalto
Analog
Analogto
Analog
Analogto
Digital
![Page 6: LINE CODING - ggn.dronacharya.info€¦ · Line coding (binary data to digital signals) Improve the efficiency of line coding Sampling (a technique for changing analog data to binary](https://reader035.fdocuments.in/reader035/viewer/2022071102/5fdc2b828f9f0067865316a3/html5/thumbnails/6.jpg)
Digital to Digital
Encoding
Unipolar Polar Bipolar
![Page 7: LINE CODING - ggn.dronacharya.info€¦ · Line coding (binary data to digital signals) Improve the efficiency of line coding Sampling (a technique for changing analog data to binary](https://reader035.fdocuments.in/reader035/viewer/2022071102/5fdc2b828f9f0067865316a3/html5/thumbnails/7.jpg)
Characteristic of Line Coding
Signal level versus data level Pulse rate versus bit rate dc components Self synchronization
![Page 8: LINE CODING - ggn.dronacharya.info€¦ · Line coding (binary data to digital signals) Improve the efficiency of line coding Sampling (a technique for changing analog data to binary](https://reader035.fdocuments.in/reader035/viewer/2022071102/5fdc2b828f9f0067865316a3/html5/thumbnails/8.jpg)
Signal Level Versus Data Level
First diagram has two signal levels and two data levels. The second diagram has three signal levels and two data levels.
![Page 9: LINE CODING - ggn.dronacharya.info€¦ · Line coding (binary data to digital signals) Improve the efficiency of line coding Sampling (a technique for changing analog data to binary](https://reader035.fdocuments.in/reader035/viewer/2022071102/5fdc2b828f9f0067865316a3/html5/thumbnails/9.jpg)
DC Component
First has a dc component, positive voltages are not cancelled by negative voltages.
DC Signal Has Zero Frequency.
![Page 10: LINE CODING - ggn.dronacharya.info€¦ · Line coding (binary data to digital signals) Improve the efficiency of line coding Sampling (a technique for changing analog data to binary](https://reader035.fdocuments.in/reader035/viewer/2022071102/5fdc2b828f9f0067865316a3/html5/thumbnails/10.jpg)
Lack of synchronization
![Page 11: LINE CODING - ggn.dronacharya.info€¦ · Line coding (binary data to digital signals) Improve the efficiency of line coding Sampling (a technique for changing analog data to binary](https://reader035.fdocuments.in/reader035/viewer/2022071102/5fdc2b828f9f0067865316a3/html5/thumbnails/11.jpg)
Self synchronization
To correctly interpret the signals, receiver’s bit intervals should exactly match with the sender’s bit intervals.
The ability to recover timing from the signal itself.
Long series of ones and zeros could cause a problem.
![Page 12: LINE CODING - ggn.dronacharya.info€¦ · Line coding (binary data to digital signals) Improve the efficiency of line coding Sampling (a technique for changing analog data to binary](https://reader035.fdocuments.in/reader035/viewer/2022071102/5fdc2b828f9f0067865316a3/html5/thumbnails/12.jpg)
Signalling rate versus bit rate
Signalling rate number of signals per second. Signal is the minimum amount of time reqd to transmit a symbol.
Bit rate number of bits per second. If a signal carries only 1 bit, the signalling rate and the bit rate are same.
Bit rate = Signalling rate * log 2 L
L is the number of data levels in the signal.
![Page 13: LINE CODING - ggn.dronacharya.info€¦ · Line coding (binary data to digital signals) Improve the efficiency of line coding Sampling (a technique for changing analog data to binary](https://reader035.fdocuments.in/reader035/viewer/2022071102/5fdc2b828f9f0067865316a3/html5/thumbnails/13.jpg)
Unipolar Encoding
(also called on-off keying, OOK) Form of digital signal with only one level of
amplitude. 1s are encoded as positive values. 0s are
encoded as a zero value.
![Page 14: LINE CODING - ggn.dronacharya.info€¦ · Line coding (binary data to digital signals) Improve the efficiency of line coding Sampling (a technique for changing analog data to binary](https://reader035.fdocuments.in/reader035/viewer/2022071102/5fdc2b828f9f0067865316a3/html5/thumbnails/14.jpg)
Limitations of unipolar encoding
dc component Lack of synchronization
Average of unipolar encoded signal is non-zero, so there is dc component.
![Page 15: LINE CODING - ggn.dronacharya.info€¦ · Line coding (binary data to digital signals) Improve the efficiency of line coding Sampling (a technique for changing analog data to binary](https://reader035.fdocuments.in/reader035/viewer/2022071102/5fdc2b828f9f0067865316a3/html5/thumbnails/15.jpg)
Polar encoding
It uses two voltage levels.positive and negative levels.
Due to two voltage levels, there is a less problem of dc component.
![Page 16: LINE CODING - ggn.dronacharya.info€¦ · Line coding (binary data to digital signals) Improve the efficiency of line coding Sampling (a technique for changing analog data to binary](https://reader035.fdocuments.in/reader035/viewer/2022071102/5fdc2b828f9f0067865316a3/html5/thumbnails/16.jpg)
Types of polar encoding
POLAR
NRZ RZ Manchester
Differential-
Manchester
![Page 17: LINE CODING - ggn.dronacharya.info€¦ · Line coding (binary data to digital signals) Improve the efficiency of line coding Sampling (a technique for changing analog data to binary](https://reader035.fdocuments.in/reader035/viewer/2022071102/5fdc2b828f9f0067865316a3/html5/thumbnails/17.jpg)
Non-return to Zero(NRZ)
Value of the signal is either positive or negative.
Types of NRZ NRZ-L NRZ-I
![Page 18: LINE CODING - ggn.dronacharya.info€¦ · Line coding (binary data to digital signals) Improve the efficiency of line coding Sampling (a technique for changing analog data to binary](https://reader035.fdocuments.in/reader035/viewer/2022071102/5fdc2b828f9f0067865316a3/html5/thumbnails/18.jpg)
NRZ-L encoding
Level of signal depends upon the type of bit that it represents
1 -ve Voltage0 +ve voltage
![Page 19: LINE CODING - ggn.dronacharya.info€¦ · Line coding (binary data to digital signals) Improve the efficiency of line coding Sampling (a technique for changing analog data to binary](https://reader035.fdocuments.in/reader035/viewer/2022071102/5fdc2b828f9f0067865316a3/html5/thumbnails/19.jpg)
Limitation of NRZ-L When data contains a long stream of 0s and 1s.
Receiver receives a continuous voltage and determines the number of bits by its clock which may or may not be synchronized with the sender clock.
![Page 20: LINE CODING - ggn.dronacharya.info€¦ · Line coding (binary data to digital signals) Improve the efficiency of line coding Sampling (a technique for changing analog data to binary](https://reader035.fdocuments.in/reader035/viewer/2022071102/5fdc2b828f9f0067865316a3/html5/thumbnails/20.jpg)
NRZ-I encoding
In NRZ-I, an inversion of the voltage level represents a 1 bit. It is the transition between a positive and a negative voltage.
It is superior to NRZ-L due to the synchronization provided by the signal change each time a 1 bit is encountered.
1 Signal Change0 No Change
![Page 21: LINE CODING - ggn.dronacharya.info€¦ · Line coding (binary data to digital signals) Improve the efficiency of line coding Sampling (a technique for changing analog data to binary](https://reader035.fdocuments.in/reader035/viewer/2022071102/5fdc2b828f9f0067865316a3/html5/thumbnails/21.jpg)
NRZ-L and NRZ-I encoding
![Page 22: LINE CODING - ggn.dronacharya.info€¦ · Line coding (binary data to digital signals) Improve the efficiency of line coding Sampling (a technique for changing analog data to binary](https://reader035.fdocuments.in/reader035/viewer/2022071102/5fdc2b828f9f0067865316a3/html5/thumbnails/22.jpg)
Figure 4.6 Polar NRZ-L and NRZ-I schemes
![Page 23: LINE CODING - ggn.dronacharya.info€¦ · Line coding (binary data to digital signals) Improve the efficiency of line coding Sampling (a technique for changing analog data to binary](https://reader035.fdocuments.in/reader035/viewer/2022071102/5fdc2b828f9f0067865316a3/html5/thumbnails/23.jpg)
NRZ
Advantages: Simplicity in implementation. No DC component.
Disadvantages: Continuous part is non-zero at 0Hz. Causes “Signal
Droop”. Does not have any error correction capability. Does not posses any clocking component for ease of
synchronisation. Is not transparent.
![Page 24: LINE CODING - ggn.dronacharya.info€¦ · Line coding (binary data to digital signals) Improve the efficiency of line coding Sampling (a technique for changing analog data to binary](https://reader035.fdocuments.in/reader035/viewer/2022071102/5fdc2b828f9f0067865316a3/html5/thumbnails/24.jpg)
RZ
uses 3 values - +ve, -ve & zero. The signal is return to zero in midway of each
duration.
1 +ve to Zero0 -ve to zero
![Page 25: LINE CODING - ggn.dronacharya.info€¦ · Line coding (binary data to digital signals) Improve the efficiency of line coding Sampling (a technique for changing analog data to binary](https://reader035.fdocuments.in/reader035/viewer/2022071102/5fdc2b828f9f0067865316a3/html5/thumbnails/25.jpg)
![Page 26: LINE CODING - ggn.dronacharya.info€¦ · Line coding (binary data to digital signals) Improve the efficiency of line coding Sampling (a technique for changing analog data to binary](https://reader035.fdocuments.in/reader035/viewer/2022071102/5fdc2b828f9f0067865316a3/html5/thumbnails/26.jpg)
Manchester Encoding
An inversion at the middle of each bit interval negative to positive transition represents
binary 1, and a positive to negative transition represents binary 0.
![Page 27: LINE CODING - ggn.dronacharya.info€¦ · Line coding (binary data to digital signals) Improve the efficiency of line coding Sampling (a technique for changing analog data to binary](https://reader035.fdocuments.in/reader035/viewer/2022071102/5fdc2b828f9f0067865316a3/html5/thumbnails/27.jpg)
![Page 28: LINE CODING - ggn.dronacharya.info€¦ · Line coding (binary data to digital signals) Improve the efficiency of line coding Sampling (a technique for changing analog data to binary](https://reader035.fdocuments.in/reader035/viewer/2022071102/5fdc2b828f9f0067865316a3/html5/thumbnails/28.jpg)
MANCHESTER Advantages:
No DC component. Does not suffer from signal droop (suitable for transmission over AC
coupled lines). Easy to synchronise with. Is Transparent.
Disadvantages: Because of the greater number of transitions it occupies a significantly
large bandwidth. Does not have error detection capability.
These characteristic make this scheme unsuitable for use in Wide Area Networks. However, it is widely used in Local Area Network such as Ethernet and TokenRing.
![Page 29: LINE CODING - ggn.dronacharya.info€¦ · Line coding (binary data to digital signals) Improve the efficiency of line coding Sampling (a technique for changing analog data to binary](https://reader035.fdocuments.in/reader035/viewer/2022071102/5fdc2b828f9f0067865316a3/html5/thumbnails/29.jpg)
Differential Manchester
inversion at the middle of the bit interval is used for synchronization, but the presence or absence of an additional transition at the beginning of the interval is used to identify the bit.
A transition means binary 0 and no transition means binary 1
1 absence of transition at the beginning of the bit interval0 presence of transition at the beginning of the bit interval
![Page 30: LINE CODING - ggn.dronacharya.info€¦ · Line coding (binary data to digital signals) Improve the efficiency of line coding Sampling (a technique for changing analog data to binary](https://reader035.fdocuments.in/reader035/viewer/2022071102/5fdc2b828f9f0067865316a3/html5/thumbnails/30.jpg)
![Page 31: LINE CODING - ggn.dronacharya.info€¦ · Line coding (binary data to digital signals) Improve the efficiency of line coding Sampling (a technique for changing analog data to binary](https://reader035.fdocuments.in/reader035/viewer/2022071102/5fdc2b828f9f0067865316a3/html5/thumbnails/31.jpg)
![Page 32: LINE CODING - ggn.dronacharya.info€¦ · Line coding (binary data to digital signals) Improve the efficiency of line coding Sampling (a technique for changing analog data to binary](https://reader035.fdocuments.in/reader035/viewer/2022071102/5fdc2b828f9f0067865316a3/html5/thumbnails/32.jpg)
Bipolar
3 voltage level-- +ve , ‘0’ & -ve. Alternate Mark Inversion (AMI) Pseudoternary
1 alternating +1/2 , -1/2 voltage0 0 voltage
![Page 33: LINE CODING - ggn.dronacharya.info€¦ · Line coding (binary data to digital signals) Improve the efficiency of line coding Sampling (a technique for changing analog data to binary](https://reader035.fdocuments.in/reader035/viewer/2022071102/5fdc2b828f9f0067865316a3/html5/thumbnails/33.jpg)
![Page 34: LINE CODING - ggn.dronacharya.info€¦ · Line coding (binary data to digital signals) Improve the efficiency of line coding Sampling (a technique for changing analog data to binary](https://reader035.fdocuments.in/reader035/viewer/2022071102/5fdc2b828f9f0067865316a3/html5/thumbnails/34.jpg)
25/45
High Density Bipolar-3 zeros (HDB3)
Bipolar with 8-Zero Substitution (B8ZS)
![Page 35: LINE CODING - ggn.dronacharya.info€¦ · Line coding (binary data to digital signals) Improve the efficiency of line coding Sampling (a technique for changing analog data to binary](https://reader035.fdocuments.in/reader035/viewer/2022071102/5fdc2b828f9f0067865316a3/html5/thumbnails/35.jpg)
Comparison of Line Codes
Self-synchronization: Manchester codes have built in timing information
because they always have a zero crossing in the center of the pulse.
Polar RZ codes tend to be good because the signal level always goes to zero for the second half of the pulse.
NRZ signals are not good for self-synchronization. Error probability:
Polar codes perform better (are more energy efficient) than Unipolar or Bipolar codes.
Channel characteristics: Depends upon the PSD of the line codes.
![Page 36: LINE CODING - ggn.dronacharya.info€¦ · Line coding (binary data to digital signals) Improve the efficiency of line coding Sampling (a technique for changing analog data to binary](https://reader035.fdocuments.in/reader035/viewer/2022071102/5fdc2b828f9f0067865316a3/html5/thumbnails/36.jpg)
Digital to Analog encoding
![Page 37: LINE CODING - ggn.dronacharya.info€¦ · Line coding (binary data to digital signals) Improve the efficiency of line coding Sampling (a technique for changing analog data to binary](https://reader035.fdocuments.in/reader035/viewer/2022071102/5fdc2b828f9f0067865316a3/html5/thumbnails/37.jpg)
Analog to analog encoding
AM FM PM
![Page 38: LINE CODING - ggn.dronacharya.info€¦ · Line coding (binary data to digital signals) Improve the efficiency of line coding Sampling (a technique for changing analog data to binary](https://reader035.fdocuments.in/reader035/viewer/2022071102/5fdc2b828f9f0067865316a3/html5/thumbnails/38.jpg)
Analog to digital encoding
Message signal(analog)
Digital bit
Sampler Quantization Encoding