line coding ukb

8/11/2019 Line Coding Ukb

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Line Coding

Unnikrishnan BSDE RTTC TVM


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Figure 4.1 Line coding and decoding


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Figure 4.1 Line coding


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Line codingis the process of convertingbinary data, a sequence of bits to a digitalsignal.


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Definitions of the components/Keywords:

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1 Binary data can be transmitted using a number of differenttypes of pulses. The choice of a particular pair of pulses torepresent the symbols 1 and 0 is called Line Coding.


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Master Layout

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1 0 1 1 0 1 1 1 0 1 0 1nput!ata

!igital"ignal


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Step 1:1

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unipolar #$% on $eturn to %ero'

Instruction for the animator Text to be displayed in the orkin! area "DT#

( The first fig should appear then thesecond fig should appear.

( In parallel to the figures the textshould be displayed.

( Bit 0 is mapped to amplitude close to zero

( Bit 1 is mapped to a positive amplitude

( D! component is present

$epresentation of 0 $epresentation of 1


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Step 2:1

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)olar #$% on $eturn to %ero'




( Bit 0 is mapped to a negative amplitude

( Bit 1 is mapped to a positive amplitude

( D! component is present



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Step 5:1

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Manchester coding




&it " is sent by having a mid'bit transition from high to low.

(&it $ is sent by having a mid'bit transition from low to high.



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The corresponding *aveforms should be sho*n in the demo part *hen aparticular line code is selected.


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+igh !ensity Bipolar &+!Bn'

modified bipolar codes *hich guaranteetransitions despite runs of eros.

thus substitute runs of more than n eros

an alternative name is Bn%" in this case substitute runs of n or moreeros

+!B- is a popular code

note +!B- is equivalent to B%"


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#eed for line codes Type of Line codes !ifferent Line codes


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Return-to-zero

Return-to-zero (RZ) describes a line codeused in telecommunications sinals in !"ic"t"e sinal drops (returns) to zero bet!eeneac" pulse# T"is ta$es place e%en i& a

number o& consecuti%e 's or 1s occur in t"esinal# T"e sinal is sel&-cloc$in# T"ismeans t"at a separate cloc$ does not need tobe sent alonside t"e sinal but su&&ers &romusin t!ice t"e band!idt" to ac"ie%e t"e

same data-rate as compared to non-return-to-zero &ormat#


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RZ and NRZ


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AMIAMI


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*nipolar encodinis a line code. / positive voltage representsa binary 1, and ero volts indicates a binary 0. t is the simplest linecode, directly encoding the bitstream, and is analogous to onoffeying in modulation.

ts dra*bacs are that it is not selfclocing and it has asignificant !C component, *hich can be halved by using returntoero, *here the signal returns to ero in the middle of the bit period.2ith a 304 duty cycle each rectangular pulse is only at a positivevoltage for half of the bit period. This is ideal if one symbol is sentmuch more often than the other and po*er considerations arenecessary, and also maes the signal selfclocing.

Traditionally, a unipolar scheme *as designed as a nonreturntoero $%' scheme, in *hich the positive voltage defines bit 1 andthe ero voltage defines bit 0. t is called #$% because the signaldoes not return to ero at the middle of the bit.


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coded mar$ in%ersion (+,I)

n telecommunication, coded mar$ in%ersion(+,I)is a nonreturntoero $%' line code. tencodes zerobits as a half bit time of erofollo*ed by a half bit time of one, and *hile onebits are encoded as a full bit time of a constant

level. The level used for onebits alternates eachtime one is coded.

+,Idoubles the bitstream frequency, *hencompared to its simple #$% equivalent, but

allo*s easy and reliable cloc recovery.


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+,I


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Non Return To Zero (NRZ)


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HDB3 substitution rules


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+!B- Coding $ules

)olarity of thepreceding pulse

#umber of Bipolar &ones')ulsessince last substitution

5dd 6ven

000 7007

7 0007 00


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MULTIPLEXIN TE!HNI"UE


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Fi 4 1 Li di


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Figure 4.1 Line coding

Fi 4 2 Si l l l d l l


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Figure 4.2 Signal level versus data level

Fi 4 3 DC


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Figure 4.3 DC component


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Example 1Example 1

A signal has two data levels with a pulse duration of 1

ms. We calculate the pulse rate and bit rate as follows:

Pulse Rate = 1/ 10Pulse Rate = 1/ 10-3-3= 1000 pulses/s= 1000 pulses/s

Bit Rate = Pulse Rate x logBit Rate = Pulse Rate x log22L = 1000 x logL = 1000 x log222 = 1000 bps2 = 1000 bps


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Example 2Example 2

A signal has four data levels with a pulse duration of 1

ms. We calculate the pulse rate and bit rate as follows:

Pulse Rate = = 1000 pulses/sPulse Rate = = 1000 pulses/s

Bit Rate = PulseRate x logBit Rate = PulseRate x log22L = 1000 x logL = 1000 x log224 = 2000 bps4 = 2000 bps

Figure 4 4 L k f h i ti


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Figure 4.4 Lack of synchronization


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Example 3Example 3

In a digital transmission, the receiver clock is 0.1 percent

faster than the sender clock. How many extra bits per

second does the receiver receive if the data rate is 1

Kbps? How many if the data rate is 1 Mbps?

SolutionSolution

At 1 Kbps:

1000 bits sent1001 bits reei!e"1 extra bps

At 1 #bps:1$000$000 bits sent1$001$000 bits reei!e"1000 extra bps

Figure 4 5 Line coding schemes


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Figure 4.5 Line coding schemes


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nipolar encoding uses only one

voltage level!

%ote:%ote:

Figure 4 6 nipolar encoding


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Figure 4.6 nipolar encoding


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Figure 4 7 &ypes of polar encoding


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Figure 4.7 &ypes of polar encoding


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'n ()*+L the level of the signal is'n ()*+L the level of the signal is

dependent upon the state of the ,it!dependent upon the state of the ,it!

%ote:%ote:


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'n ()*+' the signal is inverted if a 1 is'n ()*+' the signal is inverted if a 1 is

encountered!encountered!

%ote:%ote:

Figure 4.8 ()*+L and ()*+' encoding


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Figure 4.8 ()* L and ()* ' encoding

Figure 4.9 )* encoding


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Figure 4.9 )* encoding


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- good encoded digital signal must- good encoded digital signal must

contain a provision forcontain a provision forsynchronization!synchronization!

%ote:%ote:

Figure 4.10 .anchester encoding


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Figure 4.10 .anchester encoding


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'n .anchester encoding/ the'n .anchester encoding/ the

transition at the middle of the ,it istransition at the middle of the ,it isused for ,oth synchronization and ,itused for ,oth synchronization and ,it

representation!representation!

%ote:%ote:

Figure 4.11 Differential .anchester encoding


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g ff g


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Figure 4.12 ipolar -.' encoding


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g p g


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Figure 4.14 .L&+3 signal


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line coding ukb

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