Encoding is the process of converting data into a digital format for transmission. There are different encoding techniques for analog and digital signals. Common digital to digital encoding techniques include NRZ, NRZI, Manchester, and 4B/5B encoding. NRZ assigns a voltage level to represent each bit but can result in baseline wander with long strings of 1s or 0s. NRZI and Manchester encoding add transitions to allow for clocking but require more bandwidth. 4B/5B encoding maps 4-bit groups to 5-bit codes to avoid long runs of the same bit.

1. ENCODING TECHNIQUES
Group Members
• Goriha Naveed
• Maria Banaras
• Naila Naz
• Riffat Yaqoob

2. Encoding
Encoding is the process of putting a sequence
of characters (letters, numbers, punctuation,
and certain symbols) into a specialized digital
format for efficient transmission or transfer.
Decoding is the opposite process -- the
conversion of a digital signal into a sequence
of characters.

3. Types of Encoding
 Digital Data , Analog signals
Basis for analog signaling is a continuous, constant-frequency signal known as
the carrier frequency.
By modulating(Amplitude , Frequency , Phase)
 Analog Data ,Digital signals
Analog-to-digital conversion is an electronic process in which a continuously
variable analog signal is changed, without altering its essential content, into a
multi-level digital signal.
 Digital Data , Digital signals
Digital signal –is a sequence of discrete, discontinuous voltage pulses.
Bit duration :: the time it takes for the transmitter to emit the bit.

4. Digital To Digital Encoding Techniques
In order to transport digital bits of data across carrier
waves, encoding techniques have been developed.
some of the more common techniques are given below
Physical layer
 NRZ( non return to zero)
 NRZI(non return to zero inverted)
 MANCHESTER ENCODING
 4B/5B ENCODING

5. Encoder Decoder 1 0 1 1 01 0 1 1 0
1 0 1 1 0
Digital message
Digital Signal
Digital to digital encoding
Frame

6. NRZ encoding (Non Return to Zero)
 The most common, and easiest, way to transmit digital signals.
 Uses two different voltage levels (one positive and one negative) as the
signal elements for the two binary digits.
 Voltage does not return to zero during the bit interval.
 The voltage is constant during the bit interval .
0 negative voltage
1  positive voltage

7. NRZ Encoding
0 0 1 0 1 1 1 0 0
+
-

8. NRZ Encoding
 The problem with this is that it is difficult to distinguish a series of '1's or
'0's.
 Leads to baseline wander
 Sender and Receiver clocks have to highly precise
Reference: Data communication & networking
By Behrouz A. Forouzan
"In decoding a digital signal, the incoming signal
power is evaluated against the baseline (a running
average of the received signal power). A long string
of 0s or 1s can cause baseline wandering (a drift in
the baseline) and make it difficult for the receiver
to decode correctly."

9. 0 0 1 0 1 1 1 0 0 1 0 1 1 1
NRZ BASE LINE WONDER

10. NRZI ENCODING
NRZI stands for non return to zero inverted.
 NRZ inverted (NRZI)
 Solve the problem of consecutive 1’s.
 At zero, state of current signal remains same.
 Transition at beginning of bit time
 Transition (either low-to-high or high-to-low)
 denotes a binary 1
 No transition denotes a binary 0.

11. 1 0 1 1 0 1 0
NRZI(Non return to zero inverted)
+
-

12. Manchester encoding
 There is a transition at the middle of each bit period.
 A transition in the middle of each bit makes it possible to
synchronize the sender and receiver and also as data: low to high
represents 0, high to low represents 1
 Used by IEEE 802.3 Ethernet LAN
1  High-to-low transition
0  low-to-high transition

13. 0 0 1 0 1 1 1 0
Manchester encoding
-
+

14. Pros and Cons
 Pros
 Self-clocking: Because there is a predictable transition during
each bit time, the receiver can synchronize on that transition.
 Error detection: the absence of an expected transition can be
used to detect errors
 50% efficient(1/2 bit per transition)
 Cons
 The maximum modulation rate is twice that for NRZ
 Requires more bandwidth

15. 4B/5B Encoding
 4B/5B block encoding scheme designed to breakup long strings of 0’s and
1’s without increasing the frequency bandwidth.
 In this scheme bit sequence is broken up in to four bit blocks.
 Each block of four bit is replaced with a five bit block.
 The five bits codes were selected so that there is no more than one leading
zero and no more than two trailing zeros.
 Only half of the five bits are used for encoding , the remaining cods can be
used for other purposes.
 Thus, when the codes are strung together there can be no more than three
consecutive zeros
 The string of bits after the replacement are transmitted using NRZI.
 4B/5B encoding followed by NRZI is used in 10BaseTX (Fast Ethernet).

16. 4B/5B Encoding

17. 1 0 0 1 0 1 1 0 1 1 1 0
Bit Sequence
1 0 0 1 0 1 1 0 1 1 1 0
1 0 0 1 1 0 1 1 1 0 1 1 1 0 0
1 0 0 1 1 0 1 1 1 0 1 1 1 0 0
4B/5B Encoding
Not more than 3
consecutive zeros
4B/5B Encoding

18. NRZI
Encoder
NRZI
Decoder
1 0 1 01 0 1 0
1 0 1 1 0
Digital Signal
4B/5B
Encoder
4B/5B
Decoder
1 0 1 1 01 0 1 1 0
Digital
data Digital
data
4B/5B Encoding
Frame

19. THANK YOU