One of the best ppt of digital transmission.

1. DIGITAL
TRANSMISSION
BY HUZAIFA BUTT.

2. OUTLINE:
• Line coding
• Various line coding methode

3. LINE CODING
• Process of converting binary data in digital signals

4. PROPERTIES OF LINE CODES:

5. NO DC COMPONENT
• Every communication system such as a cable system does not
allow the transmission of a dc signal over them.
• So because of that line signal must have a zero average value.

6. SELF-CLOCKING (SYNCHRONIZING
CAPABILITY)
• Symbol or bit synchronization is necessary for every digital
communication system.
• A sufficient amount of zero crossings must occur in the line
code waveform for the receiver to be in synchronization.
• It implies that a transition must always occur after a predictable
interval; this property is referred to as the inherent
synchronizing or cloaking characteristic.

7. BANDWIDTH COMPRESSION
• The bandwidth of the line code should be as small as possible.
• Comparatively to the other codes, the multilevel course
requires less.

8. DIFFERENTIAL ENCODING
• For communication systems where the transmitted waveform
occasionally experiences an inversion, differential encoding is
helpful.
• The polarity of the encoded waveform is flipped during
differential encoding without impairing the ability to identify
data.

9. NOISE IMMUNITY
• The selected line code should have a very high noise immunity
(ability to minimize the effects of noise).
• This is necessary to have a minimum number of errors
introduced due to noise.

10. MINIMUM CROSSWALK:
• The crosswalk should be minimized which is transmitted
present between adjacent channels.

11. TYPES OF LINE CODING
• There are 3 types of Line Coding
• Unipolar
• Polar
• Bi-polar

12. UNIPOLAR SIGNALING
• Unipolar signaling is also called as On-Off Keying or simply
OOK.
• The presence of pulse represents a 1 and the absence of pulse
represents a 0.
• There are two variations in Unipolar signaling −
• Non Return to Zero NRZ
• Return to Zero RZ

13. UNIPOLAR NON-RETURN TO ZERO
• In this type of unipolar
signaling, a High in data is
represented by a positive
pulse called as Mark, which
has a duration T0 equal to the
symbol bit duration. A Low in
data input has no pulse.

14. ADVANTAGES AND DISADVANTAGES
• Advantages
• The advantages of Unipolar NRZ are
−
• It is simple.
• A lesser bandwidth is required.
• Disadvantages
• The disadvantages of Unipolar NRZ
are −
• No error correction done.
• Presence of low frequency
components may cause the signal
droop.
• No clock is present.
• Loss of synchronization is likely to
occur (especially for long strings
of 1s and 0s).

15. UNIPOLAR RETURN TO ZERO
In this type of unipolar signaling, a High in data, though represented by a Mark pulse, its
duration T0 is less than the symbol bit duration. Half of the bit duration remains high but
it immediately returns to zero and shows the absence of pulse during the remaining half
of the bit duration.

16. ADVANTAGES AND DISADVANTAGES:
• Advantages
• The advantages of Unipolar RZ
are −
• It is simple.
• The spectral line present at the
symbol rate can be used as a
clock.
• Disadvantages
• The disadvantages of Unipolar
RZ are −
• No error correction.
• Occupies twice the bandwidth as
unipolar NRZ.
• The signal droop is caused at
the places where signal is non-
zero at 0 Hz.

17. POLAR SIGNALING
• There are two methods of Polar Signaling. They are −
• Polar NRZ
• Polar RZ

18. POLAR NRZ
• In this type of Polar signaling,
a High in data is represented
by a positive pulse, while a
Low in data is represented by
a negative pulse.

19. ADVANTAGES AND DISADVANTAGES:
• Advantages
• The advantages of Polar NRZ are
−
• It is simple.
• No low-frequency components
are present.
• Disadvantages
• The disadvantages of Polar NRZ
are −
• No error correction.
• No clock is present.
• The signal droop is caused at
the places where the signal is
non-zero at 0 Hz.

20. POLAR RZ
• In this type of Polar signaling, a
High in data, though
represented by a Mark pulse, its
duration T0 is less than the
symbol bit duration. Half of the
bit duration remains high but it
immediately returns to zero and
shows the absence of pulse
during the remaining half of the
bit duration.
• However, for a Low input, a
negative pulse represents the
data, and the zero level remains
same for the other half of the bit
duration.

21. ADVANTAGES AND DISADVANTAGES:
• Advantages
• The advantages of Polar RZ are
−
• It is simple.
• No low-frequency components
are present.
• Disadvantages
• The disadvantages of Polar RZ
are −
• No error correction.
• No clock is present.
• Occupies twice the bandwidth of
Polar NRZ.
• The signal droop is caused at
places where the signal is non-
zero at 0 Hz

22. BIPOLAR SIGNALING
• This is an encoding technique which has
three voltage levels namely +, - and 0.
Such a signal is called as duo-binary
signal.
• An example of this type is Alternate Mark
Inversion AMI. For a 1, the voltage level
gets a transition from + to – or from – to
+, having alternate 1s to be of equal
polarity. A 0 will have a zero voltage level.
• Even in this method, we have two types.
• Bipolar NRZ
• Bipolar RZ
• From the models so far discussed, we
have learnt the difference between NRZ
and RZ. It just goes in the same way here
too.

23. ADVANTAGES AND DIS ADVANTAGES:
• It is simple.
• No low-frequency components are
present.
• Occupies low bandwidth than
unipolar and polar NRZ schemes.
• This technique is suitable for
transmission over AC coupled lines,
as signal drooping doesn’t occur
here.
• A single error detection capability is
present in this.
• No clock is present.
• Long strings of data causes loss of
synchronization.

24. TRANSMISSION MEDIA
BY HUZAIFA BUTT.

25. TRANSMISSION MEDIA
• A transmission medium can be broadly defined as anything that
can carry information from a source to a destination.
• The transmission medium for two people having a dinner
conversation is the air.

26. CLASSES OF TRANSMISSION MEDIA

27. GUIDED MEDIA:
• It is also referred to as Wired or Bounded transmission media.
Signals being transmitted are directed and confined in a narrow
pathway by using physical links.
Features:
• High Speed
• Secure
• Used for comparatively shorter distances

28. TYPES OF GUIDED MEDIA
• Twisted Pair Cable
• Coaxial Cable
• Optical Fiber Cable

29. TWISTED PAIR CABLE
• It consists of 2 separately insulated conductor wires wound about
each other. Generally, several such pairs are bundled together in a
protective sheath. They are the most widely used Transmission
Media. Twisted Pair is of two types:
• Unshielded Twisted Pair (UTP):
UTP consists of two insulated copper wires twisted around one
another. This type of cable has the ability to block interference and
does not depend on a physical shield for this purpose. It is used for
telephonic applications.
• Shielded Twisted Pair (STP):
This type of cable consists of a special jacket (a copper braid
covering or a foil shield) to block external interference. It is used in
fast-data-rate Ethernet and in voice and data channels of telephone
lines.

30. UNSHIELDED TWISTED PAIR

32. COAXIAL CABLE
• It has an outer plastic covering containing an insulation layer
made of PVC or Teflon and 2 parallel conductors each having a
separate insulated protection cover. The coaxial cable transmits
information in two modes: Baseband mode(dedicated cable
bandwidth) and Broadband mode(cable bandwidth is split into
separate ranges). Cable TVs and analog television networks
widely use Coaxial cables.

33. COAXIAL CABLE

34. OPTICAL FIBER CABLE
• It uses the concept of refraction of light through a core made
up of glass or plastic. The core is surrounded by a less dense
glass or plastic covering called the cladding. It is used for the
transmission of large volumes of data.
• The cable can be unidirectional or bidirectional. The WDM
(Wavelength Division Multiplexer) supports two modes, namely
unidirectional and bidirectional mode.

35. OPTICAL FIBER CABLE

36. STRIPLINE
• Stripline is a transverse electromagnetic (TEM) transmission line
medium invented by Robert M. Barrett of the Air Force
Cambridge Research Centre in the 1950s. Stripline is the
earliest form of the planar transmission line. It uses a
conducting material to transmit high-frequency waves it is also
called a waveguide. This conducting material is sandwiched
between two layers of the ground plane which are usually
shorted to provide EMI immunity.

37. MICROSTRIPLINE
• In this, the conducting material is separated from the ground
plane by a layer of dielectric.

38. UNGUIDED MEDIA
• It is also referred to as Wireless or Unbounded transmission
media. No physical medium is required for the transmission of
electromagnetic signals.
• Features:
• The signal is broadcasted through air
• Less Secure
• Used for larger distances
• There are 3 types of Signals transmitted through unguided
media:
• Radio waves
• Micro waves

39. RADIO WAVES
• These are easy to generate and can penetrate through
buildings. The sending and receiving antennas need not be
aligned. Frequency Range:3KHz – 1GHz. AM and FM radios and
cordless phones use Radio waves for transmission.

40. MICROWAVES
• It is a line of sight transmission i.e. the sending and receiving
antennas need to be properly aligned with each other. The
distance covered by the signal is directly proportional to the
height of the antenna. Frequency Range:1GHz – 300GHz. These
are majorly used for mobile phone communication and
television distribution.

41. INFRARED WAVES.
• Infrared waves are used for very short distance communication.
They cannot penetrate through obstacles. This prevents
interference between systems. Frequency Range:300GHz –
400THz. It is used in TV remotes, wireless mouse, keyboard,
printer, etc.

42. SWITCHING TECHNIQUES
BY HUZAIFA BUTT

43. INTRODUCTIO
N
• In large networks,
there can be multiple
paths from sender to
receiver. The
switching technique
will decide the best
route for data
transmission.
• Switching technique
is used to connect
the systems for
making one-to-one
communication.

44. CLASSIFICATION OF SWITCHING
TECHNIQUES

45. CIRCUIT SWITCHING
• Establishes a dedicated path between sender and receiver.
• Once the connection is established then the dedicated path will
remain to exist until the connection is terminated.
• In a network it operates in a similar way as the telephone
works.
• A complete end-to-end path must exist before the
communication takes place.

46. CIRCUIT SWITCHING
• When any user wants to send the data, a request signal is sent
to the receiver then the receiver sends back the
acknowledgment to ensure the availability of the dedicated
path. After receiving the acknowledgment, dedicated path
transfers the data.
It is used in public telephone network. It is used for voice
transmission.
Fixed data can be transferred at a time in circuit switching
technology.

47. COMMUNICATION PHASES FOR CIRCUIT
SWITCHING
• Circuit establishment
• Data transfer
• Circuit Disconnect

48. TECHNOLOGIES OF CIRCUIT SWITCHING
• Space Division Switches
• Time Division Switches

49. SPACE DIVISION SWITCHES
• A circuit switching technology in which a single transmission path is
accomplished in a switch by using a physically separate set of
crosspoints.
• It can be achieved by using crossbar switch. A crossbar switch is a
metallic crosspoint or semiconductor gate that can be enabled or
disabled by a control unit.
• The Crossbar switch is made by using the semiconductor. For
example, Xilinx crossbar switch using FPGAs.
• Space Division Switching has high speed, high capacity, and
nonblocking switches.

50. CATEGORIES.
Space Division Switches can be categorized in two ways:
• Crossbar Switch
• Multistage Switch

51. CROSSBAR SWITCH
• The Crossbar switch is a switch that has n input lines and n
output lines. The crossbar switch has n2 intersection points
known as crosspoints.
Disadvantage of Crossbar switch:
• The number of crosspoints increases as the number of stations
is increased. Therefore, it becomes very expensive for a large
switch. The solution to this is to use a multistage switch.

52. MULTISTAGE SWITCH
• Multistage Switch is made by splitting the crossbar switch into
the smaller units and then interconnecting them.
• It reduces the number of crosspoints.
• If one path fails, then there will be an availability of another
path.

53. TIME DIVISION SWITCHES
• If the coded values are transferred during the same time
interval from input to output, the technique is called Space
Switching. If the values are stored and transferred to the output
at a late time interval, the technique is called as Time
Switching.
• The incoming and outgoing signals when received and re-
transmitted in a different time slot, is called Time Division
Switching.

54. PROS AND CONS OF CIRCUIT SWITCHING
Advantages Of Circuit Switching:
• The communication channel is dedicated.
• It has fixed bandwidth.
Disadvantages Of Circuit Switching:
• The only delay occurs in the speed of data transmission.
• It takes a long time to establish a connection.
• It is more expensive than other switching techniques
• It is inefficient to use because once the path is established and no
data is transferred, then the capacity of the path is wasted.

55. MESSAGE SWITCHING
• A message is transferred as a complete unit and routed through
intermediate nodes at which it is stored and forwarded.
• No establishment of a dedicated path between the sender and receiver.
• The destination address is appended to the message. Message is routed
through the intermediate nodes based on the information available in
the message.
• Message switches are programmed in such a way so that they can
provide the most efficient routes.
• Each and every node stores the entire message and then forward it to
the next node. This type of network is known as store and forward
network.

56. ADVANTAGES OF MESSAGE SWITCHING
• Data channels are shared among the communicating devices
that improve the efficiency of using available bandwidth.
• Traffic congestion can be reduced because the message is
temporarily stored in the nodes.
• Message priority can be used to manage the network.
• The size of the message which is sent over the network can be
varied. Therefore, it supports the data of unlimited size.

57. DISADVANTAGES OF MESSAGE SWITCHING
• The message switches must be equipped with sufficient storage
to enable them to store the messages until the message is
forwarded.
• The Long delay can occur due to the storing and forwarding
facility provided by the message switching technique.

58. PACKET SWITCHING
• The message is sent in one go, but it is divided into smaller pieces(Packets),
and they are sent individually.
• Packets are given a unique number to identify their order at the receiving
end.
• Every packet contains some information in its headers such as source
address, destination address and sequence number.
• Packets will travel across the network, taking the shortest path as possible.
• All the packets are reassembled at the receiving end in correct order.
• If any packet is missing or corrupted, then the message will be sent to
resend the message.
• If the correct order of the packets is reached, then the acknowledgment
message will be sent.

59. APPROACHES OF PACKET SWITCHING:
There are two approaches to Packet Switching:
• Datagram Packet switching
• Virtual Circuit Switching

60. DATAGRAM PACKET SWITCHING
• It is a packet switching technology in which packet is known as a
datagram, is considered as an independent entity. Each packet
contains the information about the destination and switch uses this
information to forward the packet to the correct destination.
• The packets are reassembled at the receiving end in correct order.
• In Datagram Packet Switching technique, the path is not fixed.
• Intermediate nodes take the routing decisions to forward the packets.
• Datagram Packet Switching is also known as connectionless
switching.

61. VIRTUAL CIRCUIT SWITCHING
• Virtual Circuit Switching is also known as connection-oriented
switching.
• In the case of Virtual circuit switching, a preplanned route is
established before the messages are sent.
• Call request and call accept packets are used to establish the
connection between sender and receiver.
• In this case, the path is fixed for the duration of a logical
connection

62. VIRTUAL CIRCUIT SWITCHING

63. ADVANTAGES OF PACKET SWITCHING:
• Cost-effective: In packet switching technique, switching devices do
not require massive secondary storage to store the packets, so cost
is minimized to some extent. Therefore, we can say that the packet
switching technique is a cost-effective technique.
• Reliable: If any node is busy, then the packets can be rerouted. This
ensures that the Packet Switching technique provides reliable
communication.
• Efficient: Packet Switching is an efficient technique. It does not
require any established path prior to the transmission, and many
users can use the same communication channel simultaneously,
hence makes use of available bandwidth very efficiently.

64. DISADVANTAGES OF PACKET SWITCHING:
• Packet Switching technique cannot be implemented in those
applications that require low delay and high-quality services.
• The protocols used in a packet switching technique are very
complex and requires high implementation cost.
• If the network is overloaded or corrupted, then it requires
retransmission of lost packets. It can also lead to the loss of
critical information if errors are nor recovered.