The document discusses communication systems and their key components and concepts. It defines analog and digital signals, and the advantages and disadvantages of each. It explains the basic elements of a communication system, including the information source, transmitter, channel, and receiver. It also discusses different types of transmission such as simplex, full duplex, and half duplex. Modulation is introduced as a key concept for transmitting baseband signals over long distances.

2.  To understand the principles of basic
communication systems
 To define information, message and signals
 To differentiate between analog and digital signals
 To explain the elements of communication system
 To explain the terms modulation and why they are
needed in communication system
 To explain the limitations in communication system
 To define frequency and wavelength

3.  Definition of communications
 Information, message and signals
 Analog and digital signals
 Basic requirements of communication system
 Elements of communication system
 Modulation
 Limitations in communication system
 Frequency and wavelength

4. https://www.youtube.com/watch?v=1J
ZG9x_VOwA

5.  A signal is any physical phenomenon which
conveys information
 Systems respond to signals and produce new
signals
 Excitation signals are applied at system
inputs and response signals are produced at
system outputs

6.  A communication system has an information
signal plus noise signals
 This is an example of a system that consists of
an interconnection of smaller systems

8.  Analog
-Continuous Variation
-Assume the total range of frequencies/time
-All information is transmitted
 Digital
-Takes samples:-non continuous stream of
on/off pulses
-Translates to 1’s and 0’s

9.  Digital CS
Advantages:
-Inexpensive
-Privacy preserved(data
encrypted)
-Can merge different data
-error correction
Disadvantages:
-Larger bandwidth
-synchronization problem is
relatively difficult
 Analog Cs
Disadvantages:
-expensive
-No privacy preserved
-Cannot merge different data
-No error correction
capability
Advantages:
-smaller bandwidth
-synchronization problem is
relatively easier.

10.  Communications:
➢ Transfer of Information from one place to another.
➢ Should be efficient, reliable, and secured.
 Communication system:
➢ components/subsystems act together to accomplish information
transfer/exchange
 Electronic communication system
➢ transmission, reception and processing of information between two or
more locations using electronic circuits.
 Information source
➢ analog/digital form

11.  Have you ever pictured yourself living in a
world without any communication system?

13.  Importance of communication:
exchange of information between two parties
separated in distances in a more faster and
reliable way.
2 main BARRIERS: Language & Distances

14.  1844 Telegraph:
 1876 Telephony:
 1904 Radio:
 1923-1938 Television:
 1936 Armstrong’s case of FM radio
 1938-1945 World War II Radar and microwave systems
 1948-1950 Information Theory and coding. C. E.
Shannon
 1962 Satellite communications begins with
Telstar I.
 1962-1966 High Speed digital communication
 1972 Motorola develops cellular telephone.
 1989 Internet
Brief Chronology of Communication Systems

15.  Communications between human beings
➢Form of hand gestures and facial expressions
➢Verbal grunts and groans
 Long distance communications
➢Telegraph
➢Telephone
 Wireless radio signals
➢Triode vacuum tube
➢Commercial radio broadcasting

16.  Rate of information transfer:
-how fast the information can be
transferred
 Purity of signal received:
-whether the signal received is the same as
the signal being transmit
 Simplicity of the system
-The simpler the system, the better
reliability

17. https://www.youtube.com/watch?v=4Z
1BIeje_ko

20.  Information
➢The communication system exists to convey a
message.
➢Message comes from information source
➢Information forms - audio, video, text or data

21.  Transmitter:
➢Processes input signal to produce a transmitted
signal that suited the characteristic of transmission
channel.
➢E.g. modulation, coding, mixing, translate
➢Other functions performed - Amplification, filtering,
antenna
➢Message converted to into electrical signals by
transducers
➢E.g. speech waves are converted to voltage variation
by a microphone

22.  Channel (transmission media):
➢a medium that bridges the distance from source to
destination. Eg: Atmosphere (free space), coaxial
cable, fiber optics, waveguide
➢signals undergoes degradation from noise ,
interference and distortion

23.  Receiver:
➢to recover the message signal contained in the
received signal from the output of the channel, and
convert it to a form suitable for the output
transducer.
➢E.g. mixing, demodulation, decoding
➢Other functions performed: Amplification, filtering.
➢Transducer converts the electrical signal at its input
into a form desired by the system used

25. Input Transducer: The message produced by a source
must be converted by a transducer to a form suitable for
the particular type of communication system.
Example: In electrical communications, speech waves are
converted by a microphone to voltage variation.
Transmitter: The transmitter processes the input signal
to produce a signal suits to the characteristics of the
transmission channel.
Signal processing for transmission almost always
involves modulation and may also include coding. In
addition to modulation, other functions performed by
the transmitter are amplification, filtering and coupling
the modulated signal to the channel.

26. Channel: The channel can have different forms: The
atmosphere (or free space), coaxial cable, fiber optic,
waveguide, etc.
The signal undergoes some amount of degradation from noise,
interference and distortion
Receiver: The receiver’s function is to extract the desired
signal from the received signal at the channel output and to
convert it to a form suitable for the output transducer.
Other functions performed by the receiver: amplification (the
received signal may be extremely weak), demodulation and
filtering.
Output Transducer: Converts the electric signal at its input
into the form desired by the system user.
Example: Loudspeaker, personal computer (PC), tape
recorders.

27. Digital
Analog

28.  Electronic communications are classified
according to whether they are
1. One-way (simplex) or two-way (full duplex or
half duplex) transmissions
2. Analog or digital signals.

29. Simplex
◦ The simplest method of electronic communication
is referred to as simplex.
◦ This type of communication is one-way. Examples
are:
 Radio
 TV broadcasting
 Beeper (personal receiver)

30. Full Duplex
◦ Most electronic communication is two-way and is
referred to as duplex.
◦ When people can talk and listen simultaneously, it
is called full duplex. The telephone ,mobile is an
example of this type of communication.

31. Half Duplex
◦ The form of two-way communication in which only
one party transmits at a time is known as half
duplex. Examples are:
 Police, military, etc. radio transmissions
 Citizen band (CB)
 Family radio
 Amateur radio

32. TX RX
TX
TX
RX
RX
Simplex:
One-way
Duplex:
Two-way
Half duplex:
Alternate TX/RX
Full duplex:
Simultaneous
TX/RX
Channel
Channel(s)

33. https://www.youtube.com/watch?v=t_
aqmvn8mUg

34. https://www.youtube.com/watch?v=L
MRSS7ZYM50

35. Analog Signals
◦ An analog signal is a smoothly and continuously
varying voltage or current. Examples are:
 Sine wave
 Voice
 Video (TV)

36. Figure 1-5: Analog signals (a) Sine wave “tone.” (b) Voice. (c) Video (TV) signal.

37. Digital Signals
◦ Digital signals change in steps or in discrete
increments.
◦ Most digital signals use binary or two-state codes.
Examples are:
 Telegraph (Morse code)
 Continuous wave (CW) code
 Serial binary code (used in computers)

38. Figure 1-6: Digital signals (a) Telegraph (Morse code). (b) Continuous-wave
(CW) code. (c) Serial binary code.

39. Digital Signals
◦ Many transmissions are of signals that originate in
digital form but must be converted to analog form
to match the transmission medium.
 Digital data over the telephone network.
 Analog signals.
 They are first digitized with an analog-to-digital
(A/D) converter.
 The data can then be transmitted and processed
by computers and other digital circuits.

40.  Any original signals, regardless of whether it is
analog/digital, referred as base band signals.
 In Comm Sys, some info signals may be
transmitted directly by themselves over the
medium or using modulation.
 Putting the original signal directly to the
medium is called base band transmission.

41.  Baseband - The original information
signal such as audio, video, or computer
data. Can be analog or digital.
 Broadband - The baseband signal
modulates or modifies a carrier signal,
which is usually a sine wave at a
frequency much higher than the baseband
signal.

42. Data transmission:
 means movement of data which is in the
form of bits between two or more digital
devices.
 The data transmission takes place over some
physical medium from one computer to the
other.
 Transmission modes:
1.Parallel transmission
2.Serial transmission
 a) Synchronous b)Asynchronous

44.  Advantages:
 All the data bit will be transmitted simultaneously. Therefore the time
required for transmission of an N bit word is only one clock cycle
 Serial transmission will require N no of clock cycle for transmission of
same word
 Due to this, clock frequency can be kept low without affecting the speed
of operation.
 Disadvantages:
 To transmit an N-bit Word, we need N number of wires with increase in
the no. of users these wires will be too many to handle.
 Serial transmission uses only one wire for connecting the transmitter and
the receiver. Hence, practically serial transmission is always preferred.

45.  Serial Transmission:
 In this the bits of a byte are serially transmitted one after the other as shown
in fig.
Single wire used for transmission Fig. serial Transmission

◦ The byte to be transmitted is first stored in a shift register. Then these bits are
shifted from MSB to LSB bit by bit in synchronization with the clock. Bits are
shifted right by one position per clock cycle.
◦ The bit which falls out of the shift register is transmitted. Hence LSB is
transmitted first.
◦ For serial transmission only one wire is needed between the transmitter and
the receiver hence, serial transmission is preferred for long distance data
communication. This is the advantage of serial transmission over parallel
transmission.
◦ The serial transmission has a drawback. As only one bit is transmitted per
clock cycle it requires a time corresponding to 8 clock cycles to transmit one
byte. But in case of parallel transmission it needs only one clock cycle to
transmit one byte. The time can be reduced by increasing the clock frequency.
1
MSB
0 0 0 1 0 1 1
LSB

47.  Advantages of serial transmission:
 Only one wire is required.
 Reduction in cost due to less no. of conductors.
 Disadvantages of serial transmission:
◦ The speed of data transfer is low.
◦ To increase the speed of data transfer it is
necessary to increase the clock frequency.

49. Types of Serial transmission :
 Asynchronous data transmission.
 Synchronous data transmission.
◦ Asynchronous data transmission
 Transmission of data byte done at any instant of time.
 Only one byte is sent at time after sending one byte the next byte can be sent after an
arbitrary time delay.
 The transmitter and receiver operate at different clock frequency.
 As the data transmission can commence at any instant it becomes difficult for the
receiver to understand the instant at which the byte has been transmitted.
 Start and stop bits are used along with each data byte as shown in figs. Here the start
bit is always “0” and stop bit is always “1”
 The idle time in between two data bytes is not constant; the idle time is also called as
the gap between the data bytes.
 In the Asynchronous data transmission the timing of the signal is not important instead
information is received and translated by agreed upon patterns.
 As long as these patterns are being followed the receiver can retrieve the information
without any Problem.


50. •Response to the start and stop bits :
a) When the receiver detects a start bit, it set a timer and begins continuing bits as they come in.
b)After n bits the receiver searches for stop bits
c)As soon as it detects the stop bit, it waits until it detects the next start bit.
d) So the meaning of Asynchronous is actual Asynchronous at the byte level bit the bits are still
synchronized so their durations are same.

51.  Disadvantages of using start and stop bits. :
 The use of start and stop bits and the gaps between data bits will
make the asynchronous transmission slow.
 Disadvantages of Asynchronous transmission :
 Additional bits called start and stop bits are required.
 It is difficult to determine the sampling instants hence; the timing
error can take place.
Advantages of Asynchronous transmission :
 Synchronization between transmitter and receiver is not necessary.
 It is possible to transmit signals from the source having different
bit rates.
 This mode of transmission is easy to implement.
 It is cheap and effective.
Application :
 The connection of a keyboard to a computer

52.  Synchronous transmission :
 It is carried out under the control of a common master clock Here the bits
transmitted are synchronous to a reference clock.
 No START & STOP bits are used instead the bytes are transmitted as a
block in a continuous stream of bits. There is inter block idle time which is
also filled with idle characters.
 The receiver operates at exactly same clock frequency as that of
transmitter.
 This is essential for error free reception of data flag is sequence of fixed
number of bits which is prefixed to each block.
 In the synchronous transmission the bit stream to be transmitted is
combined into longer frames which may contain more than one bytes.
 There is no gap between a byte and the next data. The receiver separates
the bit stream into bytes for purpose of decoding.
 START & STOP bits are not used. Instead the bits are transmitted serially
one after the other. Grouping of byte is responsibility of the receiver.

53. Synchronous Transmission of data :
 To maintain synchronization between transmitted and received, a group of
Synchronous bits are placed at the beginning of each block. fig. shows the
arrangement of data. Each block of data may contain hundreds of even thousands
of characters. At the end of the block there is another special code (ETX) ,Signaling
the end of transmission after that there is an error bit.
Advantages :
 START & STOP bits are not needed in synchronous communication.
 Timing errors are reduced due to synchronization
 The speed of data transmission is higher than that of asynchronous Transmission.
Disadvantages :
 The transmitter and receiver should use exactly same clock frequency. This
requires proper synchronization which makes system complicated.
 The accuracy of the received data is dependent on the ability of the received to
count the received bits accurately. Hence this type of communication is less
reliable as compared to asynchronous communication.

56.  Modulation –
 It is the process of changing one or more
properties ( Amplitude, frequency or phase) of
the analog carrier in proportion with the
information signal.
 It is impractical to propagate information as it is
over standard transmission media.
 Reverse process of modulation and converting
the modulated carrier back to the original
information is known as demodulation.
 i.e. At the receiver, the base signal regenerates
by removing the carrier signal and filtering the
signal to remove any unwanted noise. This
process is ‘Demodulation’.

57.  Modulation
 We all know that most signals generated in everyday life
are sinusoidal waveforms.
 Modern signals include the basic sinusoidal form signal
containing important information.
 Modulation is the branch of science in electronics and
communication systems including varying the fundamental
properties of the basic signal by superimposing it with a
carrier signal to carry the signal from one location to the
other. This process is ‘Modulation’.

58. Why Modulation is necessary? –
 1. It is difficult to radiate LF signal from antenna in
the form of EM energy.
 2. Information signal often occupy the same
frequency band that would interfere with each
other.
 (Channel is a specific band of frequencies
allocated to a particular service.)

59. Need of Modulation
1.Reduction in the height of antenna
 For the transmission of radio signals, the antenna height must be
multiple of λ/4 , where λ is the wavelength .
 λ = c /f
 where c : is the velocity of light
 f: is the frequency of the signal to be transmitted
 The minimum antenna height required to transmit a baseband signal
of f = 10 kHz is calculated as follows :
 The antenna of this height is practically impossible to install .
 Now, let us consider a modulated signal at f = 1 MHz . The minimum
antenna height is given by,
 This antenna can be easily installed practically . Thus, modulation
reduces the height of the antenna .

60. 2. Avoids mixing of signals
 If the baseband sound signals are transmitted without using the
modulation by more than one transmitter, then all the signals will be
in the same frequency range i.e. 0 to 20 kHz .
 Therefore, all the signals get mixed together and a receiver can not
separate them from each other .
 Hence, if each baseband sound signal is used to modulate a different
carrier then they will occupy different slots in the frequency domain
(different channels).
 Thus, modulation avoids mixing of signals .
3. Increase the Range of Communication
 The frequency of baseband signal is low, and the low frequency
signals can not travel long distance when they are transmitted . They
get heavily attenuated .
 The attenuation reduces with increase in frequency of the
transmitted signal, and they travel longer distance .
 The modulation process increases the frequency of the signal to be
transmitted.
 Therefore, it increases the range of communication.

61. 4. Multiplexing is possible
 Multiplexing is a process in which two or more
signals can be transmitted over the same
communication channel simultaneously .
 This is possible only with modulation.
 The multiplexing allows the same channel to be
used by many signals.
 Hence, many TV channels can use the same
frequency range, without getting mixed with each
other or different frequency signals can be
transmitted at the same time.
5. Improves Quality of Reception
 with frequency modulation (FM) and the digital
communication techniques such as PCM, the
effect of noise is reduced to a great extent . This
improves quality of reception .

62. 62
- A digital signal is superior to an analog signal because it is
more robust to noise and can easily be recovered,
corrected and amplified.
- For this reason, the tendency today is to change an analog
signal to digital data.
- Changing analog signal to digital signal:
Sampling → Quantizing

63. 63
Pulse-code Modulation (PCM)
- Pulse-code Modulation (PCM), like PAM, is a digital
communication technique that sends samples of the analog
signal taken at a sufficiently high rate.
- PCM differs than PAM in that it quantizes the samples by
constraining them to only take a limited number of values,
and then converts each value into a binary string of bits
that are transmitted on the communication line.

64. 64
Pulse-code Modulation (PCM)
- PCM consists of three steps to digitize an analog signal:
1. Sampling
2. Quantization
3. Binary encoding
- Before we sample, we have to filter the signal to limit
the maximum frequency of the signal as it affects the
sampling rate.
- Filtering should ensure that we do not distort the signal,
i.e. remove high frequency components that affect the
signal shape.

65. 65
Components of PCM Encoder

66. 66
Sampling
- Analog signal is sampled every Ts secs.
- Ts is referred to as the sampling interval or period.
- fs = 1/Ts is called the sampling rate or sampling
frequency.
- The process is referred to as pulse amplitude
modulation PAM and the outcome is a signal with
analog (non integer) values.

67. 67
Note
- According to the Nyquist theorem,
the sampling rate must be at least 2 times the
highest frequency contained in the signal.

68. 68

69. 69
Quantization
- In order to process the sampled signal digitally, the
sample values have to be quantized to a finite
number of levels, and each value can then be
represented by a string of bits.
- To quantize a sample value is to round it to the
nearest point among a finite set of permissible
values.
- Therefore, a distortion will inevitably occur. This is
called quantization noise (or error).

70. 70
Quantization
- Sampling results in a series of pulses of varying
amplitude values ranging between two limits: a min
and a max.
- The amplitude values are infinite between the two limits.
- We need to map the infinite amplitude values onto a
finite set of known values.
- This is achieved by dividing the distance between min
and max into L zones, each of height height
 = (max - min)/L

71. 71
Quantization Levels
- The midpoint of each zone is assigned a value from
0 to L-1 (resulting in L values)
n

72. 72
- Each sample falling in a zone is then approximated
to the value of the midpoint.
n
approximating the value of the sample amplitude to the
quantized values.
0
1
2
3

73. 73
Assigning Codes to Zones
- Each zone is then assigned a binary code.
- The number of bits required to encode the zones, or
the number of bits per sample as it is commonly
referred to, is obtained as follows:
nb = log2 L
- Given our example, nb = 2
- The 4 zone (or level) codes are therefore: 00, 01,
10, 11

74. 74
Assigning Codes to Zones
n
Each zone is assigned a binary code
0
1
2
3
00
01
10
11

75. 75
Assigning Codes to Zones
Use one of the line code scheme to get the digital signal

76.  The most common technique for using digital
signals to encode analog data is PCM.
 Example: To transfer analog voice signals off a local
loop to digital end office within the phone system,
one uses a codec.
 Because voice data limited to frequencies below
4000 HZ, a codec makes 8000 samples/sec. (i.e.,
125 microsecond/sample).
 If a signal is sampled at regular intervals at a rate
higher than twice the highest signal frequency, the
samples contain all the information of the original
signal.

77.  Analog signal is sampled.
 Converted to discrete-time continuous-amplitude
signal (Pulse Amplitude Modulation)
 Pulses are quantized and assigned a digital value.
◦ A 7-bit sample allows 128 quantizing levels.
 PCM uses non-linear encoding, i.e., amplitude
spacing of levels is non-linear
◦ There is a greater number of quantizing steps for
low amplitude
◦ This reduces overall signal distortion.
 This introduces quantizing error (or noise).
 PCM pulses are then encoded into a digital bit
stream.
 8000 samples/sec x 7 bits/sample = 56 Kbps for a
single voice channel.

78. •Most common form of analog to digital modulation
•Four step process
- Signal is sampled using PAM (sampled)
- Integer values assigned to signal (PAM)
- Values converted to binary (Quantized)
- Signal is digitally encoded for transmission (Encoded)

81. 81

82. 82

83. 83
•LPF: Here, the message signal which is in the continuous time form, is allowed to
pass through a low pass filter (LPF). This LPF whose cutoff frequency is fm eliminates
the high-frequency components of the signal and passes only the frequency
components that lie below fm.
•Sampler: The output of the LPF is then fed to a sampler where the analog input
signal is sampled at regular intervals. The sampling of the signal is done at the rate
of fs. This sampling frequency is so selected that it must follow the sampling
theorem that is expressed as:
fs ≥ 2fm
The output of the sampler is a signal that is discrete time continuous amplitude
signal denoted as nTs which is nothing but a PAM signal.
Quantizer: A quantizer is a unit that rounds off each sample to the nearest discrete
level. The sampler provides a continuous range signal and hence still an analog one.
The quantizer performs the approximation of each sample thus assigning it a
particular discrete level.
As it basically rounds off the value to a certain level this shows some variation by
the actual amount. Thus we can say, quantizing a signal introduces some distortion
or noise into it. This is known as quantization error.

84. BDG(xx) 84
Encoder: An encoder performs the conversion of the
quantized signal into binary codes. This unit generates a
digitally encoded signal which is a sequence of binary
pulses that acts as the modulated output.
Transmission path in a PCM system
• A PCM system has a better control over signal
distortion introduced during transmission through the
channel than other systems.
• PCM achieves low signal distortion by employing
regenerative receivers along the transmission path.
• The channel introduces distortion in the signal during
transmission.
• This distortion is eliminated by the regenerator in order
to provide a distortionless PCM signal. Resultantly,
enhancing the transmission ability of the system.

85. 85
• The PCM signal when provided to the regenerative repeater,
• the equalizer circuit at the beginning performs the reshaping of the distorted
signal.
• At the same time, the timing circuit generates a pulse train that is a derivative
of input PCM pulses.
• This pulse train is then utilized by the decision-making device in order to
sample the PCM pulses.
• This sampling is done at the instant where maximum SNR can be achieved.
• In this way, the decision-making device generates the distortionless PCM wave.

86. 86
PCM Receiver:
•Regenerator: A regenerative repeater is placed at the receiving end also so as to have an
exact PCM transmitted signal. Here, also the regenerator works in a similar manner as that
when employed in the transmission path. It eliminates the channel induced noise and
reshapes the pulse.
•DAC and Sampler: Digital to analog converter performs the conversion of digital signal
again into its analog form by making use of the sampler. As the actual message signal was
analog thus at the receiver end there is a necessity to again convert it into its original form.
•LPF: The sampler generates analog signal but that is not the original message signal. Thus,
the output of the sampler is fed to the LPF having cutoff frequency fm. This is sometimes
termed as the reconstruction filter that produces the original message signal.
The process done at the transmitter is somewhat reversed at the receiver in order to
generate the original analog message signal

87. Transmission bandwidth in Pulse Code Modulation:
• It is associated with a number of bits per sample.
• If the number of bits per sample increases, the bandwidth also
increases.
• In order to have a good approximation, a large number of levels
must be used but that will lead to a larger bandwidth requirement.
Let us consider each quantizer level is represented by ‘n’ binary digits.
Then the levels represented by n binary digits is given as,
q = 2n
: q is the digital level of the quantizer
Every sample is changed into n bits, thus, a number of bit per sample
is ‘n’.
As we have already discussed the number of samples per second is fs.
Hence the number of bits per second which is also termed as
signalling rate is given as,
r = n fs
As transmission bandwidth is half the signalling rate,
hence, r = nfs
But we know, fs ≥ 2fm Thus the bandwidth of the PCM system is ,
BW ≥ n fm

88. 88
Advantages of PCM
1.Immune to channel induced noise and distortion.
2.Repeaters can be employed along the transmitting channel.
3.Encoders allow secured data transmission.
4.It ensures uniform transmission quality.
Disadvantages of PCM
1.Pulse code modulation increases the transmission bandwidth.
2.A PCM system is somewhat more complex than another system.
Thus , we can conclude that a PCM system, transmits data in a coded format, that
ensures secured transmission. But, this at the same time needs decoding system in
order to reproduce exact message signal that increases system complexity.

89.  Applications:
 Low speed voice band data comm. modems
 High speed data transmission systems
 Digital microwave & satellite comm. systems
 PCS (personal communication systems)
telephone

90. • Encryption is the process by which a readable message is
converted to an unreadable form to prevent unauthorized parties
from reading it.
• Decryption is the process of converting an encrypted message
back to its original (readable) format.
• The original message is called the plaintext message.
• The encrypted message is called the ciphertext message.
Digital encryption algorithms work by manipulating the digital
content of a plaintext message mathematically, using an encryption
algorithm and a digital key to produce a ciphertext version of the
message. The sender and recipient can communicate securely if the
sender and recipient are the only ones who know the key.

91. Encryption is the process of converting normal message (plaintext) into
meaningless message (Ciphertext). Whereas Decryption is the process of
converting meaningless message (Ciphertext) into its original form (Plaintext).
The major distinction between secret writing associated secret writing is that
the conversion of a message into an unintelligible kind that’s undecipherable
unless decrypted. whereas secret writing is that the recovery of the first
message from the encrypted information.

93.  Above fig. 1 shows the block diagram of data encryption
and decryption.
 In encryption process, encryption algorithm is applied to
the original text, which transforms the original text into the
encrypted or cipher text.
 During decryption process, decryption algorithm is applied
to the encrypted text to get back the original text. Same key
is used for both processes.

94.  Shared Key and Public Key Encryption
 SKIP uses a combination of shared key cryptography and public key
cryptography to protect messages sent between hosts. SKIP hosts use
shared traffic keys that change frequently to encrypt data sent from one
host to another. To protect these shared traffic keys, SKIP hosts use the
public key to calculate an implicit shared secret, which they use to
encrypt the shared traffic keys, keeping network communication
secure.
 Shared Key Encryption
 Shared key encryption uses one key to encrypt and decrypt messages.
For shared key cryptography to work, the sender and the recipient of a
message must both have the same key, which they must keep secret
from everybody else. The sender uses the shared key to encrypt a
message, shown in the following figure, and then sends the ciphertext
message to the recipient.

95. To be transmitted, Information (Data)
must be transformed to electromagnetic
signals.

96.  Cycle - One complete occurrence of a
repeating wave (periodic signal) such as
one positive and one negative
alternation of a sine wave.
 Frequency - the number of cycles of a
signal that occur in one second.
 Period - the time distance between two
similar points on a periodic wave.
 Wavelength - the distance traveled by an
electromagnetic (radio) wave during one
period.

97. One cycle
time
PERIOD AND FREQUENCY
COMPARED
Frequency = f = 1/T
T = One period

98. +
0 time
distance
Frequency and wavelength compared

f = 1/T
T

99.  = wavelength in meters
f = frequency in MHz
 = 300/f
f = 300/

100. ELF
10
3
m
10
7
m
10
4
m
10
5
m
10
6
m
10
m
1
m
10
-1
m
10
-2
m
10
-3
m
10
-4
m
10
2
m
300
Hz
30
Hz
30
kHz
3
kHz
300
kHz
30
MHz
3
MHz
300
MHz
3
GHz
300
GHz
30
GHz
THE ELECTROMAGNETIC SPECTRUM
FROM 30 HZ TO 300 GHZ
UHF
VHF
HF
MF
LF
VLF
VF SHF EHF
Frequency
Wavelength
Millimeter
waves
( = 300/f)
(f = 300/)

101.  Extremely Low Frequencies - 30 to 300 Hz
 Voice Frequencies - 300 to 3000 Hz
 Very Low Frequencies - 3 kHz to 30 kHz
 Low Frequencies - 30 kHz to 300 kHz
 Medium Frequencies - 300 kHz to 3 MHz

102.  High Frequencies
- 3 MHz to 30 MHz
 Very High Frequencies
- 30 MHz to 300 MHz
 Ultra High Frequencies
- 300 MHz to 3 GHz
(1 GHz and above =
microwaves)
 Super High Frequencies
- 3 GHz to 30 GHz
 Extremely High Frequencies
- 30 GHz to 300 GHz

103. Srno Freqn band Wavelength application
1 30Hz-300Hz
Extremely low freq
104km-103km Power transmission
2 300Hz-3KHz
Voice freq
103km-100km Audio application
3 3KHz-30KHz
Very low frequency
100km-10km Submarine communication,
Navy, military communication
4 30KHz-300KHz
low frequency
10km-1km
Long wave
Aeronautical and marine navigation acts as sub
carrier
5 300KHz-30MHz
Medium frequency
1km-100m
Medium waves
AM radio broadcast , marine and aeronautical
Communication
6 3MHz-300MHz
High freq
100m-10m
Short wave
Short wave transmission
7 30MHz-300MHz
Very high freq
10m-1m TV broadcasting ,FM broadcasting
8 300MHz-3GHz
Ultra high freq
1m -10cm
Microwave
UHF TV channel cellular phones, military
Application
9 3GHz-30GHz
Super high freq
10-1m to 10-2m Satellite communication
Radar
10 30GHz-300GHz
Extremely high freq
10-2m to 10-3m Satellite and specific radar

104. 10
-3
m
10
-4
m
300
GHz
Millimeter
waves
THE ELECTROMAGNETIC
SPECTRUM ABOVE 300 GHZ
Wavelength
0.8
x
10
-6
m
0.4
x
10
-6
m
Infrared
Visible
Ultraviolet
X-rays
Gamma
rays
Cosmic
rays
10
-5
m

105.  Infrared - 0.7 to 10 micron
 Visible light - 0.4 to 0.8 micron
 Ultraviolet - Shorter than 0.4 micron
Note: A micron is one millionth of a meter.
Light waves are measured and expressed
in wavelength rather than frequency.

106. Electromagnetic Spectrum

107.  Signal bandwidth:
 Bandwidth is that portion of electromagnet spectrum occupied
by a signal.
 It is defined as the frequency range over which an information
signal is transmitted.
 More specifically bandwidth (BW) is the difference between the
upper and lower frequency limits of the signal.
 Channel bandwidth:
 Definition: - Channel bandwidth is defined as the maximum
frequency; it can allow to pass through it without attenuating it
and without distorting the shape of a signal
 If the medium has less bandwidth than required then signal
distortion takes place.

108.  Signal bandwidth:
 Bandwidth is that portion of electromagnet
spectrum occupied by a signal.
 It is defined as the frequency range over which
an information signal is transmitted.
 More specifically bandwidth (BW) is the difference
between the upper and lower frequency limits of
the signal.

109. Definition: - Channel bandwidth is defined as
the maximum frequency; it can allow to pass
through it without attenuating it and without
distorting the shape of a signal
If the medium has less bandwidth than
required then signal distortion takes place.

111.  In any discussion of communication systems and the
receiver performance, the term signal to noise ratio is
used.
 The quantitative way to measure the effect of noise is
to use the signal to noise (s/n) ratio. S/N ratio is
simply a number that indicates the relative strengths
of the signal and noise.

 S/N Ratio (SNR) =
𝒂𝒗𝒆𝒓𝒂𝒈𝒆 𝒊𝒏𝒑𝒖𝒕 𝒔𝒊𝒈𝒏𝒂𝒍 𝒑𝒐𝒘𝒆𝒓
𝒂𝒗𝒆𝒓𝒂𝒈𝒆 𝒊𝒏𝒑𝒖𝒕 𝒏𝒐𝒊𝒔𝒆 𝒑𝒐𝒘𝒆𝒓

 If the SNR is low, the communication will be less
reliable. The design of communication equipment has
as its objective to produce the highest SNR possible

112.  The speed of data transfer is indicated by the
no of bits per sec (bits/sec).
 The bit rate is reciprocal of the time duration
of one bit (TD).
 Bit rate (Data rate) (bits/sec) =
1
𝐵𝑖𝑡 𝑖𝑛𝑡𝑒𝑟𝑣𝑎𝑙 (𝑇𝑏)
 Def: The number of bits which can be
transmitted in a second is called as bit rate.

113.  Baud is unit of signaling speed or modulation
rate or the rate of symbol transmission.
 It indicates the rate at which a signal level
change over a given period of time.

114.  Channel capacity is defined as the maximum
data rate at which the digital data can be
transmitted over the communication channel.
 The various concept related to channel
capacity are as follows
 Data rate
 Bandwidth
 Noise
 Error rate

116.  Bluetooth wireless technology is a short-range
communications technology intended to replace the cables
connecting portable and/or fixed devices while maintaining
high levels of security.
 The key features of Bluetooth technology are robustness, low
power, and low cost.
 The Bluetooth specification defines a uniform structure for a
wide range of devices to connect and communicate with each
other.
 Bluetooth enabled electronic devices connect and
communicate wirelessly through short-range, ad hoc networks
known as piconets. Each device can simultaneously
communicate with up to seven other devices within a single
piconet.

117.  Piconet is a Bluetooth network that consists of one primary (master) node and
seven active secondary (slave) nodes.
 Thus, piconet can have up to eight active nodes (1 master and 7 slaves) or
stations within the distance of 10 meters.
 There can be only one primary or master station in each piconet.
 The communication between the primary and the secondary can be one-to-one
or one-to-many.
 All communication is between master and a slave. Slave-slave communication
is not possible.
 In addition to seven active slave station, a piconet can have up to 255 parked
nodes. These parked nodes are secondary or slave stations and cannot take part
in communication until it is moved from parked state to active state.

119.  Scatternet is formed by combining various piconets.
 A slave in one piconet can act as a master or primary in
other piconet.
 Such a station or node can receive messages from the
master in the first piconet and deliver the message to its
slaves in other piconet where it is acting as master. This
node is also called bridge slave.
 Thus a station can be a member of two piconets.
 A station cannot be a master in two piconets.

120. • In laptops, notebooks and wireless PCs
• In mobile phones and PDAs (personal digital assistant).
• In printers.
• In wireless headsets.
• In wireless PANs (personal area networks) and even LANs
(local area networks)
• To transfer data files, videos, and images and MP3 or MP4.
• In wireless peripheral devices like mouse and keyboards.
• In data logging equipment.
• In the short-range transmission of data from sensors devices to
sensor nodes like mobile phones.

121.  RFID (Radio Frequency Identification)
 The origins of RFID technology lie in the 19th century when there are great inventions taken place like, Michael
Faraday’s discovery of electronic inductance, James Clerk Maxwell’s formulation of equations describing
electromagnetism, and Heinrich Rudolf Hertz’s experiments validating Faraday and Maxwell’s predictions.
 It’s a non-contact technology that’s broadly used in many industries for tasks such as personnel tracking, access
control, supply chain management, books tracking in libraries, tollgate systems and so on.
 RFID tags are microchips that attach to an antenna and are designed to receive signals from tags and send
Signals to RFID readers.
 An ADC (Automated Data Collection) technology that:
◦ uses radio-frequency waves to transfer data between a reader and a movable item to identify, categorize,
track.
◦ Is fast and does not require physical sight or contact between reader/scanner and the tagged item.
◦ Performs the operation using low cost components.
◦ Attempts to provide unique identification and backend integration that allows for wide range of applications.
 Other ADC technologies: Bar codes, OCR.

122. Ethernet
RFID
Reader
RFID Tag RF Antenna Network Workstation

123. RFID systems: logical view
3
2 4 5 6 7 8
Application
Systems
RF
Write data
to RF tags
Read
Manager
Transaction
Data Store
Items with
RF Tags
Reader
Antenna
Antenna
1
Tag/Item
Relationship
Database 9
ONS
Server
11
Other Systems
RFID Middleware
Tag Interfaces

124.  RFID system consists of two main components, a transponder or a tag which is located on the
object that we want to be identified, and a transceiver or a reader.
 The RFID reader consist of a radio frequency module, a control unit and an antenna coil which
generates high frequency electromagnetic field.
 On the other hand, the tag is usually a passive component, which consist of just an antenna and an
electronic microchip, so when it gets near the electromagnetic field of the transceiver, due to
induction, a voltage is generated in its antenna coil and this voltage serves as power for the
microchip.

125.  Now as the tag is powered, it can extract the transmitted message from
the reader, and for sending message back to the reader, it uses a
technique called load manipulation.
 Switching on and off a load at the antenna of the tag will affect the
power consumption of the reader’s antenna which can be measured as
voltage drop.
 This changes in the voltage will be captured as ones and zeros and
that’s the way the data is transferred from the tag to the reader.
 There’s also another way of data transfer between the reader and the
tag, called backscattered coupling.
 In this case, the tag uses part of the received power for generating
another electromagnetic field which will be picked up by the reader’s
antenna.

126.  We know that the Radio frequency range is from 3 kHz to 300 GHz but the RFID
generally uses Radio frequencies in ranges within the Radio frequency (RF) band
categorized as below:
• Low frequency RFID: Its range is in between 30 kHz to 500 kHz but the exact frequency
used by it is 125 kHz. Its detection range is 10 -15 cm.
• High frequency RFID: Its range is in between 3 MHz to 30 MHz, the exact frequency
used by the module is 13.56 MHz. Its detection range is up to 1.5 meters.
• Ultra High frequency RFID: Its range is 300 MHz to 960 MHz but the exact frequency
used is 433 MHz. The detection range is up to 20 meters.
• Microwave RFID: It uses a frequency of 2.45 GHz and the detection range is up to 100
meters far.
 So based on the application and the detection range required the suitable RFID should be
chosen. The detection range varies based on the size of antenna and tuning.

131. Tags can be attached to almost anything:
◦ Items, cases or pallets of products, high value goods
◦ vehicles, assets, livestock or personnel
Passive Tags
◦ Do not require power – Draws from Interrogator Field
◦ Lower storage capacities (few bits to 1 KB)
◦ Shorter read ranges (4 inches to 15 feet)
◦ Usually Write-Once-Read-Many/Read-Only tags
◦ Cost around 25 cents to few dollars
Active Tags
◦ Battery powered
◦ Higher storage capacities (512 KB)
◦ Longer read range (300 feet)
◦ Typically can be re-written by RF Interrogators
◦ Cost around 50 to 250 dollars

133. RFID 2005
IIT Bombay
13
3
… and a chip
attached to it
… on a substrate
e.g. a plastic
foil ...
an antenna,
printed,etched
or stamped ...
A paper label
with RFID inside
Source: www.rfidprivacy.org

134.  Read-only tags
◦ Tag ID is assigned at the factory during manufacturing
 Can never be changed
 No additional data can be assigned to the tag
 Write once, read many (WORM) tags
◦ Data written once, e.g., during packing or manufacturing
 Tag is locked once data is written
 Similar to a compact disc or DVD
 Read/Write
◦ Tag data can be changed over time
 Part or all of the data section can be locked

135.  Reader functions:
◦ Remotely power tags
◦ Establish a bidirectional data link
◦ Inventory tags, filter results
◦ Communicate with networked server(s)
◦ Can read 100-300 tags per second
 Readers (interrogators) can be at a fixed point such
as
◦ Entrance/exit
◦ Point of sale
 Readers can also be mobile/hand-held

136.  Assembly Line
▪ Shipping Portals
▪ Handheld Applications
Bill of Lading
Material Tracking
Wireless

137.  Manufacturing and Processing
◦ Inventory and production process monitoring
◦ Warehouse order fulfillment
 Supply Chain Management
◦ Inventory tracking systems
◦ Logistics management
 Retail
◦ Inventory control and customer insight
◦ Auto checkout with reverse logistics
 Security
◦ Access control
◦ Counterfeiting and Theft control/prevention
 Location Tracking
◦ Traffic movement control and parking management
◦ Wildlife/Livestock monitoring and tracking

138.  Add an RFID tag to all
items in the grocery.
 As the cart leaves the
store, it passes through an
RFID transceiver.
 The cart is rung up in
seconds.

139. 1. Tagged item is removed
from or placed in
“Smart Cabinet”
3. Server/Database is
updated to reflect item’s
disposition
4. Designated individuals
are notified regarding
items that need
attention (cabinet and
shelf location, action
required)
2. “Smart Cabinet”
periodically
interrogates to assess
inventory
Passive
read/write tags
affixed to caps
of containers
Reader antennas placed under each shelf

140.  Recognizes what’s been put in it
 Recognizes when things are removed
 Creates automatic shopping lists
 Notifies you when things are past their expiration
 Shows you the recipes that most closely match what
is available

141.  Track products
through their entire
lifetime.

142.  “Smart” appliances:
◦ Closets that advice on style depending on clothes available.
◦ Ovens that know recipes to cook pre-packaged food.
 “Smart” products:
◦ Clothing, appliances, CDs, etc. tagged for store returns.
 “Smart” paper:
◦ Airline tickets that indicate your location in the airport.
 “Smart” currency:
◦ Anti-counterfeiting and tracking.
 “Smart” people ??

143.  0th Generation
 Pre-cell phone mobile telephony technology in
1970s, such as radio telephones that some had in cars
before the arrival of cell phones.
 Communication was possible through voice only.
 These mobile telephones were usually mounted in
cars or trucks.
 Technologies :
PTT(Push to Talk)
MTS (Mobile Telephone System)
IMTS (Improved MTS)

145.  First generation (1G) of cellular systems introduced in the late 1970s and early 1980s
 Evolved out of the growing number of mobile communication users
 The use of semiconductor technology and microprocessors made mobile devices smaller and
lighter
 It's Speed was up to 2.4kbps.
 1G systems were based on analogue communication in the 900MHz frequency range
 This system is used for Voice transmission only – easy to tap
 The most prominent 1G systems are
 Advanced Mobile Phone Systems (AMPS) - America
 Nordic Mobile Telephone (NMT) - France
 Total Access Communications System (TACS) – UK
 Jan 1985 Vodafone introduced the TACS system

146.  Splits allocated spectrum into
30 channels, each channel is
30kHz
 Allocates a single channel to
each established phone call
 The channel is agreed with the
serving base-station before
transmission takes place on
agreed and reserved channel
 Channel used by device to
transmit and receive on this
channel
 Ineffective methods since each
analogue channel can only be
used by one user at a time
 FDMA does not take full
advantage of available
spectrum
Drawbacks of 1G System
 Poor Voice Quality
 Poor Battery Life
 Large Phone Size
 No Security
 Limited Capacity
 Poor Handoff Reliability
Frequency Division Multiple Access (FDMA)

147.  Development driven by the need to improve speech quality, system capacity, coverage and security
 First system that used digital transmission
 Examples of Second Generation (2G) cellular systems ...
 Digital AMPS (D-AMPS) (Advanced Mobile Phone Service) in the US,
 Personal Digital Communication (PDC) in Japan,
 Intrim Standard `94 (IS-94) in Korea and the US
 Global System for Mobile Communication (GSM)
 The GSM standard was defined by ETSI (European Telecommunications Standards Institute)
in 1989
 Originally called “ Groupe Spéciale Mobile which later changed to the English version
 A majority of countries over the world have adopted GSM900 and the GSM1800 which are all
based on the same original GSM specification.
 The US uses an additional GSM 1900

148.  2G technology refers to the 2nd generation which is based on GSM.
 It was launched in Finland in the year 1991.
 2G network use digital signals.
 It’s data speed was up to 64kbps.
 Features Includes:
 It enables services such as text messages, picture messages and MMS
(multi media message).
 It provides better quality and capacity .
▪ 2G requires strong digital signals to help mobile phones work. If there is no
network coverage in any specific area , digital signals would weak.
▪ These systems are unable to handle complex data such as Videos.

149.  2.5G is a technology between the second (2G) and third (3G)
generation of mobile telephony.
 2.5G is sometimes described as 2G Cellular Technology
combined with GPRS.
 Features Includes:
 Phone Calls
 Send/Receive
 E-mail Messages
 Web Browsing
 Speed : 64-144 kbps
 Camera Phones
 Take a time of 6-9 mins to download a 3 mins Mp3 song

150.  2G networks were built mainly for voice data and slow transmission. Due to
rapid changes in user expectation, they do not meet today's wireless needs.
 3G networks provide the ability to transfer voice data and non-voice data over
the same network simultaneously.
 Applications : Internet, e-mail, fax, e-commerce, music, video clips, and
videoconferencing.
 The aim of the 3G is to allow for more coverage and growth with minimum
investment.
 3G technology refer to third generation which was introduced in year 2000s.
 Data Transmission speed increased from 144kbps- 2Mbps.
 Typically called Smart Phones and features increased its bandwidth and data
transfer rates to accommodate web-based applications and audio and video files.

151. • Universal Mobile Telecommunications System (UMTS)
• UMTS is an upgrade from GSM via GPRS or EDGE.
• Combines the infrastructure of the GSM network with superior
technology of the CDMA air interface. The standard was referred
to as IMT-2000.
• The standardization work for UMTS is carried out by Third
Generation Partnership Project (3GPP)
• Data rates of UMTS are:
– 144 kbps for rural
– 384 kbps for urban outdoor
– 2048 kbps for indoor and low range outdoor
 UMTS-specific network elements—User equipment (UE) and
UMTS terrestrial radio access network (UTRAN) elements.

152.  W-CDMA is the most common radio interface for UMTS
systems.
 W-CDMA uses 5MHz of bandwidth for each channel.
 Several thousand users can be supported in each cell site.
 Offers 11Mbps download speed.
 Fast power control (PC) – Reduces the impact of channel
fading and minimizes the interference.
 Soft handover – Improves coverage, decreases interference.
 Market share for WCDMA is growing rapidly – More than
340 million WCDMA subscribers
 WCDMA Operates in the same manner as the CDMA used
in the US
 CDMA allows multiple users to communicate at the same
time over the same frequency

153.  Each of the devices is given a “Chipping code” this is known by the device and the
base station.
 This chipping code is then used to identify the signal and allows the BS to receive
the signal
 The chipping code is used to adjust the frequency of data transferred during the
transfer
 The essential point of CDMA is the use of power control
 W-CDMA – Wideband CDMA operates the same but this takes
place over a wider area of frequency
 UMTS uses 5MHz for the signal
 CDMA (narrowband) uses 200 KHz
 These communications are secure by the nature that unless the
chipping code is known, the sequence of the data can not be
known
 Communications can take place as soon as the device is ready
and frequency reuse factor is now one

154.  High Speed Packet Access (HSPA) is an amalgamation of two mobile
telephony protocols, High Speed Downlink Packet Access (HSDPA)
and High Speed Uplink Packet Access (HSUPA), that extends and
improves the performance of existing WCDMA protocols.
 3.5G introduces many new features that will enhance the UMTS
technology in future. 1xEV-DV already supports most of the features
that will be provided in 3.5G.
These include:
- Adaptive Modulation and Coding
- Fast Scheduling
- Backward compatibility with 3G
- Enhanced Air Interface

155.  4G technology refer to or short name of fourth Generation which was started from late 2000s.
 Capable of providing 100Mbps – 1Gbps speed.
 The next generations of wireless technology that promises higher data rates and expanded multimedia
services.
 Capable to provide speed 100Mbps-1Gbps. High QOS (Quality of Service) and High Security Provide
any kind of service at any time as per user requirements, anywhere.
• LTE stands for “Long Term Evolution”
• Fourth-generation (4G) cellular technology from 3GPP
• Deployed worldwide
• 4G LTE: First global standard
– Increased speed
– IP-based network (All circuits are gone/fried!)
– New air interface: OFDMA (Orthogonal Frequency-Division MultipleAccess), MIMO (multiple
antennas)
• Also includes duplexing, timing, carrier spacing, coding...
– New service paradigm (e.g., VoLTE)

156. 2G
Telecomm
Infrastructure
IP-based Internet
• Circuit-
switching
for voice
• Packet-
switching for
everything
• IP-based
3G 4G
• Circuit-
switching for
voice
• Packet-
switching for
data

157.  5G simply refers to the next and newest mobile wireless standard based on the IEEE
802.11ac standard of broadband technology.
 5G aims at a higher capacity than current 4G LTE, allowing a higher number of mobile broadband
users per area unit.
 5G research and development also aim at the improved support of machine to machine
communication, also known as the Internet of things.
 aiming at a lower cost, lower battery consumption, and lower latency and to increase the security
and connectivity for a large community.
 5G will utilize the advance access technologies such as Beam Division MultipleAccess (BDMA)
and Non and quasi-orthogonal or Filter Bank Multicarrier (FBMC) MultipleAccess.
 5G operates on 3 different spectrum bands.
1. Low-band spectrum – Expect peak speeds up to 100Mbps
2. mid-band spectrum – Expect peak speeds up to 1Gbps
3. high-band spectrum – Expect peak speeds up to 10Gbps

158. • High & increased peak bit rate (Up to 10Gbps connections to endpoints in
the field)
• Larger data volume per unit area (i.e. high system spectral efficiency)
• High capacity to allow more devices connectivity concurrently and
instantaneously (100 percent coverage)
• More bandwidth
• Lower battery consumption
• Better connectivity irrespective of the geographic region where you are in
• A larger number of supporting devices (10 to 100x number of connected
devices)
• Lower cost of infrastructural development
• Higher reliability of the communications (One millisecond end-to-end
round trip delay)