SlideShare a Scribd company logo
 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
 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
https://www.youtube.com/watch?v=1J
ZG9x_VOwA
 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
 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
 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
 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.
 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
 Have you ever pictured yourself living in a
world without any communication system?
 Importance of communication:
exchange of information between two parties
separated in distances in a more faster and
reliable way.
2 main BARRIERS: Language & Distances
 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
 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
 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
https://www.youtube.com/watch?v=4Z
1BIeje_ko
 Information
➢The communication system exists to convey a
message.
➢Message comes from information source
➢Information forms - audio, video, text or data
 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
 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
 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
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.
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.
Digital
Analog
 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.
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)
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.
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
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)
https://www.youtube.com/watch?v=t_
aqmvn8mUg
https://www.youtube.com/watch?v=L
MRSS7ZYM50
Analog Signals
◦ An analog signal is a smoothly and continuously
varying voltage or current. Examples are:
 Sine wave
 Voice
 Video (TV)
Figure 1-5: Analog signals (a) Sine wave “tone.” (b) Voice. (c) Video (TV) signal.
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)
Figure 1-6: Digital signals (a) Telegraph (Morse code). (b) Continuous-wave
(CW) code. (c) Serial binary code.
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.
 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.
 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.
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
 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.
 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
 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.
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.

•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.
 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
 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.
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.
 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’.
 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’.
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.)
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 .
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.
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
- 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
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
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
Components of PCM Encoder
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
Note
- According to the Nyquist theorem,
the sampling rate must be at least 2 times the
highest frequency contained in the signal.
68
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
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
Quantization Levels
- The midpoint of each zone is assigned a value from
0 to L-1 (resulting in L values)
n
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
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
Assigning Codes to Zones
n
Each zone is assigned a binary code
0
1
2
3
00
01
10
11
75
Assigning Codes to Zones
Use one of the line code scheme to get the digital signal
 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.
 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.
•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
82
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.
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
• 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
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
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
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.
 Applications:
 Low speed voice band data comm. modems
 High speed data transmission systems
 Digital microwave & satellite comm. systems
 PCS (personal communication systems)
telephone
• 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.
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.
 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.
 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.
To be transmitted, Information (Data)
must be transformed to electromagnetic
signals.
 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.
One cycle
time
PERIOD AND FREQUENCY
COMPARED
Frequency = f = 1/T
T = One period
+
0 time
distance
Frequency and wavelength compared

f = 1/T
T
 = wavelength in meters
f = frequency in MHz
 = 300/f
f = 300/
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/)
 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
 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
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
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
 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.
Electromagnetic Spectrum
 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.
 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.
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.
 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
 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.
 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.
 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
 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.
 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.
 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.
• 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.
 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.
Ethernet
RFID
Reader
RFID Tag RF Antenna Network Workstation
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
 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.
 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.
 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.
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
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
 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
 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
 Assembly Line
▪ Shipping Portals
▪ Handheld Applications
Bill of Lading
Material Tracking
Wireless
 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
 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.
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
 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
 Track products
through their entire
lifetime.
 “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 ??
 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)
 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
 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)
 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
 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.
 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
 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.
• 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.
 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
 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
 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
 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)
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
 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
• 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)

More Related Content

Similar to updated notes cds UNIT 6 and 7 communicationppt.pdf

Introduction to communication system lecture1
Introduction to communication system lecture1Introduction to communication system lecture1
Introduction to communication system lecture1
Jumaan Ally Mohamed
 
Lecture 1.pptx
Lecture 1.pptxLecture 1.pptx
Lecture 1.pptx
AamraArshad1
 
Communication model
Communication modelCommunication model
Communication model
DIKSHA_LAHRANI
 
Introduction to-telecommunication-rf
Introduction to-telecommunication-rfIntroduction to-telecommunication-rf
Introduction to-telecommunication-rf
Terra Sacrifice
 
Communication system 1 chapter 1 ppt
Communication system 1 chapter  1 pptCommunication system 1 chapter  1 ppt
Communication system 1 chapter 1 ppt
BetelihemMesfin1
 
Data Communication & Networks
Data Communication & NetworksData Communication & Networks
Data Communication & Networks
MiXvideos
 
Communication System (3).ppt
Communication System (3).pptCommunication System (3).ppt
Communication System (3).ppt
Prathamesh508521
 
Chapter 2.1.pptx
Chapter 2.1.pptxChapter 2.1.pptx
Chapter 2.1.pptx
Tekle12
 
Chapter 2.1.pptx
Chapter 2.1.pptxChapter 2.1.pptx
Chapter 2.1.pptx
Tekle12
 
Comm introduction
Comm introductionComm introduction
Comm introduction
Hattori Sidek
 
Comm introduction
Comm introductionComm introduction
Comm introduction
mkazree
 
Optical Fiber communication
Optical Fiber communicationOptical Fiber communication
Optical Fiber communication
Eklavya Singh
 
dc1.pdf
dc1.pdfdc1.pdf
Wolkite polytechnic college ICT Department
Wolkite polytechnic college ICT Department Wolkite polytechnic college ICT Department
Wolkite polytechnic college ICT Department
Wolkite polytechnic college
 
Wireless communication
Wireless communicationWireless communication
Wireless communication
Mukesh Chinta
 
Introduction to communication systems
Introduction to communication systemsIntroduction to communication systems
Introduction to communication systems
Mohsen Sarakbi
 
NETWORKIN2
NETWORKIN2NETWORKIN2
Computer networks and internet www.it-workss.com
Computer networks and internet   www.it-workss.comComputer networks and internet   www.it-workss.com
Computer networks and internet www.it-workss.com
Varunraj Kalse
 
Data Communication Principles
Data Communication PrinciplesData Communication Principles
Data Communication Principles
mekind
 
Communication_System_presentation_Slides.pptx
Communication_System_presentation_Slides.pptxCommunication_System_presentation_Slides.pptx
Communication_System_presentation_Slides.pptx
renur18
 

Similar to updated notes cds UNIT 6 and 7 communicationppt.pdf (20)

Introduction to communication system lecture1
Introduction to communication system lecture1Introduction to communication system lecture1
Introduction to communication system lecture1
 
Lecture 1.pptx
Lecture 1.pptxLecture 1.pptx
Lecture 1.pptx
 
Communication model
Communication modelCommunication model
Communication model
 
Introduction to-telecommunication-rf
Introduction to-telecommunication-rfIntroduction to-telecommunication-rf
Introduction to-telecommunication-rf
 
Communication system 1 chapter 1 ppt
Communication system 1 chapter  1 pptCommunication system 1 chapter  1 ppt
Communication system 1 chapter 1 ppt
 
Data Communication & Networks
Data Communication & NetworksData Communication & Networks
Data Communication & Networks
 
Communication System (3).ppt
Communication System (3).pptCommunication System (3).ppt
Communication System (3).ppt
 
Chapter 2.1.pptx
Chapter 2.1.pptxChapter 2.1.pptx
Chapter 2.1.pptx
 
Chapter 2.1.pptx
Chapter 2.1.pptxChapter 2.1.pptx
Chapter 2.1.pptx
 
Comm introduction
Comm introductionComm introduction
Comm introduction
 
Comm introduction
Comm introductionComm introduction
Comm introduction
 
Optical Fiber communication
Optical Fiber communicationOptical Fiber communication
Optical Fiber communication
 
dc1.pdf
dc1.pdfdc1.pdf
dc1.pdf
 
Wolkite polytechnic college ICT Department
Wolkite polytechnic college ICT Department Wolkite polytechnic college ICT Department
Wolkite polytechnic college ICT Department
 
Wireless communication
Wireless communicationWireless communication
Wireless communication
 
Introduction to communication systems
Introduction to communication systemsIntroduction to communication systems
Introduction to communication systems
 
NETWORKIN2
NETWORKIN2NETWORKIN2
NETWORKIN2
 
Computer networks and internet www.it-workss.com
Computer networks and internet   www.it-workss.comComputer networks and internet   www.it-workss.com
Computer networks and internet www.it-workss.com
 
Data Communication Principles
Data Communication PrinciplesData Communication Principles
Data Communication Principles
 
Communication_System_presentation_Slides.pptx
Communication_System_presentation_Slides.pptxCommunication_System_presentation_Slides.pptx
Communication_System_presentation_Slides.pptx
 

More from shubhangisonawane6

fundamentals of digital communication Unit 5_microprocessor.pdf
fundamentals of digital communication Unit 5_microprocessor.pdffundamentals of digital communication Unit 5_microprocessor.pdf
fundamentals of digital communication Unit 5_microprocessor.pdf
shubhangisonawane6
 
Fundamentals of digital communication UNIT 3 AND 4 notes.pdf
Fundamentals of digital communication UNIT 3 AND 4 notes.pdfFundamentals of digital communication UNIT 3 AND 4 notes.pdf
Fundamentals of digital communication UNIT 3 AND 4 notes.pdf
shubhangisonawane6
 
fundamentals of digital communication unit 2 notes.pdf
fundamentals of digital communication  unit 2 notes.pdffundamentals of digital communication  unit 2 notes.pdf
fundamentals of digital communication unit 2 notes.pdf
shubhangisonawane6
 
CDS Fundamentals of digital communication system UNIT 1 AND 2.pdf
CDS Fundamentals of digital communication system UNIT 1 AND 2.pdfCDS Fundamentals of digital communication system UNIT 1 AND 2.pdf
CDS Fundamentals of digital communication system UNIT 1 AND 2.pdf
shubhangisonawane6
 
SYBSC(CS)_WCIOT_Sem-II-Unit 4 Iot Applications .pdf
SYBSC(CS)_WCIOT_Sem-II-Unit 4 Iot Applications .pdfSYBSC(CS)_WCIOT_Sem-II-Unit 4 Iot Applications .pdf
SYBSC(CS)_WCIOT_Sem-II-Unit 4 Iot Applications .pdf
shubhangisonawane6
 
SYBSC(CS)_WCIOT_Sem-II-Unit 3 IoT Architecture.pdf
SYBSC(CS)_WCIOT_Sem-II-Unit 3 IoT Architecture.pdfSYBSC(CS)_WCIOT_Sem-II-Unit 3 IoT Architecture.pdf
SYBSC(CS)_WCIOT_Sem-II-Unit 3 IoT Architecture.pdf
shubhangisonawane6
 
SYBSC(CS)_WCIOT_Sem-II-Unit 2 short range .pdf
SYBSC(CS)_WCIOT_Sem-II-Unit 2 short range .pdfSYBSC(CS)_WCIOT_Sem-II-Unit 2 short range .pdf
SYBSC(CS)_WCIOT_Sem-II-Unit 2 short range .pdf
shubhangisonawane6
 
SYBSC(CS)_WCIOT_Sem-II-Unit 1 Overview of wireless communication.pdf
SYBSC(CS)_WCIOT_Sem-II-Unit 1 Overview of wireless communication.pdfSYBSC(CS)_WCIOT_Sem-II-Unit 1 Overview of wireless communication.pdf
SYBSC(CS)_WCIOT_Sem-II-Unit 1 Overview of wireless communication.pdf
shubhangisonawane6
 
UNIT 4 computer networking powerpoint presentation .pdf
UNIT 4 computer networking powerpoint presentation .pdfUNIT 4 computer networking powerpoint presentation .pdf
UNIT 4 computer networking powerpoint presentation .pdf
shubhangisonawane6
 
unit 4 cds computer networking notesnotes.pdf
unit 4 cds computer networking notesnotes.pdfunit 4 cds computer networking notesnotes.pdf
unit 4 cds computer networking notesnotes.pdf
shubhangisonawane6
 
ICPS operating system and services Unit 3 Notes .pdf
ICPS operating system and services Unit 3 Notes .pdfICPS operating system and services Unit 3 Notes .pdf
ICPS operating system and services Unit 3 Notes .pdf
shubhangisonawane6
 
computer devices and memory unit 2 notes.pdf
computer devices and memory unit 2 notes.pdfcomputer devices and memory unit 2 notes.pdf
computer devices and memory unit 2 notes.pdf
shubhangisonawane6
 
Introduction to Computer UNIT 1 notes.pdf
Introduction to Computer UNIT 1 notes.pdfIntroduction to Computer UNIT 1 notes.pdf
Introduction to Computer UNIT 1 notes.pdf
shubhangisonawane6
 
IS NOTES UNIT 4.pdf
IS NOTES UNIT 4.pdfIS NOTES UNIT 4.pdf
IS NOTES UNIT 4.pdf
shubhangisonawane6
 
IS notes unit 2_shubhangi Gaikar.pdf
IS notes unit 2_shubhangi Gaikar.pdfIS notes unit 2_shubhangi Gaikar.pdf
IS notes unit 2_shubhangi Gaikar.pdf
shubhangisonawane6
 
Laplace Transform_SHUBHANGI GAIKAR.pdf
Laplace Transform_SHUBHANGI GAIKAR.pdfLaplace Transform_SHUBHANGI GAIKAR.pdf
Laplace Transform_SHUBHANGI GAIKAR.pdf
shubhangisonawane6
 

More from shubhangisonawane6 (16)

fundamentals of digital communication Unit 5_microprocessor.pdf
fundamentals of digital communication Unit 5_microprocessor.pdffundamentals of digital communication Unit 5_microprocessor.pdf
fundamentals of digital communication Unit 5_microprocessor.pdf
 
Fundamentals of digital communication UNIT 3 AND 4 notes.pdf
Fundamentals of digital communication UNIT 3 AND 4 notes.pdfFundamentals of digital communication UNIT 3 AND 4 notes.pdf
Fundamentals of digital communication UNIT 3 AND 4 notes.pdf
 
fundamentals of digital communication unit 2 notes.pdf
fundamentals of digital communication  unit 2 notes.pdffundamentals of digital communication  unit 2 notes.pdf
fundamentals of digital communication unit 2 notes.pdf
 
CDS Fundamentals of digital communication system UNIT 1 AND 2.pdf
CDS Fundamentals of digital communication system UNIT 1 AND 2.pdfCDS Fundamentals of digital communication system UNIT 1 AND 2.pdf
CDS Fundamentals of digital communication system UNIT 1 AND 2.pdf
 
SYBSC(CS)_WCIOT_Sem-II-Unit 4 Iot Applications .pdf
SYBSC(CS)_WCIOT_Sem-II-Unit 4 Iot Applications .pdfSYBSC(CS)_WCIOT_Sem-II-Unit 4 Iot Applications .pdf
SYBSC(CS)_WCIOT_Sem-II-Unit 4 Iot Applications .pdf
 
SYBSC(CS)_WCIOT_Sem-II-Unit 3 IoT Architecture.pdf
SYBSC(CS)_WCIOT_Sem-II-Unit 3 IoT Architecture.pdfSYBSC(CS)_WCIOT_Sem-II-Unit 3 IoT Architecture.pdf
SYBSC(CS)_WCIOT_Sem-II-Unit 3 IoT Architecture.pdf
 
SYBSC(CS)_WCIOT_Sem-II-Unit 2 short range .pdf
SYBSC(CS)_WCIOT_Sem-II-Unit 2 short range .pdfSYBSC(CS)_WCIOT_Sem-II-Unit 2 short range .pdf
SYBSC(CS)_WCIOT_Sem-II-Unit 2 short range .pdf
 
SYBSC(CS)_WCIOT_Sem-II-Unit 1 Overview of wireless communication.pdf
SYBSC(CS)_WCIOT_Sem-II-Unit 1 Overview of wireless communication.pdfSYBSC(CS)_WCIOT_Sem-II-Unit 1 Overview of wireless communication.pdf
SYBSC(CS)_WCIOT_Sem-II-Unit 1 Overview of wireless communication.pdf
 
UNIT 4 computer networking powerpoint presentation .pdf
UNIT 4 computer networking powerpoint presentation .pdfUNIT 4 computer networking powerpoint presentation .pdf
UNIT 4 computer networking powerpoint presentation .pdf
 
unit 4 cds computer networking notesnotes.pdf
unit 4 cds computer networking notesnotes.pdfunit 4 cds computer networking notesnotes.pdf
unit 4 cds computer networking notesnotes.pdf
 
ICPS operating system and services Unit 3 Notes .pdf
ICPS operating system and services Unit 3 Notes .pdfICPS operating system and services Unit 3 Notes .pdf
ICPS operating system and services Unit 3 Notes .pdf
 
computer devices and memory unit 2 notes.pdf
computer devices and memory unit 2 notes.pdfcomputer devices and memory unit 2 notes.pdf
computer devices and memory unit 2 notes.pdf
 
Introduction to Computer UNIT 1 notes.pdf
Introduction to Computer UNIT 1 notes.pdfIntroduction to Computer UNIT 1 notes.pdf
Introduction to Computer UNIT 1 notes.pdf
 
IS NOTES UNIT 4.pdf
IS NOTES UNIT 4.pdfIS NOTES UNIT 4.pdf
IS NOTES UNIT 4.pdf
 
IS notes unit 2_shubhangi Gaikar.pdf
IS notes unit 2_shubhangi Gaikar.pdfIS notes unit 2_shubhangi Gaikar.pdf
IS notes unit 2_shubhangi Gaikar.pdf
 
Laplace Transform_SHUBHANGI GAIKAR.pdf
Laplace Transform_SHUBHANGI GAIKAR.pdfLaplace Transform_SHUBHANGI GAIKAR.pdf
Laplace Transform_SHUBHANGI GAIKAR.pdf
 

Recently uploaded

waterlessdyeingtechnolgyusing carbon dioxide chemicalspdf
waterlessdyeingtechnolgyusing carbon dioxide chemicalspdfwaterlessdyeingtechnolgyusing carbon dioxide chemicalspdf
waterlessdyeingtechnolgyusing carbon dioxide chemicalspdf
LengamoLAppostilic
 
Compexometric titration/Chelatorphy titration/chelating titration
Compexometric titration/Chelatorphy titration/chelating titrationCompexometric titration/Chelatorphy titration/chelating titration
Compexometric titration/Chelatorphy titration/chelating titration
Vandana Devesh Sharma
 
NuGOweek 2024 Ghent programme overview flyer
NuGOweek 2024 Ghent programme overview flyerNuGOweek 2024 Ghent programme overview flyer
NuGOweek 2024 Ghent programme overview flyer
pablovgd
 
ESR spectroscopy in liquid food and beverages.pptx
ESR spectroscopy in liquid food and beverages.pptxESR spectroscopy in liquid food and beverages.pptx
ESR spectroscopy in liquid food and beverages.pptx
PRIYANKA PATEL
 
The cost of acquiring information by natural selection
The cost of acquiring information by natural selectionThe cost of acquiring information by natural selection
The cost of acquiring information by natural selection
Carl Bergstrom
 
Basics of crystallography, crystal systems, classes and different forms
Basics of crystallography, crystal systems, classes and different formsBasics of crystallography, crystal systems, classes and different forms
Basics of crystallography, crystal systems, classes and different forms
MaheshaNanjegowda
 
Katherine Romanak - Geologic CO2 Storage.pdf
Katherine Romanak - Geologic CO2 Storage.pdfKatherine Romanak - Geologic CO2 Storage.pdf
Katherine Romanak - Geologic CO2 Storage.pdf
Texas Alliance of Groundwater Districts
 
Eukaryotic Transcription Presentation.pptx
Eukaryotic Transcription Presentation.pptxEukaryotic Transcription Presentation.pptx
Eukaryotic Transcription Presentation.pptx
RitabrataSarkar3
 
23PH301 - Optics - Optical Lenses.pptx
23PH301 - Optics  -  Optical Lenses.pptx23PH301 - Optics  -  Optical Lenses.pptx
23PH301 - Optics - Optical Lenses.pptx
RDhivya6
 
在线办理(salfor毕业证书)索尔福德大学毕业证毕业完成信一模一样
在线办理(salfor毕业证书)索尔福德大学毕业证毕业完成信一模一样在线办理(salfor毕业证书)索尔福德大学毕业证毕业完成信一模一样
在线办理(salfor毕业证书)索尔福德大学毕业证毕业完成信一模一样
vluwdy49
 
The debris of the ‘last major merger’ is dynamically young
The debris of the ‘last major merger’ is dynamically youngThe debris of the ‘last major merger’ is dynamically young
The debris of the ‘last major merger’ is dynamically young
Sérgio Sacani
 
Authoring a personal GPT for your research and practice: How we created the Q...
Authoring a personal GPT for your research and practice: How we created the Q...Authoring a personal GPT for your research and practice: How we created the Q...
Authoring a personal GPT for your research and practice: How we created the Q...
Leonel Morgado
 
aziz sancar nobel prize winner: from mardin to nobel
aziz sancar nobel prize winner: from mardin to nobelaziz sancar nobel prize winner: from mardin to nobel
aziz sancar nobel prize winner: from mardin to nobel
İsa Badur
 
Mending Clothing to Support Sustainable Fashion_CIMaR 2024.pdf
Mending Clothing to Support Sustainable Fashion_CIMaR 2024.pdfMending Clothing to Support Sustainable Fashion_CIMaR 2024.pdf
Mending Clothing to Support Sustainable Fashion_CIMaR 2024.pdf
Selcen Ozturkcan
 
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...
Sérgio Sacani
 
The binding of cosmological structures by massless topological defects
The binding of cosmological structures by massless topological defectsThe binding of cosmological structures by massless topological defects
The binding of cosmological structures by massless topological defects
Sérgio Sacani
 
(June 12, 2024) Webinar: Development of PET theranostics targeting the molecu...
(June 12, 2024) Webinar: Development of PET theranostics targeting the molecu...(June 12, 2024) Webinar: Development of PET theranostics targeting the molecu...
(June 12, 2024) Webinar: Development of PET theranostics targeting the molecu...
Scintica Instrumentation
 
Shallowest Oil Discovery of Turkiye.pptx
Shallowest Oil Discovery of Turkiye.pptxShallowest Oil Discovery of Turkiye.pptx
Shallowest Oil Discovery of Turkiye.pptx
Gokturk Mehmet Dilci
 
Micronuclei test.M.sc.zoology.fisheries.
Micronuclei test.M.sc.zoology.fisheries.Micronuclei test.M.sc.zoology.fisheries.
Micronuclei test.M.sc.zoology.fisheries.
Aditi Bajpai
 
Describing and Interpreting an Immersive Learning Case with the Immersion Cub...
Describing and Interpreting an Immersive Learning Case with the Immersion Cub...Describing and Interpreting an Immersive Learning Case with the Immersion Cub...
Describing and Interpreting an Immersive Learning Case with the Immersion Cub...
Leonel Morgado
 

Recently uploaded (20)

waterlessdyeingtechnolgyusing carbon dioxide chemicalspdf
waterlessdyeingtechnolgyusing carbon dioxide chemicalspdfwaterlessdyeingtechnolgyusing carbon dioxide chemicalspdf
waterlessdyeingtechnolgyusing carbon dioxide chemicalspdf
 
Compexometric titration/Chelatorphy titration/chelating titration
Compexometric titration/Chelatorphy titration/chelating titrationCompexometric titration/Chelatorphy titration/chelating titration
Compexometric titration/Chelatorphy titration/chelating titration
 
NuGOweek 2024 Ghent programme overview flyer
NuGOweek 2024 Ghent programme overview flyerNuGOweek 2024 Ghent programme overview flyer
NuGOweek 2024 Ghent programme overview flyer
 
ESR spectroscopy in liquid food and beverages.pptx
ESR spectroscopy in liquid food and beverages.pptxESR spectroscopy in liquid food and beverages.pptx
ESR spectroscopy in liquid food and beverages.pptx
 
The cost of acquiring information by natural selection
The cost of acquiring information by natural selectionThe cost of acquiring information by natural selection
The cost of acquiring information by natural selection
 
Basics of crystallography, crystal systems, classes and different forms
Basics of crystallography, crystal systems, classes and different formsBasics of crystallography, crystal systems, classes and different forms
Basics of crystallography, crystal systems, classes and different forms
 
Katherine Romanak - Geologic CO2 Storage.pdf
Katherine Romanak - Geologic CO2 Storage.pdfKatherine Romanak - Geologic CO2 Storage.pdf
Katherine Romanak - Geologic CO2 Storage.pdf
 
Eukaryotic Transcription Presentation.pptx
Eukaryotic Transcription Presentation.pptxEukaryotic Transcription Presentation.pptx
Eukaryotic Transcription Presentation.pptx
 
23PH301 - Optics - Optical Lenses.pptx
23PH301 - Optics  -  Optical Lenses.pptx23PH301 - Optics  -  Optical Lenses.pptx
23PH301 - Optics - Optical Lenses.pptx
 
在线办理(salfor毕业证书)索尔福德大学毕业证毕业完成信一模一样
在线办理(salfor毕业证书)索尔福德大学毕业证毕业完成信一模一样在线办理(salfor毕业证书)索尔福德大学毕业证毕业完成信一模一样
在线办理(salfor毕业证书)索尔福德大学毕业证毕业完成信一模一样
 
The debris of the ‘last major merger’ is dynamically young
The debris of the ‘last major merger’ is dynamically youngThe debris of the ‘last major merger’ is dynamically young
The debris of the ‘last major merger’ is dynamically young
 
Authoring a personal GPT for your research and practice: How we created the Q...
Authoring a personal GPT for your research and practice: How we created the Q...Authoring a personal GPT for your research and practice: How we created the Q...
Authoring a personal GPT for your research and practice: How we created the Q...
 
aziz sancar nobel prize winner: from mardin to nobel
aziz sancar nobel prize winner: from mardin to nobelaziz sancar nobel prize winner: from mardin to nobel
aziz sancar nobel prize winner: from mardin to nobel
 
Mending Clothing to Support Sustainable Fashion_CIMaR 2024.pdf
Mending Clothing to Support Sustainable Fashion_CIMaR 2024.pdfMending Clothing to Support Sustainable Fashion_CIMaR 2024.pdf
Mending Clothing to Support Sustainable Fashion_CIMaR 2024.pdf
 
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...
 
The binding of cosmological structures by massless topological defects
The binding of cosmological structures by massless topological defectsThe binding of cosmological structures by massless topological defects
The binding of cosmological structures by massless topological defects
 
(June 12, 2024) Webinar: Development of PET theranostics targeting the molecu...
(June 12, 2024) Webinar: Development of PET theranostics targeting the molecu...(June 12, 2024) Webinar: Development of PET theranostics targeting the molecu...
(June 12, 2024) Webinar: Development of PET theranostics targeting the molecu...
 
Shallowest Oil Discovery of Turkiye.pptx
Shallowest Oil Discovery of Turkiye.pptxShallowest Oil Discovery of Turkiye.pptx
Shallowest Oil Discovery of Turkiye.pptx
 
Micronuclei test.M.sc.zoology.fisheries.
Micronuclei test.M.sc.zoology.fisheries.Micronuclei test.M.sc.zoology.fisheries.
Micronuclei test.M.sc.zoology.fisheries.
 
Describing and Interpreting an Immersive Learning Case with the Immersion Cub...
Describing and Interpreting an Immersive Learning Case with the Immersion Cub...Describing and Interpreting an Immersive Learning Case with the Immersion Cub...
Describing and Interpreting an Immersive Learning Case with the Immersion Cub...
 

updated notes cds UNIT 6 and 7 communicationppt.pdf

  • 1.
  • 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
  • 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
  • 7.
  • 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?
  • 12.
  • 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
  • 18.
  • 19.
  • 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
  • 24.
  • 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.
  • 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)
  • 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
  • 43.
  • 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
  • 46.
  • 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.
  • 48.
  • 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.
  • 54.
  • 55.
  • 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.
  • 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)
  • 79.
  • 80.
  • 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.
  • 92.
  • 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/
  • 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.
  • 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.
  • 110.
  • 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
  • 115.
  • 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.
  • 118.
  • 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.
  • 127.
  • 128.
  • 129.
  • 130.
  • 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
  • 132.
  • 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)
  • 144.
  • 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)