Communication_System_presentation_Slides.pptx

Fundamentals of Signals and Systems
Signal: a function of one or more variables that convey information on
the nature of a physical phenomenon.(or)
Anything that varies in time and space and carries information from source
to destination.
Examples: v(t), i(t), x(t),heartbeat, blood pressure, temperature, vibration.
•One-dimensional signals: function depends on a single variable, e.g.,
speech signal
•Multi-dimensional signals: function depends on two or more variables,
e.g., image
3

System: an entity or operator that manipulates one or more signals to
accomplish a function, thereby yielding new signals.
Commonly encountered systems: communications systems
Automatic speaker recoginition system
Aircraft landing system
Input signal Output signal
System
4

Introduction
Communication system is a system which describes the exchange of information or data
between two stations, i.e. between transmitter and receiver.
Communication: It is the process of conveying or transferring information from one point to
another. (Or)
It is the process of establishing connection or link between two points for information exchange.
To transmit signals in communication system, it must be first processed by several stages,
beginning from signal representation, to signal shaping until encoding and modulation.
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6
Elements of Communication Systems
 Communication:
- Transfer of information (or message)
- Involves electronic transmitting /receiving /processing
- Signal is the electrical form of the message
 Communication System:
An Integrated structure of
- Hardware devices (e.g., electronic circuits, antennas,
computer processors etc.)
- Software algorithms (e.g., digital signal processing
algorithms, network protocols)

Elements of Communication System:
Information source:
The message or information to be communicated originates in information source.
Message can be words, group of words, code, data, symbols, signalsetc.
Transmitter:
The objective of the transmitter block is to collect the incoming message signal and modify it in a suitable fash
Channel:
Channel is the physical medium which connects the transmitter with that of the receiver.
The physical medium includes copper wire, coaxial cable, fibre optic cable, wave guide and free space or
atmosphere.ion(ifneeded),suchthat,itcanbetransmittedviathechosenchanneltothereceivingpoint.
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Channel:
Channel is the physical medium which connects the transmitter with that of the receiver.
The physical medium includes copper wire, coaxial cable, fibre optic cable, wave guide and free
space or atmosphere.
Receiver:
The receiver block receives the incoming modified version of the message signal from the
channel and processes it to recreate the original (non-electrical) form of the message signal.
8

Modes of Communication: Simplex, Half-
Duplex and Full-Duplex)
Simplex (SX) – one direction only, e.g. TV
Half Duplex (HDX) – both directions but not at
the same time, e.g. CB radio
Full Duplex (FDX) – transmit and receive
simultaneously between two stations, e.g.
standard telephone system.
Full/Full Duplex (F/FDX) - transmit and receive
simultaneously but not necessarily just
between two stations,
e.g. data communications circuits
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Medias for Communication
•Telephone Channel
•Mobile Radio Channel
•Optical Fiber Cable
•Satellite Channel
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Modulation
In modulation, a message signal, which contains the information is used to control the parameters of a
carrier signal, so as to impress the information onto the carrier.
It is the process of varying the characteristics of high frequency carrier in accordance with instantaneous
values of modulating or message or baseband signal.
(Or)
It is a frequency translation technique which converts baseband or low frequency signal to bandpass or
high frequency signal.
The Messages The message or modulating signal may be either: analogue – denoted by m(t) digital –
denoted by d(t) – i.e. sequences of 1's and 0's The message signal could also be a multilevel signal, rather
than binary; this is not considered further at this stage.
The Carrier The carrier could be a 'sine wave' or a 'pulse train'. Consider a 'sine wave' carrier: vc (t)=
Vccos(ωct +φc)
•If the message signal m(t) controls amplitude – gives AMPLITUDE MODULATION AM
•If the message signal m(t) controls frequency – gives FREQUENCY MODULATION FM
•If the message signal m(t) controls phase- gives PHASE MODULATION PM or
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Benefits or Need of Modulation
To reduce the length or height of antenna
For multiplexing
or narrow banding or to use antenna with single or same length
To reduce noise effect
To avoid equipment limitation or to reduce the size of the equipment.
12

Demodulation
Demodulation is the reverse process (to modulation) to recover the message signal
m(t) or d(t) at the receiver.
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Low frequencies is used in submarines because low frequencies can penetrate in water more
effectively.
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Advantages of a Communication System
1. Speedy transmission: It requires only a few seconds to communicate through electronic
media because it supports quick transmission.
2. Wide coverage: World has become a global village and communication around the globe
requires a second only.
3. Low cost: Electronic communication saves time and money. For example, Text SMS is cheaper
than the traditional letter.
4. Exchange of feedback: Electronic communication allows the instant exchange of feedback. So
communication becomes perfect using electronic media.
5. Managing global operation: Due to the advancement of electronic media, business managers
can easily control operation across the globe. Video or teleconferencing e-mail and mobile
communication are helping managers in this regard
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Disadvantages of a Communication System
1.The volume of data: The volume of telecommunication information is increasing at such a fast
rate that business people are unable to absorb it within the relevant time limit.
2. The cost of development: Electronic communication requires huge investment for
infrastructural development. Frequent change in technology also demands further investment.
3. Legal status: Data or information, if faxed, may be distorted and will cause zero value in the
eye of law.
4. Undelivered data: Data may not be retrieved due to system error or fault with the technology.
Hence required service will be delayed
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NOISE IN COMMUNICATION SYSTEMS
Noise:It is an unwanted signal which tends to interfere with the modulating signal.
Types of noise:
Noise is basically divided into,
1.ExternalNoise
2.InternalNoise
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Classification of Noise
1.External Noise:
◦ Atmospheric Noise: Radio noise caused by natural atmospheric processes, primarily lightening discharges in
thunderstorms.
◦ Extraterrestrial Noise: Radio disturbances from sources other than those related to the Earth.
◦ Cosmic Noise: Random noise that originates outside the Earth’s atmosphere.
◦ Solar Noise: Noise that originates from the Sun is called Solar noise
◦ Industrial Noise: Noise generated by auto mobile ignition, aircrafts, electric motors, Switchgears, welding etc.
2. Internal Noise:
◦ Shot Noise: Random motion of electrons in the semiconductor devices generates shot noise.
◦ Thermal or Johnson’s Noise: Random motion of electrons in the resistor is called Thermal noise.
Pn=K(T0)B
Where, K=Boltzmann constant
T0=Absolute temperature, B=Bandwidth
60

Noise Temperature and Noise Figure
61

Receiver Model for Noise calculation
•The receiver is combination of Band Pass Filter (BPF) and Demodulator.
•The BPF is combination of RF Tuned Amplifier, Mixer and Local Oscillator whose bandwidth is
equal to bandwidth of modulated signal at transmitter.
•Channel Interconnects transmitter & receiver. Channel adds noise to the modulated signal
while transmitting and it is assumed to be white noise whose Power Spectral Density is uniform.
•BPF converts white noise into color or Bandpass noise or narrow bandpass noise.
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Receiver model for noise calculation
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Communication system model for noise
calculation
•The communication system model for noise calculation contains transmitter, channel and
receiver.
•Transmitter is replaced by modulator which converts low frequency modulating signal x(t) into
high frequency bandpass signal with the help of carrier signal.
•Channel is replaced or modelled as additive noise which adds white noise with PSD η/2 and it
contains all frequencies.
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Radio receiver measurements
The important characteristics of super heterodyne radio receiver are,
•Sensitivity
•Selectivity
•Fidelity
Sensitivity:
•It is defined as the ability of receiver to amplify weak signals
•It is defined in terms of voltage which must be applied at the receiver input terminals to provide a
standard output power at the receiver output.
Sensitivity is expressed in milli volts
•For practical receivers sensitivity is expressed in terms of signal power required to produce
minimum acceptable output with minimum acceptable noise.
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Selectivity:
It is defined as the ability of receiver to reject unwanted signals.
Selectivity depends on
•Receiving frequency
•Response of IF section
69

Fidelity:
It is the ability of a receiver to reproduce all the modulating frequenciese qually.
70

WHY DIGITAL?
Digital systems are less sensitive to noise than analog.
 For long transmission lengths, the signal may be regenerated effectively error-free at different points along the path.
With digital systems, it is easier to integrate different services, for example, video and soundtrack into the same transmission scheme
The transmission scheme is independent of the source.
 For example, a digital transmission scheme that transmits voice at 10kpbs can also be used to transmit data at 10kpbs
Digital circuits are easy to manufacture and less sensitive to physical effects, such temperature
Digital signals are simpler to characterize and do not have the same amplitude range and variability as analog signals.
Good processing techniques are available for digital signals, such as medium.
◦ Data compression (or source coding)
◦ Error Correction(or channel coding)(A/D conversion)
◦ Equalization
◦ Security
There are techniques for adding controlled redundancy to a digital transmission such that errors that occur during transmission may be corrected at
the receiver. These techniques are called channel coding.Channel compensation techniques, such as equalization, are easy to implement.
Easy to mix signals and data using digital techniques
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Information Representation
Communication system converts information into electrical electromagnetic/optical signals
appropriate for the transmission medium.
Analog systems convert analog message into signals that can propagate through the
channel.
Digital systems convert bits(digits, symbols) into signals
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Types of information:
◦ Voice, data, video, music, email etc.
Types of communication systems:
◦ Public Switched Telephone Network (voice, fax, modem)
◦ Satellite systems
◦ Radio, TV broadcasting
◦ Cellular phones
◦ Computer networks (LANs, WANs, WLANs)
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Analog vs. Digital Data
Some Terms:
Data/Message
Signal/ Message signal :Information in electrical form
Signaling : Act of propagating the signal
Transmission : Involves propagation and processing both
Messages or data can be classified:
Analog
A physical quantity that varies with “time”, usually in a smooth or
continuous fashion e,g speech
Digital
Takes discrete values e.g text

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Analog vs. Digital Signal
Analog Signals
◦ Continuously varying electromagnetic wave
◦ Values are taken from an infinite set
Digital Signals
◦ Sequence of voltage pulses
◦ Values are taken from a discrete set
Binary Signals
◦ Digital signals with just two discrete values
t
t
t
1
0 0 0
1 1
0

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Signal is a function of time and frequency
Time Domain
- Continuous or Discrete - Periodic or Aperiodic
S(t)=Asin(2 ft+Ø)
Signal Characterization
t t t
t
t
A
in volts
T=1/f

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Frequency Domain
t
T1=1/f1
t
T2=1/f2
t
T1=1/f1
f
A1
f1
f
A2
f2
f
A2
f2
A1
Fourier Analysis : Any signal can be expressed as a combination
of various sinusoids
Some interesting points:
• Fundamental Frequency : All the frequency components are
integer multiple of one frequency
•Period of total signal =Period of fundamental freq.

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Phase is a relative measure. If two signals overlap with each other then they are in phase.
Otherwise they are out of phase
α

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t f
f1 f2 fn
• Spectrum : Range of frequencies contained
• Bandwidth: - Absolute : fn-f1
- Effective : fk-f1
• Signals may have infinite bandwidth but transmission media can accommodate only limited BW
• DC Component: Freq. term at f=0
fk

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Spectra , Bandwidth and Data Rate
T
T
A pulse in time domain Amplitudes of frequency components in freq domain
• If T =1 ms 1000 such pulses can be sent in 1 sec i e data rate is 1 kb/s
• Strong spectral components are below 1/T Hz i e the signal BW is 1KHz
• Channel BW 1000 Hz
• If data rate is to be increased T should be decreased
• This increases the BW ( For 10 times higher rate BW required increase 10 times)

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Medium Speed Cost
Twisted Wire 300 Bps - 10 Mbps Low
Microwave 256 Kbps - 100 Mbps
Satellite 256 Kbps - 100 Mbps
Coaxial Cable 56 Kbps - 200 Mbps
Fiber Optics 500 Kbps - 6.4 Tbps High
Bps: Bits Per Second
Kbps: Kilobits Ps, Mbps: Megabits Ps,
Gbps: Gigabits Ps, Tbps: Terabits Ps
Speeds & Cost

Digital Communication System
source
source
coding
channel
coding
modulation Tx
source
decoding
channel
decoding
demodulation Rx
Channel
o/p
noise
84

Digital symbols are transmitted as modulated carrier
A carrier is a sinusoidal time varying signal represented typically by
s(t) = A sin(2ft + )
Information can be transmitted by varying one or more of the three
defining parameters of the carrier namely – Amplitude
(A), Frequency (f) or the phase ()
Hence we have ASK, FSK and PSK as the basic modulation schemes
Modulation
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Bit-rate, Baud and the Bandwidth
Bit-rate bits / sec
Baud symbols / sec
Bandwidth baud rate, pulse shape
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Types of Digital Modulation
89

Types of Digital Modulation
• Amplitude Shift Keying (ASK)
• Frequency Shift Keying (FSK) – Binary, M-ary
• Phase Shift Keying (PSK) – Binary, QPSK
• Quadrature Amplitude Modulation – QAM
• Advanced- OQPSK, /4-QPSK, MSK, GMSK, TCM
90

Classification of
Digital Modulation Techniques
Linear Modulation
BPSK, M-ary PSK, QAM, OQPSK, /4-QPSK
Constant Envelope Modulation
FSK, MSK, GMSK
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Types of Digital Modulation - Summary
Unmodulated
FSK
ASK
PSK
ASK + PSK
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Polar Form Representation of Digitally Modulated Signals
s(t) = A sin(2ft + )  s(A, )
s(A, )
Amplitude Change Phase Change
Amp & Ph Change Frequency Change
Polar Display
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Typical Tx – Rx for I/Q Modulation
Tx Rx
Composite
signal
98

Generation Using I/Q Design
Example QPSK
S/P
i/p
bits
 A sin(2ft + )
 A cos(2ft + )
 1
 1
(0,1) (1,1)
(0,0) (1,0)
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• •
•
•
Variants of QPSK
QPSK Offset QPSK /4 QPSK
 = 0,  90,  180  = 0,  90  =  45,  135
105

16-QAM
4 bits per symbol
Symbol rate = 1/ 4 Bit Rate
32-QAM
5 bits per symbol
Symbol rate = 1/ 5 Bit Rate
Vector Diagram Constellation Diagram
As M increase, Constellation becomes denser >> BER increases
Effect of Increasing M (# Constellation Points)
# bits per Symbol = log2 M
109

Effect of Change in BT on GMSK Spectrum
118

Effect of Distortion on Digital Modulation
119

Effect of Distortions on Signal Constellation
120

Eye Diagrams for GMSK
BT = 0.3 BT = 0.5 BT = 1.0
125

Theoretical BPSK Raised Cosine  = 0.5
126

Power Efficiency Vs Bandwidth Efficiency
127

Shannon’s Channel Capacity Theorem
R  C = B * log2 {1 + (S / N)}
C – Capacity (bits/s), B – Bandwidth (Hz)
S – Signal Power (W), N – Noise Power (W)
 R/B  log2 [ 1 + (Eb/ N0)(R/B) ]
( Eb - - Energy Per Bit, N0 – Noise Power Density )
 Eb/N0  ( 2R/B -1 ) / (R/B) = ( 2 -1 ) / 
Lim (B  ) Eb / N0 = loge 2 = - 1.6 dB
Capacity of Communication Systems
128

-2 -1 6 12 18 24 30
16
8
4
2
1/2
1/4







M = 8
M = 16
M = 64
M = 4
 MPSK
 MQAM
Bandwidth
Limited
Region
Power
Limited
Region
Region for
R > C
Capacity Boundary
R = C
Shannon Limit
-1.59 dB
Eb / N0 (dB)
R/B ( b/s/Hz )
Bandwidth / Power Efficiency Plot
R/B  log2 [ 1 + (Eb/ N0)(R/B) ]
129

M-QAM Vs M-PSK
Modulation Eb / N0 R / B
8 PSK 14.0 3
8 QAM 10.6 3
16 PSK 18.3 4
16 QAM 14.5 4
64 PSK 26.5 6
64 QAM 18.8 6
130

Modulation Technique
Selection Criterion
Three-way trade-off
Power
B/W BER
132

Source Coding Theory
• What is the minimum number of bits that are required transmit a particular symbol?
• How can we encode symbols so that we achieve (or atleast come arbitrarily close to) this limit?
• Source encoding: concerned with minimizing the actual number of source bits that are
transmitted to the user
• Channel encoding: concerned with introducing redundant bits to enable the receiver to detect
and possibly correct errors that are introduced by the channel.
139

Channel Coding Theorem
Shannon, “A mathematical theory of communication,”1948
• For any channel, there exists an information capacity C (whose calculation is beyond the scope
of this course).
• If the transmission rate R ≤ C, then there exists a coding scheme such that the output of the
source can be transmitted over a noisy channel with an arbitrarily small probability of error.
Conversely, it is not possible to transmit messages without error if R > C.
• Important implication:
– The basic limitation due to noise in a communication channel is not on the reliability of
communication, but rather, on the speed of communication.
146

Error Correction: Basic Principle
149

Error Control Techniques Channel Coding in
Digital Communication Systems
Three approaches can be used to cope with data transmission errors:
1. Automatic Repeat reQuest(ARQ): Error detection
A. When a receiver circuit detects errors in a block of data, it requests that the block be retransmitted. The receiver sends a
feedback to the transmitter: Error is detected (NACK: Not-Acknowledgement) in the received packet, then retransmit that data
block, or if no errors detected (ACK: Acknowledgement), don’t resend.
B. The transmitter retransmits the previously sent packet if it receives a NACK.
C. Uses extra/redundant bits merely for error detection.
D. Full-duplex (two-way) connection between the Transmitter and the Receiver.
E. Result: Constant reliability, but varying data rate throughput due to retransmit.
2.Forward Error Correction (FEC): Error detection and correction.
A. The transmitter’s encoder adds extra/redundant bits to a block of message data bits to form a codeword, so the receiver can
both detect errors and automatically correct errors incurred during transmission, without retransmission of the data.
B. Simplex (one-way) connection between the Transmitter and the Receiver.
C. Result: Varying reliability, but constant data rate throughput.
3.Hybrid ARQ (ARQ+FEC): Error detection and correction.
A. Full-duplex connection required between the Transmitter and the Receiver.
B. Uses error detection and correction codes.
4.In general, wire-line communications (more reliable) adopts ARQ scheme, while wireless communications (relatively
less reliable) adopts FEC scheme.
150

Types of Forward Error Control Codes
Channel Coding
Major categories of Error Detection and Error Correction Codes:
1.Error DetectionCodes:
A. Parity Check codes.
B. ARC: Arithmetic Redundancy Check codes.
C. CRC: Cyclic Redundancy Check codes.
2.Block Error CorrectionCodes:
A. Hamming linear block error correcting codes.
B. BCH (Bose-Chaudhuri-Hocquenghem) cyclic block codes.
C. Reed-Solomon cyclic block codes.
D. Turbo Product Codes (TCP).
3.ConvolutionalError CorrectionCode:
A. Tradition, ViterbiDecoding.
B. Turbo ConvolutionalCode (TCC).
C. Low Density Parity Check Code.
4.Concatenated Error CorrectionCodes: Inner/Outer codes.
◦ Reed-Solomon Error Correction Codes/ Viterbi algorithm.
151

Thank You
Any Questions ??
157

Trellis Coded Modulation
(TCM)
159

Generalized Block Diagram
161

Using QPSK
QPSK Constellation Trellis Diagram
162

Spread Spectrum Modulation
163

Shannon’s Channel Capacity Theorem
C = B * log2 {1 + (S / N)}
C – Capacity (bits/s), B – Bandwidth (Hz)
S – Signal Power (W), N – Noise Power (W)
A given information transfer rate can be achieved by
increasing the bandwidth (B) of the transmitted signal
while reducing the required signal-to-noise ratio (S/N)
Capacity of Communication Systems
164

Why Spread Spectrum ??
 Low Probability of Intercept
 Anti-Jam or Jam-resistant
 Interference Rejection
 Multi-path Rejection
 Multiple Access
 Wireless LAN
 Security
 Immunity to freq selective fading
165

Spread Spectrum Techniques
 Direct Sequence (DS)
Carrier is modulated by digital code
 Frequency Hop (FH)
The carrier frequency is shifted in discrete
increments in a pattern generated by code
 Time Hop (TH)
The transmission slot is governed by code
 Hybrid
DS + FH
166

DSSS- Basic principles
c(t) b(t)
Input
b(t)
c(t)
Code
Interference
i(t)
r(t)

m(t) = c(t) b(t)
Transmit Signal
m(t)
Code
c(t)
r(t) = m(t) + i(t)
Output
b'(t)
C
H
A
N
N
E
L
Spreading
De-spreading
r(t)
Received Signal
167

DSSS
Tb = L Tc
Tc
t
+1
-1
1 1 0
• Information is multiplied with higher rate digital sequence
(spreading code). The sequence has many “chips” for every
data bit.
• The resultant signal modulates the RF carrier.
168

Processing Gain
Processing Gain is a measure of the amount of rejection
offered by spread spectrum system to the interference
Processing Gain (Gp) =
Information bit period (Tb )
Chip Period (Tc )
Spreaded Bandwidth
Input signal Bandwidth
=
169

Noise Noise
Noise Noise
Noise
Signal
Signal
Signal
Signal
Signal A
Signal
Signal B
Interference
Interference
Signal A
Signal B
Low Probability of Intercept
Interference Rejection / Anti-Jam
DSSS Properties
DSSS
Rx
DSSS
Rx
DSSS
Rx
Multiple Access
170

FHSS
time
f1
f2
f3
fn-2
fn-1
fn
Frequency Hopping pattern of transmission frequency
is selected based on a PN code
T 2T 3T
frequency
171

DS Vs FH
DSSS
Advantages
• Most difficult to intercept
• Better AJ performance in presence
of wideband jammer
Disadvantages
• Large Bandwidth
• Long Acquisition Time
• Suffers from near-far effect
FHSS
Advantages
• Better AJ performance in presence
of narrow band jammer
• No Near-far effect (being freq
avoidance)
Disadvantages
• Complex frequency synthesizer
• Requires Error correction
By using a Hybrid System (DSFH) benefits of both can be combined.
The system can have a low probability of interception
and negligible near-far effect at the same time.
172

Application of Spread Spectrum
 Military Communication
 Multiple Access
 GPS
 Wireless LAN
 Indoor Wireless Communication
173

Case Study
Some Voice Grade Modems
176

Some Standard Modems
V.22 bis
16 QAM, 600 baud, carrier = 1200 / 2400 Hz
FDX, Adaptive Equalizer
V.32
16 QAM (TCM), 2400/1200 baud
FDX, Echo Canceller, Adaptive Equalizer
V.26 ter
QPSK, 1200 baud, carrier = 1800 Hz
FDX, Echo Canceller, Adaptive Equalizer
177

Thank You
Any Questions ??
178

1. CT and DT signals:
Classification of signals
179

Classification of signals (cont.)
For many cases, x[n] is obtained by sampling x(t) as:
x[n] = x(nT) , n =0,+1,+2,…
Are there any requirements for the sampling?
180

 2. Even and odd signals:
Even:
x(−t) = x(t)
x[−n] = x[n]
Odd:
x(−t) = −x(t)
x[−n] = −x[n]
 Any signal x(t) can be expressed as
x(t) = xe(t) + xo(t) )
x(−t) = xe(t) − xo(t)
where xe(t) = 1/2(x(t) + x(−t)), xo(t) = 1/2(x(t) − x(−t))
181

 3. Periodic and non-periodic signals:
 CT signal: if x(t) = x(t + T), then x(t) is periodic.
 Smallest T=Fundamental period: To
 Fundamental frequency fo = 1/To (Hz or cycles/second)
 Angular frequency: o = 2 /To (rad/seconds)
 DT signal: if x[n] = x[n + N], then x[n] is periodic.
 min(No): fundamental period
 Fo = 1/No (cycles/sample)
 =2 /N (rads/sample). If the unit of n is designated as dimensionless,
 then is simply in radians.
 Note: A sampled CT periodic signal may not be DT periodic.
Any Condition addition of two periodic CT signals, resultant
must be periodic signal ?




182

4. Deterministic and random signals.
•Deterministic signal: No uncertainty with respect to its value at any time
•Completely specified at any time
•Random signal: Uncertain before it occurs. E.g., thermal noise.
183

Energy and power signals:
•CT signal x(t):
Energy: E =
Power: P =
2
( )
x t dt



2
1
( )
2
lim
T
T T
x t dt
T
 

184

•DT signal x[n]:
Energy: E =
Power:
Energy signal: if 0 < E <
Power signal: if 0 < P <
 
2
x n



 
2
1
2 1
lim
N
N n N
x n
N
 




185

Analog Signal and Digital Signal
186

Basic operations on signals
Basic Operations on Signal
187

• Rule for time shifting and time scaling:
See figure below. Find y(t) = x(2t + 3).
Basic Operations on Signal(cont.)
188

Elementary signals
1. Exponential
2-Sinusoidal
189

Elementary signals(cont.)
3. Step function
190

5.Unit ramp function
Elementary signals(cont.)
4.Unit impulse function
191

2.Memory /Memoryless
•Memory system: present output value depend on future/past input.
•Memoryless system: present output value depend only on present input.
•Example
System Properties(cont.)
193

Invertibility
x(t)
x(t)
y(t)
H
1

H
System Properties(cont.)
196

Series(cascade) Interconnection
Parallel, Interconnection
Interconnection of systems
System 1 System 2
System 1
System 2
+
Input Output
Input
Output
197

Interconnection of systems
•Feedback Interconnection
System 1
System 2
Input Output
198

Communication_System_presentation_Slides.pptx

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