Lecture 2 – Physical Layer Communications Wenye Wang Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 1 / 35
Lecture 2 – Physical Layer Communications
Wenye Wang
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 1 / 35
Overview of the Communication Basics
1 Physical Layer Communications: Ch 1.1, Ch 2.2, Ch 3.1, Ch 3.2What are the options of communication links?What are the solutions to imperfect links?
2 Concepts of Communications and Networking Protocols
3 Serial Communication Basics
4 Ethernet Basics
5 Wireless Local Area Networks
6 Wide Area Networks: Wired and Wireless
7 IP, UDP and TCP
8 Internet and computer communications
9 Communication System Performance
10 Communications in Smart Grid
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 2 / 35
Overview of the Communication Basics
1 Physical Layer Communications: Ch 1.1, Ch 2.2, Ch 3.1, Ch 3.2What are the options of communication links?What are the solutions to imperfect links?
2 Concepts of Communications and Networking Protocols
3 Serial Communication Basics
4 Ethernet Basics
5 Wireless Local Area Networks
6 Wide Area Networks: Wired and Wireless
7 IP, UDP and TCP
8 Internet and computer communications
9 Communication System Performance
10 Communications in Smart Grid
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 2 / 35
Overview of the Communication Basics
1 Physical Layer Communications: Ch 1.1, Ch 2.2, Ch 3.1, Ch 3.2What are the options of communication links?What are the solutions to imperfect links?
2 Concepts of Communications and Networking Protocols
3 Serial Communication Basics
4 Ethernet Basics
5 Wireless Local Area Networks
6 Wide Area Networks: Wired and Wireless
7 IP, UDP and TCP
8 Internet and computer communications
9 Communication System Performance
10 Communications in Smart Grid
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 2 / 35
Overview of the Communication Basics
1 Physical Layer Communications: Ch 1.1, Ch 2.2, Ch 3.1, Ch 3.2What are the options of communication links?What are the solutions to imperfect links?
2 Concepts of Communications and Networking Protocols
3 Serial Communication Basics
4 Ethernet Basics
5 Wireless Local Area Networks
6 Wide Area Networks: Wired and Wireless
7 IP, UDP and TCP
8 Internet and computer communications
9 Communication System Performance
10 Communications in Smart Grid
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 2 / 35
Overview of the Communication Basics
1 Physical Layer Communications: Ch 1.1, Ch 2.2, Ch 3.1, Ch 3.2What are the options of communication links?What are the solutions to imperfect links?
2 Concepts of Communications and Networking Protocols
3 Serial Communication Basics
4 Ethernet Basics
5 Wireless Local Area Networks
6 Wide Area Networks: Wired and Wireless
7 IP, UDP and TCP
8 Internet and computer communications
9 Communication System Performance
10 Communications in Smart Grid
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 2 / 35
Overview of the Communication Basics
1 Physical Layer Communications: Ch 1.1, Ch 2.2, Ch 3.1, Ch 3.2What are the options of communication links?What are the solutions to imperfect links?
2 Concepts of Communications and Networking Protocols
3 Serial Communication Basics
4 Ethernet Basics
5 Wireless Local Area Networks
6 Wide Area Networks: Wired and Wireless
7 IP, UDP and TCP
8 Internet and computer communications
9 Communication System Performance
10 Communications in Smart Grid
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 2 / 35
Overview of the Communication Basics
1 Physical Layer Communications: Ch 1.1, Ch 2.2, Ch 3.1, Ch 3.2What are the options of communication links?What are the solutions to imperfect links?
2 Concepts of Communications and Networking Protocols
3 Serial Communication Basics
4 Ethernet Basics
5 Wireless Local Area Networks
6 Wide Area Networks: Wired and Wireless
7 IP, UDP and TCP
8 Internet and computer communications
9 Communication System Performance
10 Communications in Smart Grid
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 2 / 35
Overview of the Communication Basics
1 Physical Layer Communications: Ch 1.1, Ch 2.2, Ch 3.1, Ch 3.2What are the options of communication links?What are the solutions to imperfect links?
2 Concepts of Communications and Networking Protocols
3 Serial Communication Basics
4 Ethernet Basics
5 Wireless Local Area Networks
6 Wide Area Networks: Wired and Wireless
7 IP, UDP and TCP
8 Internet and computer communications
9 Communication System Performance
10 Communications in Smart Grid
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 2 / 35
Overview of the Communication Basics
1 Physical Layer Communications: Ch 1.1, Ch 2.2, Ch 3.1, Ch 3.2What are the options of communication links?What are the solutions to imperfect links?
2 Concepts of Communications and Networking Protocols
3 Serial Communication Basics
4 Ethernet Basics
5 Wireless Local Area Networks
6 Wide Area Networks: Wired and Wireless
7 IP, UDP and TCP
8 Internet and computer communications
9 Communication System Performance
10 Communications in Smart Grid
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 2 / 35
Overview of the Communication Basics
1 Physical Layer Communications: Ch 1.1, Ch 2.2, Ch 3.1, Ch 3.2What are the options of communication links?What are the solutions to imperfect links?
2 Concepts of Communications and Networking Protocols
3 Serial Communication Basics
4 Ethernet Basics
5 Wireless Local Area Networks
6 Wide Area Networks: Wired and Wireless
7 IP, UDP and TCP
8 Internet and computer communications
9 Communication System Performance
10 Communications in Smart Grid
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 2 / 35
Overview of the Communication Basics
1 Physical Layer Communications: Ch 1.1, Ch 2.2, Ch 3.1, Ch 3.2What are the options of communication links?What are the solutions to imperfect links?
2 Concepts of Communications and Networking Protocols
3 Serial Communication Basics
4 Ethernet Basics
5 Wireless Local Area Networks
6 Wide Area Networks: Wired and Wireless
7 IP, UDP and TCP
8 Internet and computer communications
9 Communication System Performance
10 Communications in Smart Grid
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 3 / 35
Revisit Utility Communications
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 4 / 35
Overview of the Communication Basics
1 Physical Layer Communications: Ch 1.1, Ch 2.2, Ch 3.1, Ch 3.2What are the options of communication links?What are the solutions to imperfect links?
2 Concepts of Communications and Networking Protocols
3 Serial Communication Basics
4 Ethernet Basics
5 Wireless Local Area Networks
6 Wide Area Networks: Wired and Wireless
7 IP, UDP and TCP
8 Internet and computer communications
9 Communication System Performance
10 Communications in Smart Grid
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 5 / 35
The Physical Layer – Lowest of OSI
Provides a bit pipe between transmitter/receiver pairs
More communications than networking
What we need to know? basic techniques and principles
Transmission MediumGuided medium, like copper wire, coax, fiberUnguided medium, radio, satellite, etcSingle underlying phenomenon – Electromagnetic waves
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 6 / 35
The Physical Layer – Lowest of OSI
Provides a bit pipe between transmitter/receiver pairs
More communications than networking
What we need to know? basic techniques and principles
Transmission MediumGuided medium, like copper wire, coax, fiberUnguided medium, radio, satellite, etcSingle underlying phenomenon – Electromagnetic waves
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 6 / 35
The Physical Layer – Lowest of OSI
Provides a bit pipe between transmitter/receiver pairs
More communications than networking
What we need to know? basic techniques and principles
Transmission MediumGuided medium, like copper wire, coax, fiberUnguided medium, radio, satellite, etcSingle underlying phenomenon – Electromagnetic waves
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 6 / 35
The Physical Layer – Lowest of OSI
Provides a bit pipe between transmitter/receiver pairs
More communications than networking
What we need to know? basic techniques and principles
Transmission MediumGuided medium, like copper wire, coax, fiberUnguided medium, radio, satellite, etc
Single underlying phenomenon – Electromagnetic waves
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 6 / 35
The Physical Layer – Lowest of OSI
Provides a bit pipe between transmitter/receiver pairs
More communications than networking
What we need to know? basic techniques and principles
Transmission MediumGuided medium, like copper wire, coax, fiberUnguided medium, radio, satellite, etcSingle underlying phenomenon – Electromagnetic waves
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 6 / 35
What are Electromagnetic Waves?
“Charged particles-such as electrons and protons-createlectromagnetic fields when they move, and these fields transport thetype of energy we call electromagnetic radiation, or light.”
Two important ways for energy transportationMechanical waves: caused by a disturbance or vibration in matter,whether solid, gas, liquid, or plasma.Medium: Matter that waves are traveling through is called amediumElectromagnetic waves: Electromagnetic waves differ frommechanical waves in that they do not require a medium topropagate. This means that electromagnetic waves can travel notonly through air and solid materials, but also through the vacuumof space.
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 7 / 35
What are Electromagnetic Waves?
“Charged particles-such as electrons and protons-createlectromagnetic fields when they move, and these fields transport thetype of energy we call electromagnetic radiation, or light.”
Two important ways for energy transportation
Mechanical waves: caused by a disturbance or vibration in matter,whether solid, gas, liquid, or plasma.Medium: Matter that waves are traveling through is called amediumElectromagnetic waves: Electromagnetic waves differ frommechanical waves in that they do not require a medium topropagate. This means that electromagnetic waves can travel notonly through air and solid materials, but also through the vacuumof space.
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 7 / 35
What are Electromagnetic Waves?
“Charged particles-such as electrons and protons-createlectromagnetic fields when they move, and these fields transport thetype of energy we call electromagnetic radiation, or light.”
Two important ways for energy transportationMechanical waves: caused by a disturbance or vibration in matter,whether solid, gas, liquid, or plasma.
Medium: Matter that waves are traveling through is called amediumElectromagnetic waves: Electromagnetic waves differ frommechanical waves in that they do not require a medium topropagate. This means that electromagnetic waves can travel notonly through air and solid materials, but also through the vacuumof space.
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 7 / 35
What are Electromagnetic Waves?
“Charged particles-such as electrons and protons-createlectromagnetic fields when they move, and these fields transport thetype of energy we call electromagnetic radiation, or light.”
Two important ways for energy transportationMechanical waves: caused by a disturbance or vibration in matter,whether solid, gas, liquid, or plasma.Medium: Matter that waves are traveling through is called amedium
Electromagnetic waves: Electromagnetic waves differ frommechanical waves in that they do not require a medium topropagate. This means that electromagnetic waves can travel notonly through air and solid materials, but also through the vacuumof space.
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 7 / 35
What are Electromagnetic Waves?
“Charged particles-such as electrons and protons-createlectromagnetic fields when they move, and these fields transport thetype of energy we call electromagnetic radiation, or light.”
Two important ways for energy transportationMechanical waves: caused by a disturbance or vibration in matter,whether solid, gas, liquid, or plasma.Medium: Matter that waves are traveling through is called amediumElectromagnetic waves: Electromagnetic waves differ frommechanical waves in that they do not require a medium topropagate. This means that electromagnetic waves can travel notonly through air and solid materials, but also through the vacuumof space.
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 7 / 35
Description of Electromagnetic Energy
Frequency f
The number of oscillations per second of a waveOne wave or cycle per second is called a Hertz (Hz), afterHeinrich Hertz who established the existence of radio waves
Wavelength λ
Electromagnetic waves have crests and troughs similar to those ofocean waves. The distance between crests is the wavelength.Relationship between f and λ: λ× f = c, where c is the speed oflight.
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 8 / 35
Description of Electromagnetic Energy
Frequency fThe number of oscillations per second of a wave
One wave or cycle per second is called a Hertz (Hz), afterHeinrich Hertz who established the existence of radio waves
Wavelength λ
Electromagnetic waves have crests and troughs similar to those ofocean waves. The distance between crests is the wavelength.Relationship between f and λ: λ× f = c, where c is the speed oflight.
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 8 / 35
Description of Electromagnetic Energy
Frequency fThe number of oscillations per second of a waveOne wave or cycle per second is called a Hertz (Hz), afterHeinrich Hertz who established the existence of radio waves
Wavelength λ
Electromagnetic waves have crests and troughs similar to those ofocean waves. The distance between crests is the wavelength.Relationship between f and λ: λ× f = c, where c is the speed oflight.
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 8 / 35
Description of Electromagnetic Energy
Frequency fThe number of oscillations per second of a waveOne wave or cycle per second is called a Hertz (Hz), afterHeinrich Hertz who established the existence of radio waves
Wavelength λ
Electromagnetic waves have crests and troughs similar to those ofocean waves. The distance between crests is the wavelength.
Relationship between f and λ: λ× f = c, where c is the speed oflight.
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 8 / 35
Description of Electromagnetic Energy
Frequency fThe number of oscillations per second of a waveOne wave or cycle per second is called a Hertz (Hz), afterHeinrich Hertz who established the existence of radio waves
Wavelength λ
Electromagnetic waves have crests and troughs similar to those ofocean waves. The distance between crests is the wavelength.Relationship between f and λ: λ× f = c, where c is the speed oflight.
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 8 / 35
Description of Electromagnetic Energy
Frequency fThe number of oscillations per second of a waveOne wave or cycle per second is called a Hertz (Hz), afterHeinrich Hertz who established the existence of radio waves
Wavelength λ
Electromagnetic waves have crests and troughs similar to those ofocean waves. The distance between crests is the wavelength.Relationship between f and λ: λ× f = c, where c is the speed oflight.
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 8 / 35
Description of Electromagnetic Energy
Frequency fThe number of oscillations per second of a waveOne wave or cycle per second is called a Hertz (Hz), afterHeinrich Hertz who established the existence of radio waves
Wavelength λ
Electromagnetic waves have crests and troughs similar to those ofocean waves. The distance between crests is the wavelength.Relationship between f and λ: λ× f = c, where c is the speed oflight.
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 8 / 35
Digital or Analog
Digital – concept Information can be analog or digital
EM waves – analog by definition
Analog EM signal can be made to transfer digital data
“Digital interpretation of analog signal representing digitalrepresentation of analog data”.
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 9 / 35
Digital or Analog
Digital – concept Information can be analog or digital
EM waves – analog by definition
Analog EM signal can be made to transfer digital data
“Digital interpretation of analog signal representing digitalrepresentation of analog data”.
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 9 / 35
Digital or Analog
Digital – concept Information can be analog or digital
EM waves – analog by definition
Analog EM signal can be made to transfer digital data
“Digital interpretation of analog signal representing digitalrepresentation of analog data”.
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 9 / 35
Digital or Analog
Digital – concept Information can be analog or digital
EM waves – analog by definition
Analog EM signal can be made to transfer digital data
“Digital interpretation of analog signal representing digitalrepresentation of analog data”.
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 9 / 35
The Electromagnetic Spectrum
visible light: 400-700 nm, (4.3 7.5× 1014)
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 10 / 35
Guided Medium: Coaxial Cable
Coaxial cabletwo concentric copper conductorsbidirectionalbaseband: (1) Single channel on cable and (2) Legacy Ethernet
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 11 / 35
Guided Medium: Fiber
Fiberglass fiber carrying light pulses,each pulse a bithigh-speed point-to-pointtransmission (e.g., 5 Gps)low error rate: repeaters spacedfar apart ; immune toelectromagnetic noise
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 12 / 35
Guided Medium: Fiber
Fiberglass fiber carrying light pulses,each pulse a bithigh-speed point-to-pointtransmission (e.g., 5 Gps)low error rate: repeaters spacedfar apart ; immune toelectromagnetic noise
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 12 / 35
Unguided Medium – Radio
Features
no physical “wire”bidirectionalpropagation environment effects: reflection; obstruction byobjects; and interference
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 13 / 35
Unguided Medium – Radio
Featuresno physical “wire”
bidirectionalpropagation environment effects: reflection; obstruction byobjects; and interference
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 13 / 35
Unguided Medium – Radio
Featuresno physical “wire”bidirectionalpropagation environment effects: reflection; obstruction byobjects; and interference
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 13 / 35
Overview of the Communication Basics
1 Physical Layer Communications: Ch 1.1, Ch 2.2, Ch 3.1, Ch 3.2What are the options of communication links?What are the solutions to imperfect links?
2 Concepts of Communications and Networking Protocols
3 Serial Communication Basics
4 Ethernet Basics
5 Wireless Local Area Networks
6 Wide Area Networks: Wired and Wireless
7 IP, UDP and TCP
8 Internet and computer communications
9 Communication System Performance
10 Communications in Smart Grid
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 14 / 35
How to Delivery Messages Reliably?
FunctionsBreaking up the bit stream into framesProvide a well-defined service interface to the network layer
Deal with transmission errors (Error control)Use frames to encapsulate packets from upper layer.Regulate the flow of data so that slow receivers are not swampedby fast senders (Flow control).With or without errors?
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 15 / 35
How to Delivery Messages Reliably?
FunctionsBreaking up the bit stream into framesProvide a well-defined service interface to the network layerDeal with transmission errors (Error control)Use frames to encapsulate packets from upper layer.
Regulate the flow of data so that slow receivers are not swampedby fast senders (Flow control).With or without errors?
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 15 / 35
How to Delivery Messages Reliably?
FunctionsBreaking up the bit stream into framesProvide a well-defined service interface to the network layerDeal with transmission errors (Error control)Use frames to encapsulate packets from upper layer.Regulate the flow of data so that slow receivers are not swampedby fast senders (Flow control).
With or without errors?
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 15 / 35
How to Delivery Messages Reliably?
FunctionsBreaking up the bit stream into framesProvide a well-defined service interface to the network layerDeal with transmission errors (Error control)Use frames to encapsulate packets from upper layer.Regulate the flow of data so that slow receivers are not swampedby fast senders (Flow control).With or without errors?
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 15 / 35
How to Delivery Messages Reliably?
FunctionsBreaking up the bit stream into framesProvide a well-defined service interface to the network layerDeal with transmission errors (Error control)Use frames to encapsulate packets from upper layer.Regulate the flow of data so that slow receivers are not swampedby fast senders (Flow control).With or without errors?
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 15 / 35
Framing – Breaking up the Bit Stream into Frames
Byte countFlag bytes with byte stuffingFlag bits with bit stuffing
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 16 / 35
Framing – Breaking up the Bit Stream into Frames
Byte countFlag bytes with byte stuffingFlag bits with bit stuffing
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 16 / 35
Framing – Breaking up the Bit Stream into Frames
Byte countFlag bytes with byte stuffingFlag bits with bit stuffing
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 16 / 35
A Simple Model-Binary Symmetric Channels
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 17 / 35
Why Use Error Control?
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 18 / 35
Single Parity Check
(Even) Parity Check
append a single bit to the data. If the number of 1 bits in thecodeword is even, a bit 0 is appended.E.g., 1011010→ 10110100Can it detect single errors?
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 19 / 35
Single Parity Check
(Even) Parity Checkappend a single bit to the data. If the number of 1 bits in thecodeword is even, a bit 0 is appended.
E.g., 1011010→ 10110100Can it detect single errors?
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 19 / 35
Single Parity Check
(Even) Parity Checkappend a single bit to the data. If the number of 1 bits in thecodeword is even, a bit 0 is appended.E.g., 1011010→ 10110100
Can it detect single errors?
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 19 / 35
Single Parity Check
(Even) Parity Checkappend a single bit to the data. If the number of 1 bits in thecodeword is even, a bit 0 is appended.E.g., 1011010→ 10110100Can it detect single errors?
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 19 / 35
Two-dimensional Parity Check
A two-dimensional array with oneparity check for each row and onefor each
Parity bits:
ci = si1 ⊕ si2 ⊕ si3 · · · sik
rj = s1j ⊕ s2j ⊕ s3j · · · snj
Detect all single, double errors?
Detect triple errors and quadrupleerrors?
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 20 / 35
Two-dimensional Parity Check
A two-dimensional array with oneparity check for each row and onefor each
Parity bits:
ci = si1 ⊕ si2 ⊕ si3 · · · sik
rj = s1j ⊕ s2j ⊕ s3j · · · snj
Detect all single, double errors?
Detect triple errors and quadrupleerrors?
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 20 / 35
Two-dimensional Parity Check
A two-dimensional array with oneparity check for each row and onefor each
Parity bits:
ci = si1 ⊕ si2 ⊕ si3 · · · sik
rj = s1j ⊕ s2j ⊕ s3j · · · snj
Detect all single, double errors?
Detect triple errors and quadrupleerrors?
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 20 / 35
Two-dimensional Parity Check
A two-dimensional array with oneparity check for each row and onefor each
Parity bits:
ci = si1 ⊕ si2 ⊕ si3 · · · sik
rj = s1j ⊕ s2j ⊕ s3j · · · snj
Detect all single, double errors?
Detect triple errors and quadrupleerrors?
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 20 / 35
Two-dimensional Parity Check
A two-dimensional array with oneparity check for each row and onefor each
Parity bits:
ci = si1 ⊕ si2 ⊕ si3 · · · sik
rj = s1j ⊕ s2j ⊕ s3j · · · snj
Detect all single, double errors?
Detect triple errors and quadrupleerrors?
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 20 / 35
Two-dimensional Parity Check
A two-dimensional array with oneparity check for each row and onefor each
Parity bits:
ci = si1 ⊕ si2 ⊕ si3 · · · sik
rj = s1j ⊕ s2j ⊕ s3j · · · snj
Detect all single, double errors?
Detect triple errors and quadrupleerrors?
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 20 / 35
Cyclic Redundancy Check (CRC)
Polynomial code
Bit string is represented by a polynomial with coefficients of 0 and1 only. E.g., 10011A k -bit frame is regarded as a polynomial with k terms, rangingfrom xk−1 to x0 . It is called a polynomial of degree (k − 1).If the data bits are denoted as mK−1,mK−2, · · · ,m1,m0, thepolynomial M(x) representation of the string with coefficients is
M(x) = mK−1xK−1 + mK−2xk−2 + · · · ,+m1x + m0
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 21 / 35
Cyclic Redundancy Check (CRC)
Polynomial codeBit string is represented by a polynomial with coefficients of 0 and1 only. E.g., 10011
A k -bit frame is regarded as a polynomial with k terms, rangingfrom xk−1 to x0 . It is called a polynomial of degree (k − 1).If the data bits are denoted as mK−1,mK−2, · · · ,m1,m0, thepolynomial M(x) representation of the string with coefficients is
M(x) = mK−1xK−1 + mK−2xk−2 + · · · ,+m1x + m0
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 21 / 35
Cyclic Redundancy Check (CRC)
Polynomial codeBit string is represented by a polynomial with coefficients of 0 and1 only. E.g., 10011A k -bit frame is regarded as a polynomial with k terms, rangingfrom xk−1 to x0 . It is called a polynomial of degree (k − 1).
If the data bits are denoted as mK−1,mK−2, · · · ,m1,m0, thepolynomial M(x) representation of the string with coefficients is
M(x) = mK−1xK−1 + mK−2xk−2 + · · · ,+m1x + m0
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 21 / 35
Cyclic Redundancy Check (CRC)
Polynomial codeBit string is represented by a polynomial with coefficients of 0 and1 only. E.g., 10011A k -bit frame is regarded as a polynomial with k terms, rangingfrom xk−1 to x0 . It is called a polynomial of degree (k − 1).If the data bits are denoted as mK−1,mK−2, · · · ,m1,m0, thepolynomial M(x) representation of the string with coefficients is
M(x) = mK−1xK−1 + mK−2xk−2 + · · · ,+m1x + m0
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 21 / 35
CRC Polynomial
Step 1: Both the sender and receiver agree upon a generatorpolynomial, G(x) of degree r . E.g, x2 + 1.
Step 2: Let r be the degree of G(x), append r zero bits to thelow-order end of the frame, that is x r M(x).
Step 3: Divide the G(x) into x r M(x) and obtain the remainderRemainder [x r M(x)
G(x) ].
Step 4: The CRC polynomial T (x) is obtained by
T (x) = x r M(x)− Remainder [x r M(x)
G(x)]
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 22 / 35
CRC Polynomial
Step 1: Both the sender and receiver agree upon a generatorpolynomial, G(x) of degree r . E.g, x2 + 1.
Step 2: Let r be the degree of G(x), append r zero bits to thelow-order end of the frame, that is x r M(x).
Step 3: Divide the G(x) into x r M(x) and obtain the remainderRemainder [x r M(x)
G(x) ].
Step 4: The CRC polynomial T (x) is obtained by
T (x) = x r M(x)− Remainder [x r M(x)
G(x)]
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 22 / 35
CRC Polynomial
Step 1: Both the sender and receiver agree upon a generatorpolynomial, G(x) of degree r . E.g, x2 + 1.
Step 2: Let r be the degree of G(x), append r zero bits to thelow-order end of the frame, that is x r M(x).
Step 3: Divide the G(x) into x r M(x) and obtain the remainderRemainder [x r M(x)
G(x) ].
Step 4: The CRC polynomial T (x) is obtained by
T (x) = x r M(x)− Remainder [x r M(x)
G(x)]
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 22 / 35
CRC Polynomial
Step 1: Both the sender and receiver agree upon a generatorpolynomial, G(x) of degree r . E.g, x2 + 1.
Step 2: Let r be the degree of G(x), append r zero bits to thelow-order end of the frame, that is x r M(x).
Step 3: Divide the G(x) into x r M(x) and obtain the remainderRemainder [x r M(x)
G(x) ].
Step 4: The CRC polynomial T (x) is obtained by
T (x) = x r M(x)− Remainder [x r M(x)
G(x)]
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 22 / 35
Error Detection with CRC
Divisible (Detectable) or not divisible (not detectable)
T (x) is divisible by G(x), so the remainder should be zero forcorrect transmissionAssume there is an error occurs, so the received bit string isT (x) + E(x). If no errors occur, then E(x) = 0.
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 23 / 35
Error Detection with CRC
Divisible (Detectable) or not divisible (not detectable)T (x) is divisible by G(x), so the remainder should be zero forcorrect transmission
Assume there is an error occurs, so the received bit string isT (x) + E(x). If no errors occur, then E(x) = 0.
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 23 / 35
Error Detection with CRC
Divisible (Detectable) or not divisible (not detectable)T (x) is divisible by G(x), so the remainder should be zero forcorrect transmissionAssume there is an error occurs, so the received bit string isT (x) + E(x). If no errors occur, then E(x) = 0.
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 23 / 35
Standards
XPX-16g(x) = 1 + x2 + x15 + x16
CRC-ITU-Tg(x) = 1 + x5 + x12 + x16
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 24 / 35
Example
CRC Coding and Detection
Consider the following generator polynomials to be used in a CRCscheme: G1(x) = x5 + x3 + x2 + 1 and G2(x) = x7 + x5 + x + 1.While transmitting a CRC encoded message, the followingpolynomial is received.
T1(x) = x7 + x5 + x4 + x2
Is T1(x) detectable with G1(x) and G2(x), or can any errors bedetected or not?If G1(x) is used as CRC, and another polynomial is received
T2(x) = x6 + x5 + x4 + x2 + x + 1
Assume T1(x) and T2(x) are the results of the same message andthere is no error in T1(x). What is the error in T2(x)? How tocorrect T2(x) to obtain T (x)?
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 25 / 35
Example
CRC Coding and DetectionConsider the following generator polynomials to be used in a CRCscheme: G1(x) = x5 + x3 + x2 + 1 and G2(x) = x7 + x5 + x + 1.While transmitting a CRC encoded message, the followingpolynomial is received.
T1(x) = x7 + x5 + x4 + x2
Is T1(x) detectable with G1(x) and G2(x), or can any errors bedetected or not?If G1(x) is used as CRC, and another polynomial is received
T2(x) = x6 + x5 + x4 + x2 + x + 1
Assume T1(x) and T2(x) are the results of the same message andthere is no error in T1(x). What is the error in T2(x)? How tocorrect T2(x) to obtain T (x)?
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 25 / 35
Example
CRC Coding and DetectionConsider the following generator polynomials to be used in a CRCscheme: G1(x) = x5 + x3 + x2 + 1 and G2(x) = x7 + x5 + x + 1.While transmitting a CRC encoded message, the followingpolynomial is received.
T1(x) = x7 + x5 + x4 + x2
Is T1(x) detectable with G1(x) and G2(x), or can any errors bedetected or not?
If G1(x) is used as CRC, and another polynomial is received
T2(x) = x6 + x5 + x4 + x2 + x + 1
Assume T1(x) and T2(x) are the results of the same message andthere is no error in T1(x). What is the error in T2(x)? How tocorrect T2(x) to obtain T (x)?
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 25 / 35
Example
CRC Coding and DetectionConsider the following generator polynomials to be used in a CRCscheme: G1(x) = x5 + x3 + x2 + 1 and G2(x) = x7 + x5 + x + 1.While transmitting a CRC encoded message, the followingpolynomial is received.
T1(x) = x7 + x5 + x4 + x2
Is T1(x) detectable with G1(x) and G2(x), or can any errors bedetected or not?If G1(x) is used as CRC, and another polynomial is received
T2(x) = x6 + x5 + x4 + x2 + x + 1
Assume T1(x) and T2(x) are the results of the same message andthere is no error in T1(x). What is the error in T2(x)? How tocorrect T2(x) to obtain T (x)?
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 25 / 35
Summary
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 26 / 35
Overview of the Communication Basics
1 Physical Layer Communications: Ch 1.1, Ch 2.2, Ch 3.1, Ch 3.2What are the options of communication links?What are the solutions to imperfect links?
2 Concepts of Communications and Networking Protocols
3 Serial Communication Basics
4 Ethernet Basics
5 Wireless Local Area Networks
6 Wide Area Networks: Wired and Wireless
7 IP, UDP and TCP
8 Internet and computer communications
9 Communication System Performance
10 Communications in Smart Grid
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 27 / 35
Overview of the Communication Basics
1 Physical Layer Communications: Ch 1.1, Ch 2.2, Ch 3.1, Ch 3.2What are the options of communication links?What are the solutions to imperfect links?
2 Concepts of Communications and Networking Protocols
3 Serial Communication Basics
4 Ethernet Basics
5 Wireless Local Area Networks
6 Wide Area Networks: Wired and Wireless
7 IP, UDP and TCP
8 Internet and computer communications
9 Communication System Performance
10 Communications in Smart Grid
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 28 / 35
Overview of the Communication Basics
1 Physical Layer Communications: Ch 1.1, Ch 2.2, Ch 3.1, Ch 3.2What are the options of communication links?What are the solutions to imperfect links?
2 Concepts of Communications and Networking Protocols
3 Serial Communication Basics
4 Ethernet Basics
5 Wireless Local Area Networks
6 Wide Area Networks: Wired and Wireless
7 IP, UDP and TCP
8 Internet and computer communications
9 Communication System Performance
10 Communications in Smart Grid
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 29 / 35
Overview of the Communication Basics
1 Physical Layer Communications: Ch 1.1, Ch 2.2, Ch 3.1, Ch 3.2What are the options of communication links?What are the solutions to imperfect links?
2 Concepts of Communications and Networking Protocols
3 Serial Communication Basics
4 Ethernet Basics
5 Wireless Local Area Networks
6 Wide Area Networks: Wired and Wireless
7 IP, UDP and TCP
8 Internet and computer communications
9 Communication System Performance
10 Communications in Smart Grid
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 30 / 35
Overview of the Communication Basics
1 Physical Layer Communications: Ch 1.1, Ch 2.2, Ch 3.1, Ch 3.2What are the options of communication links?What are the solutions to imperfect links?
2 Concepts of Communications and Networking Protocols
3 Serial Communication Basics
4 Ethernet Basics
5 Wireless Local Area Networks
6 Wide Area Networks: Wired and Wireless
7 IP, UDP and TCP
8 Internet and computer communications
9 Communication System Performance
10 Communications in Smart Grid
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 31 / 35
Overview of the Communication Basics
1 Physical Layer Communications: Ch 1.1, Ch 2.2, Ch 3.1, Ch 3.2What are the options of communication links?What are the solutions to imperfect links?
2 Concepts of Communications and Networking Protocols
3 Serial Communication Basics
4 Ethernet Basics
5 Wireless Local Area Networks
6 Wide Area Networks: Wired and Wireless
7 IP, UDP and TCP
8 Internet and computer communications
9 Communication System Performance
10 Communications in Smart Grid
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 32 / 35
Overview of the Communication Basics
1 Physical Layer Communications: Ch 1.1, Ch 2.2, Ch 3.1, Ch 3.2What are the options of communication links?What are the solutions to imperfect links?
2 Concepts of Communications and Networking Protocols
3 Serial Communication Basics
4 Ethernet Basics
5 Wireless Local Area Networks
6 Wide Area Networks: Wired and Wireless
7 IP, UDP and TCP
8 Internet and computer communications
9 Communication System Performance
10 Communications in Smart Grid
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 33 / 35
Overview of the Communication Basics
1 Physical Layer Communications: Ch 1.1, Ch 2.2, Ch 3.1, Ch 3.2What are the options of communication links?What are the solutions to imperfect links?
2 Concepts of Communications and Networking Protocols
3 Serial Communication Basics
4 Ethernet Basics
5 Wireless Local Area Networks
6 Wide Area Networks: Wired and Wireless
7 IP, UDP and TCP
8 Internet and computer communications
9 Communication System Performance
10 Communications in Smart Grid
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 34 / 35
Overview of the Communication Basics
1 Physical Layer Communications: Ch 1.1, Ch 2.2, Ch 3.1, Ch 3.2What are the options of communication links?What are the solutions to imperfect links?
2 Concepts of Communications and Networking Protocols
3 Serial Communication Basics
4 Ethernet Basics
5 Wireless Local Area Networks
6 Wide Area Networks: Wired and Wireless
7 IP, UDP and TCP
8 Internet and computer communications
9 Communication System Performance
10 Communications in Smart Grid
Wenye Wang (NC State University) ECE 592-017 - Communication Systems for Electric Power Systems 35 / 35