SlideShare uma empresa Scribd logo
1 de 17
Baixar para ler offline
Digital Data Communications
Techniques
Transmission Mode
• How many bits can be sent in one clock cycle?
• Serial mode
—Only one bit is sent in one clock cycle
• Parallel mode
—n bits are sent in one clock cycle
—Uses n wires to send n bits
Parallel Transmission
Serial Transmission
• Used for long distance transmission. Why?
• Two types: Asynchronous and synchronous
• Asynchronous
• One byte of data sent serially
• Start bit = 0, Stop bit=1  In total, ten bits are sent
• Next byte may not follow previous byte immediately
– i.e. there may be idle time between bytes
• It is asynchronous only at the byte level. Individual bits
are still synchronized.
Asynchronous Serial
Asynchronous …
• Data transmitted on character at a time
—5 to 8 bits
• Timing only needs maintaining within each
character
• Resynchronize with each character
Asynchronous (diagram)
Asynchronous - Behavior
• In a steady stream, interval between characters
is uniform (length of stop element)
• In idle state, receiver looks for transition 1 to 0
• Then samples next seven intervals (char length)
• Then looks for next 1 to 0 for next char
• Simple
• Cheap
• Overhead of 2 or 3 bits per char (~20%)
• Good for data with large gaps (keyboard)
Synchronous Serial
• Bits are sent one after another without gap
—No start and stop bits
• Receiver must organize bits into bytes
• Synchronous sends more data bits than
asynchronous
• Synchronous: used for high speed transmission
• Asynchronous: for low speed transmission
Synchronous
Types of Error
• An error occurs when a bit is altered between
transmission and reception
• Single bit errors
—One bit altered
—Adjacent bits not affected
—White noise
• Burst errors
—Length B
—Contiguous sequence of B bits in which first last and any
number of intermediate bits in error
—Impulse noise
—Fading in wireless
—Effect greater at higher data rates
Error Detection Process
Error Detection
• Additional bits added by transmitter for error
detection code
• Parity
—Value of parity bit is such that character has even
(even parity) or odd (odd parity) number of ones
—Even number of bit errors goes undetected
Cyclic Redundancy Check
• For a block of k bits transmitter generates n bit
sequence
• Transmit k+n bits which is exactly divisible by
some number
• Receiver divides frame by that number
—If no remainder, assume no error
Error Correction
• Correction of detected errors usually requires
data block to be retransmitted
• Not appropriate for wireless applications
—Bit error rate is high
• Lots of retransmissions
—Propagation delay can be long (satellite) compared
with frame transmission time
• Would result in retransmission of frame in error plus many
subsequent frames
• Need to correct errors on basis of bits received
Error Correction Process
Diagram
The End

Mais conteúdo relacionado

Semelhante a Datalink controls

Semelhante a Datalink controls (20)

Chap4 d t-d conversion
Chap4 d t-d conversionChap4 d t-d conversion
Chap4 d t-d conversion
 
Dc4 t1
Dc4 t1Dc4 t1
Dc4 t1
 
Serial vs Parallel communication & Synchronous and Asynchronous transmission
Serial vs Parallel communication & Synchronous and Asynchronous transmissionSerial vs Parallel communication & Synchronous and Asynchronous transmission
Serial vs Parallel communication & Synchronous and Asynchronous transmission
 
Line coding
Line codingLine coding
Line coding
 
Data transmission
Data transmissionData transmission
Data transmission
 
CS553_ST7_Ch05-SignalEncodingTechniques.ppt
CS553_ST7_Ch05-SignalEncodingTechniques.pptCS553_ST7_Ch05-SignalEncodingTechniques.ppt
CS553_ST7_Ch05-SignalEncodingTechniques.ppt
 
CS553_ST7_Ch06-DigitalDataComm.ppt
CS553_ST7_Ch06-DigitalDataComm.pptCS553_ST7_Ch06-DigitalDataComm.ppt
CS553_ST7_Ch06-DigitalDataComm.ppt
 
L8 signal encoding techniques
L8 signal encoding techniquesL8 signal encoding techniques
L8 signal encoding techniques
 
Digital & analog transmission
Digital & analog transmissionDigital & analog transmission
Digital & analog transmission
 
Sak
SakSak
Sak
 
Modes of Transmission
Modes of TransmissionModes of Transmission
Modes of Transmission
 
Ch05
Ch05Ch05
Ch05
 
Lec 5
Lec 5Lec 5
Lec 5
 
DCCN S1.ppt
DCCN S1.pptDCCN S1.ppt
DCCN S1.ppt
 
Parity check(Error Detecting Codes)
Parity check(Error Detecting Codes)Parity check(Error Detecting Codes)
Parity check(Error Detecting Codes)
 
Asynchronous and synchronous
Asynchronous and synchronousAsynchronous and synchronous
Asynchronous and synchronous
 
Transmission mode
Transmission modeTransmission mode
Transmission mode
 
7.multiplexing upload
7.multiplexing upload7.multiplexing upload
7.multiplexing upload
 
Osi model
Osi model Osi model
Osi model
 
Chapter2-PhysicalLayer.ppt
Chapter2-PhysicalLayer.pptChapter2-PhysicalLayer.ppt
Chapter2-PhysicalLayer.ppt
 

Último

PREPARING YOUR LOVED ONE FOR A HOSPITAL STAY
PREPARING YOUR LOVED ONE FOR A HOSPITAL STAYPREPARING YOUR LOVED ONE FOR A HOSPITAL STAY
PREPARING YOUR LOVED ONE FOR A HOSPITAL STAYbilalpakweb
 
Rendezvous Arts on Chicago Tribune March20 2024
Rendezvous Arts on Chicago Tribune March20 2024Rendezvous Arts on Chicago Tribune March20 2024
Rendezvous Arts on Chicago Tribune March20 2024danwonclarinet
 
Meal Planning, Nutrition, and Digestion / TREATING CONSTIPATION
Meal Planning, Nutrition, and Digestion / TREATING CONSTIPATIONMeal Planning, Nutrition, and Digestion / TREATING CONSTIPATION
Meal Planning, Nutrition, and Digestion / TREATING CONSTIPATIONbilalpakweb
 
Digital Marketing Creative Portfolio - Xandra Somera
Digital Marketing Creative Portfolio - Xandra SomeraDigital Marketing Creative Portfolio - Xandra Somera
Digital Marketing Creative Portfolio - Xandra SomeraXandra26
 
its a wip forever because i said so yeuh
its a wip forever because i said so yeuhits a wip forever because i said so yeuh
its a wip forever because i said so yeuhangelicafronda7
 
Recycle Ann Arbor Brand Guide Presentation
Recycle Ann Arbor Brand Guide PresentationRecycle Ann Arbor Brand Guide Presentation
Recycle Ann Arbor Brand Guide Presentationmakaiodm
 
Alex Matus - Professional Best Photographer
Alex Matus - Professional Best PhotographerAlex Matus - Professional Best Photographer
Alex Matus - Professional Best PhotographerAlex Matus Photography
 
Adventures in Soup Storyboard Clickthrough
Adventures in Soup Storyboard ClickthroughAdventures in Soup Storyboard Clickthrough
Adventures in Soup Storyboard ClickthroughLillyKocurek
 
Flowering lilacs for celebrate spring 17
Flowering lilacs for celebrate spring 17Flowering lilacs for celebrate spring 17
Flowering lilacs for celebrate spring 17sandamichaela *
 
Music Magazine contents page inspiration
Music Magazine contents page inspirationMusic Magazine contents page inspiration
Music Magazine contents page inspirationLydiaAittayeb
 
Schaduw - a short story by Petra van Berkum
Schaduw - a short story by Petra van BerkumSchaduw - a short story by Petra van Berkum
Schaduw - a short story by Petra van Berkumberkumpje1
 
WILLS AND TRUSTS DIFFERENTIATING BETWEEN WILLS AND TRUSTS
WILLS AND TRUSTS DIFFERENTIATING BETWEEN WILLS AND TRUSTSWILLS AND TRUSTS DIFFERENTIATING BETWEEN WILLS AND TRUSTS
WILLS AND TRUSTS DIFFERENTIATING BETWEEN WILLS AND TRUSTSbilalpakweb
 
04. MEMORY CARE: DEALING WITH DEMENTIA WHAT IS DEMENTIA?
04. MEMORY CARE: DEALING WITH DEMENTIA WHAT IS DEMENTIA?04. MEMORY CARE: DEALING WITH DEMENTIA WHAT IS DEMENTIA?
04. MEMORY CARE: DEALING WITH DEMENTIA WHAT IS DEMENTIA?bilalpakweb
 
Music magazine inspiration - media studies
Music magazine inspiration - media studiesMusic magazine inspiration - media studies
Music magazine inspiration - media studiesLydiaAittayeb
 
Recycle Ann Arbor Brand Guide Presentation
Recycle Ann Arbor Brand Guide PresentationRecycle Ann Arbor Brand Guide Presentation
Recycle Ann Arbor Brand Guide Presentationmakaiodm
 
Smudge Animated Short Thumbnails Version 2
Smudge Animated Short Thumbnails Version 2Smudge Animated Short Thumbnails Version 2
Smudge Animated Short Thumbnails Version 2micahhansonart
 
Miss Illusion- beginning boards yayyyyyy
Miss Illusion- beginning boards yayyyyyyMiss Illusion- beginning boards yayyyyyy
Miss Illusion- beginning boards yayyyyyycwang48
 
Black Art Colonial Spaces at The Museum of Fine Arts, Boston
Black Art Colonial Spaces at The Museum of Fine Arts, BostonBlack Art Colonial Spaces at The Museum of Fine Arts, Boston
Black Art Colonial Spaces at The Museum of Fine Arts, BostonProfessorNordell
 

Último (20)

PREPARING YOUR LOVED ONE FOR A HOSPITAL STAY
PREPARING YOUR LOVED ONE FOR A HOSPITAL STAYPREPARING YOUR LOVED ONE FOR A HOSPITAL STAY
PREPARING YOUR LOVED ONE FOR A HOSPITAL STAY
 
Rendezvous Arts on Chicago Tribune March20 2024
Rendezvous Arts on Chicago Tribune March20 2024Rendezvous Arts on Chicago Tribune March20 2024
Rendezvous Arts on Chicago Tribune March20 2024
 
Meal Planning, Nutrition, and Digestion / TREATING CONSTIPATION
Meal Planning, Nutrition, and Digestion / TREATING CONSTIPATIONMeal Planning, Nutrition, and Digestion / TREATING CONSTIPATION
Meal Planning, Nutrition, and Digestion / TREATING CONSTIPATION
 
Digital Marketing Creative Portfolio - Xandra Somera
Digital Marketing Creative Portfolio - Xandra SomeraDigital Marketing Creative Portfolio - Xandra Somera
Digital Marketing Creative Portfolio - Xandra Somera
 
its a wip forever because i said so yeuh
its a wip forever because i said so yeuhits a wip forever because i said so yeuh
its a wip forever because i said so yeuh
 
Recycle Ann Arbor Brand Guide Presentation
Recycle Ann Arbor Brand Guide PresentationRecycle Ann Arbor Brand Guide Presentation
Recycle Ann Arbor Brand Guide Presentation
 
Alex Matus - Professional Best Photographer
Alex Matus - Professional Best PhotographerAlex Matus - Professional Best Photographer
Alex Matus - Professional Best Photographer
 
Adventures in Soup Storyboard Clickthrough
Adventures in Soup Storyboard ClickthroughAdventures in Soup Storyboard Clickthrough
Adventures in Soup Storyboard Clickthrough
 
Flowering lilacs for celebrate spring 17
Flowering lilacs for celebrate spring 17Flowering lilacs for celebrate spring 17
Flowering lilacs for celebrate spring 17
 
Music Magazine contents page inspiration
Music Magazine contents page inspirationMusic Magazine contents page inspiration
Music Magazine contents page inspiration
 
Schaduw - a short story by Petra van Berkum
Schaduw - a short story by Petra van BerkumSchaduw - a short story by Petra van Berkum
Schaduw - a short story by Petra van Berkum
 
BELSOSI
BELSOSIBELSOSI
BELSOSI
 
WILLS AND TRUSTS DIFFERENTIATING BETWEEN WILLS AND TRUSTS
WILLS AND TRUSTS DIFFERENTIATING BETWEEN WILLS AND TRUSTSWILLS AND TRUSTS DIFFERENTIATING BETWEEN WILLS AND TRUSTS
WILLS AND TRUSTS DIFFERENTIATING BETWEEN WILLS AND TRUSTS
 
04. MEMORY CARE: DEALING WITH DEMENTIA WHAT IS DEMENTIA?
04. MEMORY CARE: DEALING WITH DEMENTIA WHAT IS DEMENTIA?04. MEMORY CARE: DEALING WITH DEMENTIA WHAT IS DEMENTIA?
04. MEMORY CARE: DEALING WITH DEMENTIA WHAT IS DEMENTIA?
 
Music magazine inspiration - media studies
Music magazine inspiration - media studiesMusic magazine inspiration - media studies
Music magazine inspiration - media studies
 
Shadow Creation Service | CPH Graphics Media
Shadow Creation Service | CPH Graphics MediaShadow Creation Service | CPH Graphics Media
Shadow Creation Service | CPH Graphics Media
 
Recycle Ann Arbor Brand Guide Presentation
Recycle Ann Arbor Brand Guide PresentationRecycle Ann Arbor Brand Guide Presentation
Recycle Ann Arbor Brand Guide Presentation
 
Smudge Animated Short Thumbnails Version 2
Smudge Animated Short Thumbnails Version 2Smudge Animated Short Thumbnails Version 2
Smudge Animated Short Thumbnails Version 2
 
Miss Illusion- beginning boards yayyyyyy
Miss Illusion- beginning boards yayyyyyyMiss Illusion- beginning boards yayyyyyy
Miss Illusion- beginning boards yayyyyyy
 
Black Art Colonial Spaces at The Museum of Fine Arts, Boston
Black Art Colonial Spaces at The Museum of Fine Arts, BostonBlack Art Colonial Spaces at The Museum of Fine Arts, Boston
Black Art Colonial Spaces at The Museum of Fine Arts, Boston
 

Datalink controls

  • 2. Transmission Mode • How many bits can be sent in one clock cycle? • Serial mode —Only one bit is sent in one clock cycle • Parallel mode —n bits are sent in one clock cycle —Uses n wires to send n bits
  • 4. Serial Transmission • Used for long distance transmission. Why? • Two types: Asynchronous and synchronous • Asynchronous • One byte of data sent serially • Start bit = 0, Stop bit=1  In total, ten bits are sent • Next byte may not follow previous byte immediately – i.e. there may be idle time between bytes • It is asynchronous only at the byte level. Individual bits are still synchronized.
  • 6. Asynchronous … • Data transmitted on character at a time —5 to 8 bits • Timing only needs maintaining within each character • Resynchronize with each character
  • 8. Asynchronous - Behavior • In a steady stream, interval between characters is uniform (length of stop element) • In idle state, receiver looks for transition 1 to 0 • Then samples next seven intervals (char length) • Then looks for next 1 to 0 for next char • Simple • Cheap • Overhead of 2 or 3 bits per char (~20%) • Good for data with large gaps (keyboard)
  • 9. Synchronous Serial • Bits are sent one after another without gap —No start and stop bits • Receiver must organize bits into bytes • Synchronous sends more data bits than asynchronous • Synchronous: used for high speed transmission • Asynchronous: for low speed transmission
  • 11. Types of Error • An error occurs when a bit is altered between transmission and reception • Single bit errors —One bit altered —Adjacent bits not affected —White noise • Burst errors —Length B —Contiguous sequence of B bits in which first last and any number of intermediate bits in error —Impulse noise —Fading in wireless —Effect greater at higher data rates
  • 13. Error Detection • Additional bits added by transmitter for error detection code • Parity —Value of parity bit is such that character has even (even parity) or odd (odd parity) number of ones —Even number of bit errors goes undetected
  • 14. Cyclic Redundancy Check • For a block of k bits transmitter generates n bit sequence • Transmit k+n bits which is exactly divisible by some number • Receiver divides frame by that number —If no remainder, assume no error
  • 15. Error Correction • Correction of detected errors usually requires data block to be retransmitted • Not appropriate for wireless applications —Bit error rate is high • Lots of retransmissions —Propagation delay can be long (satellite) compared with frame transmission time • Would result in retransmission of frame in error plus many subsequent frames • Need to correct errors on basis of bits received