Transcript Chapter Asynchronous and Synchronous Transmission © N. Ganesan, Ph.D. , All rights reserved.

Chapter
Asynchronous and Synchronous
Transmission
© N. Ganesan, Ph.D. , All rights reserved.
Chapter Objectives
• Explain the features of asynchronous
and synchronous transmission and
possible areas of application for each
transmission type
Chapter Modules
• Asynchronous Transmission
• Synchronous Transmission
Module
Asynchronous Transmission
© N. Ganesan, Ph.D. , All rights reserved.
Questions
• What is the characterizing feature of
asynchronous transmission?
• Give some examples of asynchronous
transmission
• Can asynchronous transmission be
conducted at high and low speeds?
Give examples in each case
Asynchronous Transmission
• Burst mode transmission
• Sender and receiver are not
synchronized with respect to the flow
of the information
• However, the sender and receiver are
synchronized with respect to the timing
of the characters that are transmitted
A Note on Asynchronous
Transmission
• In the past, asynchronous transmission
referred only to character by character
transmission where each character
contained information about timing etc.
– Note the use of start and stop bits
• At present, the concept of asynchronous
transmission can be extended to cover
packet transmissions as well
The Use of the Word Asynchronous
• Asynchronous Transmission
– Generally refers to the transmission of
characters with each character carrying
information about timing
• Asynchronous Communication
– Refers to overall communication between
two points
• An example in this case would be ATM
Asynchronous Transmission
Applied to Characters
Stop Bit
Start Bit
Character Frame
Each character is individually timed.
Asynchronous Transmission
Applied to Packets
Burst of Data
Packets of data
Packets of data
A
B
Intermittent transmission of packets of data
Analogy
Intermittent of burst arrival
of guests
Host expecting the
arrival of guests
Asynchronous
Transmission/Communication
Application
• Character by character transmission
• Data packet transmission at present
Speed Variations In
Asynchronous Transmission
• Low and high-speed transmissions are
possible
• Low speed
– Almost all modem based communications fall
into this category
• High speed
– Asynchronous Transfer Mode (ATM)
• Internet is a good example where
asynchronous communication is used
predominantly to carry the information
Questions
• What is the characterizing feature of
asynchronous transmission?
• Give some examples of asynchronous
transmission
• Can asynchronous transmission be
conducted at high and low speeds?
Give examples in each case
End of Module
Module
Synchronous Transmission
© N. Ganesan, Ph.D. , All rights reserved.
Questions
• How does synchronous transmission
differ from asynchronous transmission?
• Where is synchronous transmission
used in practice?
Synchronous Transmission
• Sender and receiver are synchronized with
respect to the sending and receiving of
information
• Each character need not have a start-bit and a
stop-bit as the sender and the receiver are
both synchronized
• Requires more hardware and software
resources
• High speed communication is the norm
A Note on Synchronous
Transmission
• The definition of synchronous
transmission refers to the transmission
of characters
• However, the use of the word
synchronous can be extended to cover
packet transmission as well
Usage in Practice
• Which one of the two transmissions is
used widely in the real world? Explain.
Examples of Synchronous
Transmission
• High-speed communication links
established using synchronous modems
– It is now possible to establish high speed
links based on asynchronous transmission
• Used in a number of mainframe
installations
– Collective exchange of information
between the mainframe and the peripheral
devices is based on synchronous
transmission
In Summary
• Synchronous transmission plays a
smaller role compared to asynchronous
transmission in practice
• Implementation of synchronous
transmission requires more resources
• Asynchronous technology has advanced
– It is no more necessary to rely on
synchronous communication to establish a
high speed communication link
End of Module
End of Chapter