• सुखार्थी त्यजते विद्यं विध्यार्थी त्यजते सुखम्सु sखर्थीन: कुतॊ विद्या कुतॊ विध्यार्थीन: सुखम् ||
  • “Luxury people leave knowledge, but a student leaves Luxury No knowledge for one who seeks Luxury, No luxury for student”
  • न चोर हार्यं न च राज हार्यं न भात्रू भाज्यं न च भारकारि |व्ययं कृते वर्धत एव नित्यं विद्याधनं सर्वधनप्रधानम ||
  • Cannot be snatched away by thief, cannot be snatched away by king, Cannot be divided among brothers, Not heavy either If spent daily, it always keeps growing. The wealth of knowledge is the precious of wealth of all”

Asynchronous and Synchronous transmission




Asynchronous Transmission

In asynchronous transmission the timing of signal is not important.

Both sender and receiver transfer data on agreed upon patterns consist of both data and control bits.

 

If the signal is not synchronized the receiver will not be able to distinguish when the next group of bits will arrive. To overcome this the data is preceded by a start bit, usually binary 0, the byte is then sent and a stop bit or bits are added to the end.

 


In addition to the control data small gaps are inserted between each chunk to distinguish each group.

 

 

 

Advantages and disadvantages:

Asynchronous transmission is relatively slow due to the increased number of bits and gaps. It is a cheap and effective form of serial transmission and is particularly suited for low speed connections such as keyboard and mouse.

For example, the connection of a keyboard to a computer is a natural application for asynchronous transmission. A user types only one character at a time, types extremely slowly in data processing terms, and leaves unpredictable gaps of time between each character.

In communication one example of asynchronous transfer is Asynchronous Transfer Mode (ATM) switching. ATM allows voice, data and video to be transmitted in fixed length cells of 53 bytes.

Synchronous Transmission

In synchronous transmission, data are transmitted as an unbroken string of 1s and 0s.


Bit synchronization is established between sender and receiver by timing. Both sender and receiver operates on same clock frequency.

 

It is responsibility of receiver to separate the string into the bytes, or characters, it needs to reconstruct the information.

 

Advantages of synchronous transmission:

Synchronous transmission is faster than asynchronous transmission as no extra bits or gaps are introduced at the sending end and removed at the receiving end.

 

For this reason, it is more useful for high-speed applications such as the transmission of data from one computer to another.

 

 Byte synchronization is accomplished in the data link layer.

Isochronous:

In real-time audio and video, uneven delays between frames are not acceptable. For these applications, synchronization between characters is not enough, entire stream must be synchronized.

 

We use isochronous transmission for real time data so that data arrives at a fixed rate.

Related Questions

Question:     Differentiate between asynchronous and synchronous transmission.    [5 marks]

Answer