Bit synchronization and Modulation techniques

What is bit synchronization?

Determining the boundary (start and end) of signal cell is known as clock or bit synchronization.

Why bit and frame synchronization techniques are used?

Bit and frame synchronization techniques are used to make sure that  the signals sent from one host of the communication can be rightly decoded by the receiver.

Uses of Synchronization techniques

• To guide the receiver in finding where data blocks start and end.
• To determine the time interval at which the sampling result is more accurate (with least errors).

Data Transmission modes

Asynchronous transmission

• Asynchronous transmission is a transmission in which there is no synchronization of sender and receiver clocks.
•  In this mode, each transmission element (character or byte) is treated independently.
• The receiver need to determine the boundary (starting and  ending) of each byte or character. 
• This mode is used whenever data has to be transferred in irregular intervals of time.
• Application example: UARTs – Universal Asynchronous Receivers/Transmitters – used in serial ports or internal modems.

Synchronous communication

• Synchronous transmission is a transmission in which the clocks of transmitter and receiver need to run in sync for the transfer time of one block. The next block may have new synchronization.
• Application examples: Ethernet & FDDI.

What is Signal Modulation?

Conversion of digital signals to analog signals is called modulation and the reversing of analog to digital signals is called demodulation.

Why signals need modulation?

To transfer binary (digital) data, it needs to travel through analog media. In the real world, there is no binary transmission medium. Electrical signals, optical signals and also radio waves, all are analog signals. So, the digital signals should be encoded by the sender and decoded at the other end to have communication between them. 

Common Modulation Techiques

1. Amplitude shift keying
2. Frequency shift keying
3. Phase shift keying
4. Quantization of signals.

Reference
Bit and Frame Synchronization Techniques
Martin Probst , Lars Trieloff
Hasso-Plattner-Institute for Software System Engineering
Free Download Link: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.5.7173&rep=rep1&type=pdf


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