Block Coding in Digital Communication | Computer Networks Course | Lecture 24

Summary

In this video, the concept of block coding is introduced as a technique used to add redundancy to digital data for transmission. It explains how block coding improves line coding by incorporating extra bits for error detection and synchronization. The process includes dividing data into blocks of m bits, replacing each block with n bits, and then combining them to form a longer stream. These additional bits help ensure accurate data transmission, allowing for error detection and synchronization between sender and receiver. The video concludes with a preview of upcoming block coding schemes to be discussed in future lessons.

Takeaways

• 😀 Block coding is a technique used alongside line coding to enhance data transmission.
• 😀 Block coding involves adding redundant bits to the original binary data for error detection and synchronization.
• 😀 Redundancy is essential to synchronize the sender and receiver clocks during data transmission.
• 😀 Error detection is about identifying whether there is an error in the data, while error correction deals with fixing it.
• 😀 Block coding improves line coding by converting m bits into n bits, where n > m.
• 😀 The process of block coding divides the data stream into blocks of equal sizes, replacing each block with a larger block of n bits.
• 😀 Extra bits added during block coding help with synchronization and error detection.
• 😀 The three main steps of block coding are division, substitution, and combination.
• 😀 In the division step, the data is broken into blocks of m bits, which are then replaced with blocks of n bits during substitution.
• 😀 After substitution, the n-bit blocks are combined to form a longer data stream, which is sent to the receiver.
• 😀 The extra bits in block coding are used for control operations, error detection, and synchronization to ensure accurate data reception.

Q & A

What is block coding?

Block coding is a technique used in digital communication where a block of 'm' bits is replaced by 'n' bits, where 'n' is greater than 'm'. This technique introduces redundant bits into the data stream for purposes such as synchronization and error detection.

Why is redundancy added in block coding?

Redundancy is added in block coding primarily for two reasons: synchronization and error detection. Redundant bits help synchronize the sender's and receiver's clocks and allow for error detection in the transmitted data.

What does synchronization mean in the context of block coding?

Synchronization refers to ensuring that the sender and receiver start and end their transmission at the same time. It helps the receiver to properly receive data and know when the data transmission begins and ends.

How is error detection different from error correction?

Error detection simply involves identifying whether an error has occurred during transmission, whereas error correction involves actually fixing those errors. Block coding only focuses on detecting errors, not correcting them.

What does the term 'm/n coding' represent in block coding?

'm/n coding' represents a block coding scheme where 'm' is the number of bits in the original data block and 'n' is the number of bits in the coded block. In block coding, 'n' is always greater than 'm' to introduce extra bits for synchronization and error detection.

What are the three steps involved in block coding?

The three steps in block coding are: 1) Division – dividing the bit stream into blocks of 'm' bits; 2) Substitution – replacing each 'm' bit group with a block of 'n' bits; 3) Combination – combining all the 'n' bit blocks into a continuous data stream.

Why does the resulting data stream after block coding contain more bits than the original stream?

After block coding, the resulting data stream contains more bits because each 'm' bit block is replaced with an 'n' bit block, where 'n' is greater than 'm'. This extra data is used for control operations, synchronization, and error detection.

Can you explain the division step in block coding with an example?

In the division step, the original bit stream is divided into groups. For example, if the original stream is '101011' and 'm' is 4, it will be divided into two groups: '1010' and '11'. Each group of 'm' bits is then processed further in the substitution step.

What happens during the substitution step in block coding?

During the substitution step, each group of 'm' bits is replaced with a corresponding group of 'n' bits. For example, a group of 4 bits might be replaced with a group of 5 bits, and this change is done to introduce redundancy for error detection and synchronization.

What role do the extra bits in block coding play?

The extra bits introduced during block coding are used for control operations, error detection, and synchronization. These additional bits help the receiver identify when data begins, ends, and whether any errors occurred during transmission.