8B/10B Encoding: Advantages and Disadvantages

This page explores the advantages and disadvantages of 8B/10B block coding, detailing its benefits and drawbacks.

What is 8B/10B Encoding?

Introduction: 8B/10B is a block coding technique that, similar to 4B/5B encoding, uses redundancy to ensure synchronization and improve performance. It also offers inherent error detection capabilities. The name “8B/10B” signifies that the encoding process takes 8-bit blocks as input and produces 10-bit blocks as output.

The 8B/10B block coding scheme is a combination of 5B/6B and 3B/4B encoding, as illustrated below:

The most significant bits (MSBs) of the 8-bit block are fed into a 5B/6B encoder, while the 3 least significant bits (LSBs) are fed into a 3B/4B encoder module. The coding has 2¹⁰ - 2⁸ redundant groups.

Benefits or Advantages of 8B/10B Encoding

The following are the benefits or advantages of 8B/10B encoding:

1. Disparity Control: It employs a disparity controller to keep track of excess 0s over 1s (or vice versa). This helps to prevent long runs of consecutive 0s or 1s, which can cause synchronization issues.
2. Error Detection: The redundant groups can be used for disparity checking and error detection, improving the reliability of the transmitted data.
3. Superior to 4B/5B: It offers better performance than 4B/5B coding due to its built-in error checking capability and improved synchronization.

Drawbacks or Disadvantages of 8B/10B Encoding

The following are the drawbacks or disadvantages of 8B/10B encoding:

1. Overhead: The redundant data introduces overhead, increasing the overall bandwidth requirements.