Multi-Level Signal Encoding for DC Balance With Low Coding Overhead
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Solution Overview
Problem
Existing multi-level signaling methods, such as PAM-4, face challenges in achieving DC balance without significant coding overhead and data length limitations, leading to signal integrity issues and increased load on data bandwidth.
Innovation Solution
An encoding apparatus and method that generate candidate patterns through symbol-based inversion, calculate disparity values, and select transmission data based on cumulated disparity and transition counts to ensure DC balance, allowing for flexible data lengths and reduced coding overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If 8-B/10-B encoder is used for PAM-4 DC balancing, then DC balance is achieved, but coding overhead increases to 25% and data bandwidth is increased
Solution Approach 1:
The input data is divided into blocks of 2N bits, and the encoding is performed block-by-block. This segmentation allows the encoder to process data in manageable units while maintaining DC balance across the entire data stream, reducing the need for excessive overhead bits compared to byte-oriented approaches.
Solution Approach 2:
The invention uses a variable block size parameter (2N bits) that can be adjusted based on the application requirements. By changing the block size parameter, the system can optimize the trade-off between DC balance performance and coding overhead, allowing flexibility that fixed 8-B/10-B encoding does not provide.
2Reliability
If 8-B/10-B encoder is used for PAM-4 DC balancing, then DC balance is achieved, but the encoder can only process data lengths corresponding to Byte×2 (16-B)
Solution Approach 1:
The encoder dynamically adapts to different data lengths by using a variable block size of 2N bits. The encoding logic is designed to work with any N value, making the system dynamic and flexible rather than fixed to a specific data length like the traditional 16-B constraint.
Solution Approach 2:
The encoding apparatus is designed to universally handle various data lengths through the 2N-bit block structure. This universal design allows the same encoder to process different data lengths (by changing N) without requiring separate encoding logic for each specific length, achieving multi-functionality.
3Reliability
If mapping based on look-up table is used to eliminate high slew rate transition, then upper/lower eye characteristic is opened wider, but application to data length other than Byte (8-B) is impossible and coding overhead of 25% occurs
Solution Approach 1:
Instead of using a fixed look-up table approach that eliminates high slew rate transitions, the invention inverts the approach by using a variable block size (2N bits) that can accommodate different data lengths. This allows the system to maintain good eye characteristics while adapting to various data lengths without being constrained to fixed 8-B inputs.
Data Source
AI summary
The present invention relates to an encoding apparatus for multi-level signaling, the encoding apparatus including: a candidate pattern generator (1) generating a set of candidate patterns from input data by using symbol-based inversion; a controller (2) generating a cumulated disparity value that is a result of calculating disparity indicating a degree to which transmission data up to previous transmission deviates from DC balance, storing the cumulated disparity value, and determining a transmission control code by using the cumulated disparity value and a set of disparity values that is a result of calculating disparity indicating a degree to which each of the candidate patterns deviates from DC balance; and a data selector (3) selecting one candidate pattern from the set of the candidate patterns as data to be transmitted, according to the determined transmission control code.