Nibble Combining for Constant-Latency Byte-Based Ethernet Encoding
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Solution Overview
Problem
Existing Ethernet systems experience variability in latency due to misalignment of nibbles, leading to inaccuracies in time synchronization and sub-optimal performance, especially when dealing with odd numbers of nibbles in packets and preambles.
Innovation Solution
A physical layer device with a nibble combining module that aligns and combines nibbles into bytes, using encoding and decoding modules to maintain constant latency across various nibble configurations, including odd and even starting boundaries, and employing 8N/(8N+1) encoding to manage control symbols.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If byte-based encoding is used for Ethernet frames, then data transmission efficiency is improved, but latency variability increases due to nibble misalignment
Solution Approach 1:
The nibble combining module performs preliminary alignment of nibbles to byte boundaries before encoding. It buffers incoming nibbles and combines them into complete bytes in advance, ensuring that encoding always starts at a byte boundary regardless of the number of nibbles received. This preliminary action eliminates latency variability caused by misalignment.
Solution Approach 2:
The nibble combining module acts as an intermediary between the nibble-based MII interface and the byte-based encoder. It translates between the two formats by accumulating nibbles and forming complete bytes, thereby mediating the interface between different data unit requirements and eliminating timing mismatches.
2Adaptability or versatility
If nibble-based interface is used between MAC and PHY, then flexibility in handling various packet sizes is improved, but time synchronization accuracy deteriorates
Solution Approach 1:
The patent segments the nibble stream into complete byte groups before encoding. The nibble combining module divides the continuous nibble flow into discrete byte-sized chunks, ensuring that each encoded group represents a complete byte boundary. This segmentation maintains the flexibility of nibble-based interfaces while achieving the precision of byte-aligned encoding.
3Adaptability or versatility
If odd number of nibbles are handled in packets, then adaptability to various data lengths is improved, but latency consistency worsens
Solution Approach 1:
The nibble combining module performs preliminary buffering and alignment of odd numbers of nibbles before encoding. It waits until a complete byte can be formed from the accumulated nibbles, then processes the complete byte. This preliminary waiting and alignment ensures that even odd numbers of nibbles result in consistent byte-aligned encoding operations, maintaining latency consistency.
Data Source
AI summary
A physical layer device includes a nibble combining module configured to receive a plurality of types of packets, wherein the plurality of types of packets include an even or odd number of nibbles and an even or odd starting boundary. The nibble combining module is configured to combine the nibbles of the plurality of types of packets into a plurality of bytes. An encoding module is configured to encode the plurality of bytes of the packet. A transmitter is configured to transmit the encoded plurality of bytes. Latency of the nibble combining module for the plurality of types of packets is the same.