Idle Sequence Code Word Replacement for Frame Synchronization

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Solution Overview

Problem

In communication systems, determining the starting point of a frame is challenging when the length of the idle sequence is unknown, and the idle sequence alone does not indicate its end, leading to difficulties in synchronization and frame detection.

Innovation Solution

The solution involves encoding an idle sequence with a basic idle sequence modified by replacing certain code words with alternative code words, maintaining a bounded running disparity, and using the difference between the basic and modified idle sequences to determine the frame's starting point, ensuring the absolute value of running disparity is kept lower than a predetermined value.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the idle sequence length is made variable and unknown, then the system becomes more flexible in handling gaps between packets, but the receiving node cannot determine the starting point of the following frame

Engineering Contradiction:

Improveflexibility in handling gap lengthsVSAvoidframe starting point detection

Core Design Contradiction:

Adaptability or versatilityVSDifficulty of detecting and measuring

Solution Approach 1:

The patent introduces an intermediary mechanism using a delimiter code word that separates the idle sequence from the following frame. This delimiter acts as a mediator signal that the receiving node can detect to determine where the idle sequence ends and the next frame begins, solving the ambiguity caused by variable idle sequence lengths.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent uses a distinct delimiter code word that is different from both the basic idle sequence code words and the frame code words. This creates a visible 'color change' or distinct pattern in the signal that allows the receiving node to easily identify the transition point and determine frame boundaries despite the variable and unknown idle sequence length.

Inventive Principle:

Principle #32Color changes

2Difficulty of detecting and measuring

If alternative code words are used in the idle sequence, then the receiving node can identify the end of the idle sequence, but the running disparity may become unbounded

Engineering Contradiction:

Improveidle sequence end identificationVSAvoidrunning disparity balance

Core Design Contradiction:

Difficulty of detecting and measuringVSStability of the object's composition

Solution Approach 1:

The patent carefully selects and defines the properties of alternative code words, specifically requiring that they have the same weight (number of ones) as the basic idle sequence code words. This parameter change constraint ensures that substituting alternative code words for basic idle sequence code words does not alter the running disparity accumulation, maintaining DC balance while still enabling frame boundary detection.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite idle sequence structure that combines basic idle sequence code words with alternative code words. This composite structure maintains the desirable properties of the basic idle sequence (including running disparity balance) while incorporating the frame boundary indication capability through the strategically placed delimiter code words.

Inventive Principle:

Principle #40Composite materials

3Difficulty of detecting and measuring

If the idle sequence is modified with alternative code words, then frame boundary detection is enabled, but the transition density and DC-balance may be affected

Engineering Contradiction:

Improveframe boundary detection capabilityVSAvoidDC-balance and transition density

Core Design Contradiction:

Difficulty of detecting and measuringVSReliability

Solution Approach 1:

The patent imposes specific parameter constraints on the alternative code words, requiring them to have the same Hamming weight as the basic idle sequence code words. This parameter preservation ensures that the modification of the idle sequence with alternative code words does not affect the running disparity or DC-balance properties, maintaining reliability while enabling frame boundary detection.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS9270403B2Indicating end of idle sequence by replacing expected code words while maintaining running disparity

Publication Date: 2016.02.23 VALENS SEMICON

AI summary

Methods and systems for indicating an end of an idle sequence residing between first and second frames, while maintaining bounded running disparity, including: encoding the first frame; encoding a basic idle sequence utilizing a first line-code; producing an idle sequence by replacing M code words of the basic idle sequence with M alternative code words; encoding the second frame; transmitting the first frame, the idle sequence, and the second frame; and receiving the second frame by a second communication node. Each one of the M alternative code words is equal to a code word of the basic idle sequence. And the second communication node is unable to determine a starting point of the second frame based only on the idle sequence and the second frame, but is able to determine the starting point of the second frame based on difference between the basic idle sequence and the idle sequence.