Recursive Filter Circuit for Timestamp Jitter Reduction

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Solution Overview

Problem

Cloud radio access networks (C-RAN) face challenges in maintaining high accuracy time synchronization between radio heads due to clock domain crossings, leading to significant jitter in timestamp synchronization, which affects the performance of 5G and IoT wireless technologies.

Innovation Solution

A circuit employing recursive filter logic, specifically a recursive least-squares (RLS) filter, is used to generate a filtered timestamp by reducing jitter in received timestamps, thereby improving timestamp accuracy across multiple clock domains.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If timestamp synchronization is performed across multiple clock domains, then time synchronization is achieved, but jitter increases significantly

Engineering Contradiction:

Improvetime synchronization accuracyVSAvoidtimestamp jitter

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

A recursive filter is introduced as an intermediary component between the timestamp synchronization process and the final timestamp output. The filter processes the synchronized timestamp to reduce jitter while preserving the synchronization accuracy, effectively mediating between the conflicting requirements of reliability and measurement precision.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the temporal parameters of the timestamp by applying a recursive filtering operation. The filter modifies the timestamp sequence by combining current and previous timestamp values with weighted coefficients, thereby transforming the jitter characteristics while maintaining the underlying synchronization relationship.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If recursive filtering is applied to reduce jitter, then timestamp accuracy improves, but processing complexity increases

Engineering Contradiction:

Improvetimestamp accuracyVSAvoidfilter processing complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The recursive filter is designed to be self-sufficient, using only its own previous output and the current input timestamp to generate the next output. This self-service characteristic eliminates the need for external complex processing or large buffer memory, reducing overall system complexity while maintaining filtering effectiveness.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The recursive filter operates continuously on every incoming timestamp without interruption or batch processing. This continuous operation allows the filter to progressively reduce jitter accumulation over time while maintaining a simple, steady-state processing structure that does not require periodic complex computations.

Inventive Principle:

Principle #20Continuity of useful action

Data Source

PatentUS20250310229A1Circuit and Method for Timestamp Jitter Reduction

Publication Date: 2025.10.02 MARVELL ASIA PTE LTD

AI summary

A circuit and corresponding method generate a filtered timestamp. The circuit comprises recursive filter logic. The circuit generates the filtered timestamp from a received timestamp by filtering the received timestamp via the recursive filter logic. The recursive filter logic reduces jitter in the filtered timestamp relative to jitter of the received timestamp. The jitter represents a deviation of the received timestamp from a target (ideal) timestamp. The circuit outputs the filtered timestamp generated. The filtered timestamp is a more accurate representation of the target timestamp, relative to the received timestamp, due to the jitter reduced.