Base Station Clock Synchronization for Broadband Wireless Access

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Solution Overview

Problem

Broadband wireless access (BWA) systems face challenges in synchronizing frame clock sources between base and subscriber stations, leading to data rate discrepancies due to fluctuations in frame clock frequencies, which affect the transmission of synchronized data frames.

Innovation Solution

A synchronization process is implemented where the base station calculates and broadcasts the relative change relationship between its modem and frame clock sources, allowing the subscriber station to adjust its frame clock source to match the base station's frequency, using a phase lock loop and numerical controlled oscillators to achieve synchronization.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If frame clock sources are used for data transmission in BWA systems, then data communication can be established, but frequency fluctuations cause data rate discrepancies and synchronization issues

Engineering Contradiction:

Improvesynchronization reliabilityVSAvoiddata rate accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent implements a feedback mechanism where the base station measures the relative change relationship between its frame clock and modem clock, then broadcasts this information to subscriber stations. The subscriber stations use this feedback to adjust their frame clock frequencies, creating a closed-loop synchronization system that maintains accurate data rates despite frequency fluctuations

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The subscriber station copies the relative change relationship information from the base station and applies it to adjust its own frame clock frequency. This allows the subscriber station to replicate the synchronization characteristics of the base station, ensuring both stations operate at consistent data rates

Inventive Principle:

Principle #26Copying

2Reliability

If frame clock frequency adjustments are made to achieve synchronization, then data rate consistency is improved, but the complexity of the synchronization process increases

Engineering Contradiction:

Improvedata rate consistencyVSAvoidsynchronization process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The system enables self-service synchronization where each station automatically adjusts its own frame clock frequency based on broadcast information from the base station. The subscriber station independently calculates and applies the necessary frequency adjustments without requiring manual intervention or complex centralized control mechanisms

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent changes the operating parameter of the frame clock frequency dynamically. By adjusting the frame clock frequency based on the relative change relationship, the system adapts to frequency variations while maintaining data rate consistency, transforming a static synchronization approach into a dynamic one

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This synchronization method ensures that the subscriber station's frame clock frequency aligns with the base station's, maintaining consistent data rates and improving the reliability of data transmission in BWA systems.

Implementation Method 1

using a phase lock loop and numerical controlled oscillators to achieve synchronization

Methodology Applied

Scientific EffectPhase lock loop:

Implementation Method 2

using a phase lock loop and numerical controlled oscillators to achieve synchronization

Methodology Applied

Scientific EffectNumerical controlled oscillator:

Data Source

PatentUS7577222B2Methods and apparatus with logic to determine a relative change relationship between modem and frame clocks

Publication Date: 2009.08.18 APPLE INC

AI summary

Methods and apparatus to determine a relative change relationship between modem and frame clocks are generally described herein. Other embodiments may be described and claimed.