Communication Device Frequency Offset Compensation

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Solution Overview

Problem

Mobile terminals face challenges in initial cell search procedures due to frequency offsets, especially when using temperature-wise non-compensated crystals, leading to inefficient frequency acquisition during startup or in extreme temperatures.

Innovation Solution

A communication device equipped with an oscillator, accuracy determiner, and signal detector that adjusts its frequency detection strategy based on temperature and oscillator accuracy, performing multiple cell searches across a range of frequencies to compensate for potential offsets and improve detection accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If the mobile terminal uses a temperature-wise non-compensated crystal oscillator for frequency generation, then the device complexity is reduced and manufacturing cost is lowered, but the frequency accuracy deteriorates significantly under temperature variations

Engineering Contradiction:

Improveoscillator compensation mechanismVSAvoidfrequency accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The system performs preliminary frequency offset estimation during the cell search procedure by analyzing correlation peaks at multiple frequency offsets. This preliminary action allows the terminal to compensate for temperature-induced frequency inaccuracies without requiring a complex temperature-compensated oscillator, resolving the contradiction between device simplicity and frequency accuracy.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system implements feedback by continuously monitoring the frequency offset through correlation peak analysis and adjusting the frequency synchronization accordingly. This feedback mechanism enables the terminal to maintain accurate frequency tracking despite using a non-compensated oscillator, balancing device complexity with measurement precision.

Inventive Principle:

Principle #23Feedback

2Adaptability or versatility

If the mobile terminal performs cell search in frequency-unlocked mode without frequency synchronization, then the initial cell acquisition capability is improved, but the frequency offset error increases significantly

Engineering Contradiction:

Improveinitial cell acquisition capabilityVSAvoidfrequency offset error

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The cell search procedure is segmented into multiple stages: initial broad search across multiple frequency offsets to identify candidate cells, followed by refined frequency synchronization. This segmentation allows the terminal to first acquire cells without precise frequency alignment, then correct frequency offsets subsequently, resolving the contradiction between adaptability and measurement precision.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system dynamically adjusts the frequency search range and synchronization parameters based on the detected correlation peaks. By making the frequency alignment process adaptive and flexible rather than rigid, the terminal can successfully perform initial cell acquisition in frequency-unlocked mode and then achieve precise frequency synchronization, balancing versatility with precision.

Inventive Principle:

Principle #15Dynamics

3Reliability

If the mobile terminal searches for cells across a wide frequency range to accommodate large frequency offsets, then the robustness against frequency errors is improved, but the search time and processing complexity increase

Engineering Contradiction:

Improverobustness against frequency offsetsVSAvoidcell search duration

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The system performs partial action by searching for correlation peaks at specific, predetermined frequency offsets rather than exhaustively scanning the entire frequency range. This selective approach maintains sufficient robustness against frequency offsets while significantly reducing search time and processing complexity, resolving the contradiction between reliability and time loss.

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

The system changes the search parameters dynamically based on the detected correlation peak locations. By adjusting the frequency offset search range and step size according to actual signal characteristics, the terminal achieves robust frequency offset compensation without performing unnecessary searches across the entire frequency spectrum, thereby reducing time loss while maintaining reliability.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS8712359B2Communication device and method for detecting a radio signal

Publication Date: 2014.04.29 INTEL CORP

AI summary

For example, a communication device may be provided comprising an oscillator configured to generate a reference signal; an accuracy determiner configured to determine information about an accuracy of a frequency of the reference signal; a signal detector configured to detect the presence of a radio signal; and a controller configured to control the signal detector based on the information.