PSYNC Module Frequency Offset Estimation for WCDMA Terminals
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Solution Overview
Problem
The challenge in wireless communication systems is the high cost and complexity of wireless terminals due to the need for accurate crystal oscillators to synchronize with WCDMA base stations, which are expensive and difficult to replace with less costly alternatives without compromising synchronization.
Innovation Solution
A wireless terminal with a Primary Synchronization (PSYNC) module that includes multiple PSYNC correlation branches, each capable of phase rotating and correlating WCDMA signals with a PSCH code, producing correlation energies to estimate the frequency offset between the wireless terminal clock and the base station clock, allowing synchronization even with less accurate oscillators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If accurate crystal oscillators are used for synchronization, then synchronization reliability is improved, but device cost increases
Solution Approach 1:
The patent replaces expensive high-accuracy crystal oscillators with cheaper, less accurate oscillators in wireless terminals. The cost reduction is achieved by accepting that the oscillator will drift over time, and the system compensates for this drift through frequency offset estimation and correction mechanisms rather than relying on inherently stable hardware
Solution Approach 2:
The patent changes the operating parameters of the synchronization system by introducing frequency offset estimation and compensation. Instead of relying on hardware stability, the system dynamically adjusts for frequency drift by estimating the offset between terminal and base station clocks and correcting the received signal accordingly
2Measurement precision
If high-accuracy base station clocks are used, then network synchronization quality is improved, but terminal complexity increases
Solution Approach 1:
The patent introduces an intermediary frequency offset estimation and compensation mechanism between the base station clock and terminal clock. This intermediary layer allows the terminal to work with cheaper oscillators while the base station's high-accuracy clock provides the reference, with the offset compensation acting as a mediator that bridges the accuracy gap
Solution Approach 2:
The patent implements feedback through frequency offset estimation, where the terminal continuously monitors and estimates the frequency offset between its oscillator and the base station clock, then uses this feedback to correct subsequent synchronization operations, creating a closed-loop system that maintains precision without requiring expensive hardware
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 solution enables wireless terminals to synchronize with WCDMA base stations using less costly oscillators, reducing component costs while maintaining effective synchronization, thereby improving network performance and user experience.
Implementation Method 1
Each PSYNC correlation branch is operable to: phase rotate the WCDMA signal based upon a respective frequency offset
Implementation Method 2
correlate the phase rotated WCDMA signal with a Primary Synchronization Channel (PSCH) code over a plurality of sampling positions
Data Source
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AI summary
A wireless terminal is operable to receive a Wideband Code Division Multiple Access (WCDMA) signal from a base station and includes clock circuitry, a wireless interface, and a Primary Synchronization (PSYNC) module (708). The clock circuitry generates a wireless terminal clock using a wireless terminal oscillator. The wireless interface receives the WCDMA signal, which is produced by the base station using a base station clock that is produced using a base station oscillator that is more accurate than the wireless terminal oscillator. The PSYNC module includes a plurality of PSYNC correlation branches (808A-808N). Each PSYNC correlation branch phase rotates the WCDMA signal based upon a respective frequency offset (806), correlates the phase rotated WCDMA signal with a Primary Synchronization Channel (PSCH) code over a plurality of sampling positions (808), and produces PSYNC correlation energies based upon the correlations for each of the plurality of sampling positions (810).