Receiver DRX Cycle Adjustment for Crystal Oscillator Frequency Error
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Solution Overview
Problem
Communication systems face challenges in maintaining synchronization accuracy between mobile communication terminals and base stations, particularly when operating in discontinuous reception mode, due to the use of low-cost, uncompensated crystal oscillators, which result in frequency errors that exceed acceptable limits.
Innovation Solution
A method and apparatus that estimate frequency errors in receivers and adjust the internal DRX cycle to ensure synchronization with the base station clock, allowing for periodic re-synchronization and maintaining accuracy within specified limits, even with uncompensated crystal oscillators, by activating the receiver for shorter intervals than the assigned DRX cycle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If uncompensated crystal oscillators are used in mobile terminals, then production costs are reduced, but frequency error exceeds acceptable synchronization limits
Solution Approach 1:
The patent applies periodic action by implementing discontinuous reception (DRX) cycles where the receiver is activated periodically to measure frequency error and perform compensation. Instead of continuous operation, the system periodically wakes up to check synchronization status and adjust timing advance values, thereby maintaining frequency accuracy while using low-cost uncompensated oscillators and reducing power consumption.
Solution Approach 2:
The patent implements feedback mechanisms where the receiver continuously monitors frequency error relative to the base station clock and uses this information to adjust timing advance values. The system measures frequency error during DRX activation periods and feeds this information back to compensate for oscillator drift, ensuring synchronization accuracy is maintained despite using inexpensive uncompensated crystal oscillators.
2Measurement precision
If the receiver is activated frequently to maintain synchronization, then frequency error is reduced, but power consumption increases
Solution Approach 1:
The patent resolves this contradiction by using periodic DRX activation cycles instead of continuous receiver operation. The receiver is activated at specific intervals to perform frequency error measurement and compensation, then remains inactive to conserve power. This periodic approach maintains synchronization accuracy while dramatically reducing power consumption compared to continuous operation.
Solution Approach 2:
The patent applies dynamics by making the receiver activation schedule adaptive rather than fixed. The system dynamically adjusts the timing and duration of receiver activations based on measured frequency error characteristics and network conditions, optimizing the balance between maintaining synchronization accuracy and minimizing power consumption in varying operational scenarios.
3Device complexity
If uncompensated crystal oscillators are used without temperature compensation, then device complexity is reduced, but frequency error varies with temperature
Solution Approach 1:
The patent uses feedback to compensate for temperature-induced frequency variations. The receiver measures frequency error relative to the base station clock during DRX activation periods, and this measured error is used to adjust timing advance values. This feedback mechanism effectively compensates for temperature drift without requiring complex temperature-compensated oscillators or additional temperature sensors.
Solution Approach 2:
The system performs self-service by using the existing receiver and base station signals to measure and compensate for frequency errors. Rather than adding separate temperature sensing and compensation circuits, the system uses the communication signal itself to detect frequency drift and automatically adjusts timing parameters to maintain synchronization, keeping the device simple while achieving temperature stability.
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 approach enables mobile communication terminals to meet synchronization accuracy requirements of ±0.1 ppm over a wide temperature range, reducing the need for costly temperature-compensated oscillators and eliminating the need for temperature sensors, while maintaining low production costs and minimizing power consumption.
Implementation Method 1
estimating the frequency error includes down-converting signals received from the transmitter using an uncompensated crystal oscillator, and assessing in the down-converted signals the frequency error
Data Source
AI summary
A method includes, in a receiver that includes an uncompensated crystal oscillator, receiving signals from a transmitter by activating the receiver periodically at intervals corresponding to a specified wake-up time period. In response to detecting at the receiver that the specified wake-up time period is insufficient for maintaining synchronization between the receiver and the transmitter using the uncompensated crystal oscillator, an actual wake-up time period, smaller than the specified wake-up time period, is selected. The receiver is activated periodically according to the selected actual wake-up time period.