Radio Device Frequency Offset Estimation for Synchronization
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Solution Overview
Problem
In asymmetric power and processing capability scenarios between radio devices, such as in Passive Keyless Entry systems, accurate synchronization is challenging due to frequency reference drifts, leading to increased power consumption and system latency, especially in IR-UWB systems with heavy duty-cycling and long silences between signals.
Innovation Solution
An apparatus and method that estimate and adapt the carrier and symbol frequencies of a response signal to account for offsets in the reference clock frequency of a less powerful radio device, allowing for reduced synchronization overhead and power consumption by using a first and second synchronization mode with varying numbers of synchronisation symbols, and controlling frequency offsets or multiplication ratios to generate the response signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the second radio device uses a larger number of synchronization symbols to ensure accurate synchronization with the first radio device, then synchronization accuracy is improved, but transmission time and system latency increase
Solution Approach 1:
The patent applies preliminary action by having the second radio device estimate the carrier and symbol frequencies of the first radio device before transmitting the response signal. This frequency estimation allows the second device to pre-compensate for frequency offsets, enabling accurate synchronization with fewer synchronization symbols, thus reducing system latency while maintaining synchronization accuracy.
Solution Approach 2:
The patent changes the frequency parameters (carrier frequency and symbol frequency) of the response signal based on the estimated frequency offset of the first radio device. By adjusting these parameters, the system achieves accurate synchronization with reduced synchronization overhead, resolving the contradiction between synchronization accuracy and system latency.
2Use of energy by moving object
If the second radio device transmits response signal with frequency offset compensation, then power consumption of the first radio device is reduced, but processing complexity of the second radio device increases
Solution Approach 1:
The patent uses frequency estimation as an intermediary process. The second radio device performs frequency estimation on the incoming signal from the first device, uses this estimation to compensate for frequency offsets in the response signal, and transmits the compensated signal. This intermediary step enables the first device to synchronize more efficiently with lower power consumption, while the added processing complexity is concentrated in the second device which has more processing capability.
Solution Approach 2:
The patent exploits the asymmetric power and processing capabilities between the two radio devices. The second device (with more power and processing) performs the complex frequency estimation and compensation, while the first device (with limited power) benefits from reduced synchronization overhead. This asymmetric approach optimizes overall system efficiency by placing computational burden on the more capable device.
3Device complexity
If the system uses traditional synchronization methods without frequency estimation, then device complexity is reduced, but synchronization accuracy deteriorates due to frequency reference drifts
Solution Approach 1:
The patent applies preliminary frequency estimation before the main synchronization process. The second radio device estimates the carrier and symbol frequencies of the first device's signal, and uses this preliminary information to adjust its response signal's frequency parameters. This preliminary action compensates for frequency reference drifts that would otherwise degrade synchronization accuracy, while adding only moderate complexity to the system.
Data Source
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AI summary
An apparatus configured to; based on a first signal comprising one or more data transmission frames received from a first radio device by a second radio device, the first signal having a particular carrier frequency of a carrier wave thereof and the one or more data transmission frames comprising a plurality of symbols provided at a particular symbol frequency, the carrier frequency and symbol frequency based on a reference clock frequency of the first radio device; determine one or more of an estimate of the particular carrier frequency and an estimate of the particular symbol frequency relative to a reference clock frequency of the second radio device and provide for transmission of a response signal from the second radio device to the first radio device, the response signal provided with one or more of a reply carrier wave having a carrier frequency comprising the determined estimate of the particular carrier frequency and a plurality of symbols of one or more data transmission frames of the response signal provided at a reply symbol frequency comprising the determined estimate of the particular symbol frequency.