UWB Mobile Device Frequency Offset Estimation
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Solution Overview
Problem
Existing UWB communication systems face challenges in accurately estimating clock frequency offsets in mobile devices relative to a controller clock, leading to systematic errors and decreased localization performance, especially when one of the two data packets is lost during the TDoA round, increasing radio activity and energy consumption.
Innovation Solution
A method that estimates the clock frequency offset in a mobile device by determining anchor clock frequency offsets relative to the controller clock and combining this information with mobile device clock frequency offsets, eliminating the need for direct determination through dedicated pairs of controller messages, and using carrier frequency offset estimation and statistical processing to improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the controller sends two packets within each TDoA round for frequency offset compensation, then the mobile device can compensate for its frequency offset, but radio activity increases and energy consumption increases
Solution Approach 1:
The patent introduces an intermediary approach where mobile devices estimate frequency offset using broadcast packets from anchors rather than receiving dedicated controller packets. The mobile device uses the broadcast packet's timestamp and its own reception timestamp to estimate offset, reducing radio activity while maintaining compensation capability
Solution Approach 2:
The patent extracts the frequency offset estimation function from the controller's dedicated packet exchange and relocates it to the mobile device's processing of broadcast packets. This eliminates the need for separate controller packets while preserving the offset compensation capability
2Measurement precision
If the controller sends two packets within each TDoA round for frequency offset compensation, then the mobile device can compensate for its frequency offset, but radio activity increases
Solution Approach 1:
The patent makes the broadcast packets serve multiple functions: they provide both location information for TDoA calculation and frequency offset estimation data. This multi-functionality eliminates the need for separate dedicated compensation packets, maintaining accuracy while improving throughput
3Reliability
If one of the two data packets is lost, then the mobile device cannot estimate its frequency offset, but a systematic error is introduced and TDoA localization performance decreases
Solution Approach 1:
The patent prepares mobile devices to handle packet loss by using multiple broadcast packets from different anchors for offset estimation. Instead of relying on a single packet pair, the system has pre-established multiple potential sources, cushioning against the loss of any individual packet
Solution Approach 2:
The patent uses broadcast packets from multiple anchors as intermediaries for frequency offset estimation. Rather than depending on a single controller packet pair, the mobile device can use any available broadcast packet, providing redundant pathways for offset estimation and maintaining reliability
Data Source
AI summary
A method of estimating a clock frequency offset in a mobile device relative to a clock frequency of a controller within a UWB network comprises (a) determining, for each of a plurality of anchors, an anchor clock frequency offset relative to the controller clock frequency, (b) broadcasting an anchor data packet from each anchor, the anchor data packet including the respective anchor clock frequency offset, (c) receiving at least one anchor data packet at the mobile device, (d) estimating a mobile device clock frequency offset relative to the anchor clock frequency of the anchor from which the at least one anchor data packet was received, and (e) estimating the clock frequency offset in the mobile device based on the estimated mobile device clock frequency offset and the anchor clock frequency offset included in the at least one received anchor data packet. Furthermore, a TDoA-based localization method and a TDoA-based localization system are described.