Positioning Reference Signal Timing Adjustment for IoT
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Solution Overview
Problem
Low sampling rates in NB-IoT and eMTC devices result in inaccurate positioning due to reduced accuracy in time of arrival measurements, which is undesirable as increasing sampling rates increases battery consumption and device complexity.
Innovation Solution
The infrastructure equipment adjusts the timing of Positioning Reference Signals (PRS) transmissions with finer granularity than the UE's sampling rate, allowing the UE to build a more accurate channel impulse response by combining different copies of the received signal, effectively reducing the sampling period without increasing the sampling rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the sampling rate of the mobile device is increased to improve time of arrival measurement accuracy, then positioning accuracy is improved, but battery consumption and device complexity increase
Solution Approach 1:
Instead of increasing the UE's sampling rate to improve measurement accuracy, the patent inverts the approach by having the infrastructure equipment transmit multiple PRS signals with different timing adjustments. The UE combines these differently-timed signals to achieve higher effective sampling accuracy without actually increasing its sampling rate, thus resolving the contradiction between measurement precision and device complexity
Solution Approach 2:
The patent introduces infrastructure equipment as an intermediary that performs the complex timing adjustment and signal transmission operations. The base station transmits multiple PRS signals with precisely controlled timing differences, acting as a mediator that enables high-accuracy positioning measurements without requiring the UE to have high sampling capabilities, thereby reducing UE complexity while maintaining measurement accuracy
2Measurement precision
If the sampling rate of the mobile device is increased to improve time of arrival measurement accuracy, then positioning accuracy is improved, but battery consumption increases
Solution Approach 1:
The patent inverts the conventional approach by having the infrastructure equipment rather than the mobile device perform the high-rate sampling equivalent through multiple timed transmissions. The UE combines these signals to achieve high measurement accuracy without actually operating at high sampling rates, thereby avoiding the increased battery consumption that would result from higher sampling operations
3Measurement precision
If multiple position reference signals are transmitted with different timing adjustments to improve measurement accuracy, then positioning accuracy is improved, but network complexity increases
Solution Approach 1:
The patent segments the positioning reference signal transmissions into multiple separate PRS signals with different timing adjustments. Each PRS signal is transmitted in a different subframe with a specific timing offset, allowing the UE to combine them for higher accuracy. This segmentation enables precise timing measurements while distributing the complexity across multiple simple, standardized transmissions rather than requiring a single complex signal
Data Source
AI summary
Infrastructure equipment for transmitting data to and receiving data from a mobile device on a communications network is described. The infrastructure equipment comprising: transmitter circuitry configured to transmit the data to the mobile device; and controller circuitry configured to control the transmitter circuitry to transmit a first position reference signal in a first subframe and a second position reference signal in a second subframe, wherein the second position reference signal is a time adjusted version of the first position reference signal, the amount of time adjustment being determined by the sample time at which the mobile device samples the position reference signal.