Transmit Path Group Delay Compensation for 5G Positioning
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Solution Overview
Problem
Existing mobile communication systems face challenges in accurately compensating for group delay variations in filters, which affect the timing of signal transmission and reception, leading to positioning errors in systems like 5G New Radio (NR) due to in-band group delay ripple and residual absolute delay.
Innovation Solution
Implementing a group delay compensation module that estimates the transfer function of transmit and receive paths using feedback signals, compensating for both in-band group delay ripple and residual absolute delay through iterative filtering and parameterization, with adjustments based on carrier frequency, bandwidth, and environmental factors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If filters are used in transmit and receive paths, then signal quality is improved, but group delay variations cause positioning errors
Solution Approach 1:
The system performs preliminary characterization of the transmit and receive paths to determine their transfer functions and group delay characteristics before actual positioning measurements. This pre-characterization allows the system to compensate for known filter-induced delays, establishing a consistent reference point at the antenna and eliminating positioning errors caused by group delay variations.
Solution Approach 2:
The system uses feedback from received positioning reference signals to continuously monitor and estimate the actual group delay experienced in the transmit and receive paths. This feedback mechanism allows dynamic adjustment of timing measurements, compensating for filter effects and ensuring accurate positioning despite the presence of filters with non-ideal group delay characteristics.
2Measurement precision
If group delay compensation is implemented, then positioning accuracy is improved, but system complexity increases
Solution Approach 1:
The compensation module uses the existing positioning reference signals transmitted and received by the system itself to characterize and compensate for group delay effects. Rather than requiring external calibration equipment or additional infrastructure, the system performs self-characterization using its own transmit and receive paths, reducing overall system complexity while maintaining positioning accuracy.
Solution Approach 2:
The system parameterizes the filter characteristics in terms of easily measurable quantities such as 3 dB bandwidth and center frequency. By expressing group delay compensation in terms of these standard filter parameters rather than requiring full transfer function characterization, the system reduces computational complexity while achieving effective compensation for filter-induced timing errors.
Data Source
AI summary
A method, apparatus and computer program is described comprising: providing a filtered transmit signal for transmission using a transmit forward path of a transmitter of a mobile communication system; receiving a receive signal using a wideband transmit feedback path of the transmitter of the mobile communication system; generating an estimate of a transfer function of the transmit forward path; and calculating a filter function for compensating for said estimated transfer function of the transmit forward path.