RF Branch Calibration via Downlink Resource Multiplexing
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Solution Overview
Problem
Existing calibration procedures for radio access network nodes and radio frequency equipment face challenges such as resource overhead, interruption of normal traffic data, and scheduling complexities due to antenna calibration signals, particularly in time division duplex (TDD) and frequency division (FDD) systems.
Innovation Solution
A method and network node that co-schedules downlink time/frequency resources to calibrate radio frequency branches by analyzing signals via an internal coupler unit, adjusting amplitude/phase settings to minimize interference and resource utilization, compatible with TDD regulation restrictions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If antenna calibration signal is transmitted to measure amplitude and phase difference between radio frequency branches, then beamforming performance is improved, but time/frequency resources are consumed and normal traffic transmission is interrupted
Solution Approach 1:
The patent combines the calibration signal transmission with normal downlink traffic transmission by multiplexing them in the time/frequency domain. The calibration signal is transmitted on resource blocks allocated to terminal devices during their downlink reception periods, merging calibration functionality with existing traffic resources to avoid dedicated resource allocation and interruption.
Solution Approach 2:
The downlink resource blocks serving terminal devices are made multi-functional: they serve both as data transmission channels for terminal devices and as calibration signal transmission channels. This universal usage allows the same physical resources to perform both communication and calibration functions simultaneously without requiring separate dedicated resources.
2Productivity
If antenna calibration signal is transmitted in TDD system during downlink traffic time period, then calibration is performed without interrupting traffic, but regulation-not-allowed emission may occur during guard period
Solution Approach 1:
The patent applies different transmission characteristics to different parts of the signal. The calibration signal is transmitted with specific power levels and timing characteristics that are localized to avoid guard period emissions, while maintaining calibration effectiveness. The signal parameters are adjusted locally in time and frequency to comply with regulatory requirements during TDD guard periods.
3Productivity
If more radio frequency branches are added to increase system capacity, then spatial multiplexing performance is improved, but more time/frequency resources are needed for calibration signal transmission
Solution Approach 1:
As the number of radio frequency branches increases, the patent merges calibration signal transmission with the downlink traffic resources of terminal devices. The calibration signal is multiplexed with data signals in the time/frequency domain, allowing calibration of additional branches without requiring proportionally more dedicated calibration resources, thus supporting system capacity scaling.
Data Source
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AI summary
There is provided mechanisms for calibrating radio frequency branches of a radio transceiver device in a radio access network node. A method is performed by a network node. The method comprises co-scheduling downlink time/frequency resources for terminal devices in accordance with a set of terminal device identifiers. 5 One of the terminal device identifiers is not of any terminal device served by the radio access network node. The downlink time/frequency resources for this terminal device identifier define time/frequency resources for calibrating the radio frequency branches. The method comprises determining a difference in amplitude/phase between the radio frequency branches by analysing a signal as received via an 10 internal coupler unit in the radio transceiver device. The signal represents the time/frequency resources as transmitted over at least some of the radio frequency branches. The method comprises calibrating the radio frequency branches by adjusting an amplitude/phase setting of at least one of the radio frequency branches according to the determined difference. 15 (Fig. 3)