IQ Tracking Reference Signal for Uplink Shared Channel
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Solution Overview
Problem
Wireless communications systems face impairments due to in-phase and quadrature-phase (IQ) imbalances, which introduce noise floors and limit the use of higher modulation schemes despite ideal channel conditions, as these imbalances are independent of channel conditions and occur due to analog characteristics of devices.
Innovation Solution
The implementation of an in-phase and quadrature-phase tracking reference signal (IQTRS) that is transmitted and measured to compensate for IQ imbalances, allowing for the allocation of resources such that the base station can filter both the upconverted reference signal and its mirrored image, enabling signal adjustments and reducing noise floors, thereby supporting higher QAM constellations without the need for expensive transmit chain calibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If transmit chain calibration is performed to compensate for IQ imbalances, then communication quality is improved, but device complexity and cost increase
Solution Approach 1:
Instead of calibrating the transmit chain at the transmitter to compensate for IQ imbalances, the patent inverts the approach by having the receiver estimate and compensate for the impairments using received reference signals. This shifts the calibration burden from the transmit side to the receive side, avoiding complex transmit chain calibration while maintaining communication quality.
Solution Approach 2:
The patent employs feedback mechanisms where the receiver estimates IQ imbalance parameters using received reference signals and feeds back compensation information to correct the received signal. This feedback-based compensation allows for continuous adaptation to IQ variations without requiring complex transmit chain calibration.
2Productivity
If higher QAM constellations are used to increase data rate, then productivity is improved, but sensitivity to IQ imbalances increases
Solution Approach 1:
The patent uses feedback-based IQ imbalance estimation and compensation, where the receiver continuously monitors signal quality and adjusts compensation parameters accordingly. This enables the system to maintain higher QAM constellations for increased data rate while dynamically compensating for IQ imbalances to preserve reliability.
Solution Approach 2:
The patent dynamically adjusts compensation parameters based on estimated IQ imbalance characteristics. By changing compensation parameters in response to measured signal conditions, the system can optimize performance for higher QAM constellations while maintaining robustness against IQ imbalances.
3Measurement precision
If reference signal resources are allocated to enable IQ tracking, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent designs reference signals that serve multiple functions: they provide channel estimation, signal quality measurement, and IQ imbalance tracking simultaneously. This multi-functionality allows the system to achieve precise IQ imbalance measurement without requiring separate dedicated resources, thereby reducing overall device complexity.
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. A user equipment (UE) may receive, from a base station, a configuration indicating a set of resources for a reference signal to track an in-phase and quadrature-phase imbalance of the UE. The set of resources may include a first subset of resources for transmitting the reference signal and a second subset of resources for a mirror image signal that is generated during upconversion of the reference signal. The UE may upconvert the reference signal to a set of subcarriers corresponding to the first subset of resources and transmit the upconverted reference signal on the first subset of resources. The base station may receive the reference signal and the mirror image signal and determine a signal adjustment for communications with the UE based on the received reference signal and the received mirror image signal.