IQ-Imbalance Compensation Using Preliminary Estimation
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Solution Overview
Problem
Existing methods for IQ-imbalance compensation in wireless communication systems are inadequate when frequency offset compensation is applied, leading to suboptimal IQ-imbalance estimation and compensation, particularly in OFDM-based systems, due to the interference caused by frequency offset compensation.
Innovation Solution
A method that applies frequency offset compensation to a received wireless communication signal, determines adjustment values, and then estimates and compensates for IQ-imbalance using these values, taking into account the symmetry between sub-carrier frequency pairs and utilizing pilot symbols and channel values for accurate estimation and compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If frequency offset compensation is applied to correct frequency offset, then frequency offset is reduced, but IQ-imbalance estimation accuracy deteriorates due to interference from frequency offset compensation
Solution Approach 1:
The patent performs IQ-imbalance estimation before frequency offset compensation is applied to the received signal. By estimating the IQ-imbalance parameter using the received signal that still contains the frequency offset, the system captures the true combined effect of both impairments. This preliminary estimation allows the subsequent frequency offset compensation to proceed without interfering with the IQ-imbalance measurement, thereby resolving the contradiction between maintaining frequency offset correction and preserving IQ-imbalance estimation accuracy.
2Reliability
If conventional IQ-imbalance compensation methods are used after frequency offset compensation, then IQ-imbalance compensation is applied, but the compensation is suboptimal due to interference from frequency offset compensation
Solution Approach 1:
The patent performs IQ-imbalance estimation before frequency offset compensation is applied to the received signal. By estimating the IQ-imbalance parameter using the received signal that still contains the frequency offset, the system captures the true combined effect of both impairments. This preliminary estimation allows the subsequent frequency offset compensation to proceed without interfering with the IQ-imbalance measurement, thereby resolving the contradiction between maintaining frequency offset correction and preserving IQ-imbalance estimation accuracy.
3Reliability
If expensive radio design is used to meet high SNR demands, then signal-to-noise ratio is improved, but device cost increases
Solution Approach 1:
The patent changes the temporal parameter of IQ-imbalance estimation by performing it before frequency offset compensation rather than after. This parameter change in the processing sequence allows the system to achieve accurate IQ-imbalance estimation and compensation using standard, cost-effective radio hardware design. By compensating for IQ-imbalance at the stage when the signal still contains frequency offset, the system achieves high SNR performance without requiring expensive radio design modifications, thus resolving the contradiction between improving signal-to-noise ratio and reducing device cost.
Data Source
AI summary
An arrangement for processing a received wireless communication signal is disclosed. The arrangement comprises a frequency offset compensation unit adapted to apply a frequency offset compensation to the received wireless communication signal, determination circuitry adapted to determine one or more adjustment values associated with the frequency offset compensation, and an FFT-unit adapted to transform the frequency offset compensated received signal to a frequency domain. The arrangement also comprises an IQ-imbalance estimator adapted to estimate an IQ-imbalance, and an IQ-imbalance compensation unit adapted to perform IQ-imbalance compensation of the received wireless communication signal based on the estimated IQ-imbalance. At least one of the IQ-imbalance estimator and the IQ-imbalance compensation unit is adapted to base its operation on the one or more adjustment values. Corresponding method and computer program product are also disclosed.