I-Q Decoupled OFDM Modulation for Phase Imbalance Correction
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Solution Overview
Problem
Existing OFDM modulation systems suffer from I-Q imbalance, leading to interference between the desired data sequence and its image sequence, particularly in wireless communication networks, which can result in inter-subcarrier interference and degrade signal quality.
Innovation Solution
The implementation of modified DC-OFDM modulation and demodulation techniques, where the frequency-domain data sequence is split into two disjoint subsequences, each processed independently to generate conjugate symmetric sequences, and zero values are inserted to address I-Q phase imbalance, allowing for independent estimation and correction of phase offsets in the receiver.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If regular OFDM modulation is used, then data communication is achieved, but I-Q imbalance causes interference between desired data sequence and image sequence
Solution Approach 1:
The frequency-domain data sequence is divided into two disjoint subsequences: one for generating the in-phase component and another for generating the quadrature-phase component. This segmentation allows independent processing of I and Q components, preventing interference between them and resolving the I-Q imbalance issue while maintaining data communication effectiveness.
2Reliability
If I-Q decoupled OFDM modulation is implemented, then I-Q imbalance interference is reduced, but device complexity increases due to separate processing of I and Q components
Solution Approach 1:
The in-phase and quadrature-phase components are generated separately through conjugate symmetric sequences and then merged by placing them into even and odd index positions respectively in the time-domain sequence. This merging approach maintains the benefits of I-Q decoupling while integrating the components into a unified OFDM signal structure, managing complexity through systematic combination.
3Measurement precision
If zero values are inserted to address I-Q phase imbalance, then phase offset correction is enabled, but data transmission efficiency decreases
Solution Approach 1:
Zero values are strategically inserted into the frequency-domain subsequences at specific positions to create known reference points that enable phase offset estimation and correction. These zero insertions are minimal and targeted, extracting only the necessary information for phase correction while preserving the majority of data subcarriers for efficient transmission, thus balancing precision and productivity.
Data Source
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AI summary
In some examples, an apparatus includes a transmitter configured to apply input data as a frequency-domain data sequence to modulate a set of subcarriers, and separate the frequency-domain data sequence into a first subsequence of elements and a second subsequence of elements. A first conjugate symmetric subsequence that is based on inserting a zero value into the first subsequence is formed, and a second conjugate symmetric subsequence that is based on inserting a zero value into the second subsequence is formed, where the zero values are inserted at different positions in the first and second subsequences. A time-domain sequence comprising a first component that is a function of the first conjugate symmetric subsequence, and a second component that is a function of the second conjugate symmetric subsequence is generated.