Inter-Carrier Interference Measurement in OFDM Systems
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Solution Overview
Problem
In Orthogonal Frequency Division Multiplexing (OFDM) systems, inter-carrier interference (ICI) occurs due to imperfections at the transmitter and receiver, causing performance degradation, and existing methods lack effective measurement techniques to assess this interference.
Innovation Solution
A system that includes a test symbol generator to create an N*N orthogonal matrix of test symbols, which is transmitted through the OFDM system, and an ICI measuring module at the receiver to detect and rearrange these symbols into an ICI matrix, quantifying interference between sub-carriers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If OFDM system uses multiple sub-carriers for high rate transmission, then transmission rate is improved, but inter-carrier interference occurs due to loss of orthogonality
Solution Approach 1:
The patent applies preliminary action by generating a specific test symbol sequence with known orthogonal properties before actual transmission. This test sequence allows the system to pre-assess ICI conditions and characterize the channel before normal data transmission, enabling proactive identification and compensation of interference patterns that would otherwise degrade high-rate transmission performance
2Adaptability or versatility
If transmitter and receiver components are used to enable OFDM operation, then communication functionality is achieved, but component variations and imperfections cause loss of sub-carrier orthogonality
Solution Approach 1:
The patent implements feedback by using the received test symbol sequence to measure actual ICI levels and characteristics, then using this measured information to characterize system imperfections. This feedback loop enables the system to adapt to component variations and maintain reliable operation despite losses in orthogonality caused by real-world transmitter and receiver imperfections
3Measurement precision
If ICI measurement is implemented to assess OFDM performance, then system performance assessment capability is improved, but measurement complexity increases
Solution Approach 1:
The patent applies copying by creating a simplified test model that replicates the essential ICI measurement function without requiring complex measurement infrastructure. The test symbol sequence serves as a copy or representation of normal data transmission, allowing ICI characteristics to be measured using straightforward correlation operations rather than complex analysis systems
Data Source
AI summary
A system for measuring inter-carrier interference (ICI) in an OFDM system includes a test symbol generator coupled to a transmitter of the OFDM system to generate an N*N orthogonal matrix having N*N test symbols, and to send the test symbols in a test symbol stream via the transmitter to a receiver of the OFDM system. The N*N test symbols are arranged by the test symbol generator into an N*N orthogonal matrix before being sent to the receiver. The system also includes an ICI measuring module coupled to the receiver to detect the N*N test symbols received in the receiver and to arrange the test symbols as a receiving matrix in the same way as the orthogonal matrix in the transmitter. The ICI measuring module outputs the receiving matrix as an ICI matrix of the OFDM system, wherein an element on the kth row, lth column of the ICI matrix represents interference from the lth sub-carrier on the kth sub-carrier, wherein k≠l.