Variable Guard Interval OFDM for Throughput Optimization
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Solution Overview
Problem
Conventional CP-OFDM systems lack flexibility in guard interval length and content, leading to inefficient transmission capacity and throughput, especially in multi-user environments, as the GI length is fixed and cannot be tailored to individual channel conditions or users.
Innovation Solution
The introduction of a variable-guard OFDM (VG-OFDM) system, where the guard interval length and content can be adapted based on channel delay spread, modulation, coding sets, MIMO layers, and link direction, allowing for user-specific and time-variant adjustments within a fixed frame structure, decoupling GI flexibility from OFDM symbol length and frame format.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the guard interval length is fixed to cover the worst-case channel dispersion, then the reliability of transmission is improved, but the transmission capacity and throughput deteriorate due to substantial loss of useful transmission time
Solution Approach 1:
The patent implements dynamic guard interval length adaptation where the GI length is no longer fixed but can be adjusted based on channel conditions. The system dynamically selects from multiple predefined GI lengths (e.g., 1/4, 1/8, 1/16, 1/32 of OFDM symbol length) according to the actual channel dispersion characteristics, allowing the GI to be as short as necessary while maintaining reliability protection.
Solution Approach 2:
The patent changes the parameter of guard interval length from a fixed value to a variable parameter that can be selected from multiple discrete lengths. This parameter adaptation is controlled based on channel dispersion measurements, enabling the system to optimize the trade-off between reliability and throughput by selecting the minimum sufficient GI length for current channel conditions.
2Adaptability or versatility
If the guard interval length is adapted from one OFDM symbol to another within a frame, then the adaptability to channel conditions is improved, but the device complexity and frame structure management worsen
Solution Approach 1:
The patent segments the frame into multiple OFDM symbols, each capable of having its own guard interval length selected from predefined options. This segmentation allows independent adaptation of GI length per symbol while maintaining overall frame structure through standardized signaling mechanisms that indicate GI length choices without requiring complete frame restructuring.
Solution Approach 2:
The patent creates a universal frame structure that can accommodate multiple GI length configurations within the same frame format. The system maintains a standardized frame template that is flexible enough to support variable GI lengths through signaling, allowing the same frame structure to serve multiple channel conditions without requiring separate frame formats for each GI length.
3Adaptability or versatility
If the frame format is changed to accommodate variable GI lengths, then the flexibility of the system is improved, but the manufacturing precision and standardization worsen due to difficulty in casting variable-length symbols into fixed-length frames
Solution Approach 1:
The patent maintains a fixed frame format structure while allowing parameter changes within the frame, specifically the guard interval length of individual OFDM symbols. This approach preserves frame format standardization and manufacturing precision by keeping the overall frame structure constant, while achieving GI flexibility through parameter adaptation of constituent symbols using predefined GI length options.
4Reliability
If a conservative GI length is chosen to cover the worst-case scenario, then the reliability is improved, but the loss of transmission capacity and throughput worsens under typical channel conditions
Solution Approach 1:
The patent implements parameter adaptation of the guard interval length based on actual channel conditions rather than using a conservative fixed length. The system selects from predefined GI length parameters (e.g., 1/4, 1/8, 1/16, 1/32 of OFDM symbol length) according to measured channel dispersion, thereby minimizing the GI length to what is actually necessary and reducing the transmission capacity loss while maintaining sufficient reliability protection.
Data Source
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AI summary
A method including processing a data frame, the data frame having a predetermined frame size and including at least one data symbol configured to form a plurality of sub-carriers in the frequency domain, wherein each of the at least one data symbol comprises a user data portion and a guard interval portion, wherein each of the at least one data symbol includes a plurality of sub-symbols, and wherein at least one of the following parameters is variable during the processing : a size of the guard interval portion, a size of the user data portion, a size of the at least one data symbol, a number of data symbols the data frame comprises, a content of the guard interval portion, and a configuration of the sub-symbol boundaries.