OFDM Transmitter Dynamic Guard Interval Adjustment
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Solution Overview
Problem
Conventional OFDM systems face challenges in maintaining good reception characteristics in multi-user environments due to the need for varying guard interval lengths, which complicates band allocation and reduces transmission efficiency when guard intervals are set too long to prevent inter-carrier interference.
Innovation Solution
An OFDM transmitter and receiver system that dynamically adjusts the guard interval length for each transmission symbol period without altering the frame length, using a guard interval length decider and changer in the transmitter and a determiner in the receiver to determine optimal guard intervals based on feedback and self-correlation analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the guard interval length is increased to prevent inter-carrier interference in multi-path environments, then reception reliability is improved, but transmission efficiency deteriorates due to reduced useful data transmission time
Solution Approach 1:
The patent implements dynamic guard interval length adjustment where the guard interval is varied across different transmission symbol periods based on channel conditions. The guard interval length changer modifies the guard interval length for each transmission symbol period while maintaining a constant frame length, allowing the system to adapt to varying multi-path delay characteristics and optimize both reliability and transmission efficiency
Solution Approach 2:
The system changes the guard interval parameter dynamically by receiving feedback signals indicating received signal quality and adjusting the guard interval length accordingly. When signal quality is good, shorter guard intervals are used to improve transmission efficiency; when signal quality deteriorates, longer guard intervals are applied to maintain reliability
2Reliability
If the guard interval length is varied for each transmission symbol period to adapt to different communication environments, then reception characteristics are improved, but device complexity increases due to additional control mechanisms
Solution Approach 1:
The patent employs a feedback mechanism where the receiver evaluates received signal quality and transmits feedback signals to the transmitter. The guard interval length decider uses these feedback signals to determine appropriate guard interval lengths, and the guard interval length changer applies the decided lengths, creating a closed-loop control system that adapts to channel conditions without requiring complex open-loop prediction mechanisms
Solution Approach 2:
The frame structure is segmented into multiple transmission symbol periods, each capable of having a different guard interval length. This segmentation allows independent optimization of each symbol period's guard interval based on instantaneous channel conditions, improving reception characteristics while maintaining manageable system complexity through modular control
3Ease of operation
If the frame length is kept constant while adjusting guard interval lengths, then band allocation is simplified for multi-user environments, but the flexibility to optimize each transmission symbol period is reduced
Solution Approach 1:
The patent resolves the contradiction by moving the optimization flexibility from the frame level to the transmission symbol period level. While the frame length remains constant to simplify band allocation, the guard interval length can be independently adjusted for each transmission symbol period within the frame, providing optimization flexibility in the time dimension without affecting frame-level resource management
Data Source
AI summary
An OFDM transmitter transmits an OFDM signal by a frame having a plurality of transmission symbol periods constituted of an effective symbol period for transmitting an information bit and a guard interval. The OFDM transmitter includes a guard interval length decider configured to decide a guard interval length in accordance with a feedback signal from an OFDM receiver; and a guard interval length changer configured to change a guard interval length in each transmission symbol period, in accordance with a decided guard interval length without changing a frame length.