Multicarrier Transmission Apparatus Guard Interval Design
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Solution Overview
Problem
Existing wireless communication systems face interference and degraded transmission efficiency due to inter-symbol interference (ISI) caused by arrival waves exceeding the normal guard interval, which affects the accuracy of propagation channel estimation.
Innovation Solution
A transmission apparatus that multicarrier-modulates symbols with different guard intervals, where a first guard interval is added to some symbols and a longer second guard interval is added to others, allowing for phase rotation and multiplexing in the frequency domain, followed by inverse Fourier transform and guard interval insertion, to improve resistance to ISI without degrading transmission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a guard interval longer than the normal GI is added to all OFDM symbols in a subframe to eliminate ISI, then communication quality is improved, but transmission efficiency is degraded due to increased redundant interval
Solution Approach 1:
The patent applies different guard interval lengths to different types of symbols within the same subframe. Specifically, pilot symbols and control symbols are assigned a longer guard interval (second GI) to ensure accurate channel estimation and robustness against ISI, while data symbols use a normal guard interval (first GI) to maintain transmission efficiency. This localized differentiation resolves the contradiction by providing enhanced protection only where necessary rather than uniformly across all symbols.
Solution Approach 2:
The patent segments the subframe into different symbol types (pilot symbols, control symbols, and data symbols) and assigns different guard interval configurations to each segment. This segmentation allows the system to optimize for both reliability (by protecting critical symbols with longer GI) and efficiency (by using normal GI for data symbols), thereby resolving the technical contradiction between communication quality and transmission efficiency.
2Productivity
If a normal guard interval is used for all symbols, then transmission efficiency is maintained, but accuracy of propagation channel estimation is degraded due to ISI from arrival waves exceeding the GI
Solution Approach 1:
The patent provides pilot symbols (which are used for channel estimation) with a longer guard interval (second GI) than the normal guard interval (first GI) used for data symbols. This local enhancement ensures that arrival waves exceeding the normal GI do not cause ISI that would degrade channel estimation accuracy, while maintaining overall transmission efficiency by not extending the GI for all symbols.
3Measurement precision
If scattered pilot symbols are arranged in the frequency and time direction to follow amplitude and phase changes, then channel estimation accuracy is improved, but the system becomes more vulnerable to ISI when arrival waves exceed the normal GI
Solution Approach 1:
The patent enhances the robustness of pilot symbols (which are scattered in frequency and time for accurate channel estimation) by assigning them a longer guard interval (second GI). This local quality enhancement ensures that the pilot symbols used for tracking amplitude and phase changes remain accurate even when arrival waves exceed the normal guard interval, thereby maintaining both channel estimation accuracy and robustness against ISI.
Data Source
AI summary
In a transmission apparatus which multicarrier-modulates and transmits symbols, which are basic units of digital signals, a subcarrier in which a symbol is arranged in a first multicarrier symbol having a first guard interval and a subcarrier in which a symbol is arranged in a second multicarrier symbol having a second guard interval longer than the first guard interval are scattered among a plurality of subcarriers constituting a multicarrier at the same time. Therefore, it is possible to improve the resistance to inter-symbol interference without substantially degrading transmission efficiency.