OFDM Synchronization Channel PAPR Reduction via Selective Subcarrier Allocation
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Solution Overview
Problem
In multi-carrier transmission schemes like OFDM, the amplification of subcarrier signals in transmission amplifiers is challenging due to peak-to-average power ratio (PAPR) issues, leading to reduced average power and degraded synchronization channel detection accuracy, and the fixed allocation of radio resources to synchronization channels results in inefficient system performance.
Innovation Solution
A transmitter and receiver system that employs amplitude adjustment sequences with constant amplitude and optimal autocorrelation properties to reduce PAPR, allowing for improved synchronization channel detection accuracy and flexible power allocation to synchronization channels, using techniques such as CAZAC, GCL, and Golay codes to enhance timing detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If synchronization channel is transmitted throughout all subcarriers in burst manner, then detection accuracy is improved, but PAPR increases and average power decreases
Solution Approach 1:
The patent applies local quality by transmitting synchronization signals only on specific subcarriers (e.g., DC subcarrier and odd-numbered subcarriers) rather than all subcarriers. This selective subcarrier allocation reduces the peak-to-average power ratio while maintaining adequate detection accuracy through strategic frequency domain placement of synchronization signals.
Solution Approach 2:
The patent uses partial action by allocating synchronization channels to only a portion of available subcarriers instead of all subcarriers. This partial subcarrier allocation reduces the energy loss and PAPR while still providing sufficient synchronization functionality through the selected subcarrier set.
2Measurement precision
If transmission power of synchronization channel is increased, then detection accuracy is improved, but system efficiency decreases due to overhead
Solution Approach 1:
The patent improves system efficiency by allocating synchronization channels to specific local regions in the frequency domain (certain subcarriers) rather than uniformly across all subcarriers. This localized allocation reduces the overhead proportion while maintaining detection accuracy through strategic subcarrier selection.
Solution Approach 2:
The patent changes the parameter of subcarrier allocation from full-bandwidth to partial-bandwidth assignment. By modifying the subcarrier allocation pattern (e.g., using DC and odd-numbered subcarriers), the system reduces synchronization channel overhead while maintaining adequate detection performance.
3Stability of the object's composition
If clipping processing is applied to avoid distortion, then waveform distortion is reduced, but detection accuracy of synchronization channels deteriorates
Solution Approach 1:
The patent applies preliminary anti-action by designing the synchronization signal to have inherently low PAPR through selective subcarrier allocation. This prevents the need for clipping processing that would otherwise distort the waveform and degrade detection accuracy. The low PAPR design anticipates and prevents the need for aggressive power amplifier back-off or clipping.
Data Source
Figure 1
Figure 2A~2B
Figure 3~4A
AI summary
A transmitter comprises a generation unit generating a frame, which includes a plurality of OFDM symbols; and a transmission unit transmitting the generated frame, wherein the generation unit arranges a primary synchronization channel for detecting a symbol timing at an end OFDM symbol of the frame and a secondary synchronization channel for detecting a reception frame at an OFDM symbol preceding the end OFDM symbol, and the generation unit further arranges a cyclic prefix at each of the plurality of OFDM symbols and applies any of specified different cyclic prefix lengths.