Hierarchical CAZAC Preamble Structure for High-Speed Communication
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Solution Overview
Problem
Conventional block transmission systems, such as OFDM and SCBT, face challenges with high preamble overhead and peak-to-average power ratio (PAPR), which reduce bandwidth efficiency and impose limitations on transmitter power usage, especially in high-rate communication systems.
Innovation Solution
The system employs a preamble structure composed of circularly orthogonal sequences, specifically hierarchical pseudo-circularly symmetric and full circularly symmetric Constant Amplitude Zero Auto-Correlation (CAZAC) sequences, eliminating the need for cyclic prefixes or zero padding, and reducing PAPR by about 3 dB compared to conventional systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional block transmission systems (OFDM, SCBT) use repeated auto-orthogonal sequences separated with Cyclic Prefix or Zero Padding for training sequences, then time synchronization and frequency offset estimation can be performed, but the Peak to Average Power Ratio (PAPR) becomes high and bandwidth efficiency is reduced
Solution Approach 1:
The patent extracts and removes the Cyclic Prefix and Zero Padding components from the conventional training sequence structure. By eliminating these redundant elements while retaining the core auto-orthogonal sequence repetitions, the system achieves the same synchronization and estimation functions with reduced overhead, thereby improving bandwidth efficiency without sacrificing reliability
Solution Approach 2:
The patent changes the structural parameters of the training sequence by using simple repetitions of auto-orthogonal sequences without Cyclic Prefix or Zero Padding. This parameter change reduces the overall length and complexity of the preamble while maintaining the essential correlation properties needed for synchronization and frequency offset estimation
2Reliability
If conventional preambles use repeated sequences with Cyclic Prefix or Zero Padding, then synchronization and channel estimation can be performed, but the Peak to Average Power Ratio (PAPR) increases, limiting transmitter power
Solution Approach 1:
The patent removes the Cyclic Prefix and Zero Padding components that contribute to high PAPR. By extracting only the essential auto-orthogonal sequence repetitions, the system maintains synchronization and channel estimation capabilities while significantly reducing peak power requirements, thus improving transmitter power efficiency
Solution Approach 2:
The patent changes the temporal and structural parameters of the preamble by eliminating the prefix and padding elements. This parameter modification reduces the signal's peak amplitude variations while preserving the autocorrelation and cross-correlation properties necessary for reliable synchronization and channel estimation
3Measurement precision
If long preambles are used for synchronization, AGC gain setting, frequency offset estimation, and channel estimation, then accurate receiver functions can be achieved, but bandwidth efficiency is reduced
Solution Approach 1:
The patent extracts and removes the redundant Cyclic Prefix and Zero Padding portions from the training sequence. By keeping only the essential repeated auto-orthogonal sequences, the system performs all necessary receiver functions (synchronization, AGC, frequency offset estimation, channel estimation) with a shorter preamble, thereby improving bandwidth efficiency while maintaining measurement precision
Solution Approach 2:
The patent segments the training sequence into essential functional components (repeated auto-orthogonal sequences) and eliminates non-essential segments (Cyclic Prefix, Zero Padding). This segmentation approach retains the core functionality for accurate receiver operations while reducing the overall preamble length to improve bandwidth efficiency
Data Source
AI summary
The system (700), apparatus (600), and method of the present invention provide an hierarchical pseudo-circularly symmetric and full circularly symmetric training sequence structure (100) for high-speed communication system. The hieratical pseudo-circularly symmetric part (101) is preferably used for burst detection, coarse frequency and timing error estimation and AGC gain setting. The full circularly symmetric part (102) is preferably used for channel estimation, fine frequency error estimation. The resulting sequence has a very good peak-to-average power (PAPR) property, making it suitable for many applications. The bandwidth efficiency is also improved due to using symmetric sequences.