VHT Long Training Field Sequence Construction for PAPR Reduction
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Solution Overview
Problem
Current Very High Throughput (VHT) wireless systems face challenges in constructing a Long Training Field (LTF) sequence with low peak-to-average power ratio (PAPR) for transmission preambles, particularly in VHT 5 GHz and 60 GHz specifications, which affects data rate and efficiency.
Innovation Solution
The method involves determining a VHT-LTF sequence by combining interpolating sequences with LTF tone values, repeating and rotating tones across subcarriers, and replacing tones at pilot locations with specific values to minimize PAPR, utilizing a combination of 802.11a and 802.11n tone values and phase rotation patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional LTF sequences are used in VHT systems, then compatibility with existing standards is maintained, but peak-to-average power ratio (PAPR) becomes excessively high
Solution Approach 1:
The patent modifies the LTF sequence parameters by incorporating interpolating sequences with specific tone values and applying phase rotation patterns. The tone values are carefully selected and repeated across subcarriers, while phase rotation is applied per bandwidth to transform the sequence characteristics, thereby reducing PAPR while preserving standard compatibility.
Solution Approach 2:
The patent constructs a composite LTF sequence by combining multiple interpolating sequences with specific tone values. This composite structure integrates different sequence components (including extra tone values) to achieve both standard compatibility and reduced PAPR, similar to how composite materials combine different materials to achieve superior properties.
2Productivity
If LTF sequence is optimized for low PAPR, then transmission efficiency improves, but sequence construction complexity increases
Solution Approach 1:
The patent divides the LTF sequence construction into manageable segments: interpolating sequences with specific tone values, repetition patterns across subcarriers, and phase rotation applications. This segmentation allows systematic optimization of PAPR while maintaining organized construction processes, balancing efficiency improvement with manageable complexity.
3Productivity
If bandwidth is increased to 80 MHz for higher data rates, then throughput doubles, but PAPR reduction becomes more difficult
Solution Approach 1:
The patent applies different characteristics to different portions of the bandwidth by using phase rotation patterns specific to each bandwidth segment. The LTF tone values are repeated for different subcarriers with localized phase adjustments, allowing PAPR reduction to be addressed locally across the 80 MHz bandwidth while maintaining high throughput.
Data Source
AI summary
Techniques are provided for constructing or determining a training sequence as a part of transmission preamble to minimize (or at least reduce) a peak-to-average power ratio (PAPR) at a transmitting node. In one example, a long training field (LTF) sequence of a preamble is determined that combines a set of interpolating sequences with LTF tone values. The LTF tone values may cover at least a portion of bandwidth of a first size, with each of the LTF tone values repeated for different subcarriers. The phases of tones of the LTF sequence may be rotated per bandwidth of the first size and certain tones of the LTF sequence may have a stream of values at pilot locations. For example, the phases of tones of the LTF sequence may be rotated in an effort to reduce PAPR during a transmission of the LTF sequence.