DFT-Spread OFDM Symbol Formation for Flexible Data-Pilot Ratio Control
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Solution Overview
Problem
DFT-spread OFDM modulation lacks the ability to control the data/pilot sub-carriers ratio effectively while maintaining low Peak to Average Power Ratio (PAPR) properties, which is crucial for accurate channel estimation and efficient power management.
Innovation Solution
A method and device that form a DFT-spread OFDM symbol by creating a pilot symbol with distinct parts, including front pilots and null values, and precoding data to compensate for data contribution, allowing for flexible data/pilot ratio adjustment without disrupting the low PAPR characteristics, enabling accurate channel estimation and efficient power management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If pilots are inserted in the frequency domain as Zadoff-Chu sequences to maintain low PAPR properties, then PAPR properties are preserved, but the ability to control the data/pilot sub-carriers ratio is lost
Solution Approach 1:
The pilot symbol is segmented into multiple parts: a first part containing front pilots, a second part containing null values, and optionally a third part containing end pilots. This segmentation allows flexible control of the data/pilot ratio while maintaining the structured format needed for low PAPR properties. The front pilots provide channel estimation references, the null values create separation, and the overall structure preserves single-carrier characteristics.
Solution Approach 2:
The pilot symbol is prepared in advance with a specific structure before modulation. The front pilots are positioned at the beginning of the symbol, followed by null values, creating a predetermined pattern that maintains low PAPR properties while enabling flexible data/pilot ratio control. This preliminary structuring allows the system to adapt to different channel conditions without disrupting the power envelope.
2Productivity
If scattered pilots are used to reduce pilot overhead, then spectral efficiency is improved, but channel estimation accuracy deteriorates in frequency selective channels
Solution Approach 1:
Instead of uniformly distributing pilots across all sub-carriers, the invention concentrates pilots locally in the first part of the symbol (front pilots). This local concentration provides sufficient channel estimation accuracy for the beginning of the symbol where power fluctuations are most critical, while reducing overall pilot overhead. The null values in the second part further isolate the pilot region, improving estimation accuracy where needed.
3Measurement precision
If more pilots are inserted to improve channel estimation accuracy, then channel estimation accuracy is improved, but spectral efficiency deteriorates due to increased pilot overhead
Solution Approach 1:
The invention applies partial action by inserting pilots only in the first part of the symbol rather than uniformly across all sub-carriers. The front pilots provide sufficient channel estimation accuracy for the critical regions, while the null values in the second part reduce pilot overhead. This partial pilot insertion strategy achieves adequate channel estimation without the spectral efficiency penalty of full pilot symbols.
Data Source
AI summary
A method and a device for forming a DFT-spread OFDM symbol including data and pilots, comprising:forming a pilot symbol in the time domain, the pilot symbol comprising at least two parts, a first part of the pilot symbol comprising samples of front pilots, a second part of the pilot symbol comprising null values,performing a DFT-spread OFDM modulation of the pilot symbol,precoding the data,putting the precoded data under the form of a data symbol in the time domain, the data symbol comprising at least two parts, a first part of the data symbol comprising null values, a second part of the data symbol comprising the data,performing a DFT-spread OFDM modulation of the data symbol,modifying a part of the DFT-spread OFDM modulated data symbol,combining the modified DFT-spread OFDM modulated data to the DFT-spread OFDM modulated pilot symbol.