SC-FDMA Sub-channel Clipping for Frequency Efficiency
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Solution Overview
Problem
Current SC-FDMA systems face limitations in accommodating a greater number of users within a limited frequency band and achieving high transmission rates due to tight frequency resource constraints.
Innovation Solution
The system reduces the number of sub-carriers per frequency channel by deleting specific signals from the spread spectrum signals allocated to frequency channels, transforming them into time-domain signals, and using non-linear iterative equalization to reproduce the transmitted signals, allowing for more efficient frequency usage and higher transmission rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of sub-carriers per sub-channel is increased to accommodate more users, then the frequency usage efficiency improves, but the transmission power requirements increase and PAPR performance deteriorates
Solution Approach 1:
The patent segments the frequency band into multiple sub-channels, each carrying multiple sub-carriers. By dividing the total frequency resources into manageable sub-channels, the system can accommodate more users without requiring each user to occupy the entire frequency band, thus reducing individual power requirements while maintaining overall frequency efficiency.
Solution Approach 2:
The patent introduces a hierarchical structure where sub-channels are further divided into resource blocks, and time resources are divided into slots and symbols. This multi-dimensional resource allocation (frequency-subchannel-time-symbol) allows the system to accommodate more users and increase frequency usage efficiency without proportionally increasing transmission power requirements.
2Power
If the number of sub-carriers per sub-channel is reduced to lower PAPR, then the transmission power efficiency improves, but the frequency usage efficiency deteriorates
Solution Approach 1:
By segmenting the frequency band into multiple sub-channels, each with a manageable number of sub-carriers, the patent maintains low PAPR performance for each sub-channel while the collective system achieves high frequency usage efficiency. The segmentation allows the system to balance between power efficiency and frequency efficiency.
Solution Approach 2:
The patent employs dynamic resource allocation where the number of active sub-channels and resource blocks can be adjusted based on system conditions. This dynamic adaptation allows the system to optimize between PAPR performance and frequency usage efficiency according to actual traffic demands and channel conditions.
3Quantity of substance
If more users are accommodated in a limited frequency band, then the system capacity increases, but the transmission rate per user decreases
Solution Approach 1:
The patent segments frequency resources into sub-channels and time resources into slots, creating a grid-like allocation structure. This segmentation allows for flexible assignment of resources to users, enabling the system to accommodate more users while maintaining acceptable transmission rates through optimized resource distribution.
Solution Approach 2:
The patent changes the allocation parameters dynamically, adjusting the number of active sub-channels, resource blocks, and time slots based on system conditions. This allows the system to optimize the balance between the number of accommodated users and the transmission rate per user by adapting resource allocation parameters in real-time.
Data Source
AI summary
To provide a system that can accommodate a greater number of terminals within a limited band and can obtain a higher transmission rate. While the number of frequency signals (spectrums) output in parallel by performing a spread spectrum from the DFT unit of each terminal is 12, the number of sub-carriers constituting one sub-channel is set at 10 or 11. In this case, the users (users A and G) allocated to the sub-channels at both ends of the band will not perform transmission of one frequency signal at the end (one sub-carrier) of all the frequency signals output from the DFT unit, whereas the users (users B to F) allocated to the other sub-channels will not perform transmission of the frequency signals at the ends (two sub-carriers). This transmission can be realized by deleting (clipping) the associated number of signals from both ends or from one end of the frequency signals output from the DFT unit of each terminal and allocating the frequency signals after clipping, to individual sub-channels.