Sub-Band Power Allocation for High-Rate OFDMA Coding
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Solution Overview
Problem
Beyond 4G (B4G) radio systems face challenges in maintaining high spectrum efficiency due to the poor performance of Orthogonal Frequency Division Multiple Access (OFDMA) when using high coding rates, as they are sensitive to weak subcarriers and interference, leading to frequent packet retransmissions and reduced spectral efficiency.
Innovation Solution
A method is introduced to allocate transmission power between sub-bands based on their relative radio channel qualities and the coding rate, allowing for adaptive power control to compensate for channel variations and improve spectral efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a high coding rate is used to increase spectral efficiency, then the proportion of net information per gross information increases, but OFDMA performance deteriorates due to sensitivity to weak subcarriers and interference
Solution Approach 1:
The patent applies local quality by differentiating power allocation across different sub-bands based on their individual channel qualities. Instead of uniform power distribution, the system identifies sub-bands with poor channel conditions and allocates additional power specifically to those regions, while maintaining standard power levels in good sub-bands. This localized approach allows high coding rates to be used overall while providing targeted protection to vulnerable subcarriers, resolving the contradiction between spectral efficiency and reliability.
2Reliability
If transmission power is increased to compensate for weak subcarriers, then OFDMA performance improves, but power efficiency deteriorates
Solution Approach 1:
The patent changes the power allocation parameter from a uniform value to a variable value that depends on sub-band channel quality. By measuring or estimating the channel quality of different sub-bands and dynamically adjusting power levels accordingly, the system achieves reliable transmission on weak subcarriers only where necessary. This parameter change enables the system to maintain OFDMA performance without the penalty of uniformly increasing power across all sub-bands, thus preserving power efficiency.
3Reliability
If the MCS is selected according to the worst sub-carries to maintain OFDMA performance, then reliability improves, but spectrum efficiency deteriorates
Solution Approach 1:
The patent segments the frequency band into multiple sub-bands and evaluates each sub-band's channel quality independently. Instead of selecting a single MCS that satisfies the worst sub-carrier across the entire bandwidth, the system can apply different coding rates and modulation schemes to different sub-bands based on their individual qualities. This segmentation allows good sub-bands to utilize higher spectral efficiency configurations while only providing enhanced protection to poor sub-bands, thereby maintaining overall spectrum efficiency while ensuring reliability.
Data Source
AI summary
Improved adaptation to a frequency band comprising sub-bands is provided by receiving a coding rate of an error correction coding scheme for encoding modulation symbols to be transmitted on sub-bands of a frequency band in radio communications, determining relative radio channel qualities of the sub-bands of the frequency band, and allocating transmission power between the sub-bands at least on the basis of the relative radio channel qualities of the sub-bands and the received coding rate.