Combined-OFDM Subsymbol Processing for Noise Robustness
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Solution Overview
Problem
Existing OFDM systems face limitations in robustness against noise and efficiency in data transmission due to the sequential transmission of OFDM symbols, which can lead to interference and reduced data rate.
Innovation Solution
The method involves dividing data symbols into groups and transforming each group into time-domain subsymbols using a subset of subcarriers, then combining these subsymbols to form a combined modulated symbol, which is more robust against noise and can be transmitted with increased duration to improve data rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If OFDM symbols are transmitted sequentially using traditional methods, then the system structure is simple, but the robustness against noise is reduced and data transmission efficiency is limited
Solution Approach 1:
The patent divides data symbols into multiple groups and transforms each group into time-domain subsymbols using subsets of subcarriers. This segmentation allows independent processing and transmission of subsymbols, improving noise robustness while maintaining manageable system complexity through modular structure
Solution Approach 2:
The patent combines multiple time-domain subsymbols into a single combined modulated symbol that is transmitted together. This merging of subsymbols from different data symbol groups enhances noise resistance and increases data transmission efficiency while maintaining the same bandwidth as traditional OFDM systems
2Productivity
If OFDM symbols are transmitted sequentially, then the transmission duration is short, but the data rate is reduced
Solution Approach 1:
The patent transmits multiple subsymbols within a single combined OFDM symbol duration, effectively continuing the useful data transmission action throughout the symbol period. This approach increases data rate by utilizing the transmission duration more efficiently without requiring extended transmission time
3Reliability
If data symbols are grouped and transformed into subsymbols using subsets of subcarriers, then noise robustness is improved, but the processing complexity increases
Solution Approach 1:
The patent segments data symbols into groups and assigns subsets of subcarriers to each group for independent transformation into subsymbols. This segmentation enables parallel processing and improves noise robustness while keeping processing complexity manageable through systematic division of tasks
Solution Approach 2:
The patent transforms data symbols into subsymbols by changing the domain from frequency to time and by varying the subset of subcarriers used for each group. These parameter changes enhance noise robustness while the systematic approach to parameter transformation keeps processing complexity controlled
Data Source
AI summary
In one embodiment, a transmitter converts digital input data into combined-OFDM signals and a receiver recovers data from the transmitted combined-OFDM signals. For transmission, digital data is mapped into data symbols using a commonly known modulation technique, such as QAM or DQPSK. The data symbols are subsequently divided into two or more groups according to a specified grouping pattern. Each group of data symbols is then converted into a separate OFDM subsymbol using IFFT processing. The OFDM subsymbols are then combined according to a specified combining pattern to create a combined-OFDM symbol. Combined-OFDM symbols are then prepared for transmission by affixing cyclic prefixes, converting the symbols to analog format, and performing spectral shaping of the analog signal. Upsampling may be employed to increase the signal bandwidth. In alternative embodiments, OFDM subsymbols may be combined using interleaving to create an interleaved-OFDM symbol.