ECC Symbol Modification for Lower-PAPR OFDM Transmission
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Solution Overview
Problem
Modern communication systems face issues with high Peak-to-Average Power ratios (PAPR) and bit-error rates due to distortion and interference, particularly in OFDM-based systems like 4G LTE and 5G networks, where current solutions like clipping and modulation scheme downgrading are inefficient.
Innovation Solution
The system intentionally modifies symbols in the bitstream before transmission using error correction codes to optimize communication metrics such as reducing PAPR and bit-error rates by changing symbols to lower power levels or more discriminable constellation points, utilizing the ECC's correction capacity to maintain data integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If clipping is used to reduce PAPR, then PAPR is reduced, but distortion and adjacent channel interference increase
Solution Approach 1:
The system performs preliminary actions by modifying symbols in advance before transmission to prevent high PAPR from occurring. The transmitter identifies symbols that would contribute to high PAPR and proactively changes them to alternative symbols that maintain data integrity while reducing peak power, thereby avoiding the need for clipping and its harmful effects.
Solution Approach 2:
The system converts the potential harm of high PAPR into a benefit by using the error correction code's redundancy to intentionally modify symbols. The redundancy that would normally only correct errors is instead used proactively to prevent PAPR issues, turning a passive error correction capability into an active PAPR reduction mechanism.
2Reliability
If modulation scheme is downgraded to reduce bit-error rate, then bit-error rate is reduced, but data rate decreases
Solution Approach 1:
The system changes parameters by modifying individual symbols within the existing modulation scheme rather than downgrading to a lower-order modulation. By altering specific symbols that cause errors and using error correction codes to maintain reliability, the system achieves improved bit-error rate performance while preserving the higher data rate capability of the original modulation scheme.
3Power
If symbols are modified to reduce PAPR, then PAPR is reduced, but bit-error rate may increase
Solution Approach 1:
The system uses feedback mechanisms where the receiver detects errors and sends acknowledgments back to the transmitter. The transmitter monitors these feedback signals and adjusts its symbol modification strategy accordingly, ensuring that PAPR reduction actions do not push the bit-error rate beyond acceptable thresholds. This closed-loop control balances PAPR reduction with error rate maintenance.
Solution Approach 2:
The system converts the potential harm of symbol modification into a benefit by using error correction codes to compensate. The same code redundancy that would normally only correct random errors is instead utilized to correct the intentional modifications made for PAPR reduction, thereby maintaining reliability while achieving power optimization.
Data Source
AI summary
Disclosed in some examples are methods, systems, devices, and machine-readable mediums which optimize one or more metrics of a communication system by intentionally changing symbols in a bitstream after encoding by an error correction coder, but prior to transmission. The symbols may be changed to meet a communication metric optimization goal, such as decreasing a high PAPR, reducing an error rate, reducing an average power level (to save battery), or altering some other communication metric. The symbol that is intentionally changed is then detected by the receiver as an error and corrected by the receiver utilizing the error correction coding.