HARQ Bit Reliability via Constellation Rearrangement
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Solution Overview
Problem
Existing hybrid automatic repeat request (HARQ) schemes in digital communication systems face challenges in maintaining uniform bit reliability across transmissions, as bits modulating amplitude or phase of carrier waves have different susceptibilities to errors, leading to fluctuating reliability.
Innovation Solution
The proposed method involves modifying constellation diagrams and bit rearrangements for each retransmission, where bits are rearranged or inverted to ensure that all data bits have similar reliability, using techniques such as constellation rearrangement, bit interleaving, and subcarrier swapping, to balance bit reliabilities across multiple symbols and subcarriers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional HARQ schemes transmit data bits modulating carrier waves without rearrangement, then the transmission process is simple, but bits have different susceptibilities to errors causing fluctuating reliability
Solution Approach 1:
The patent applies dynamics by making the constellation diagram configurable and changeable based on transmission requirements. The system dynamically selects and switches between different constellation diagrams (e.g., 16-QAM, 64-QAM, 256-QAM) and applies bit rearrangement patterns differently for initial transmissions versus retransmissions. This dynamic adaptation allows the system to optimize bit reliability by assigning less significant bits to more reliable modulation positions during retransmissions, while maintaining simpler schemes for initial transmissions.
Solution Approach 2:
The patent changes the modulation parameters by modifying constellation diagrams and bit mapping schemes. Specifically, it alters the assignment of data bits to modulation symbols by applying different rearrangement patterns (such as swapping positions of less significant bits) in retransmissions compared to initial transmissions. This parameter change ensures that bits with different error susceptibilities are distributed more uniformly across transmissions, improving overall reliability without requiring complete system redesign.
2Reliability
If bits are rearranged or inverted to ensure similar reliability across all data bits, then bit reliability is improved, but the processing complexity increases
Solution Approach 1:
The patent segments the data bits into different significance groups (most significant bits and least significant bits) and applies different handling strategies to each segment. During retransmissions, it specifically rearranges only the less significant bits that have higher error susceptibility, while keeping the more significant bits in their original positions. This selective segmentation approach achieves uniform bit reliability without requiring complete rearrangement of all bits, thereby reducing processing complexity.
Solution Approach 2:
The patent applies partial action by implementing bit rearrangement only when necessary (i.e., during retransmissions) and only for specific bit positions (less significant bits). Rather than applying complex rearrangement algorithms to all bits in all transmissions, the system selectively applies simplified rearrangement patterns only to the bits that benefit most from it, achieving uniform reliability with minimal additional processing complexity.
3Reliability
If constellation diagrams are modified for each retransmission to balance bit reliabilities, then frame error rate performance improves, but the required bit energy to noise ratio increases
Solution Approach 1:
The patent uses copying by transmitting multiple versions of the same data through different constellation diagrams and bit arrangements. Instead of using a single high-energy robust modulation scheme, it transmits copies of the data using varied modulation patterns (different constellation diagrams with different bit mappings) across initial transmissions and retransmissions. The receiver combines these copies to achieve more reliable decoding, effectively reducing the required bit energy to noise ratio compared to using a single fixed high-reliability scheme.
Data Source
AI summary
A method of error control, including forming a plurality of first data symbols from a plurality of data bits, transmitting a first signal including the plurality of first data symbols, receiving a request for retransmission, forming a plurality of second data symbols from the plurality of data bits, and transmitting a second signal including the plurality of second data symbols. At least one of the first data symbols is formed from several of the plurality of data bits such that none of the second data symbols is formed from the several of the plurality of data bits.