HARQ Bit Mapping for Wireless Retransmission Decoding
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Solution Overview
Problem
Current wireless communication networks face challenges in maintaining error-free communication due to high bit error rates, even with robust error correcting codes and HARQ algorithms, particularly in varying channel conditions, which can lead to inefficiencies in retransmission mechanisms.
Innovation Solution
Implementing a non-random mapping rule for retransmitting encoded bits in wireless communication networks, where at least a portion of the encoded bits are mapped to different bit locations within modulated symbols, such as reversing or switching the first and last encoded bits, or applying a bit location offset, to improve decoding performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If encoded bits are mapped to fixed bit locations in modulated symbols for retransmission, then the decoding process is simple, but the reliability of communication deteriorates under varying channel conditions due to high bit error rates
Solution Approach 1:
The patent applies dynamics by making the bit location mapping adaptive rather than fixed. The mapping rule changes based on transmission type (initial vs. retransmission) and channel conditions. Specifically, retransmitted encoded bits are mapped to different bit locations within modulated symbols compared to initial transmission, allowing the system to dynamically respond to varying channel conditions and improve reliability without requiring overly complex predetermined mappings
Solution Approach 2:
The patent changes the mapping parameter (bit location) based on transmission context. For retransmissions, the bit locations are deliberately shifted or reversed compared to initial transmission. This parameter change allows the receiver to combine information from multiple transmissions with different error patterns, improving overall reliability while keeping the mapping rule itself relatively simple to implement
2Reliability
If robust error correcting codes and HARQ algorithms are used, then error correction capability is improved, but additional retransmissions are still required under high bit error rate conditions, increasing transmission time
Solution Approach 1:
The patent applies preliminary action by pre-planning different mapping rules for initial transmission versus retransmission. The transmitter and receiver both know in advance that retransmitted bits will be mapped differently, allowing the receiver to prepare appropriate combining strategies. This preliminary arrangement reduces the need for additional retransmissions by making the most of each retransmitted packet, thereby reducing overall transmission time
3Productivity
If encoded bits are mapped to the same bit locations in retransmissions, then the mapping process is efficient, but the probability of correct decoding decreases when channel conditions vary
Solution Approach 1:
The patent applies asymmetry by deliberately making the mapping different for retransmissions compared to initial transmission. Instead of using symmetric (identical) mapping rules, the system uses asymmetric mapping where retransmitted bits are placed in different bit locations within modulated symbols. This asymmetry ensures that errors affecting one transmission are less likely to affect the same bits in retransmission, improving decoding accuracy while maintaining reasonable mapping efficiency through predefined rules
Data Source
AI summary
Aspects of the present disclosure relate to retransmissions of data within wireless communication networks. For a retransmission, at least a portion of the encoded bits of an original transmission may be mapped to different bit locations in one or more modulated symbols based on a non-random mapping rule. In some examples, the encoded bits of a symbol may be reversed within the symbol for a retransmission. In other examples, the first and last encoded bits within a symbol may be switched for a retransmission. Other non-random mapping rules, such as a bit location offset, may also be used to map encoded bits to different bit locations in the modulated symbol within a retransmission.