Variable Sub-Carrier Mapping for HARQ Frequency Diversity
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Solution Overview
Problem
In next-generation mobile communication systems, the HARQ transmission mechanism faces challenges due to consecutive data packets experiencing similar channel fading, leading to deep fading of sub-carriers during transmission and retransmission, which increases the probability of transmission failure and average retransmission times, thereby reducing system throughput.
Innovation Solution
A variable sub-carrier mapping method is introduced, where different bit interleaving or symbol-to-sub-carrier mapping schemes are applied in each HARQ process to distribute the same bits across different sub-carriers, achieving frequency diversity and reducing the likelihood of deep fading, thereby reducing average retransmission times and improving system throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the same sub-carrier mapping scheme is used for consecutive HARQ transmissions, then the implementation is simple, but the transmission reliability deteriorates due to deep fading on the same sub-carriers
Solution Approach 1:
The patent applies dynamics by making the sub-carrier mapping scheme variable rather than fixed. Different mapping schemes are selected for different HARQ transmissions based on channel conditions, allowing the system to adapt to changing fading patterns and avoid consistent deep fading on the same sub-carriers.
Solution Approach 2:
The patent changes the mapping parameter (sub-carrier assignment) between HARQ transmissions. By varying which sub-carriers carry which data bits across retransmissions, the system exploits frequency diversity to overcome deep fading conditions that affect specific sub-carriers.
2Reliability
If variable sub-carrier mapping is applied to achieve frequency diversity, then transmission reliability improves, but system complexity increases
Solution Approach 1:
The patent segments the data bits into different groups that are mapped to different sub-carriers across HARQ transmissions. This segmentation allows the system to distribute bits experiencing deep fading across multiple retransmissions on different sub-carriers, improving reliability while managing complexity through structured organization.
Solution Approach 2:
The patent implements dynamic sub-carrier mapping where the mapping relationship between data bits and sub-carriers changes between HARQ transmissions. This dynamic approach enables the system to adapt to channel conditions and achieve frequency diversity, improving transmission reliability despite increased complexity.
Data Source
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AI summary
A variable sub-carrier mapping method comprising steps of: applying different bit interleaving schemes to different transmissions of a hybrid automatic retransmission request(HARQ) process in side of transmitter; and in the side of the transmitter, modulating symbols onto sub-carriers for transmitting. Different transmissions in one HARQ process adopt different bit interleavers or different symbol-to-sub-carrier mapping methods so as to realize that the same bit of different transmissions in one HARQ process is transmitted via different sub-carriers. Therefore, the system achieves the frequency diversity gain and reduces the probability of failure of HARQ transmission caused by that some bits are always transmitted via the sub-carrier with the same deep fading. In this way, the average HARQ retransmission times can be reduced and the system throughput can be improved.