LDPC Base Graph Signaling for Reliable Retransmission Decoding
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Solution Overview
Problem
In wireless communication systems, particularly in LTE and 5G networks, the use of multiple base graphs for LDPC codes can lead to difficulties in retransmissions, especially when the initial transmission's base graph is unknown, causing confusion and potential failure in decoding the retransmission due to mismatched transport block sizes and coding rates.
Innovation Solution
The implementation of techniques for explicit signaling or identification of base graphs, using RRC configuration or DCI, to determine the appropriate base graph for decoding, and the creation of tables to handle base graph selection, ensuring successful retransmissions by matching the initial and retransmission parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple base graphs are used for LDPC codes to improve coding performance, then reliability is improved, but device complexity increases due to the need to manage and select between multiple base graphs
Solution Approach 1:
The patent uses parameter changes by selecting different base graphs based on transport block size and coding rate parameters. The system determines which base graph to use by evaluating these parameters, allowing flexible adaptation to different communication conditions while maintaining reliable decoding performance across various scenarios.
Solution Approach 2:
The patent applies preliminary action by determining and indicating the base graph selection before the actual data transmission and decoding process. This advance determination ensures that both transmitter and receiver are aligned on which base graph to use, preventing decoding failures and simplifying the reception-side processing.
2Adaptability or versatility
If base graph selection is made dynamically based on transmission parameters, then adaptability is improved, but ease of operation deteriorates due to the complexity of determining and signaling the correct base graph
Solution Approach 1:
The patent introduces an intermediary indication mechanism that mediates between the transmitter's base graph selection and the receiver's decoding process. This indication (through signaling) carries the base graph selection information from transmitter to receiver, simplifying the receiver's operation while maintaining adaptability to different transmission conditions.
Solution Approach 2:
The system changes operational parameters by selecting different base graphs based on transport block size and coding rate. This parameter-based selection approach enables automatic adaptation to varying communication conditions without requiring complex manual configuration or intervention.
3Reliability
If explicit signaling of base graph is implemented, then reliability of retransmission decoding is improved, but use of energy increases due to additional signaling overhead
Solution Approach 1:
The patent achieves multi-functionality by using existing signaling mechanisms to convey base graph indication information. Rather than creating a completely new signaling channel, the system leverages existing downlink control information structures to carry the base graph selection indication, thereby reducing additional energy consumption while ensuring reliable retransmission decoding.
Data Source
AI summary
Certain aspects of the present disclosure generally relate to wireless communication. In some aspects, a device may determine a nominal coding rate of a communication based at least in part on a modulation and coding scheme (MCS) of the communication; determine whether to use a first base graph or a second base graph for decoding or transmission of the communication, wherein the determination of whether to use the first base graph or the second base graph is based at least in part on the nominal coding rate and a transport block size (TBS) of the communication, and wherein the TBS is based at least in part on a nominal number of resources and the MCS of the communication; and perform the decoding or transmission based at least in part on the determination of whether to use the first base graph or the second base graph. Numerous other aspects are provided.