Turbo Decoder CRC Flow With Soft Combining for Fewer Retransmissions
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Solution Overview
Problem
Conventional LTE uplink data processing is inefficient due to excessive re-transmissions and computational load on the baseband processor, as it performs CRC checks on all code blocks regardless of failures, wasting time and air interface resources.
Innovation Solution
A method that performs cyclic redundancy checks on each code block until failure, requests retransmissions only for failed blocks, and uses soft combining of retransmitted blocks with original blocks to form combined code blocks, reducing unnecessary retransmissions and computational load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If CRC check is performed on all code blocks unconditionally, then reliability of error detection is improved, but processing time and computational load increase
Solution Approach 1:
The patent segments the code blocks into two groups: those that need CRC checking and those that don't. By identifying which code blocks failed in previous transmissions and only checking those, the system avoids unnecessary CRC operations on successfully decoded blocks, thereby reducing processing time while maintaining error detection reliability.
Solution Approach 2:
Instead of performing CRC checks on all code blocks (excessive action), the patent performs CRC checks only on the necessary subset of code blocks that are suspected to have errors based on previous transmission failures. This partial action approach reduces computational load and processing time while maintaining sufficient error detection capability.
2Reliability
If CRC check is performed on all code blocks unconditionally, then completeness of error detection is improved, but device complexity increases
Solution Approach 1:
The baseband processor is designed to segment the error detection task by maintaining tracking information about which code blocks have failed previously. This segmentation allows the processor to focus computational resources only on problematic code blocks, reducing overall device complexity while maintaining complete error detection for necessary blocks.
Solution Approach 2:
The system performs preliminary tracking of code block transmission status and failure information before performing CRC checks. By preparing and storing information about which code blocks need checking in advance, the baseband processor avoids the complexity of evaluating all code blocks, thus reducing device complexity while ensuring complete error detection where needed.
3Reliability
If re-transmission is requested for all code blocks, then reliability of data delivery is improved, but loss of air interface resources increases
Solution Approach 1:
The patent segments the re-transmission request to include only those code blocks that actually failed CRC checks, rather than requesting re-transmission of all code blocks. This selective re-transmission approach maintains data delivery reliability for failed blocks while avoiding unnecessary air interface resource consumption for blocks that were successfully decoded.
Solution Approach 2:
The system extracts and identifies only the specific code blocks that require re-transmission based on CRC check results and previous transmission failure tracking. By separating the failed blocks from successfully decoded blocks and requesting re-transmission only for the extracted failed blocks, the system improves data delivery reliability while minimizing air interface resource loss.
Data Source
AI summary
Disclosed is a method for processing code blocks as implemented by a baseband processor. The method involves performing a cyclic redundancy check on decoded and deinterleaved code blocks until one fails its CRC check. On first failure the baseband processor requests a retransmission of the code blocks and resumes CRC checks on the retransmitted code blocks, beginning at the code block that had failed. In the event of subsequent failures, the baseband processor performs a soft combine on the failed retransmitted block with its original transmitted counterpart. Only if the soft combined code block fails does the baseband processor request another retransmission. In this case, subsequent CRC failures result in soft combines of three corresponding code words, making the process more robust. The method reduces the number of retransmissions as well as the computing resources needed for processing incoming code blocks.