5G NR LLR Buffer Reuse for In-Place De-Interleaving and HARQ Combining
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Solution Overview
Problem
The 5G NR technology faces challenges in reducing memory area requirements for buffering LLRs due to the need for large buffers resulting from the repetition rate matching scheme, which leads to significant circuitry implementation penalties.
Innovation Solution
Implementing multiple interleaver and rate matching engines in parallel on the transmit side and multiple de-interleaver and de-rate matching engines on the receive side, allowing for on-the-fly de-interleaving and de-rate matching, which reduces the memory needed for buffering LLRs and combines HARQ processes within the de-rate matching and de-interleaving processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If repetition rate matching scheme is used, then reliability of 5G NR communication is improved, but memory area requirement for buffering LLRs increases significantly
Solution Approach 1:
The patent divides the buffering operation into two distinct phases: a first buffering operation that stores received signals with interleaving and rate matching, and a second buffering operation that performs de-interleaving and de-rate matching before HARQ combining. This segmentation allows the system to maintain reliability through proper signal processing while reducing the peak memory requirement by reusing the first buffer for the second operation, thereby resolving the contradiction between reliability and memory area requirement
Solution Approach 2:
The first buffer is designed to serve multiple functions: it buffers received signals during the first buffering operation and is reused to buffer de-interleaved and de-rate matched signals during the second buffering operation. This multi-functionality eliminates the need for separate memory banks for different buffering stages, reducing overall memory area while maintaining the reliability benefits of the repetition rate matching scheme
2Reliability
If large buffers are allocated for LLR buffering, then HARQ combination accuracy is improved, but circuit area and implementation complexity increase
Solution Approach 1:
The patent merges the first buffering operation and the second buffering operation into a unified process where the same buffer memory is reused for both purposes. The controller coordinates these operations to ensure that de-interleaving and de-rate matching are completed before the buffer is overwritten, thereby maintaining HARQ combination accuracy while eliminating the need for separate memory banks and reducing circuit implementation complexity
3Speed
If multiple memory banks are used for LLR buffering, then data access speed is improved, but memory area and cost increase
Solution Approach 1:
The controller performs preliminary actions by completing the de-interleaving and de-rate matching operations before the buffer data is overwritten during the second buffering operation. This timing coordination ensures that the buffer is fully utilized without data loss, achieving efficient data access speed with a single memory bank rather than requiring multiple parallel memory banks
Data Source
AI summary
An apparatus (e.g., receive chain) for wireless communications may perform de-interleaving, de-rate matching, and hybrid automatic repeat request (HARQ) combining in a single step. The apparatus may include a data pool configured to store HARQ log likelihood ratio (LLR) data from previous transmissions. The apparatus may include a HARQ onload controller configured to load HARQ LLR data from the HARQ data pool into a HARQ buffer. The apparatus may include an LLR buffer configured to store received demodulated, interleaved, and rate matched LLR data. The apparatus may include a plurality of processing engines configured to, starting at different locations of the LLR buffer: receive new input data from the LLR buffer; combine the HARQ LLR data from the HARQ buffer with the new input data to generate de-interleaved, de-rate matched, and HARQ combined data; and write the de-interleaved, de-rate matched, and HARQ combined data into the HARQ buffer.