Dynamic HARQ Soft Buffer Allocation for LTE Carrier Aggregation
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Solution Overview
Problem
In LTE mobile communication networks, the existing HARQ memory space management is inadequate for carrier aggregation, leading to a mismatch between eNB rate matching and UE soft buffer storing, resulting in performance degradation due to insufficient HARQ processes and buffer size issues, especially in scenarios with multiple component carriers.
Innovation Solution
A method of dynamic HARQ memory space management and soft buffer allocation is proposed, where the UE dynamically allocates HARQ soft buffers to various HARQ processes, allowing for larger buffer sizes when needed and supporting more HARQ processes by releasing part of the original buffer, using techniques like per-CC and common buffer pooling with fixed or variable resolution to optimize buffer allocation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the buffer size for each HARQ process is equally divided among serving cells in CA scenarios, then backward compatibility is maintained, but the received coded bits may be bigger than the buffer size causing performance degradation
Solution Approach 1:
The patent applies dynamics by making the buffer allocation adaptive rather than fixed. The eNB dynamically adjusts the buffer allocation based on the actual number of active HARQ processes and the size of received coded bits. When the number of active HARQ processes is small, the eNB allocates larger buffer sizes to reduce mismatch with rate matching. When more HARQ processes are active, the buffer allocation is adjusted accordingly, creating a dynamic balance between backward compatibility and performance.
Solution Approach 2:
The patent changes the buffer size parameter dynamically based on system conditions. The eNB modifies the buffer allocation parameter according to the actual HARQ process activity and coded bit size, transitioning from a static equal division approach to a dynamic parameter adjustment approach that optimizes performance while maintaining compatibility.
2Productivity
If the total soft channel bit buffer size is increased for UE category 6-7, then more HARQ processes can be supported, but the buffer is still designed to be backwards compatible to UE category four
Solution Approach 1:
The patent makes buffer management dynamic by allowing the eNB to adjust buffer allocation based on the actual number of active HARQ processes. Instead of a fixed buffer size designed for backward compatibility, the system dynamically allocates buffer resources, enabling UE category 6-7 to utilize more buffer space when needed for higher throughput while maintaining compatibility with UE category four when fewer processes are active.
Solution Approach 2:
The buffer management mechanism serves multiple functions: it maintains backward compatibility with UE category four while simultaneously supporting enhanced performance for UE category 6-7. The eNB universally applies the same dynamic allocation principle across different UE categories, allowing the system to adapt to varying requirements without requiring category-specific buffer configurations.
3Adaptability or versatility
If different TDD UL-DL configuration among aggregated cells are supported, then carrier aggregation flexibility is improved, but the maximum number of required HARQ processes may not be the same causing different HARQ performance among different serving cells
Solution Approach 1:
The patent applies dynamics by making HARQ buffer allocation adaptive to the actual number of active processes across different serving cells. When different TDD UL-DL configurations cause varying HARQ process requirements, the eNB dynamically adjusts buffer allocation per cell based on actual activity, ensuring consistent performance across all serving cells while maintaining CA flexibility.
Solution Approach 2:
The patent applies local quality by allowing different buffer allocation strategies for different serving cells based on their specific TDD configurations and activity levels. Each cell receives buffer allocation tailored to its actual HARQ process requirements rather than a uniform allocation, ensuring optimal performance for each cell's specific characteristics while maintaining overall system flexibility.
Data Source
AI summary
A user equipment (UE) receives and decodes a first erroneous transport block (TB) from a base station in a mobile communication network. The UE allocates a first soft buffer having a first buffer size. The first soft buffer is associated with a first HARQ process for storing the first TB. The UE then receives and decodes a second erroneous TB from the base station. The UE allocates a second soft buffer having a second buffer size. The second soft buffer is associated with a second HARQ process for storing the second TB. The UE releases a portion of the first soft buffer to be allocated as part of the second soft buffer. The dynamic buffer allocation method reduces mismatch between rate matching and soft buffer storing when the total number of HARQ processes is small. In addition, more HARQ processes can be supported when the corresponding TB size is small.