HARQ Feedback Channel Resource Allocation for Carrier Aggregation
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Solution Overview
Problem
The existing HARQ feedback channel design in LTE systems is inadequate for carrier aggregation, leading to inefficient resource utilization and format mismatch between user equipment (UE) and evolved NodeBs (eNBs) due to asymmetric UL and DL carrier configurations, resulting in unreliable decoding and increased computation complexity.
Innovation Solution
A predefined rule for HARQ format switching based on UE capability and CC configuration information, combined with efficient resource allocation schemes using explicit and hybrid methods to determine physical resources for ACK/NACK feedback, reduces the risk of format mismatch and improves resource utilization efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If carrier aggregation with asymmetric UL and DL component carriers is implemented to improve system throughput, then the payload size of uplink HARQ feedback increases significantly, but the existing PUCCH channel format can only support up to 4 bits for HARQ feedback information
Solution Approach 1:
The patent segments the HARQ feedback information by introducing multiple PUCCH channel formats (Format 1a, 1b, 2, 3) with different payload capacities. Format 1a/1b handle 1-2 bits, Format 2 handles 3-4 bits, and the new Format 3 handles larger payloads up to 20 bits, allowing the system to divide the feedback task across appropriate formats based on carrier aggregation configuration
Solution Approach 2:
The patent implements dynamic selection of PUCCH formats based on the number of downlink component carriers and uplink component carriers configured for carrier aggregation. The system dynamically adapts the HARQ feedback payload size and format to match the actual carrier aggregation scenario, transitioning from static 4-bit limitation to dynamic scalability up to 20 bits
2Adaptability or versatility
If multiple PUCCH channel formats are introduced to support different HARQ payload sizes, then the system can accommodate carrier aggregation configurations, but format mismatch between UE and eNB increases computation complexity and reduces reliability
Solution Approach 1:
The patent establishes predefined rules and tables that map carrier aggregation configurations (number of DL CCs and UL CCs) to specific PUCCH formats and resource allocation schemes before actual HARQ feedback transmission. This preliminary configuration approach, where the eNB signals the appropriate format through higher-layer signaling, prevents format mismatch and eliminates the need for complex blind decoding at the eNB side
Solution Approach 2:
The patent implements a feedback mechanism where the eNB configures the UE with specific PUCCH format parameters through higher-layer signaling (RRC configuration), and the UE confirms adherence to this configuration. This closed-loop feedback ensures both UE and eNB operate with the same format understanding, reducing blind decoding requirements
3Productivity
If implicit resource allocation based on downlink scheduler logical address is used in non-CA systems, then resource utilization efficiency is improved, but this approach becomes unreliable for CA systems with multiple DL component carriers
Solution Approach 1:
The patent segments the resource allocation approach by introducing explicit resource allocation through higher-layer signaling for CA systems, separate from the implicit allocation used in non-CA systems. This segmentation allows CA systems to receive dedicated resource assignments that are reliable across multiple component carriers, while non-CA systems continue to use the efficient implicit method
Solution Approach 2:
The patent applies different resource allocation strategies locally to different system configurations: implicit resource allocation based on logical address is applied to non-CA single-carrier scenarios where it provides high efficiency, while explicit resource allocation through RRC configuration is applied to CA multi-carrier scenarios where reliability is paramount, optimizing each scenario with its most suitable method
Data Source
AI summary
An efficient uplink HARQ feedback channel resource allocation scheme is adopted for carrier aggregation in a multi-carrier LTE/LTE-A system. Two resource allocation schemes (e.g., explicit and hybrid) for HARQ ACK/NACK (A/N) are applied. Part of the resources is allocated based on explicit method via RRC configuration. Another part of the resources is allocated based on hybrid method via both RRC and implicit information carried by downlink schedulers. In an explicit method, the physical resource for A/N feedback information is determined based on a resource index in a DL scheduling grant. The DL grant corresponds to transport blocks over a configured CC. The resource index points to a physical resource from a set of candidate uplink A/N physical resources reserved for the CC. In an implicit method, the A/N physical resources are determined based on a logical address of the DL scheduling grant.