Control Channel Element Indexing for LTE-Advanced
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Solution Overview
Problem
The existing LTE systems face excessive uplink signaling overhead due to the lack of an efficient indexing scheme for eCCEs in the LTE-Advanced system, particularly when enhanced PDCCH is used, which complicates implicit HARQ-ACK resource allocation and increases the risk of collisions.
Innovation Solution
A method and apparatus for a control channel element indexing scheme that determines eCCE indices based on partitioning of channel resource elements, incorporating a collision avoidance mechanism through specific field modifications and mappings, allowing for efficient and flexible implicit HARQ-ACK resource allocation by signaling ePDCCH PRBs and eCCE allocations to user equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a straightforward extension of Rel-8 CCE indexing approach is used for ePDCCH, then the indexing scheme is simple to implement, but the uplink signaling overhead becomes excessive
Solution Approach 1:
The patent segments the eCCE indexing process into multiple hierarchical levels: first determining a base CCE index from the ePDCCH location, then applying offsets and modulo operations to derive the final PUCCH resource index. This segmentation allows the system to handle the large number of eCCEs in ePDCCH without requiring a one-to-one mapping to PUCCH resources, thereby reducing uplink signaling overhead while maintaining implementation feasibility
Solution Approach 2:
The patent introduces multiple parameters including cceOffset, nPUCCH, and nPRB to transform the raw eCCE index into the final PUCCH resource index. These parameter changes enable flexible control over the mapping process, allowing the system to adapt to different network configurations and reduce signaling overhead by not requiring explicit signaling of all resource allocations
2Ease of operation
If one-to-one mapping between eCCE index and PUCCH resource index is used, then resource allocation is straightforward, but the number of required PUCCH resources becomes excessively large
Solution Approach 1:
The patent merges multiple eCCE indices into a smaller set of PUCCH resource indices by using modulo operations and shared offset values. Multiple eCCEs can map to the same PUCCH resource, effectively combining their resource requirements. This merging reduces the total number of PUCCH resources needed while maintaining the ability to distinguish between different users and resources through the indexing scheme
Solution Approach 2:
The patent creates a universal indexing scheme where the same set of PUCCH resources can serve multiple eCCEs and multiple users. The formulated equation nPUCCH = (nCCE + cceOffset) mod nPUCCH_total makes the PUCCH resource allocation universal, allowing the same resource pool to be shared across different ePDCCH allocations without requiring dedicated resources for each eCCE
3Loss of substance
If implicit PUCCH resource determination is used for ePDCCH, then uplink overhead is minimized, but collisions between PUCCH resources for ePDCCH and PDCCH occur
Solution Approach 1:
The patent introduces an intermediary offset parameter cceOffset that acts as a mediator between the ePDCCH eCCE indexing and the PUCCH resource allocation. This offset creates a separation or buffer between the resource allocations for ePDCCH and PDCCH, preventing direct collisions while maintaining the implicit determination mechanism. The offset can be configured to ensure that ePDCCH and PDCCH resources do not overlap
Solution Approach 2:
The patent applies preliminary actions by pre-configuring the cceOffset parameter and the mapping relationship between eCCE indices and PUCCH resources before actual resource allocation occurs. This preliminary setup ensures that collisions are avoided from the outset rather than being resolved dynamically, maintaining both low overhead and high reliability
Data Source
AI summary
The present invention provides a method, a apparatus and computer program product relating to a control channel element indexing scheme. The present invention includes obtaining information regarding first partition elements related to a first partitioning of channel resource elements carrying in downlink a configurable first control channel associated with a data channel, determining a number of second partition elements related to a second partitioning of channel resource elements per first partition element, determining for at least one second partition element a second-partition element index based on information regarding the first partition elements and the determined number, determining for at least one third partition element related to a third partitioning of channel resource elements, a third-partition element index, wherein the second partitioning is related to the allocation of channel resources of the first control channel, and wherein the third partitioning is related to allocating channel resources of a second control channel.