ePDCCH Resource Allocation Signaling for LTE Control Channels
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Solution Overview
Problem
Current wireless communication systems face challenges in enhancing control channel capacity and capabilities, particularly in supporting increased control channel capacity, frequency-domain inter-cell interference coordination, spatial reuse of control channel resources, and coexistence with legacy UEs, as seen in the development of the enhanced Physical Downlink Control Channel (ePDCCH) within 3GPP LTE systems.
Innovation Solution
The method involves transmitting an indication of the type and number of physical resource block (PRB) pairs allocated for ePDCCH transmission to user equipment (UE), using 2 or 3 bits, and employing a signaling mechanism to reserve resources within the Physical Downlink Shared Channel (PDSCH) transmissions, allowing for localized or distributed ePDCCH transmission, and supporting various aggregation levels and antenna port associations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If ePDCCH is multiplexed with PDSCH in pure FDM manner, then control channel capacity is improved, but resource allocation complexity increases
Solution Approach 1:
The ePDCCH search space is segmented into multiple candidate positions defined by formulas involving aggregation levels (L=1,2,4,8) and candidate indices (m=0,1,2,3). This segmentation allows the UE to efficiently search for its specific control information without having to decode the entire PDSCH, thus improving control channel capacity while managing resource allocation complexity through structured division of the search space.
Solution Approach 2:
The patent pre-defines search space configurations including aggregation levels, candidate positions, and RNTI-based indexing before actual ePDCCH transmission. The UE is provided with configuration parameters (searchSpaceList) that specify search space identities, aggregation levels, and candidate counts in advance. This preliminary configuration enables the UE to perform blind decoding efficiently without real-time complex resource allocation decisions.
2Reliability
If blind decoding is performed across multiple aggregation levels, then reliability of control information detection is improved, but decoding complexity increases
Solution Approach 1:
The search space is segmented into multiple aggregation levels (L=1,2,4,8) with specific candidate positions for each level. The UE performs blind decoding at each aggregation level independently, checking only the predefined candidate positions rather than all possible positions. This segmentation maintains detection reliability across multiple levels while controlling decoding complexity through the structured candidate position formulas.
Solution Approach 2:
Different aggregation levels are assigned different numbers of candidates and specific position patterns tailored to their reliability requirements. Higher aggregation levels (L=4,8) use fewer candidates with more robust coding, while lower levels (L=1,2) use more candidates with less redundancy. This local optimization of search space quality at each aggregation level improves overall detection reliability while minimizing total decoding complexity.
3Adaptability or versatility
If ePDCCH uses localized or distributed transmission, then spatial reuse and interference coordination are improved, but signaling overhead increases
Solution Approach 1:
The patent merges the indication of transmission type (localized or distributed) with the resource allocation signaling. The search space configuration parameters that define candidate positions and aggregation levels serve dual purposes: they both allocate resources and implicitly indicate the transmission type. This merging reduces signaling overhead by encoding transmission type information within existing resource allocation fields rather than adding separate indication bits.
Data Source
AI summary
A method implemented in a base station used in a wireless communications system is disclosed. The method includes transmitting, to a user equipment (UE), an indication of a type of enhanced physical downlink control channel (ePDCCH) transmission, where the type of ePDCCH transmission comprises either localized transmission or distributed transmission, and transmitting, to the UE, an indication of the number of physical resource block (PRB) pairs allocated for the ePDCCH transmission, where the indication of the number of PRB pairs allocated for the ePDCCH transmission is conveyed in 2 or 3 bits. Other methods, apparatuses, and systems also are disclosed.