Control Channel Element Mapping for Relay Interference
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Solution Overview
Problem
In 3GPP LTE systems, relay nodes face challenges in detecting physical downlink control channel information due to limited visibility of OFDM symbols, leading to interference and inefficient resource allocation in control channel regions, especially when relay backhaul and access links operate on the same frequency spectrum.
Innovation Solution
A new structure for the control channel region is introduced, dividing it into equal-sized control channel elements through frequency and time division, allowing for distributed and localized mapping of control information, which enables efficient resource allocation and minimizes interference by separating relay backhaul and access link operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If relay backhaul and access links operate on the same frequency spectrum, then spectrum utilization is improved, but interference between links increases
Solution Approach 1:
The control channel region is segmented into multiple control channel elements (CCEs) that can be independently allocated. This segmentation allows the system to separate backhaul and access link control information in the frequency domain, reducing interference while maintaining spectrum utilization. Each CCE can be assigned to different links, enabling orthogonal resource allocation.
Solution Approach 2:
The patent introduces a new dimension for resource allocation by organizing control channels in a two-dimensional structure (time and frequency) with multiple aggregation levels. This allows backhaul and access links to be separated not only in frequency but also in time and aggregation level, providing multiple degrees of freedom for interference management.
2Adaptability or versatility
If control channel region uses traditional structure, then compatibility with existing systems is maintained, but resource allocation efficiency deteriorates
Solution Approach 1:
The control channel element aggregation level is made dynamic rather than fixed. The patent allows flexible aggregation of multiple CCEs (e.g., 1, 2, 4, or 8 CCEs per control channel) depending on channel conditions and traffic requirements. This dynamic aggregation enables efficient resource allocation while maintaining compatibility with existing systems that use traditional fixed structures.
Solution Approach 2:
The patent changes key parameters of the control channel structure, including the number of CCEs, aggregation levels, and resource element grouping. By adjusting these parameters, the system can optimize resource allocation efficiency for relay scenarios while maintaining backward compatibility with legacy systems through configurable parameter sets.
3Reliability
If control information is mapped to distributed CCEs, then reliability is improved through diversity, but device complexity increases
Solution Approach 1:
The patent applies local quality by allowing different aggregation levels and mapping patterns for different control channels. Instead of uniformly distributing all control information, the system can assign localized CCE groups to specific users or links based on channel conditions. This reduces the complexity of distributed mapping while maintaining diversity gains for reliability.
Data Source
AI summary
The invention relates to a new structure of a control channel region within a sub-frame of a 3GPP-based based communication system using OFDM in the downlink. This new structure of a control channel region is inter alia particularly suitable for conveying physical downlink control channel information from a donor eNodeB to a relay node. The control channel region is divided in CCEs that have equal size irrespective of the presence of further cell-specific and/or UE-specific reference signals within the control channel region. This is achieved by dividing the control channel region in plural sub-CCEs that are combined to CCEs all having equal size (in terms of resource elements that can be used for the signaling of control information). The control channel region is divided in the frequency domain and/or time domain in a FDM respectively TDM fashion in order to obtain the sub-CCEs.