CoMP Downlink Rate-Matching via DCI CRS RE Signaling
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Solution Overview
Problem
In LTE wireless networks, CoMP (Coordinated Multi-Point Transmission) systems face challenges in dynamically switching downlink transmission points and managing inter-cell interference, where UEs need to adapt CRS (Cell-Specific Reference Symbols) patterns for PDSCH rate-matching during fall-back operations, but current DCI formats lack necessary signaling for CRS REs and timing information.
Innovation Solution
Incorporating an n-bit information field in the DCI format for DL CoMP scheduling to signal CRS RE sets and using RRC higher-layer signaling to configure CRS patterns for PDSCH rate-matching, and dynamically indicating PDSCH timing assumptions within the DCI format to ensure accurate rate-matching and demodulation during fall-back transmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If CoMP systems dynamically switch downlink transmission points, then CoMP performance and signal-to-noise ratio are improved, but inter-cell interference management becomes more complex and requires additional signaling for CRS REs and timing information
Solution Approach 1:
The patent segments the CRS RE configuration into two parts: RRC higher-layer signaling for static CRS RE set configuration and DCI dynamic signaling for selecting among configured sets. This segmentation allows the system to maintain CoMP performance while reducing the complexity of complete CRS pattern signaling in each DCI message.
Solution Approach 2:
The patent applies preliminary action by having the RRC layer pre-configure multiple CRS RE sets before dynamic scheduling. This allows the eNodeB to prepare multiple reference signal patterns in advance, so that when dynamic switching is needed, the UE already has the necessary CRS configurations ready, eliminating the need for complete re-signaling.
2Device complexity
If compact DCI format is used for fall-back scheduling, then device complexity and signaling overhead are reduced, but the UE cannot determine which CRS RE sets to use for PDSCH rate-matching
Solution Approach 1:
The patent makes the RRC configured CRS RE sets universal by having them serve multiple purposes: they provide reference signals for CoMP operations, serve as fallback scheduling reference signals, and enable PDSCH rate-matching. This multi-functionality allows compact DCI formats to work with CoMP UEs without requiring additional specialized signaling.
Solution Approach 2:
The patent applies self-service by having the UE use its own pre-configured CRS RE sets (via RRC signaling) to handle fall-back scheduling. The UE autonomously determines which CRS RE sets to use based on its configuration, eliminating the need for the network to send additional CRS RE information in the DCI message.
3Adaptability or versatility
If multiple CRS RE sets are configured for CoMP, then adaptability to different transmission points is improved, but the UE complexity for determining correct rate-matching increases
Solution Approach 1:
The patent applies dynamics by enabling the eNodeB to dynamically select and signal which pre-configured CRS RE set should be used for each scheduling decision. The UE dynamically adapts its rate-matching behavior based on the indicated CRS RE set, allowing flexible transmission point switching while maintaining manageable UE complexity through predefined options.
Data Source
AI summary
Systems and methods for fall-back rate-matching and timing for user equipment (UE) configured for downlink (DL) Coordinated Multi-Point Transmission (CoMP) are disclosed. In one embodiment, when a UE configured in DL CoMP receives a fall-back transmission, PDSCH is rate-matched around the serving cell CRS. In an alternative embodiment, when a UE configured in DL CoMP receives a fall-back transmission, PDSCH is rate-matched or uses timing around one of the cell-specific reference symbol (CRS) resource element (RE) set indicated by RRC-higher layer signaling. For example, PDSCH may be rate-matched or use timing around the first RRC higher layer configured CRS RE set.