UE-RS Scrambling Initialization for Interference Reduction
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Solution Overview
Problem
In LTE and LTE-A systems, UE-specific demodulation reference signals (UE-RS) are scrambled based on the physical cell ID, leading to coherent interference from multiple transmission points, which complicates signal differentiation for user equipment (UEs) receiving signals from different transmission points.
Innovation Solution
Implementing dynamic UE-RS scrambling methods that utilize CSI-RS configuration parameters such as resourceConfig, subframeConfig, and antennaPortsCount to initialize UE-RS scrambling, allowing for UE-specific or TP-specific scrambling, thereby reducing coherent interference and enhancing signal differentiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If UE-RS scrambling is initialized based on physical cell ID, then cell-specific signal structure is maintained, but coherent interference occurs from multiple transmission points making signal differentiation difficult
Solution Approach 1:
The patent changes the initialization parameters of UE-RS scrambling from cell-specific parameters (physical cell ID) to UE-specific or TP-specific parameters. By initializing the scrambling sequence with UE-specific RNTI or TP-specific virtual cell IDs, the system enables different UEs and transmission points to use distinct scrambling sequences, thereby reducing coherent interference and improving signal differentiation capability in heterogeneous networks.
2Reliability
If dynamic UE-RS scrambling is implemented using CSI-RS configuration parameters, then signal distinction is improved, but system complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-configuring virtual cell IDs and scrambling identities through higher-layer signaling (RRC configuration) before actual data transmission. The base station and UE establish the scrambling initialization parameters in advance, so that during dynamic transmission, the scrambling can be efficiently applied without real-time computation complexity, thus improving signal distinction while managing system complexity.
3Object-affected harmful factors
If UE-specific scrambling is applied, then interference reduction is achieved, but compatibility with legacy systems decreases
Solution Approach 1:
The patent implements universality by designing a multi-functional scrambling initialization mechanism that can operate in multiple modes. The system can initialize UE-RS scrambling based on physical cell ID for legacy compatibility, or based on UE-specific RNTI and TP-specific virtual cell IDs for enhanced interference reduction. This flexible initialization approach allows the system to serve both legacy and advanced UEs, maintaining backward compatibility while enabling interference reduction capabilities.
Data Source
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AI summary
A user equipment (UE) is configured to communicate with a plurality of base stations in a wireless network. The UE includes a processor that receive a downlink grant scheduling a physical downlink shared channel (PDSCH) for the UE, the downlink grant being transmitted in a physical downlink control channel (PDCCH) or an enhanced physical downlink control channel (ePDCCH). The processor also receives UE-specific demodulation reference signals (UE-RS) provided for demodulation of the PDSCH, wherein the UE-RS are scrambled according to a scrambling sequence initialized with an initialization value. The downlink grant includes a one-bit scrambling identifier (SCID) information field configured to indicate a pair of values comprising a scrambling identifier and a virtual cell ID out of two candidate pairs, the pair of values to be used for determining the initialization value for the UE-RS.