Orthogonal DMRS Ports for Interference Cancellation in LTE
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Solution Overview
Problem
Current interference mitigation techniques in LTE networks, such as CoMP, RNTP, and ABS-based eICIC, are inadequate for highly dense small cell deployments, particularly when small cells operate on different frequency bands, leading to unsuitable backhaul latency and interference cancellation challenges.
Innovation Solution
Implementing advanced receiver-based interference mitigation using coordinated reference signals, specifically orthogonal DMRS ports and zero power CSI-RS configurations, to enable accurate interference estimation and cancellation at the user equipment (UE) side, reducing the reliance on transmitter coordination and backhaul latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If transmitter coordination techniques (CoMP, RNTP, ABS-based eICIC) are used for interference mitigation, then interference cancellation capability is improved, but backhaul latency increases and device complexity increases
Solution Approach 1:
The UE performs interference measurement and estimation autonomously using reference signals from neighboring cells without requiring real-time transmitter coordination. The advanced receiver calculates interference covariance matrices and suppresses interference locally, making the system self-sufficient and eliminating backhaul latency dependencies.
Solution Approach 2:
Reference signals (CRS, CSI-RS, DMRS) serve as intermediaries that carry interference information from neighboring cells to the UE. These signals enable the UE to measure and estimate interference characteristics without direct transmitter-transceiver coordination, bridging the information gap efficiently.
2Reliability
If transmitter coordination techniques are used for interference mitigation, then interference cancellation capability is improved, but device complexity increases
Solution Approach 1:
The patent changes the approach from coordinate-based interference avoidance to statistical interference suppression. By estimating interference covariance matrices and using advanced signal processing parameters (weighting vectors, projection operators), the receiver achieves superior interference cancellation without complex transmitter coordination mechanisms.
3Productivity
If dense small cell deployment is implemented, then network capacity is improved, but interference measurement accuracy deteriorates
Solution Approach 1:
The system performs preliminary interference measurement and estimation using reference signals before actual data reception. By pre-calculating interference covariance matrices and characterizing interference conditions in advance, the UE can accurately measure and suppress interference even in dense small cell environments with rapidly changing conditions.
Data Source
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AI summary
A method for communication in a wireless communications network is provided. The method comprises: transmitting, by a network element in a first cell, a first DMRS on a first DMRS port; transmitting, by the network element, a first PDSCH on the first DMRS port; and transmitting, by the network, information indicating that the first DMRS port is used to transmit the first PDSCH, and information about a second DMRS port that is not used to transmit the first PDSCH but is used to transmit a second DMRS, wherein the first DMRS and the second DMRS are orthogonal to one another.