Configuring Downlink CSI Reference Signals for LTE-A Channel Measurement
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Solution Overview
Problem
In LTE-A systems, there is a lack of solutions for sending downlink CSI reference signals, which is necessary for channel measurements, especially with increased antenna ports, leading to inefficiencies and increased pilot expenses.
Innovation Solution
A method and device for configuring and sending downlink CSI reference signals, where an eNB configures and sends configuration information including a starting subframe number and cycle to UE, allowing flexible configuration based on antenna port configurations and measurement requirements, reducing pilot expenses and impact on R8 users.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If downlink CSI reference signals are sent for each antenna port in LTE-A system, then channel measurement capability is improved, but pilot overhead and system complexity increase significantly
Solution Approach 1:
The patent segments the downlink reference signals by separating CSI reference signals from demodulation reference signals. CSI reference signals are specifically designed for channel quality indicator measurement and are segmented to be transmitted only on physical downlink shared channels (PDSCH), while demodulation reference signals handle other functions. This segmentation reduces overall pilot overhead while maintaining channel measurement capability.
Solution Approach 2:
The patent applies local quality by making CSI reference signals neighborhood-specific rather than cell-specific. The reference signals are configured based on local channel conditions and antenna port requirements, allowing different configurations for different spatial neighborhoods. This reduces the need for full-band pilots across all antenna ports while maintaining measurement precision where needed.
2Measurement precision
If full-band pilots are transmitted at each sub-frame for all antenna ports, then channel estimation accuracy is improved, but pilot expense and resource consumption increase
Solution Approach 1:
The patent implements periodic action by configuring CSI reference signals to be transmitted at specific periodic intervals rather than continuously at every sub-frame. The periodicity is configurable based on channel coherence time and measurement requirements, reducing pilot transmission frequency while maintaining estimation accuracy. This allows the system to trade off between measurement freshness and energy consumption.
Solution Approach 2:
The patent applies partial action by transmitting CSI reference signals only on PDSCH resources rather than across the entire frequency band. The reference signals are configured for specific antenna ports and frequency resources based on actual channel conditions and service requirements, avoiding the excessive pilot transmission of full-band pilots while maintaining sufficient channel estimation accuracy for CSI feedback.
3Productivity
If the number of antenna ports is increased to eight in LTE-A, then spatial selectivity and system capacity are improved, but the number of required pilots increases significantly
Solution Approach 1:
The patent applies universality by designing a unified CSI reference signal structure that serves multiple antenna ports through configurable resource allocation. Instead of requiring separate dedicated pilots for each of the eight antenna ports, the same reference signal structure can be configured to serve different antenna ports by changing resource allocation parameters. This reduces the total number of pilots required while maintaining support for eight antenna ports and the associated spatial selectivity.
4Quantity of substance
If CSI reference signals are configured flexibly based on system requirements, then pilot overhead is reduced, but configuration complexity increases
Solution Approach 1:
The patent applies parameter changes by introducing configurable parameters for CSI reference signals including periodicity, starting subframe, frequency domain allocation, and antenna port mapping. These parameters can be adjusted based on channel conditions, service requirements, and system load. The flexibility is managed through standardized parameter sets and default configurations, which reduces the perceived configuration complexity while maintaining the ability to optimize pilot overhead for different scenarios.
Data Source
AI summary
A method for configuring and sending a downlink CSI reference signal is provided. The method comprises: an eNB configures the downlink CSI reference signal and sends configuration information of the downlink CSI reference signal to a UE, wherein the configuration information comprises a starting subframe number and/or a cycle of the downlink CSI reference signal; the eNB sends the downlink CSI reference signal to the UE according to the configuration information of the downlink CSI reference signal.