Double-Stage Codebook for LTE Channel State Information Feedback
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Solution Overview
Problem
Current channel state information (CSI) feedback mechanisms in LTE Rel-8/9 are inadequate for multi-user scenarios, as they fail to realize double-stage feedback and exhibit redundancy in report contents and processes between PUCCH and PUSCH, leading to increased overheads and inefficiencies.
Innovation Solution
Implementing a two-stage codebook-based method where user terminals select and report precoding matrix indicators (PMI) and calculate channel quality indications (CQI) using both PUCCH and PUSCH, combining long-term/broadband and short-term/frequency selective channel information without increasing overheads, by using codebooks reflecting different channel characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If double codebook feedback is supported in both PUCCH and PUSCH independently, then CSI feedback accuracy is improved, but feedback overheads increase
Solution Approach 1:
The patent merges the PUCCH and PUSCH reporting mechanisms into a unified reporting framework. When PUSCH is available, the UE reports both wideband PMI and subband PMI together; when only PUCCH is available, the UE reports wideband PMI. This unified approach eliminates redundant reporting while maintaining CSI feedback accuracy across different transmission scenarios.
Solution Approach 2:
The patent introduces dynamic reporting behavior that adapts to available resources. The reporting mode switches between PUCCH-only, PUSCH-only, and combined PUCCH-PUSCH modes based on scheduling decisions. This dynamic adaptation allows the system to optimize feedback accuracy when resources permit while reducing overhead when resources are constrained.
2Adaptability or versatility
If new reporting modes are added to support double codebook feedback in both PUCCH and PUSCH, then CSI feedback capability is improved, but device complexity increases
Solution Approach 1:
The patent designs the reporting mechanism to serve multiple functions through existing reporting modes. The same reporting mode structure handles both single-codebook and double-codebook scenarios, as well as both PUCCH and PUSCH transmissions. This multi-functionality avoids the need for separate dedicated modes for each scenario, reducing overall system complexity.
Solution Approach 2:
The patent segments the PMI reporting into wideband PMI (reported via PUCCH or PUSCH) and subband PMI (reported via PUSCH when available). This segmentation allows flexible combination of reporting methods without requiring a completely new unified mode, simplifying the implementation while maintaining versatility.
3Ease of operation
If PUCCH and PUSCH report contents are made independent, then reporting flexibility is improved, but redundancy increases
Solution Approach 1:
The patent implements a feedback mechanism where the eNB's scheduling decision (whether PUSCH is allocated) directly influences the UE's reporting behavior. This feedback loop allows the system to dynamically adjust reporting content based on available resources, eliminating redundancy while preserving flexibility. The UE monitors PUSCH allocation and adapts its reporting strategy accordingly.
Solution Approach 2:
The patent establishes predetermined reporting rules that specify what to report in different scenarios before transmission occurs. The UE is configured with clear guidelines: report wideband PMI via PUCCH always, and report subband PMI via PUSCH when PUSCH is available. This preliminary configuration eliminates the need for dynamic negotiation while avoiding redundancy through pre-planned conditional reporting.
Data Source
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AI summary
The present invention discloses a method and device of reporting channel state information, including: user terminal selects the codebook used in reporting precoding matrix indicator (PMI) from double-stage codebook and selects PMI from the codebook; double-stage codebook involves codebook reflecting long-term / broadband information and that reflecting short-term / frequency selective channel information; and user terminal calculates channel quality indication; therein, when reporting through physical uplink control channel (PUCCH), the parameter used in calculating channel quality indication (CQI) includes the precoding matrix indicator (PMI) reported by user terminal through physical uplink shared channel (PUSCH); when reporting through physical uplink shared channel (PUSCH), the parameter used in calculating CQI includes the precoding matrix indicator (PMI) reported by user terminal through physical uplink control channel (PUCCH); user terminal selects the PMI and calculates CQI according to the specified reporting mode and reporting RI, The present invention can realize double-stage feedback by using the present feedback channel.