CSI Report Repetition for Uplink Coverage Extension
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Solution Overview
Problem
Current LTE systems face coverage bottlenecks in channel state information (CSI) reporting, particularly in the uplink direction, due to lack of subframe bundling and HARQ support, leading to imbalances between different UL channels and limited CSI coverage area.
Innovation Solution
Implementing techniques such as slowing down the CSI measurement cycle at the user equipment (UE) side and reporting the same CSI report multiple times to the base station, along with subframe bundling and coherent combining of reports, to enhance CSI coverage area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If CSI measurement cycle is slowed down and same CSI report is transmitted multiple times, then CSI coverage area is improved, but uplink resource consumption increases
Solution Approach 1:
The patent implements periodic transmission of the same CSI report across multiple uplink subframes. Instead of transmitting CSI once, the system periodically repeats the transmission in bundled subframes, allowing the receiver to combine multiple instances and improve coverage while using a structured periodic pattern that controls resource consumption.
Solution Approach 2:
The patent merges multiple uplink subframes into a bundled group where the same CSI report is transmitted across all subframes in the bundle. This combining approach allows the receiver to accumulate signal energy across subframes, improving coverage area while confining resource usage to specific bundled groups rather than continuous transmission.
2Reliability
If subframe bundling is implemented for CSI reporting, then coverage bottleneck is improved, but device complexity increases
Solution Approach 1:
The patent introduces dynamic subframe bundling where the bundling configuration can be adjusted based on channel conditions and coverage requirements. The system can dynamically configure which subframes are bundled together and how many subframes per bundle, allowing flexibility in balancing coverage improvement against device complexity for different operational scenarios.
Solution Approach 2:
The patent changes key parameters such as bundling size, bundling pattern, and transmission periodicity to optimize the balance between coverage reliability and device complexity. By adjusting these parameters, the system can adapt to different coverage scenarios without requiring fundamentally complex device architecture.
3Measurement precision
If CSI is reported more frequently with larger payloads, then link adaptation accuracy is improved, but processing complexity increases
Solution Approach 1:
The patent uses copying by transmitting identical CSI report copies across multiple bundled subframes. Instead of generating new CSI measurements for each subframe, the system copies the same CSI report multiple times, allowing the receiver to combine these copies for improved accuracy while keeping the UE's processing complexity relatively low since the same measurement is reused.
Solution Approach 2:
The patent performs preliminary CSI measurement and reporting in the first subframe of the bundle, then reuses this preliminary result across subsequent subframes. This preliminary action provides sufficient accuracy for link adaptation while avoiding the need to perform complex measurements and processing in every subframe, thus reducing overall processing complexity.
Data Source
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AI summary
The application relates to channel state feedback reporting in wireless communication networks and in particular to modifications of the procedure for reporting CSI as specified by section 7.2 of 3GPP TS 36.213 V10.3.0. and the corresponding RRC protocol as specified by 3GPP TS 36.331 V10.2.0. The current cycle for CSI measurement and reporting is such that the UE performs separate CSI measurements for each report. However, the coverage area of CSI measurement reporting is lower than other uplink reporting such as e.g. ACK/NACK on PUCCH which supports subframe repetition, leading to an imbalance. Therefore, it is rather clear that it is highly beneficial to support coverage extension for CSI reports. The issue then arises as to how to realize the CSI coverage enhancement on top of existing/evolving CSI reporting framework. The application proposes to realize said CSI coverage enhancement by reporting (450) the same CSI report multiple times from the UE (110) to an eNB (220).