CSI Reference Resource Derivation for MTC Repetitions
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Solution Overview
Problem
Current LTE systems face challenges in determining Channel State Information (CSI) and Channel Quality Indicator (CQI) reporting, particularly for Machine-Type Communication (MTC) devices with reduced bandwidth, which affects their ability to efficiently communicate and maintain low power consumption.
Innovation Solution
The method involves deriving channel feedback for physical channels based on the number of transmission repetitions, allowing for improved CSI and CQI reporting by associating a code rate with an effective channel code rate that occupies a group of physical resources, including subframes, and considering frequency hopping patterns to enhance link adaptation and system throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If transmission repetitions are used for MTC devices in Coverage Enhancement modes, then reliability of communication is improved, but latency increases due to multiple transmissions occupying multiple subframes
Solution Approach 1:
The system pre-configures the number of transmission repetitions and selects appropriate CQI tables before actual data transmission. The UE is provided with multiple CQI tables corresponding to different numbers of repetitions, allowing the system to prepare optimal transmission parameters in advance based on channel conditions and device capabilities, thus reducing actual transmission latency while maintaining reliability.
2Device complexity
If reduced bandwidth of 1.4 MHz is allocated to MTC UEs, then device cost and complexity are reduced, but channel state information accuracy deteriorates due to limited frequency diversity
Solution Approach 1:
The patent extends the CSI reference resource definition from a single subframe to multiple subframes. By aggregating channel measurements across multiple time instances (subframes), the system compensates for the limited frequency diversity in 1.4 MHz bandwidth. This temporal dimension extension allows accurate CSI estimation despite the restricted frequency range, enabling low-cost UEs to achieve reliable channel state reporting.
3Adaptability or versatility
If multiple CQI tables are maintained for different repetition numbers, then adaptability to various coverage enhancement scenarios is improved, but signaling overhead and processing complexity increase
Solution Approach 1:
The system designs CQI tables with a unified structure that can serve multiple coverage enhancement scenarios. The CQI tables are organized such that different tables correspond to different repetition numbers but follow the same format and interpretation rules. This universal design allows the UE to efficiently select and use appropriate tables based on configured repetition numbers, reducing processing complexity while maintaining high adaptability across various MTC deployment scenarios.
Data Source
AI summary
Systems and methods are provided for deriving channel feedback for a physical channel based on an indication of the number of transmission repetitions. In some embodiments, a method for use in a wireless device for determining channel feedback for a physical channel includes receiving control signaling including an indication of a number of transmission repetitions of the physical channel. The method also includes deriving the channel feedback for the physical channel based on the indication of the number of transmission repetitions, where a code rate corresponding to the channel feedback corresponds to an effective channel code rate of the physical channel occupying a group of physical resources including the number of transmission repetitions. In this way, the wireless device may report channel conditions that are better than the channel conditions corresponding to a single transmission, according to some embodiments.