Distinguishing Subframes in Downlink Transmission Bursts
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Solution Overview
Problem
In License-Assisted Access (LAA) systems, channel state information (CSI) measurements are inaccurate due to varying transmission powers of cell-specific reference signals (CRS) and CSI reference signals (CSI-RS) across different downlink transmission bursts, leading to incorrect channel quality indicators (CQI) reports and misinterpretation by eNodeBs.
Innovation Solution
The proposed solution involves the UE receiving indication information from the eNodeB to distinguish CSI measurements based on power differences between CRS/CSI-RS transmission powers within a burst, subframe indexes for measurements, and identification of DL transmission bursts, using modified downlink control information (DCI), Physical Control Format Indicator Channel (PCFICH), or CRS to accurately perform CSI measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If transmission power varies across downlink transmission bursts, then power efficiency and adaptability are improved, but CSI measurement accuracy deteriorates
Solution Approach 1:
The eNodeB transmits indication information in advance within the DL transmission burst to inform the UE about the transmission power level or power offset. This preliminary information allows the UE to correctly interpret reference signals and perform accurate CSI measurements despite power variations across bursts.
Solution Approach 2:
Indication information acts as an intermediary between the eNodeB and UE, conveying transmission power characteristics. This intermediary enables the UE to compensate for power variations and maintain measurement accuracy without requiring complex signal processing.
2Measurement precision
If indication information is transmitted in every subframe, then CSI measurement accuracy is improved, but control signaling overhead increases
Solution Approach 1:
The indication information is segmented and transmitted only in specific subframes within the DL transmission burst rather than every subframe. This selective transmission reduces signaling overhead while maintaining sufficient information for accurate CSI measurements.
Solution Approach 2:
Instead of providing complete power information in every subframe, the system uses partial information (indication information in selected subframes) that is sufficient for the UE to perform accurate measurements, avoiding excessive signaling.
Data Source
AI summary
Technology for a user equipment (UE) operable to perform channel state information (CSI) measurements in a License Assisted Access (LAA) system is disclosed. The UE can process information received from a base station in the LAA system. The information can be received within a downlink (DL) transmission burst from the base station. The information can indicate one of: a cell-specific reference signal (CRS) or channel state information reference signal (CSI-RS) transmission power offset value for the DL transmission burst, one or more subframes in the DL transmission burst for which the UE is to perform CSI measurements, or a subframe boundary of the DL transmission burst. The UE can perform a CSI measurement for the DL transmission burst based on the information received from the base station. Subframes of the DL transmission burst can be associated with a substantially similar transmission power.