MTC UE CSI Reporting via Multi-Subframe Reference Resource
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Solution Overview
Problem
Current wireless communication systems face challenges in accurately and efficiently measuring and transmitting channel state information (CSI) in machine type communication (MTC) environments, particularly due to limitations in CSI reference resource configuration and channel quality indicator (CQI) measurement methods.
Innovation Solution
The method involves selecting a set of downlink subframes as a CSI reference resource for MTC user equipment (UE), measuring channel quality indicators (CQI) based on a cell-specific reference signal (CRS), and transmitting CSI reports to a base station through uplink subframes, with the number of downlink subframes determined by a higher layer parameter, allowing for repeated signal transmission via frequency hopping across subbands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single downlink subframe is used as CSI reference resource, then the measurement process is simple, but the channel estimation accuracy deteriorates due to frequency hopping variations
Solution Approach 1:
The patent merges multiple downlink subframes into a unified CSI reference resource set. Instead of measuring CQI in a single subframe, the UE measures CQI across multiple downlink subframes (e.g., subframes n-4, n-3, n-2, n-1, n-6) and combines these measurements to determine the final CQI value for uplink subframe n. This combining approach compensates for frequency hopping variations and improves channel estimation accuracy.
Solution Approach 2:
The patent performs preliminary CQI measurements in multiple downlink subframes before the actual uplink transmission. By pre-measuring the channel quality in advance subframes and storing these measurements, the system prepares accurate channel state information before the uplink subframe occurs, ensuring reliable CSI feedback even with frequency hopping.
2Reliability
If CQI is measured in every downlink subframe, then the channel state information is up-to-date, but the power consumption increases
Solution Approach 1:
The patent applies partial action by measuring CQI in a selective subset of downlink subframes rather than every downlink subframe. The UE determines which specific downlink subframes to measure based on configuration parameters and channel conditions, performing measurements only when necessary to maintain accurate CSI feedback while reducing overall measurement activity and power consumption.
Solution Approach 2:
The patent implements periodic CQI measurement intervals where the UE measures channel quality at predetermined periods rather than continuously. By configuring measurement periodicity and selecting specific downlink subframes for measurement, the system maintains reliable channel state information while significantly reducing the frequency of measurements and associated power consumption.
3Reliability
If frequency hopping is used for repeated signal transmission, then the coverage is improved, but the channel estimation accuracy deteriorates due to channel variations across subbands
Solution Approach 1:
The patent creates equipotentiality by measuring CQI across multiple downlink subframes that experience different frequency hopping instances. By aggregating measurements from subframes transmitted on different subbands (e.g., subframes n-4, n-3, n-2, n-1, n-6), the system averages out frequency-specific variations and achieves a representative channel quality value that reflects overall channel conditions rather than being biased by any single frequency instance.
Data Source
AI summary
A method of reporting channel state information (CSI) at a machine type communication (MTC) user equipment (UE) in a wireless communication system, includes selecting a set of M downlink subframes as a CSI reference resource and a subband among a set of N subbands; measuring a wideband channel quality indicator (CQI) for the set of N subbands and a subband CQI for the subband through the CSI reference resource; and transmitting, to a base station, the wideband CQI and the subband CQI through an uplink subframe, wherein the MTC UE measures the wideband CQI and the subband CQI based on a cell-specific reference signal (CRS) received through the M downlink subframes which are located before the uplink subframe, and wherein the set of N subbands is configured to perform frequency hopping.