Reference Symbol Transmission for Narrowband Coverage
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Solution Overview
Problem
MTC devices in wireless communications systems face signal attenuation issues due to their location, leading to inadequate channel estimation and coverage problems, as they require higher transmission power but cannot have varying reference signal powers without disrupting channel estimation.
Innovation Solution
A method is introduced where data is transmitted to reduced capability devices using a virtual carrier with specific reference symbols inserted at a higher power when the transmission power difference exceeds a threshold, ensuring reliable channel estimation and improved coverage for MTC devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If reference signals are transmitted at higher power to improve coverage for MTC devices, then coverage is improved, but channel estimation is disrupted because reference signal power cannot be varied
Solution Approach 1:
The patent segments reference signals into two distinct types: common reference signals (CRS) transmitted at a first power level for general channel estimation, and specific reference signals (UE-specific reference signals) transmitted at a second power level for dedicated MTC devices. This segmentation allows different power levels to coexist without disrupting the channel estimation process, as each signal type serves a specific purpose with appropriate power scaling.
Solution Approach 2:
The patent applies local quality by transmitting specific reference signals at a higher second power level targeted specifically at MTC devices experiencing signal attenuation, while common reference signals continue at the first power level for other devices. This localized power enhancement improves coverage for MTC devices without causing interference or disruption to the overall channel estimation system.
2Power
If data symbols are transmitted at higher power to extend coverage for MTC devices, then coverage is extended, but the difference in transmission power between data symbols and reference symbols becomes problematic for channel estimation
Solution Approach 1:
The patent changes the power parameter of specific reference signals to match the higher second power level used for data symbols transmitted to MTC devices. By adjusting the reference signal power to be consistent with the data symbol power, the patent eliminates the power differential that would otherwise disrupt channel estimation, while still enabling extended coverage for MTC devices through overall power boosting.
3Area of stationary object
If MTC devices are deployed in locations with significant attenuation (indoors, underground), then coverage area is expanded, but signal attenuation increases making reliable reception difficult
Solution Approach 1:
The patent applies local quality by providing targeted power enhancement through specific reference signals transmitted at a second power level specifically for MTC devices in attenuated locations, while maintaining first power level transmissions for devices in better locations. This allows the network to expand coverage area to include indoor and underground locations without compromising signal quality for all devices.
Data Source
Figure 1A
Figure 1B~1C
Figure 2
AI summary
To facilitate a selective transmission power boost in a narrowband subsystem of a wideband host carrier, where the narrowband subsystem is preferentially allocated to reduced capability communications devices, both data symbols and dedicated reference symbols are transmitted at a higher power within the narrowband. Where the benefits of inserting dedicated reference symbols are outweighed by the loss of data capacity, no dedicated reference symbols are inserted.