Uplink Power Control for Mixed TTI Lengths in 5G
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Solution Overview
Problem
In future radio communication systems like LTE after Rel.13 and 5G, the mixing of TTIs with different time lengths poses challenges for proper communication, particularly affecting channel estimation accuracy and transmission power control when using a combination of normal and shortened TTIs.
Innovation Solution
Implementing a radio communication method that allows for different transmission power control between user terminals assigned to normal and shortened TTIs, using individual and common parameters for each TTI length to optimize throughput and prevent interference, while maintaining compatibility with existing systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If transmission power control is applied uniformly across all TTIs in future radio communication systems, then system simplicity is maintained, but channel estimation accuracy deteriorates when shortened TTI is used
Solution Approach 1:
The patent applies different transmission power control mechanisms to different TTI types. Specifically, accumulated TPC commands are used for normal TTI while non-accumulated TPC commands are used for shortened TTI. This local differentiation ensures that channel estimation accuracy is maintained for shortened TTI (which requires precise power control) while keeping the overall system manageable.
2Loss of time
If mixed TTI lengths are used to reduce delay, then latency is reduced, but communication reliability deteriorates due to control mismatches
Solution Approach 1:
The patent segments the TPC command handling into two distinct paths: one for normal TTI (using accumulated TPC commands) and another for shortened TTI (using non-accumulated TPC commands). This segmentation prevents control mismatches that would otherwise occur when mixing different TTI lengths, thereby maintaining communication reliability while enabling latency reduction through shortened TTI usage.
Solution Approach 2:
The system dynamically selects the appropriate TPC command processing mode based on the TTI type. When shortened TTI is detected, the system switches to non-accumulated TPC command processing; when normal TTI is used, accumulated TPC command processing is applied. This dynamic adaptation ensures reliable communication across mixed TTI scenarios.
3Productivity
If individual parameters are set for each TTI length to optimize performance, then throughput is improved, but system complexity increases
Solution Approach 1:
The patent changes the TPC command accumulation parameter based on TTI length. For normal TTI, the accumulation parameter is enabled; for shortened TTI, it is disabled. This parameter change approach allows the system to optimize throughput for each TTI type while managing complexity through a single, well-defined parameter (accumulation enable/disable) rather than requiring multiple independent parameter sets.
Data Source
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AI summary
In order that a user terminal properly performs communication even when a plurality of TTIs with different time lengths is present, a user terminal of the present invention transmits an uplink shared channel in a normal TTI and/or a shortened TTI including the smaller number of symbols than the normal TTI. The user terminal controls transmission power of the uplink shared channel based on an individual parameter individually set according to a TTI length for transmitting the uplink shared channel.