Grant-Free Uplink Power Control for Initial Reference Signals
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Solution Overview
Problem
In 5G mobile communication, uplink transmission without dynamic scheduling can lead to collisions between initial and retransmission signals from different user equipment, reducing the detection reliability and successful decoding probability of initial transmissions.
Innovation Solution
The method involves configuring a higher transmission power for initial reference signals compared to retransmitted reference signals, using power control parameters to determine the transmission powers for both, thereby reducing the impact of retransmitted signals on initial signals and enhancing decoding reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If uplink transmission without dynamic scheduling is used, then signaling overhead is reduced and access delay is shortened, but collision between initial transmission and retransmission of different UEs occurs
Solution Approach 1:
The patent changes the transmission power parameter of reference signals based on transmission type. Initial transmissions use higher power than retransmissions, creating a power differential that allows the base station to distinguish between initial and retransmitted signals even when they collide in time-frequency resources. This parameter change resolves the contradiction by maintaining reliability through power-based differentiation while preserving the low-latency benefits of grant-free transmission.
2Loss of information
If time-frequency resources are pre-configured for different UEs, then signaling overhead is reduced, but collision between initial transmission and retransmission occurs
Solution Approach 1:
The patent introduces transmission power as an additional parameter dimension to differentiate signals. By configuring different power levels for initial transmissions versus retransmissions, the system can reliably distinguish between the two types of transmissions even when they occupy the same time-frequency resources, thus maintaining detection reliability while preserving the low signaling overhead of pre-configured resources.
Solution Approach 2:
The patent uses power differential as a temporary, disposable distinction mechanism. The power level difference is applied only during the critical initial transmission phase and is not a permanent resource allocation change. This allows the system to maintain simple, reusable time-frequency resource configurations while temporarily using power differentiation to resolve collisions when they occur.
3Reliability
If retransmission is performed with same power as initial transmission, then transmission reliability is maintained, but impact of retransmitted signals on initial signals increases
Solution Approach 1:
The patent changes the power parameter specifically for retransmissions, making them transmit at lower power than initial transmissions. This power reduction minimizes the interference that retransmitted signals cause to initial transmissions from other UEs, while the system maintains overall transmission reliability through the repeated transmission mechanism and the base station's ability to identify and prioritize initial transmissions based on their higher power level.
Data Source
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AI summary
Embodiments of this application relate to the communications field, and provide a repeated transmission method and an apparatus, to increase a probability of successful decoding of a user equipment. The method includes: performing, by a user equipment, first transmission of uplink data, and sending a first reference signal to a network device based on a first transmit power, where the first reference signal is used to demodulate the first transmission of the uplink data; and performing, by the user equipment, Nth transmission of the uplink data, and sending a second reference signal to the network device based on a second transmit power, where N is an integer greater than or equal to 2, the second reference signal is used to demodulate the Nth transmission of the uplink data, and the second transmit power is less than the first transmit power. The embodiments of this application are applied to an uplink transmission process in a grant-free mode.