Base Station Transmit Power Control in Shared Channels
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Solution Overview
Problem
In Evolved UTRA, the existing power control methods for uplink shared channels fail to accurately control transmit power for user apparatuses, especially when uplink scheduling grants are not transmitted, leading to suboptimal power adjustments in varying radio environments.
Innovation Solution
A method where a base station transmits independent transmit power control information using predefined radio resources, even in the absence of uplink scheduling grants, allowing user apparatuses to adjust their transmit power accurately, using a separate TPC bit that is not tied to data transmission opportunities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If transmit power control is performed only when uplink scheduling grants are transmitted, then device complexity is reduced, but transmit power control accuracy deteriorates when no scheduling grants are transmitted
Solution Approach 1:
The system performs preliminary power control adjustments by transmitting TPC commands in downlink scheduling grants before uplink data transmission occurs. This preliminary action ensures that when no scheduling grants are transmitted, the user equipment can still maintain accurate transmit power levels based on previously received TPC commands, thus resolving the contradiction between simplified device complexity and maintained power control accuracy.
Solution Approach 2:
The system implements a feedback mechanism where the base station measures uplink signal quality and sends TPC commands back to user equipment via downlink scheduling grants. This feedback loop allows the system to maintain accurate power control even during intervals without scheduling grants, as the feedback information is cached and applied continuously, balancing device complexity with control precision.
2Productivity
If TPC bits are multiplexed into control channel elements, then information transmission efficiency is improved, but the ability to control power independently when no data transmission occurs is reduced
Solution Approach 1:
The downlink scheduling grant is designed to serve multiple functions simultaneously: it carries both uplink data scheduling information and transmit power control commands. By making the scheduling grant multi-functional, the system can efficiently transmit both types of information through the same control channel elements while maintaining the ability to control power independently, thus resolving the contradiction between transmission efficiency and adaptability.
Solution Approach 2:
The system merges the TPC command transmission with the downlink scheduling grant transmission. Instead of using separate dedicated channels for TPC commands, the TPC bits are combined with scheduling information in the same control message. This merging improves information transmission efficiency while preserving independent power control capability, as the combined message can be sent whenever scheduling is needed.
3Productivity
If channels are shared among multiple users to improve radio resource utilization, then resource efficiency is improved, but the complexity of maintaining individual power control for each user increases
Solution Approach 1:
The system segments power control management by allocating dedicated TPC command fields within the shared downlink scheduling grant for each user equipment. This segmentation allows individual power control to be maintained for each user even though they share the same uplink resources. The scheduling grant is divided into user-specific portions, each containing relevant TPC commands, thus resolving the contradiction between resource sharing efficiency and individual power control complexity.
Solution Approach 2:
The system applies local quality by providing customized TPC commands tailored to each user equipment's specific radio conditions and power requirements within the shared scheduling grant. Each user receives locally optimized power control instructions based on their individual channel quality, data buffer status, and interference conditions. This localized approach enables efficient resource sharing while maintaining simple individual power control for each user.
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
Even if no uplink transmission grant is assigned from a base station, transmit power can be controlled in uplinks with accuracy to some extent. An aspect of the present invention relates to a base station apparatus for use in a radio communication system using a shared channel, comprising: a transmit power control information generation unit configured to generate transmit power control information for a user apparatus based on an uplink signal transmitted from the user apparatus; a radio resource control unit configured to transmit the generated transmit power control information together with an uplink assignment message if an uplink radio resource is assigned to the user apparatus and to supply radio resource assignment information to transmit the generated transmit power control information as independent transmit power control information if no uplink radio resource is assigned to the user apparatus.