Uplink Power Control via Cross-Cell TPC for Multi-Cell Interference
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Solution Overview
Problem
In wireless communication systems, controlling uplink transmit power in multiple serving cells is challenging due to differences in timing advance and propagation properties, leading to interference between user equipment (UEs) and difficulties in maintaining proper time alignment.
Innovation Solution
A method and apparatus for controlling uplink transmit power by transmitting a random access preamble to a secondary cell, receiving a random access response from a primary cell that includes a transmit power command (TPC), and adjusting the uplink transmit power based on the TPC for the secondary cell, while not adjusting the power for the primary cell, allowing for independent time alignment and power control for each serving cell.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the transmit power of the UE is increased to ensure reliable uplink reception, then the reception reliability is improved, but the interference caused to other UEs increases
Solution Approach 1:
The patent applies different transmit power levels to different UEs based on their specific conditions (cell center vs. cell edge locations). Each UE's transmit power is locally optimized according to its propagation characteristics and interference environment, rather than using a uniform power level for all UEs. This resolves the contradiction by allowing reliable reception for each UE while minimizing overall interference through localized power control.
Solution Approach 2:
The patent implements a feedback mechanism where the base station measures uplink signal quality and transmit power from each UE, then uses this information to adjust and control the transmit power of each UE. This closed-loop feedback system enables dynamic power adjustment to maintain reliable reception while preventing excessive interference to other users.
2Object-generated harmful factors
If the transmit power of the UE is decreased to reduce interference, then the interference to other UEs is reduced, but the reception reliability deteriorates
Solution Approach 1:
The patent applies different transmit power levels to different UEs based on their specific conditions (cell center vs. cell edge locations). Each UE's transmit power is locally optimized according to its propagation characteristics and interference environment, rather than using a uniform power level for all UEs. This resolves the contradiction by allowing reliable reception for each UE while minimizing overall interference through localized power control.
Solution Approach 2:
The patent implements a feedback mechanism where the base station measures uplink signal quality and transmit power from each UE, then uses this information to adjust and control the transmit power of each UE. This closed-loop feedback system enables dynamic power adjustment to maintain reliable reception while preventing excessive interference to other users.
3Device complexity
If a conventional random access procedure is used for multiple serving cells, then the procedure complexity is reduced, but the time alignment precision deteriorates
Solution Approach 1:
The patent segments the time alignment control by introducing separate timing advance parameters (Ta,1 for primary cell, Ta,2 for secondary cell) for different serving cells. This segmentation allows independent time alignment optimization for each cell, improving precision while maintaining manageable complexity through structured parameter separation.
Solution Approach 2:
The patent extends the conventional single-cell random access procedure to multi-cell operation by adding another dimension of time advance control (separate Ta parameters for different cells). This dimensional extension enables precise time alignment across multiple cells without significantly increasing procedure complexity, as the existing random access framework is enhanced rather than fundamentally changed.
Data Source
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AI summary
Provided are a method and apparatus for controlling uplink transmission power in a wireless communication system. A terminal transmits a random access preamble in a secondary cell, and receives a random access response in a primary cell. The terminal determines a transmission power for an uplink channel transmitted in the second cell based on the transmit power command (TPC) within the random access response.