PRACH Power Control in Dual Connectivity
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Solution Overview
Problem
In LTE systems using dual connectivity, the simultaneous transmission of multiple Physical Random Access Channels (PRACHs) can lead to improper power allocation, resulting in decreased system throughput due to the risk of exceeding maximum transmission power limits.
Innovation Solution
A user terminal with PHY and MAC layer processing sections controls PRACH transmission power, prioritizing the first cell group and implementing power-ramping and power-scaling to manage total transmission power, ensuring it does not exceed allowable limits, thereby maintaining system throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple PRACHs are simultaneously transmitted in dual connectivity, then connection establishment and synchronization are improved, but transmission power allocation becomes improper and system throughput deteriorates
Solution Approach 1:
The patent applies local quality by differentiating power allocation strategies for different cell groups. The first cell group (containing PCell) receives preferential power allocation to ensure reliable connection establishment, while the second cell group's power is adjusted accordingly. This localized differentiation resolves the contradiction by ensuring critical connections are maintained while managing overall power resources efficiently.
Solution Approach 2:
The patent changes the power allocation parameter dynamically based on transmission conditions. When total power would exceed maximum limits, the system adjusts the power distribution between first and second cell groups, applying power-ramping for retransmissions and power-scaling for simultaneous transmissions. This parameter adjustment resolves the contradiction between maintaining reliable connections and preventing throughput deterioration.
2Reliability
If transmission power of PRACHs is increased to ensure reliable transmission, then connection reliability is improved, but total transmission power exceeds allowable maximum
Solution Approach 1:
The patent dynamically adjusts power parameters based on transmission conditions. For simultaneous PRACH transmissions, power-scaling is applied to reduce individual power levels while maintaining total power within limits. For retransmissions, power-ramping is used to gradually increase power only when necessary. This resolves the contradiction by adapting power levels to actual transmission needs rather than using fixed high power.
Solution Approach 2:
The patent applies partial action by allocating power preferentially to the first cell group's PRACH transmissions, which are critical for connection establishment. The second cell group receives reduced or scaled power when total power limits are approached. This partial allocation strategy ensures critical functions are maintained while preventing total power from exceeding maximum allowable levels.
3Reliability
If power allocation is prioritized for the first cell group, then connection establishment reliability is improved, but power available for the second cell group is reduced
Solution Approach 1:
The patent applies local quality by giving preferential treatment to the first cell group's PRACH transmissions, which contain the PCell and are critical for overall connection reliability. However, it simultaneously ensures the second cell group receives sufficient scaled power for its operations. This localized priority approach resolves the contradiction by ensuring critical functions are maintained while providing adequate power to secondary functions.
Solution Approach 2:
The patent uses partial action by allocating a primary portion of available power to the first cell group for reliable connection establishment, while allocating a secondary scaled portion to the second cell group. This partial allocation strategy ensures that critical first cell group transmissions are maintained with sufficient power while the second cell group operates with reduced but adequate power levels.
Data Source
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AI summary
To suppress decrease in throughput of a system in the radio communication system using dual connectivity, a user terminal according to one aspect of the present invention communicates with a plurality of radio base stations each of which sets a cell group comprised of one or more cells, and has a PHY layer processing section that controls transmission power of a UL signal of each cell group, and a MAC layer processing section that controls retransmission of the UL signal. Based on instructions of the MAC layer processing section, the PHY layer processing section reduces transmission power of a second PRACH so that total transmission power of a first PRACH to a master base station and the second PRACH to a secondary base station that are simultaneously transmitted is allowable maximum transmission power or less, and based on notification on a power-limited state of the second PRACH reported from the PHY layer processing section, the MAC layer processing section controls power-ramping in retransmission of the second PRACH.