Transmit Power Control for Cellular Mobile Terminals
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Solution Overview
Problem
In WCDMA systems, the current transmit power control methods by NodeB lead to power peaks and increased Rise over Thermal (RoT) due to abrupt interference changes between active and passive states of Mobile Terminals (MTs), affecting network performance.
Innovation Solution
A controlling node that classifies MTs into active and passive states and uses distinct Transmit Power Control (TPC) methods based on Signal to Interference Ratio (SIR), Signal to Interference and Noise Ratio (SINR), or Rise over Thermal (RoT) for each state to adapt power control, reducing power peaks and interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a passive MT raises its transmission power substantially when transitioning to active state to maintain SIR target, then the SIR is maintained close to target, but power peaks occur and RoT increases in the cell
Solution Approach 1:
The invention applies preliminary action by having the MT anticipate the state transition and adjust its transmission power before actually transitioning from passive to active state. The MT uses predicted SIR values based on historical data and current channel conditions to pre-adjust power, avoiding abrupt power peaks when the transition occurs.
Solution Approach 2:
The invention implements dynamics by making the TPC command determination adaptive and time-varying. The system dynamically adjusts TPC commands based on the MT's current state (active/passive), transition timing, and predicted SIR, rather than using a static power control approach. This allows smooth power transitions that follow the dynamic nature of channel conditions and scheduling decisions.
2Reliability
If an MT transmits with high power when entering active TTI, then the SIR target is exceeded, but this causes increased RoT in the cell and interference to other users
Solution Approach 1:
The invention applies feedback by using predicted SIR values and actual channel conditions to continuously adjust TPC commands. The system monitors the MT's state transitions and channel quality, then provides feedback through adaptive TPC commands that prevent excessive power transmission. This closed-loop control ensures the MT achieves sufficient SIR without transmitting at unnecessarily high power levels that would cause interference.
Solution Approach 2:
The invention implements parameter changes by dynamically modifying the TPC command parameters based on the MT's operational state and channel conditions. Instead of using fixed power control parameters, the system adjusts TPC command values, adjustment increments, and timing based on whether the MT is in active or passive state, thereby optimizing power transmission to achieve SIR targets without excessive interference.
3Ease of operation
If the NodeB controls transmission power using standard TPC commands, then power control is maintained, but abrupt interference changes occur during state transitions between active and passive MTs
Solution Approach 1:
The invention applies preliminary action by having the MT prepare for state transitions in advance. When the MT anticipates transitioning from passive to active state (or vice versa), it pre-adjusts its transmission power based on predicted SIR and historical patterns. This prevents abrupt interference changes during the actual transition by smoothing the power adjustment over time.
Solution Approach 2:
The invention implements dynamics by making the power control system adaptive to state transitions. The TPC command generation becomes dynamic, taking into account the MT's current state, transition timing, and channel conditions. This allows the system to maintain ease of operation through automated control while simultaneously stabilizing interference by adapting power commands to the dynamic nature of state transitions.
Data Source
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AI summary
A controlling node (125) for a cellular communications system (100), arranged to determine and transmit commands for Transmit Power Control, TPC, to one or more Mobile Terminals, MTs (110, 115, 120), in at least one cell (105) in the system. The controlling node (125) is arranged to classify an MT (110, 115, 120) as being in one of a number of states, and to use differing methods for determining an MT's TPC command depending on which state the MT (110, 115, 120) is in, so that one method is used for determining TPC commands to an MT in the active state and another method is used for determining TPC commands to an MT in the passive state.