OFDM Transmit Power Equalization for Amplifier Efficiency
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Solution Overview
Problem
In mobile communication systems employing OFDM, accurately maintaining transmission power levels within the maximum allowable limit while ensuring high power levels for pilot signals to improve channel estimation and amplification efficiency is challenging, especially when the types and distribution of data signals across subcarriers are unknown, leading to potential distortion and reduced amplification efficiency.
Innovation Solution
The solution involves controlling the transmission power to equalize the total power level across all time slots by setting a higher power density for reference signals than data signals, and preventing data signal mapping in specific subcarriers to allocate unused power to reference signals, allowing for consistent power amplification and accurate channel estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pilot signals are transmitted with a higher power level to improve channel estimation accuracy, then channel estimation accuracy is improved, but the total power level may exceed the maximum allowable transmission power level
Solution Approach 1:
The patent applies local quality by assigning different power densities to different signal types within the same transmission. Specifically, reference signals are allocated a first power density while data signals are allocated a second power density, allowing pilot signals to receive higher power locally without exceeding the overall maximum power limit. This resolves the contradiction by enabling high power for channel estimation where needed while maintaining total power control.
2Power
If a large margin is reserved for power density of data to limit total power level below maximum allowable power, then total power level is controlled, but transmission power amplifier efficiency is reduced
Solution Approach 1:
The patent implements dynamic power allocation by adjusting the power density of reference signals and data signals based on actual transmission needs. Instead of reserving a fixed large margin, the system dynamically controls power distribution: when reference signals are transmitted, they receive higher power density; when not transmitted, data signals can utilize the full power budget. This dynamic approach maintains total power control while maximizing amplifier efficiency by eliminating unnecessary power reserves.
3Measurement precision
If power density of reference signals is increased to improve channel estimation, then channel estimation accuracy is improved, but the power distribution becomes uneven across time slots
Solution Approach 1:
The patent resolves the power distribution unevenness by introducing a power balancing mechanism that adjusts the power density of data signals in time slots containing reference signals. When reference signals are transmitted with higher power density, the system compensates by reducing the power density of data signals in the same time slot, ensuring that the total power level remains constant across all time slots. This parameter adjustment maintains both high channel estimation accuracy and stable power distribution.
Data Source
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AI summary
A transmitting device includes a transmission signal generating unit configured to generate a transmission signal by inverse-Fourier-transforming reference signals and data signals mapped to subcarriers and a transmitting unit configured to wirelessly transmit the transmission signal. In the transmitting device, a total power level allocated to signals to be transmitted in a time slot is equal to a total power level allocated to signals to be transmitted in any other time slot, and a power density per unit bandwidth of the reference signals is greater than a power density per unit bandwidth of the data signals. This configuration makes it possible to equalize the total transmission power level of all time slots and thereby to improve the power amplification efficiency. Also, with this configuration, since the reference signals are transmitted with a higher power than that for other signals, it is possible to improve the accuracy of channel estimation.