Transmit Power Calibration in FDD Wireless Systems
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Solution Overview
Problem
In frequency division multiplexed wireless systems, maintaining accurate transmit power is challenging due to rapidly changing transmission bandwidth and frequency, leading to significant errors and loss in spectral efficiency in 3GPP LTE networks without proper calibration mechanisms.
Innovation Solution
A method and apparatus for transmit power calibration in user equipment (UE) that involves mapping a power control calibration region to an uplink symbol in a subframe, using a calibration waveform to adjust transmit power, and transmitting data at the calibrated power level on subsequent symbols, with optional reserved time-frequency regions and adaptive calibration based on power change thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If transmit power is adjusted dynamically based on changing bandwidth and frequency allocations, then spectral efficiency is improved, but transmit power accuracy deteriorates due to hardware implementation challenges
Solution Approach 1:
The patent applies preliminary action by performing transmit power calibration before actual data transmission. The UE determines calibration parameters (such as calibration subframe, calibration symbol, and calibration resource block) in advance, transmits calibration signals, and measures received power levels before正式 transmission. This allows the UE to pre-adjust its power control parameters to account for changing bandwidth and frequency allocations, ensuring accurate transmit power when data transmission begins.
2Adaptability or versatility
If the number of subcarriers allocated to a UE changes significantly in each subframe, then adaptability is improved, but transmit power stability deteriorates leading to significant power errors
Solution Approach 1:
The patent implements feedback by having the base station measure the received power level of calibration signals transmitted by the UE and send power control commands back to the UE. The UE adjusts its transmit power based on this feedback loop. Specifically, the UE transmits calibration signals at a predetermined power level, the base station measures the received power, and compares it to an expected threshold, then provides feedback to correct any deviations. This feedback mechanism maintains transmit power stability even when the number of subcarriers changes significantly between subframes.
3Measurement precision
If power control calibration is performed frequently to maintain accuracy, then transmit power precision is improved, but system overhead increases due to additional calibration signaling
Solution Approach 1:
The patent applies partial action by performing calibration only when necessary rather than continuously. The UE determines calibration parameters based on specific conditions such as changes in bandwidth allocation or frequency assignments. The calibration is performed at selective intervals and only for the specific resource blocks that have changed, rather than calibrating all resources continuously. This reduces calibration overhead while maintaining sufficient accuracy for dynamic bandwidth and frequency allocations.
Data Source
AI summary
The present disclosure describes a method and apparatus for transmit power calibration in a frequency division multiplexed wireless system (100). The method may include receiving (320), at a user equipment (120), a signal from a base station (130) in a frequency division multiplexed wireless system and mapping (330), in response to receiving the signal from the base station, a power control calibration region to an uplink symbol in a subframe to establish a mapped uplink symbol using predetermined criteria. The method can also include calibrating (350) a transmit power based on transmission in the calibration region and transmitting (360) data at the calibrated transmit power on at least one other symbol following the mapped uplink symbol.