OFDMA Receiver Gain Control Using Frequency-Domain Pilot Power
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Solution Overview
Problem
In OFDMA systems like LTE, measuring signal power in the time domain leads to large errors due to dynamic resource allocation and narrow band allocations, making it challenging to set accurate gain for receiver components, especially when signals lack a preamble for reliable power measurement.
Innovation Solution
The solution involves measuring signal power in the frequency domain using reference signals (pilots) included in each sub-frame, which are transmitted with predetermined power independent of resource allocation, allowing for accurate power estimation and gain adjustment based on these measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If signal power is measured in the time domain, then the measurement process is simple, but the measurement precision deteriorates due to dynamic resource allocation and narrow band allocations
Solution Approach 1:
The patent transitions the measurement from time domain to frequency domain by applying FFT transformation. This dimensional change allows measurement of signal power on individual subcarriers, eliminating the interference from dynamic resource allocation patterns that plague time-domain measurements. The frequency domain representation separates different frequency components, enabling precise power measurement of reference signals independent of time-varying resource allocation.
2Ease of operation
If gain is adjusted based on time domain power measurement, then the control process is straightforward, but the reliability deteriorates due to large measurement errors
Solution Approach 1:
The patent replaces the direct time-domain power measurement mechanism with a frequency-domain analysis mechanism. Instead of measuring total power in the time domain and using it for gain control, the system transforms signals to frequency domain, measures power of specific reference signal subcarriers, and uses this accurate measurement for gain adjustment. This substitution fundamentally improves reliability by eliminating the measurement errors caused by dynamic resource allocation.
3Measurement precision
If reference signals are used for power measurement, then the measurement becomes independent of resource allocation, but the device complexity increases due to FFT transformation requirements
Solution Approach 1:
The patent leverages the existing FFT module that is already required for OFDMA signal processing and channel estimation. The same FFT transformation that is necessary for demodulation and channel equalization is also utilized for power measurement purposes. This multi-functional use of the FFT module avoids additional hardware complexity while enabling accurate frequency-domain power measurement of reference signals.
Data Source
AI summary
A receiver of a wireless communication device, the receiver including a fast Fourier transform module, a first power measuring module, and a gain control module. The fast Fourier transform module is configured to convert a signal from a time domain to a frequency domain. The signal includes a plurality of reference signals. The reference signals have a predetermined power. The first power measuring module is configured to generate a first power measurement of the signal in the frequency domain based on the plurality of reference signals. The gain control module is configured to adjust a gain of the receiver based on the first power measurement.