Digital AGC Gain Control for Frame-to-Frame OFDMA Power Variation
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Solution Overview
Problem
Conventional digital automatic gain controllers (AGC) in orthogonal frequency division multiple access (OFDMA) communication systems face challenges in accurately detecting effective bits due to significant power changes from frame to frame, as they are designed to control gain based on average power measurements from previous frames, which is inadequate for systems with high power variation.
Innovation Solution
The solution involves an apparatus and method that estimates the signal-to-noise ratio (SNR) and uplink power of the next frame using channel assignment information and target carrier-to-interference plus noise ratio (CINR), allowing for precise gain calculation for the digital AGC based on these estimates, thereby adapting to power changes between frames.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional digital AGC controls gain based on average power measurement from previous frame, then device complexity is reduced, but measurement precision deteriorates due to significant power changes from frame to frame in OFDMA systems
Solution Approach 1:
The patent applies preliminary action by estimating the SNR of the next frame in advance using current frame information (channel assignment, target CINR, and received power). This forward-looking estimation allows the AGC to prepare appropriate gain values before the actual power changes occur, resolving the contradiction between simple control mechanisms and accurate power measurement in dynamic OFDMA environments
Solution Approach 2:
The patent implements feedback by using the measured received power of the current frame to update and refine the SNR estimation for the next frame. This closed-loop approach continuously adapts the gain control based on actual power measurements, improving measurement precision while maintaining manageable device complexity through iterative refinement rather than complex real-time control
2Ease of operation
If digital AGC uses previous frame's average power for gain calculation, then ease of operation is improved, but adaptability deteriorates in systems with high power variation between frames
Solution Approach 1:
By estimating next frame SNR in advance using current frame parameters, the system prepares adaptive gain values before power changes occur. This maintains ease of operation through automated control while achieving adaptability to power variations by continuously updating predictions based on actual measurements
Solution Approach 2:
The patent introduces dynamics by making the gain control adaptive rather than static. The SNR estimation and gain calculation continuously adjust based on current frame conditions (channel assignment, target CINR, received power), enabling the system to adapt to power variations while maintaining simple automated operation through algorithmic adjustment
3Device complexity
If conventional AGC assumes low power variation rate, then device complexity is minimized, but reliability deteriorates in OFDMA systems with frame-by-frame scheduling causing significant power changes
Solution Approach 1:
The patent applies preliminary action by calculating next frame SNR estimates before actual transmission, using current frame's channel assignment and target CINR information. This forward planning ensures reliable effective bit detection in OFDMA systems with significant power changes, while maintaining minimized device complexity through algorithmic prediction rather than complex real-time power control mechanisms
Solution Approach 2:
The patent implements feedback by using actual received power measurements from the current frame to refine next frame SNR predictions. This closed-loop approach improves reliability of effective bit detection by continuously adapting to actual power conditions, while maintaining simple device architecture through iterative estimation rather than complex power control hardware
Data Source
AI summary
An apparatus and method for controlling a digital AGC in a communication system in which power changes significantly from frame to frame. In the digital AGC controlling apparatus, an SNR estimator estimates an uplink SNR of a next frame. A power measurer measures uplink received power of every frame. A gain calculator estimates uplink power of an nth frame using an SNR estimate of an (n−1)th frame received from the SNR estimator and a received power measurement of the (n−1)th frame received from the power measurer, and calculates a gain to be applied to the nth frame in the digital AGC using the uplink power estimate of the nth frame.