Initial Acquisition Gain Control for OFDM Pilot Overshoot
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Solution Overview
Problem
In wireless communication systems, particularly OFDM systems, initial acquisition failures occur due to incorrect gain settings caused by preceding OFDM symbols not transmitted at full power, leading to overshoot and distortion during transceiver startup or wake-up, which degrades receiver performance.
Innovation Solution
A method and apparatus that measure signal power over a prescribed time period and unidirectionally adjust the transceiver gain to ensure it is set sufficiently low for full power acquisition pilot symbols, preventing overshoot by accounting for the highest power symbol received.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If automatic gain control sets gain based on measured power of received symbols, then gain adaptation to signal strength is improved, but gain overshoot and signal distortion occur when preceding symbols are not transmitted at full power
Solution Approach 1:
The system performs preliminary power measurements over a prescribed time period before final gain setting. By measuring signal power multiple times at predetermined time increments and identifying the maximal power value in advance, the system prepares the appropriate gain setting before actual acquisition, preventing gain overshoot when full-power symbols arrive.
Solution Approach 2:
The system counteracts the potential harmful effect of gain overshoot by unidirectionally adjusting the gain downward when higher power is detected in preliminary measurements. This preliminary anti-action prevents the distortion that would occur if gain were set based on lower-power preceding symbols alone.
2Ease of operation
If gain is set based on preceding OFDM symbols, then gain control responds to current signal conditions, but gain is set too high for subsequent full power acquisition symbols causing overshoot
Solution Approach 1:
The system uses feedback from multiple power measurements taken over time to determine the appropriate gain setting. By continuously monitoring signal power at predetermined increments and using the maximal measured power as feedback, the system adjusts gain to match actual signal conditions while preventing overshoot.
Solution Approach 2:
The system changes the gain parameter dynamically based on measured signal power characteristics. By unidirectionally adjusting gain downward when higher power is detected in preliminary measurements, the system optimizes the gain parameter for accurate full-power symbol acquisition.
3Loss of time
If power measurement is taken immediately before acquisition symbol, then gain setting is timely, but measurement may be affected by non-full-power preceding symbols
Solution Approach 1:
The system performs power measurements in advance over a prescribed time period that includes multiple symbols before the acquisition symbol. This preliminary measurement approach ensures accurate detection of the maximal signal power without being influenced by non-full-power preceding symbols, while still maintaining timely gain setting.
Solution Approach 2:
The system continuously measures signal power at predetermined time increments throughout the prescribed time period, ensuring that the measurement process is ongoing and captures the true signal characteristics. This continuous measurement approach maintains timing efficiency while improving measurement accuracy.
Data Source
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AI summary
Methods and apparatus for initial acquisition gain control in a communication system a method for use in a wireless communication system are 'disclosed. A disclosed methodology includes measuring the power of a signal received by a transceiver a number of times over a prescribed time period, the signal including a number of symbols. A gain of the transceiver can only be decreased when a currently measured power is greater than a previously measured power during the prescribed time period until a maximal power level is measured. By iteratively decreasing the gain to accommodate a maximal power value, which is the same as the power level of an acquisition pilot symbol, overshoot and distortion by the transceiver are avoided during initial timing and frequency acquisition. Corresponding apparatus are also disclosed.