OFDMA Mobile Station Power Control with Subchannel Gain Adjustment
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Solution Overview
Problem
In OFDMA systems, the signal-to-noise ratio (SNR) and transmit output are reduced due to variations in the number of subchannels, which is not effectively addressed by conventional power control methods that only consider received signal strength and distance from the base station.
Innovation Solution
A mobile station with a modulator, variable gain amplifier, gain controller, and power controller that adjusts the gain of the output signal based on the number of subchannels, using a subchannel-gain value and power control gain to maintain constant SNR and transmit power, regardless of subchannel variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of subchannels is increased to improve communication capacity, then the data transmission rate is improved, but the signal-to-noise ratio and transmit output are reduced
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the gain value based on the number of subchannels. When the number of subchannels changes, the gain value is modified accordingly to compensate for SNR degradation. This transforms the system from a fixed gain configuration to a variable gain configuration that adapts to different subchannel conditions, thereby maintaining consistent transmit output and SNR performance across varying communication capacities.
2Stability of the object's composition
If conventional power control methods are used to maintain constant received signal strength, then the signal strength at the base station is stabilized, but the variation in SNR due to subchannel changes is not compensated
Solution Approach 1:
The patent implements feedback mechanisms where the mobile station monitors the number of subchannels allocated and uses this information to adjust the gain value. The base station also provides feedback regarding received signal conditions, which the mobile station uses to further refine power control decisions. This dual feedback approach ensures both signal strength stability and SNR compensation by continuously adapting to changing subchannel conditions.
Solution Approach 2:
The patent applies preliminary action by pre-calculating and storing gain values corresponding to different numbers of subchannels before actual transmission occurs. When subchannel allocation is determined, the appropriate gain value is already prepared and can be immediately applied, preventing SNR degradation before it occurs rather than reacting to it after the fact.
3Device complexity
If the gain value is kept constant to simplify the power control algorithm, then the system complexity is reduced, but the transmit output varies with subchannel variations
Solution Approach 1:
The patent transforms the static gain value into a dynamic parameter that changes according to the number of subchannels. Instead of using a fixed gain, the system now employs a variable gain that adapts to different subchannel configurations. This dynamic approach maintains transmit output stability while adding minimal complexity, as the gain adjustment follows a predetermined relationship with subchannel count rather than requiring complex real-time calculations.
Data Source
AI summary
The present invention relates to a mobile station of an OFDMA system and a transmit power control method thereof. The mobile station includes a modulator, a variable gain amplifier, a gain controller, and a power controller. The modulator modulates transmit data according to the number of allocated subchannels, and the variable gain amplifier amplifies the transmit data. The gain controller controls a gain of the transmit data inputted to the variable gain amplifier according to a subchannel gain value corresponding to the number of subchannels. The power controller calculates a power control gain for controlling power of the transmit data except the subchannel gain value based on the signal received from the base station and outputs the power control gain to the variable gain amplifier.