Uplink MIMO Power Allocation with PAR Backoff
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Solution Overview
Problem
In wireless communication systems, especially for uplink MIMO transmissions, equal power allocation across all transmit antennas is not feasible due to peak-to-average ratio (PAR) considerations, leading to signal distortion and reduced performance.
Innovation Solution
A method that involves determining a power allocation (PA) value based on a received PAR backoff value, which is partially based on modulation type, allowing different PA backoffs for various modulation schemes like QPSK and 16 QAM, and using channel quality index (CQI) feedback to adjust power allocation dynamically, ensuring efficient power use across different antenna streams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If equal power allocation is used across all transmit antennas in UL MIMO, then the system is simple to implement, but signal distortion occurs and performance is reduced due to amplifier non-linearity
Solution Approach 1:
The patent applies different power allocation strategies to different transmit antennas based on their individual characteristics and the modulation scheme being used. Specifically, it calculates separate power values for each antenna stream, allowing each to operate within its optimal power range to avoid amplifier non-linearity while maintaining overall system performance.
Solution Approach 2:
The patent dynamically adjusts power allocation parameters based on modulation type (QPSK, 16QAM, 64QAM) and channel conditions. It modifies the power values assigned to each antenna stream according to the selected modulation scheme, thereby optimizing the balance between maintaining signal quality and managing peak-to-average power ratio.
2Reliability
If different power allocations are applied to different antenna streams, then signal distortion is reduced, but the system complexity increases
Solution Approach 1:
The patent segments the power allocation process into distinct calculations for different antenna streams and modulation schemes. It divides the overall transmission into multiple independent power allocation decisions, each tailored to specific antenna-stream-modulation combinations, thereby managing complexity through structured segmentation.
Solution Approach 2:
The patent incorporates feedback mechanisms where the system monitors transmission conditions and adjusts power allocations accordingly. By using channel quality indicators and modulation scheme information as feedback, the system dynamically optimizes power distribution without requiring complex manual configuration.
3Productivity
If higher modulation orders like 64 QAM are used, then data rate increases, but PAR backoff requirement increases leading to more conservative power allocation
Solution Approach 1:
The patent implements dynamic power allocation that adapts to the selected modulation scheme. When higher order modulations like 64QAM are used, the system dynamically adjusts the power values for each antenna stream to account for the increased PAR backoff requirements, rather than using fixed conservative allocations. This allows the system to maintain higher data rates while managing power constraints effectively.
Data Source
AI summary
A method for a wireless communication includes receiving or storing a peak to average (PAR) back off value; and applying the PAR back off value to determine the transmission power and rate for SIMO and MIMO transmissions. In one aspect, the PAR back off value is at least partially based on modulation type. In another aspect, the PAR back off value is more for higher order QAM than for QPSK. The power allocation algorithm for different UL MIMO schemes is described as follows. For MIMO without antenna permutation (e.g. per antenna rate control), different PAR back off values are considered for different data streams. For MIMO with antenna permutation or other unitary transformation such as virtual antenna mapping or precoding, the PAR back off are determined based on combined channel. The transmission data rate depends on power and also the receiver algorithms such as a MMSE receiver or MMSE-SIC receiver.