MIMO Precoding for Mixed-Modulation Spatial Diversity
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Solution Overview
Problem
Current MIMO communication systems face challenges in optimizing data transmission quality and diversity gain due to variations in modulation schemes and power levels between multiple antennas, which affect reception quality and spatial diversity.
Innovation Solution
The proposed solution involves a transmission method where two streams are modulated using different modulation schemes (e.g., QPSK, 16QAM, 64QAM, 256QAM) and precoded using specific matrices to ensure equal average power and optimal spatial diversity gain, with the precoding matrix adjusted based on symbol number to maintain high data reception quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If different modulation schemes are used for multiple antennas, then data transmission rate is improved, but reception quality deteriorates due to power level variations
Solution Approach 1:
The patent applies parameter changes by adjusting the precoding matrix based on the symbol number to compensate for power level variations caused by different modulation schemes. Specifically, the precoding matrix is modified to normalize the average power of signals transmitted from multiple antennas, ensuring that QPSK, 16QAM, 64QAM, and 256QAM signals all contribute equally to the received signal power, thereby maintaining reception quality while enabling high-rate transmission
Solution Approach 2:
The patent implements dynamics by making the precoding matrix time-varying rather than static. The precoding matrix changes according to the symbol number, allowing the system to adaptively compensate for power imbalances that occur when different modulation schemes are used across multiple antennas. This dynamic adjustment ensures consistent reception quality throughout the transmission process
2Reliability
If precoding matrix is adjusted based on symbol number, then spatial diversity gain is optimized, but system complexity increases
Solution Approach 1:
The patent uses parameter changes to optimize spatial diversity gain by adjusting specific parameters of the precoding matrix based on the symbol number. The adjustment follows a predetermined pattern that compensates for the effects of different modulation schemes, allowing the system to maintain optimal spatial diversity without requiring complex real-time calculations or adaptive algorithms
3Productivity
If multiple modulation schemes are used simultaneously, then communication rate is enhanced, but signal point distribution in I-Q plane becomes suboptimal
Solution Approach 1:
The patent applies parameter changes to the precoding matrix to normalize the average power of signals from multiple antennas using different modulation schemes. This ensures that signal points from QPSK, 16QAM, 64QAM, and 256QAM are properly distributed in the I-Q plane with optimal spacing and power levels, preventing degradation of signal quality despite the use of multiple modulation schemes
Data Source
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AI summary
In a transmission method according to one aspect of the present disclosure, a encoder performs error correction coding on an information bit string to generate a code word. A mapper modulates a first bit string in which the number of bits is the integral multiple of (X + Y) in the code word using a first scheme, the first scheme being a set of a modulation scheme in which an X-bit bit string is mapped to generate a complex signal and a modulation scheme in which a Y-bit bit string is mapped to generate a complex signal, and modulates a second bit string in which the first bit string is removed from the code word using a second scheme different from the first scheme.