Phase Rotation for MIMO DMRS Power Imbalance
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Solution Overview
Problem
In multiple-input multiple-output (MIMO) wireless communications, power imbalances between demodulation reference signals (DMRS) symbols can lead to undesirable transmitter behavior, such as loss of phase continuity and power ramping issues, affecting signal quality and transmission efficiency.
Innovation Solution
Applying a phase rotation scheme in addition to the orthogonal cover code and precoder to DMRS symbols, ensuring balanced power across DMRS symbols and antenna ports, with the phase rotation scheme selected based on the precoder or OCC to meet power imbalance thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a particular combination of OCC and precoder is applied to DMRS, then the DMRS can be transmitted using multiple antennas, but power imbalance between adjacent DMRS symbols occurs causing undesirable transmitter behavior
Solution Approach 1:
The patent applies phase rotation to the DMRS symbols, which changes the phase parameter of the transmitted signal. By rotating the phase of specific DMRS symbols, the patent balances the power distribution across adjacent symbols while maintaining the MIMO transmission structure. This parameter change (phase rotation) directly addresses the power imbalance issue without sacrificing productivity.
2Reliability
If phase rotation scheme is applied to DMRS symbols, then power balance between DMRS symbols is improved, but device complexity increases
Solution Approach 1:
The patent applies phase rotation selectively to specific DMRS symbols rather than all symbols uniformly. The phase rotation is applied locally to adjacent DMRS symbols that exhibit power imbalance, leaving other symbols unchanged. This localized approach maintains power balance while minimizing the overall processing complexity and computational overhead.
3Productivity
If zero power DMRS symbols are transmitted adjacent to non-zero power DMRS symbols, then spectral efficiency is maintained, but phase continuity is lost causing signal quality degradation
Solution Approach 1:
The patent applies phase rotation in advance to prevent the formation of zero-power DMRS symbols. By rotating the phase of adjacent DMRS symbols before transmission, the patent ensures that no symbol has zero power, thereby preventing phase discontinuities before they occur. This preliminary action maintains both spectral efficiency and phase continuity.
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. A transmitting device may identify multiple demodulation reference signal (DMRS) symbols corresponding to multiple DMRS ports of a multiple input multiple output configuration. The transmitting device may generate multiple phase-rotated and precoded DMRS symbols by applying an orthogonal cover code, a phase rotation scheme, and a precoding matrix to the identified DMRS symbols. The transmitting device may map the phase-rotated and precoded DMRS symbols to time-frequency resources corresponding to multiple antenna ports, and transmit a DMRS based on the mapped phase-rotated and precoded DMRS symbols. The transmitting device may transmit the DMRS using multiple antennas that correspond to the antenna ports.