STFBC Pre-coder Phase Rotation Optimization
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Solution Overview
Problem
Current space-time frequency block coding methods in mobile communication systems with three antennas do not maximize coding gain effectively, as the phase rotation angle calculated by existing design rules can degrade system performance.
Innovation Solution
A transmitter with three antennas uses a pre-coder to rotate input symbol sequences by a phase rotation angle optimized for each modulation scheme, such as atan(1/3) or pi/2-atan(1/3), to reconstruct real and imaginary parts, and then encodes these using an Alamouti scheme for transmission, maximizing coding gain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional phase rotation angle calculation methods are used in STFBC coding, then the system can operate with standard modulation schemes, but coding gain is not maximized and system performance degrades
Solution Approach 1:
The patent optimizes the phase rotation angle parameter in the pre-coder of the STFBC scheme. By changing this parameter from conventional values to optimized values (such as π/8, 3π/8, 5π/8, 7π/8 for QPSK), the coding gain is maximized. This parameter optimization resolves the contradiction by improving reliability through better coding gain while keeping the complexity manageable since it only requires selecting from a finite set of optimized angle values rather than continuous optimization.
2Reliability
If the phase rotation angle is optimized for each modulation scheme, then coding gain is maximized, but the system complexity increases due to multiple angle configurations
Solution Approach 1:
The patent applies different optimized phase rotation angles for different modulation schemes (QPSK, 16QAM, 64QAM). Each modulation scheme has its own locally optimized angle set, which maximizes performance for that specific scheme. This local quality approach resolves the contradiction by providing specialized optimization for each modulation type rather than using a one-size-fits-all approach, thereby improving system performance while maintaining clear adaptability rules.
Solution Approach 2:
The patent defines specific parameter sets for different modulation schemes: QPSK uses {π/8, 3π/8, 5π/8, 7π/8}, 16QAM uses {π/16, 3π/16, 5π/16, 7π/16, 9π/16, 11π/16, 13π/16, 15π/16}, and 64QAM uses {π/32, 3π/32, 5π/32, 7π/32, 9π/32, 11π/32, 13π/32, 15π/32, 17π/32, 19π/32, 21π/32, 23π/32, 25π/32, 27π/32, 29π/32, 31π/32}. This parameter change strategy allows the system to adapt to different modulation schemes while maintaining optimized performance through predefined angle sets.
Data Source
AI summary
The present invention relates to a transmitter and a transmission method in communication system using three Tx antennas in order to maximize STFBC coding gain. An input symbol sequence is transmitted through a plurality of Tx antennas in a predetermined method.