Phase-Offset Alamouti Space-Time Coding for RF Dynamic Range Reduction
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Solution Overview
Problem
Existing digital wireless communication systems face challenges in reducing the dynamic range of RF signals transmitted through multiple antennas, leading to non-linear distortion and the need for expensive power amplifiers that can handle wider dynamic ranges without distortion.
Innovation Solution
The implementation of Alamouti space-time block coding with phase-offset constellations reduces the dynamic range of RF signals by applying phase rotation to symbols before transmission, allowing for the use of less expensive power amplifiers that operate within a reduced dynamic range and minimizing non-linear distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional space-time block coding is used without phase offset, then the transmission structure is simple and easy to implement, but the RF signal dynamic range is large causing non-linear distortion and requiring expensive power amplifiers
Solution Approach 1:
The patent applies phase offset modulation to the Alamouti space-time block coding scheme by modifying the phase parameter of the constellation symbols. Specifically, the second symbol in each Alamouti block is rotated by a phase offset θ, transforming the standard Alamouti code structure into a phase-offset variant that reduces signal dynamic range while maintaining the fundamental space-time coding operation. This parameter modification allows the use of less expensive power amplifiers with reduced dynamic range capabilities.
2Reliability
If power amplifiers with wide dynamic range are used to avoid non-linear distortion, then signal quality is maintained, but system cost increases significantly
Solution Approach 1:
The patent applies phase offset modulation as a preliminary signal processing step before the RF power amplification stage. By pre-modulating the constellation symbols with a phase offset, the signal dynamic range is reduced in advance, allowing subsequent power amplifiers to operate within their linear region even though they have reduced dynamic range capabilities. This preliminary action prevents the need for expensive wide dynamic range power amplifiers while maintaining signal quality.
3Ease of manufacture
If the dynamic range of RF signals is reduced, then cheaper power amplifiers can be used, but signal distortion may increase
Solution Approach 1:
The patent modifies the phase parameter of the modulation constellation to reduce signal dynamic range. By applying a phase offset θ to the constellation symbols (where θ is typically π/M for MPSK or π/4 for QAM), the signal envelope variations are reduced, allowing power amplifiers with reduced dynamic range to operate in their linear region. This parameter change simultaneously achieves cost reduction and maintains signal quality by preventing non-linear distortion.
Data Source
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AI summary
An apparatus, and an associated methodology, for facilitating communication of data in a wireless communication systems. Binary data are modulated to form modulated symbols on parallel paths. The symbols formed on one of the parallel paths are phase-offset by a phase rotator to form phase-offset symbols. The parallel paths of symbols provide the symbols, both the phase-offset symbols and the symbols that are not phase-offset, to an Alamouti encoder. As a result, the dynamic range of the transmitted RF signals is reduced due to the introduction of the phase offset between the symbols of the parallel paths applied to the Alamouti encoder.