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Low-complexity feed-forward carrier phase estimation for M-ary QAM based on phase search acceleration by quadratic
Optics Express
|September 15, 2015
Summary
This study introduces a faster carrier phase estimation (CPE) method for M-QAM systems using quadratic approximation in blind phase search (BPS). The new approach significantly reduces computational complexity while maintaining excellent laser linewidth tolerance.
Area of Science:
- Optical communication systems
- Digital signal processing
Background:
- Blind phase search (BPS) algorithm offers high tolerance to laser linewidth in M-QAM systems.
- Traditional BPS suffers from high computational complexity (CC).
Purpose of the Study:
- To reduce the computational complexity of BPS for M-QAM.
- To improve the efficiency of carrier phase estimation (CPE) in optical systems.
Main Methods:
- Theoretically derived the quadratic relationship between test angle and distance matrix in BPS.
- Proposed a two-stage BPS with quadratic approximation (QA) for CPE.
- Developed a guideline for optimizing summing filter block length.
Main Results:
- Achieved significant CC reduction: 2.96x/3.05x for 16QAM, 4.55x/4.67x for 64QAM, and 2.27x/2.3x for 256QAM (multipliers/adders).
- Proposed scheme demonstrates comparable performance to traditional BPS with optimized filter length.
- Achieved laser linewidth tolerance (Δf⋅T(S)) of 1.7 × 10⁻⁴, 6 × 10⁻⁵, and 1.5 × 10⁻⁵ for 16/64/256-QAM, respectively.
Conclusions:
- The proposed QA-based CPE significantly reduces computational complexity for M-QAM.
- The method maintains excellent laser linewidth tolerance, crucial for high-speed optical communications.
- Provides a practical approach for optimizing CPE in advanced modulation formats.
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