Phase-Aided Adaptive Modulation for Phase Noise Mitigation
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Solution Overview
Problem
Existing digital communication systems face performance limitations due to phase noise impairments, particularly in high-order QAM constellations, where common mitigation methods like pilot-aided algorithms reduce data rate and introduce phase ambiguity.
Innovation Solution
A transceiver system that employs a dual set of channel symbols, where the primary set carries data and adapts to channel conditions, and a secondary set with fixed known phase acts as a phase pilot, allowing data transmission while avoiding phase ambiguity, thereby enhancing communication over phase noise impaired channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pilot-aided algorithms are used to estimate and compensate phase noise, then phase noise mitigation is achieved, but data rate is reduced due to insertion of known symbols
Solution Approach 1:
The patent combines data transmission and phase reference functions into a single set of channel symbols. The receiver uses knowledge of the signal constellation to extract phase information from the same symbols that carry data, eliminating the need for separate pilot symbols and thereby maintaining data rate while achieving phase noise compensation.
Solution Approach 2:
The channel symbols serve dual purposes: they carry data information and simultaneously provide phase reference for noise compensation. This multi-functionality is achieved by leveraging the receiver's knowledge of the signal constellation to separate phase effects from data modulation.
2Productivity
If QPSK payload symbols are used as phase references, then data rate loss is recovered, but phase ambiguity is introduced reducing tolerance to frequency offset and phase noise
Solution Approach 1:
The patent uses the known signal constellation structure as an intermediary to extract phase information. Instead of using QPSK symbols that introduce ambiguity, the system leverages the receiver's knowledge of the full signal constellation to serve as a phase reference, avoiding phase ambiguity while maintaining data rate.
Solution Approach 2:
The patent replaces the mechanical insertion of dedicated pilot symbols with a signal processing approach that extracts phase information from the data symbols themselves. This substitution eliminates the need for separate phase reference symbols and avoids the phase ambiguity issues associated with QPSK-based solutions.
3Productivity
If high-order QAM constellations are used to increase spectrum efficiency, then data throughput is improved, but performance is severely limited by phase noise impairments
Solution Approach 1:
The patent implements a feedback mechanism where the receiver continuously estimates phase noise from the received signal constellation and sends compensation information back to the transmitter. This feedback loop enables the system to maintain high-order QAM performance by dynamically compensating for phase noise effects.
Solution Approach 2:
The system performs preliminary phase noise estimation and compensation before final data detection. By using the known constellation structure to pre-compensate for phase effects, the system prepares the signal in advance, making the subsequent data extraction more robust against phase noise impairments.
Data Source
AI summary
The present invention relates to a method and apparatus in a digital communication system that employs phase-aided adaptive modulation to overcome phase noise impairments. The transceiver is configured to transmit a message comprising channel symbols from a primary and a secondary set of channel symbols, wherein the primary set of channel symbols comprises channel symbols having different phase with respect to one another and the secondary set of channel symbols comprises only channel symbols with a fixed known phase.