DPSK Symbol Detection Using Multiple Previous Phase References
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Solution Overview
Problem
Differential phase shift keying (DPSK) communication devices face challenges in accurately determining symbols due to phase errors, leading to error propagation, which can affect the reliability of soft-output values and reduce accuracy even with error-detecting codes like cyclic redundancy check (CRC).
Innovation Solution
A method is introduced to calculate phase differences between consecutive signals, determining target likelihoods for each symbol based on these differences, and using these likelihoods to determine an expected symbol or phase difference, thereby reducing error propagation. This involves calculating first and second phase differences between previous and target signals, and using them to generate expected phase differences or symbols.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional DPSK demodulation is used to determine symbols based on phase difference between consecutive signals, then the demodulation process is simple and fast, but error propagation occurs when phase errors are present, reducing reliability
Solution Approach 1:
The patent performs preliminary actions by calculating phase differences between the target signal and multiple previous signals (first previous signal and second previous signal) before making the final symbol determination. This preliminary calculation of multiple phase differences (first phase difference and second phase difference) allows the system to anticipate and compensate for potential error propagation by having redundant reference points ready before the critical decision point.
Solution Approach 2:
The patent introduces an intermediary mechanism by using the second previous signal as an additional reference point between the target signal and the first previous signal. This intermediary reference allows the system to calculate multiple phase differences and use likelihood calculations to determine the most reliable symbol, thereby mediating the error propagation problem that would otherwise directly affect symbol determination.
2Measurement precision
If phase error correction is performed using multiple previous signals, then error propagation is reduced and symbol accuracy improves, but the calculation complexity and processing time increase
Solution Approach 1:
The patent applies partial action by selectively using multiple previous signals (first previous signal and second previous signal) rather than processing all available historical signals. This partial approach to phase difference calculation provides sufficient accuracy improvement without the excessive computational burden of analyzing every possible reference signal, thereby balancing precision gains with processing time constraints.
3Reliability
If likelihood calculations are performed for multiple symbols based on phase differences, then the most reliable symbol can be selected, but the computational load increases
Solution Approach 1:
The patent applies local quality by performing likelihood calculations specifically for the critical phase differences that directly impact symbol determination (first phase difference between target and first previous signal, and second phase difference between target and second previous signal). Rather than uniformly processing all possible signal combinations, the system focuses computational resources on the locally critical phase difference calculations that most directly affect soft-output reliability.
Data Source
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AI summary
An method of determining a symbol according to a phase difference between input signals input in order of time may include calculating a first phase difference between a phase of a first previous signal received prior to a target signal and a phase of a second previous signal received prior to the first previous signal; calculating a second phase difference between a phase of the target signal and the phase of the second previous signal; calculating target likelihoods based on the first phase difference and the second phase difference; and determining an expected phase difference between the target signal and the first previous signal or an expected symbol for the target signal, based on the target likelihoods.