Continuous Phase Modulation Pre-compensation for Inter-symbol Interference
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Solution Overview
Problem
Continuous phase modulation methods suffer from significant inter-symbol interference, making it difficult for receivers to accurately determine the initial state of symbols, and existing demodulation techniques are complex and inefficient.
Innovation Solution
A method that transforms digital data symbols by applying a non-linear function to differences between consecutive symbols, combined with a shaping filter and phase modulator, to minimize interference between modulated symbols, using an iterative process to identify optimal transformation parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If continuous phase modulation is used to maximize signal range and reduce spectral width, then signal power efficiency and bandwidth occupation are improved, but inter-symbol interference increases making receiver demodulation complex and difficult
Solution Approach 1:
The patent applies preliminary action by transforming the symbol sequence before modulation to pre-compensate for inter-symbol interference. The transformation modifies symbols based on their differences from previous symbols, anticipating and counteracting the interference that would otherwise occur during reception and demodulation.
Solution Approach 2:
The patent changes the parameters of the symbol sequence by applying a non-linear transformation that modifies symbol values based on their differences from consecutive symbols. This parameter transformation alters the signal characteristics to reduce inter-symbol interference while maintaining the benefits of continuous phase modulation.
2Reliability
If conventional continuous phase modulation is used, then constant envelope and spectral efficiency are achieved, but inter-symbol interference distorts received symbols requiring complex equalization and maximum likelihood sequence estimation
Solution Approach 1:
The transformation is applied in advance to the symbol sequence before modulation, pre-compensating for the inter-symbol interference that would otherwise require complex equalization and maximum likelihood sequence estimation at the receiver. This preliminary transformation simplifies the receiver architecture.
Solution Approach 2:
The patent extracts and compensates for the inter-symbol interference component by transforming symbols based on their differences from consecutive symbols. This separation of the interference effect allows for its cancellation through the transformation process.
3Productivity
If the number of possible symbol states increases to improve data rate, then information transmission capacity is improved, but receiver decision complexity and inter-symbol interference disruption increase
Solution Approach 1:
The patent applies a non-linear transformation to the symbol parameters that reduces inter-symbol interference while maintaining the high-order modulation format. This allows the system to achieve high data rates with multiple symbol states without proportionally increasing receiver complexity.
Solution Approach 2:
By transforming the symbol sequence before transmission, the system pre-compensates for interference effects that would otherwise make high-order modulation difficult to demodulate, enabling higher data rates with manageable receiver complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Almost complete suppression of inter-symbol interference, simplifying receiver complexity and improving demodulation performance by ensuring the modulated signal's phase on reception matches the emitted signal's phase, thus reducing spectral width and maintaining constant power.
Implementation Method 1
modulating the sequence of filtered symbols with a phase modulator in order to obtain a sequence of modulated symbols
Data Source
AI summary
A continuous phase modulation method comprises the following steps: receiving a sequence of digital data symbols a(n) to be emitted; transforming the sequence of symbols a(n) to be emitted into a transformed sequence of symbols b(n), each symbol b(n) of which is equal to the sum of a symbol a(n) to be emitted and of a corrective factor equal to a transformation Tf applied to a plurality of differences (a(n)-a(n−1)) between two consecutive symbols to be emitted, the transformation Tf applied being a combination c of at least two differences between two consecutive symbols of the sequence to be emitted, transformed by the application of a non-linear function f; filtering the sequence of transformed symbols b(n) with a shaping filter and modulating the filtered sequence with a phase modulator; said transformation Tf being defined so as to minimize interference between modulated symbols filtered by a receiving filter.